CN113204911A - Fluid-solid coupling simulation method and system for trailing edge deflection process of ram parafoil - Google Patents
Fluid-solid coupling simulation method and system for trailing edge deflection process of ram parafoil Download PDFInfo
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Abstract
The invention discloses a fluid-solid coupling simulation method and a fluid-solid coupling simulation system for a trailing edge deflection process of a ram parafoil, relates to the field of fluid-solid coupling simulation, researches a bulge phenomenon of a trailing edge deflection state of a parafoil air chamber in an inflation process and a fluid-solid coupling dynamics simulation method, can predict fluid-solid coupling dynamics behaviors of the parafoil air chamber in the inflation process, and observes a three-dimensional change process of a fluid and a structure. The research method can obviously improve the maneuverability of the precise air-drop system and is used for the design analysis of the precise air-drop system of the parafoil as a reliable simulation tool.
Description
Technical Field
The invention relates to the field of fluid-solid coupling simulation, in particular to a fluid-solid coupling simulation method and system in a trailing edge deflection process of a ram parafoil.
Background
The parafoil is a flexible rectangular wing with a double-layer structure, the upper wing surface and the lower wing surface are divided into a plurality of air chambers by wing-shaped ribs, wherein the air chambers are in a bulge state, which means a state when the air chambers are filled with air. The ram parafoil realizes maneuvering actions such as maneuvering turning, sparrow descending and the like by pulling off the trailing edge in the flying process, and relates to the coupling action process of a flexible fabric structure and aerodynamic force. The upper wing surface mainly bears aerodynamic force, the lower wing surface bears parachute opening impact force, and the damage of the local damage of the lower wing surface cannot cause the damage of the aerodynamic performance of the whole parafoil. The canopy is made of tear-resistant silk with extremely low air permeability, the front edge of the wing profile is opened, and 'ram air' is formed in forward flight to maintain the internal pressure of an air chamber so as to keep the wing profile. Compared with the traditional parachute, the maximum advantage of the parafoil system is that the research on maneuverability, control mechanism and flight dynamics and control is also a key technology and hot problem for the application of the parafoil recovery system.
The working process of the parafoil is a typical aeroelasticity problem, is a nonlinear system, relates to the interaction of a canopy structure and pneumatic pressure, and the solution of the fluid-solid coupling process is always concerned by people as a difficult problem in the field of parachute research. This is mainly because: the canopy is used as a flexible fabric and has a nonlinear mechanical behavior of a large deformation structure; aerodynamic force distribution of a flow field around the canopy is complex and changeable; the canopy has a strong coupling effect with the flow field, so that the solution is not easy to solve, and the parachute opening performance is more difficult to accurately predict.
At present, the dynamic mechanism of the fluid-solid coupling process of the parafoil specially aimed at home and abroad is lack of very deep and extensive research. Based on the fluid-solid coupling research foundation of the traditional parachute, the method is researched by adopting a complete test method, a semi-test semi-theoretical method and a complete theoretical method. The method lacks a three-dimensional simulation specially aiming at the trailing edge deflection dynamic process of the parafoil, and lacks an effective simulation technical means for predicting the non-constant field flow phenomenon and the structural response in the manipulation process.
Disclosure of Invention
Aiming at the technical problem that the fluid-solid coupling simulation of the trailing edge deflection process of the parafoil is lacked in the prior art, the invention provides a fluid-solid coupling simulation method and system for the trailing edge deflection process of a stamping parafoil.
In order to achieve the above object, the present invention provides a method for simulating fluid-solid coupling during trailing edge deflection of a ram parachute, comprising:
carrying out geometric modeling on a parafoil structure to obtain a three-dimensional geometric shape of the parafoil structure, wherein the parafoil structure is in an unfolded state, and an air chamber of the parafoil structure is in a bulge state;
meshing the three-dimensional geometric shape to obtain a meshing result, and obtaining a first mesh model of the parafoil structure based on the meshing result and the material parameters of the canopy fabric;
determining a geometric parameter of a first fluid domain that encloses the first mesh model based on a geometric parameter of the parafoil structure;
setting a first characteristic parameter of the first fluid domain boundary grid points based on the shell cell grid size of the first grid model, and generating a second grid model of the first fluid domain based on the first characteristic parameter;
generating a fluid-solid coupled mesh model based on the first mesh model and the second mesh model;
and performing fluid-solid coupling simulation on the surrounding air field of the parafoil structure and the parafoil structure based on the fluid-solid coupling grid model, the material parameters, the boundary conditions of the first fluid domain, the constraint parameters of the parafoil structure, the load conditions of the parafoil structure and fluid-solid coupling solving related parameters.
The method comprises the steps of obtaining a first grid model of the parafoil structure by geometrically modeling the parafoil structure, generating a second grid model of a first fluid domain, determining a fluid-solid coupling grid model through the two models, and inputting corresponding parameters and models into simulation software or equipment to realize fluid-solid coupling simulation in the trailing edge deflection process of the ram parafoil.
Wherein the material parameters are parameters of the umbrella-coat fabric material, including the density, the elastic modulus and the Poisson ratio of the fabric material; the boundary conditions of the first fluid domain include: the boundary conditions of the first fluid domain include: the entrance is an incoming flow velocity boundary, and the rest boundaries are set as non-reflection boundary conditions; the structure of the parafoil is constrained in such a way that full constraint is applied to a node at the notch of the front edge of the parafoil; the loading conditions of the parafoil structure were: applying a pull-down load curve at the rear edge of the parafoil structure; the fluid-solid coupling solution related parameters comprise: the contact penalty function stiffness coefficient and solution time between the parafoil structure and the first fluid domain node include computation time and mass scaling factors.
Preferably, the fluid-solid coupling simulation includes:
a first simulation stage: simulating and simulating the fluid-solid coupling dynamic performance of the surrounding air field of the parafoil structure and the parafoil structure, wherein the load condition is that the load curve parameter value is 0;
and a second simulation stage: and applying a deflected load curve to the rear edge part of the parafoil structure to carry out the fluid-solid coupling dynamic simulation of the rear edge deflection state, wherein the load condition is that the parameter value of the load curve is greater than 0.
The method comprises the following steps of simulating the fluid-solid coupling dynamic performance of a surrounding air field of a parafoil structure and the parafoil structure, wherein the first step mainly simulates the fluid-solid coupling dynamic performance of the parafoil structure, a deflected load curve is not applied to the rear edge part of the parafoil structure in the first step, the simulation enters the second step after the simulation is finished in the first step, the deflected load curve is applied to the rear edge part of the parafoil structure to simulate the fluid-solid coupling dynamic in a rear edge deflection state, and the fluid-solid coupling simulation in the trailing edge deflection process of the stamping parafoil is realized.
Preferably, the dynamical control equation of the parafoil structure in the method is as follows:
wherein the content of the first and second substances,
is the material density of the parafoil structure,
is the tension of the Coriolis stress,
for external forces acting on the parafoil structure,
is the velocity vector of the structural particle of the parafoil,
in order to calculate the time of day,
is the sign of partial differential operation.
Preferably, the parafoil canopy structure is made of flexible fabric materials, can only bear the effect of the in-plane stretching direction, and can be neglected in the thickness direction, so that finite element division can be performed by adopting two-dimensional units. In order to more accurately simulate the in-plane stress behavior of the canopy structure, the method adopts the film units to perform meshing on the three-dimensional geometric shape, and the constitutive equation of the film units is as follows:
wherein the content of the first and second substances,
longitudinal strain of the membrane unit in the parafoil structure,
is the longitudinal stress of the parafoil structural film unit,
is the longitudinal Poisson ratio of the parafoil structural membrane unit,
is the longitudinal elastic modulus of the parafoil structural film unit,
is the transverse strain of the parafoil structural membrane unit,
is the transverse stress of the parafoil structural membrane unit,
is the transverse Poisson ratio of the parafoil structure membrane unit,
is the transverse elastic modulus of the parafoil structural film unit,
is the tangential strain of the parafoil structural membrane unit,
is the shear stress of the parafoil structural film unit,
is the shear modulus of the parafoil structural membrane unit,
is the nonlinear coefficient of the parafoil structural film unit.
Preferably, in the method, the kinetic equation of the first fluid domain is:
wherein the content of the first and second substances,
is the density of the fluid domain units in the first fluid domain gas,
is the velocity vector of the fluid domain unit in the first fluid domain,
for external forces acting on the fluid domain unit in said first fluid domain,
being the stress tensor of the fluid domain element in the first fluid domain,
in the form of a Hamiltonian operator,
to obtain the divergence of the velocity tensor for the fluid domain elements in the first fluid domain,
in order to be a sign of the partial differential operation,
to calculate the time.
Preferably, in the method, the lagrangian euler control equation of the first fluid domain is as follows:
wherein the content of the first and second substances,
is the density of the fluid domain units in the first fluid domain gas,vandwthe first fluid domain unit particle velocity and the first fluid domain unit material grid point velocity are respectively the fluid domain unit particle velocity and the fluid domain unit material grid point velocity;u f is the velocity of the fluid domain unit in the first fluid domain,u f =v-w，
in order to be a sign of the partial differential operation,
to resolve the divergence of the fluid domain units in the first fluid domain,
to calculate the time;
being the stress tensor of the fluid domain element in the first fluid domain,
is the external normal force tensor to which the fluid domain elements are subjected in the first fluid domain.
Preferably, the key of fluid-solid coupling simulation calculation lies in a coupling information transfer method between the fluid domain and the structural domain unit, and the penalty function method is used for information transfer in a mode of applying an interaction force through a relative movement distance and a rigidity coefficient between interfaces and is initially applied to simulating contact collision behavior, so that the problem of information transfer between the fluid and the structure in the fluid-solid coupling simulation calculation process can be effectively solved. The method is based on a penalty function method to carry out transfer calculation of node force information between the fluid domain unit in the first fluid domain and the domain unit in the parafoil structure.
Preferably, when the time step is
When, the structural domain of the parafoilThe penetration depth of the unit node isd n Then the penetration depth of the domain unit node in the parafoil structure of the next moment iteration isd n+1：
Wherein the content of the first and second substances,
by penetration depth is meant the relative distance between the master node of a domain unit in the first fluid domain and the slave node of a domain unit in the parafoil structure,
in order to integrate the number of time steps,
the relative velocity of the master node of a domain unit in the first fluid domain and the slave node of a domain unit in the parafoil structure for an intermediate time instant is:
wherein the content of the first and second substances,
for the node velocities of the domain units in the parafoil structure at intermediate times,
the velocity of a fluid domain unit node in the first fluid domain at an intermediate time;
the coupling force between the nodes of the domain units in the parafoil structure and the nodes of the fluid domain units in the first fluid domain is
：
Wherein the content of the first and second substances,
is the stiffness coefficient;
applying a balanced force between a master node of a fluid domain unit in the first fluid domain and a slave node of a domain unit in the parafoil structure
:
Passing the force experienced by the fluid domain elements in the first fluid domain through a shape function
Nodes distributed to domain units in the parafoil structureiEach of said parafoil structure nodes of domain units being subjected to a fluid domain force of
：
Wherein the content of the first and second substances,
a master node being a fluid domain unit in the first fluid domain,
is a slave node of a domain unit in the parafoil structure,
is a coupling interface.
Preferably, the method applies full constraint to a node at a parafoil leading edge notch of the parafoil structure, and applies a pull-down load curve to the parafoil trailing edge of the parafoil structure.
The invention also provides a fluid-solid coupling simulation system in the trailing edge deflection process of the ram parafoil, which comprises the following components:
the device comprises a geometric modeling unit, a data processing unit and a data processing unit, wherein the geometric modeling unit is used for performing geometric modeling on a parafoil structure to obtain a three-dimensional geometric shape of the parafoil structure, the parafoil structure is in an unfolded state, and an air chamber of the parafoil structure is in a bulge state;
a first mesh model obtaining unit, configured to perform mesh division on the three-dimensional geometric shape to obtain a mesh division result, and obtain a first mesh model of the parafoil structure based on the mesh division result and material parameters of the canopy fabric;
a first fluid field geometric parameter determination unit, configured to determine a geometric parameter of a first fluid field enclosing the first mesh model based on a geometric parameter of the parafoil structure;
a second mesh model generating unit, configured to set a first characteristic parameter of the first fluid domain edge mesh point based on a shell cell mesh size of the first mesh model, and generate a second mesh model of the first fluid domain based on the first characteristic parameter;
a fluid-solid coupling mesh model generating unit, configured to generate a fluid-solid coupling mesh model based on the first mesh model and the second mesh model;
and the fluid-solid coupling simulation unit is used for carrying out fluid-solid coupling simulation on the surrounding air field of the parafoil structure and the parafoil structure based on the fluid-solid coupling grid model, the material parameters, the boundary conditions of the first fluid domain, the constraint parameters of the parafoil structure, the load conditions of the parafoil structure and fluid-solid coupling solving related parameters.
The invention also provides a stamping parafoil trailing edge deflection process fluid-solid coupling simulation device which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor realizes the steps of the stamping parafoil trailing edge deflection process fluid-solid coupling simulation method when executing the computer program.
The invention also provides a computer readable storage medium, which stores a computer program, which when executed by a processor implements the steps of the method for simulating the fluid-solid coupling during the trailing edge deflection of a ram parachute.
One or more technical schemes provided by the invention at least have the following technical effects or advantages:
the invention realizes the fluid-solid coupling simulation of the trailing edge deflection process of the parafoil.
The invention carries out numerical simulation and theoretical analysis on the fluid-solid coupling dynamic behavior of the trailing edge deflection process of the parafoil based on a transient nonlinear dynamic method. According to the invention, a dynamic grid technical means and a penalty function method based on the SALE algorithm are adopted to model the coupling field and the interface, so that the computational efficiency of simulation is improved.
The invention researches the bulge phenomenon of the trailing edge deflection state of the parafoil air chamber in the inflation process and a fluid-solid coupling dynamic simulation method. The fluid-solid coupling dynamic behavior of the parafoil air chamber in the inflation process can be predicted, and the three-dimensional change process of the fluid and the structure is observed. The research method can obviously improve the maneuverability of the precise air-drop system and is used for the design analysis of the precise air-drop system of the parafoil as a reliable simulation tool.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention;
FIG. 1 is a schematic flow chart of a simulation method of fluid-solid coupling in a trailing edge deflection process of a ram parafoil;
FIG. 2 is a schematic diagram of a simulation method of fluid-solid coupling during trailing edge deflection of the ram parachute in this embodiment;
FIG. 3 is a schematic diagram of the components of a fluid-solid coupling simulation system in the trailing edge deflection process of a ram parafoil.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments of the present invention and features of the embodiments may be combined with each other without conflicting with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described and thus the scope of the present invention is not limited by the specific embodiments disclosed below.
It should be understood that "system", "device", "unit" and/or "module" as used herein is a method for distinguishing different components, elements, parts, portions or assemblies at different levels. However, other words may be substituted by other expressions if they accomplish the same purpose.
As used in this specification and the appended claims, the terms "a," "an," "the," and/or "the" are not intended to be inclusive in the singular, but rather are intended to be inclusive in the plural, unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that steps and elements are included which are explicitly identified, that the steps and elements do not form an exclusive list, and that a method or apparatus may include other steps or elements.
Flow charts are used in this description to illustrate operations performed by a system according to embodiments of the present description. It should be understood that the preceding or following operations are not necessarily performed in the exact order in which they are performed. Rather, the various steps may be processed in reverse order or simultaneously. Meanwhile, other operations may be added to the processes, or a certain step or several steps of operations may be removed from the processes.
Example one
Referring to fig. 1, fig. 1 is a schematic flow chart of a simulation method of fluid-solid coupling in a trailing edge deflection process of a ram parafoil, the method including:
carrying out geometric modeling on a parafoil structure to obtain a three-dimensional geometric shape of the parafoil structure, wherein the parafoil structure is in an unfolded state, and an air chamber of the parafoil structure is in a bulge state;
meshing the three-dimensional geometric shape to obtain a meshing result, and obtaining a first mesh model of the parafoil structure based on the meshing result and the material parameters of the canopy fabric;
determining a geometric parameter of a first fluid domain that encloses the first mesh model based on a geometric parameter of the parafoil structure;
setting a first characteristic parameter of the first fluid domain boundary grid points based on the shell cell grid size of the first grid model, and generating a second grid model of the first fluid domain based on the first characteristic parameter;
generating a fluid-solid coupled mesh model based on the first mesh model and the second mesh model;
and performing fluid-solid coupling simulation on the surrounding air field of the parafoil structure and the parafoil structure based on the fluid-solid coupling grid model, the material parameters, the boundary conditions of the first fluid domain, the constraint parameters of the parafoil structure, the load conditions of the parafoil structure and fluid-solid coupling solving related parameters.
Fluid-solid coupling refers to the interaction between a fluid and a solid.
Referring to fig. 2, fig. 2 is a schematic diagram illustrating a fluid-solid coupling simulation method in a trailing edge deflection process of a ram parachute in the embodiment;
the method carries out modeling and simulation calculation aiming at the structural mode that the parafoil air chamber is fully filled with bulges after being unfolded, and comprises the following steps:
according to the designated parafoil structural parameters, carrying out geometric modeling of the full bulge state of the airfoil-shaped unfolded structure to obtain the three-dimensional geometric shape of the bulge state of the parafoil air chamber;
carrying out mesh division on the three-dimensional geometric appearance of the parafoil structure by using the shell unit, and inputting parameters of the canopy fabric material, including the density, the elastic modulus and the Poisson ratio of the fabric material, to obtain a finite element model of the parafoil structure; the shell unit is applied to simulate a structure, the dimension (thickness) of the structure in one direction is far smaller than the dimension of the structure in other directions, and the stress in the thickness direction is ignored;
considering the geometric parameters of the parafoil structure, including the sizes in the length direction, the width direction and the height direction, and determining the geometric parameters of a fluid domain of a three-dimensional finite element model completely wrapping the parafoil structure according to the principle of equal proportional multiple growth, including the sizes in the length direction, the width direction and the height direction; because the unfolded parafoil structure is in a flat shape in the unfolding direction, a cuboid can be selected as a fluid domain geometric model;
in combination with the size of the shell element grid of the finite element model of the parafoil structure, in order to ensure the energy conservation of information transmission between the fluid domain element and the structure domain element and simultaneously avoid the calculation divergence caused by the hourglass phenomenon which is a non-physical characteristic possibly occurring in the explicit dynamics integration process due to the overlarge size difference between the fluid and the structure element, the element size between the flow field grid and the parafoil structure grid should be as close as possible to 1: 1, setting characteristic parameters of grid points on a fluid domain side line (length, width and height) for generating a fluid domain grid;
setting boundary conditions of a fluid domain for the divided parafoil structure and a surrounding flow field grid model, wherein the boundary conditions of the fluid domain comprise: the entrance is an incoming flow velocity boundary, and the rest boundaries are set as non-reflection boundary conditions; the parafoil domain then needs to set constraints and loading conditions: applying full constraint to a node at the notch of the front edge of the parafoil, and applying a pull-down load curve at the position of the rear edge of the parafoil;
setting fluid-solid coupling control parameters, mainly including contact penalty function rigidity coefficients between parafoil structure nodes and flow field nodes, and setting solving time control including calculating time and mass scaling factors, wherein the mass scaling factors are reasonably selected according to unit size and solving time due to calculation simulation in an explicit dynamics integration mode, so that solving divergence is avoided;
importing an input parameter file containing grid model unit information, material information, boundary condition information, load curve information and solving control parameter information into nonlinear transient dynamics analysis software to carry out simulation calculation: firstly, simulating the fluid-solid coupling dynamic performance of an air chamber in a full-bulge state without trailing edge pull-down, wherein the load curve parameter value of the trailing edge is 0; calculating a process flow field domain, and automatically generating a structured fluid grid according to grid point characteristic parameters on set fluid domain side lines (length, width and height) and hexahedron units; observing that the surrounding flow field structure is stable after the parafoil fluid-solid coupling simulation in the bulge state is performed for a period of time, and starting to perform fluid-solid coupling dynamic simulation in the trailing edge deflection state on a load curve applying deflection to the trailing edge part after the change of the surrounding flow field structure is not obvious any more along with the time;
and generating a calculation result and carrying out fluid-solid coupling dynamics performance analysis.
In this embodiment, the dynamical control equation of the parafoil domain is:
wherein the content of the first and second substances,
is the material density of the parafoil structure,
is the tension of the Coriolis stress,
for external forces acting on the parafoil structure,
is the velocity vector of the structural particle of the parafoil,
in order to calculate the time of day,
is the sign of partial differential operation.
The method comprises the following steps of carrying out grid division on a parafoil structure by using shell units to generate a finite element model, considering the structural dynamics nonlinear characteristic of canopy, and adopting film units, wherein the constitutive equation is as follows:
wherein the content of the first and second substances,
longitudinal strain of the membrane unit in the parafoil structure,
is the longitudinal stress of the parafoil structural film unit,
is the longitudinal Poisson ratio of the parafoil structural membrane unit,
is the longitudinal elastic modulus of the parafoil structural film unit,
is the transverse strain of the parafoil structural membrane unit,
is the transverse stress of the parafoil structural membrane unit,
is the transverse Poisson ratio of the parafoil structure membrane unit,
is the transverse elastic modulus of the parafoil structural film unit,
is the tangential strain of the parafoil structural membrane unit,
is the shear stress of the parafoil structural film unit,
is the shear modulus of the parafoil structural membrane unit,
is the nonlinear coefficient of the parafoil structural film unit. The fabric structure material of the parafoil is generally made of anti-brocade silk with extremely low air permeability, and the air permeability of the canopy is not considered.
The kinetic equations needed to solve the fluid domain are:
wherein the content of the first and second substances,
is the density of the fluid domain units in the first fluid domain gas,
is the velocity vector of the fluid domain unit in the first fluid domain,
for external forces acting on the fluid domain unit in said first fluid domain,
being the stress tensor of the fluid domain element in the first fluid domain,
in the form of a Hamiltonian operator,
to obtain the divergence of the velocity tensor for the fluid domain elements in the first fluid domain,
in order to be a sign of the partial differential operation,
to calculate the time. By introducing an Arbitrary Lagrange Euler (ALE) format, the finite mesh can be moved freely. The fluid particle coordinates are, wherein, according to the N-S equation, the control equation in the ALE format for the incompressible fluid domain is:
wherein the fluid velocity isu f =v-w，vAndwreference is made to the fluid mass point velocity and the material mesh point velocity in the configuration, respectively, ifv = wThe formula is in the form of lagrange.
In the whole fluid-solid coupling simulation process of the parafoil, the canopy structure deformation interacts with the change of the flow field around the canopy, in the coupling calculation process, the key is the transmission of coupling interface information between the structure and the flow field unit, the energy conservation is ensured in the transmission process, and usually, a finite element model is difficult to realize the complete matching of fluid and a structural grid. The invention carries out the transfer of node force information between the fluid and the canopy structure based on a penalty function method under the Euler-Lagrange description, and the method allows non-matching fluid and structural grids.
Assuming that the fluid is a permeable medium, an explicit kinetic integration method is adopted when the time step is as follows
When the penetration depth of the structure domain unit node in the parafoil structure isd n Then the penetration depth of the domain unit node in the parafoil structure of the next moment iteration isd n+1：
Wherein the content of the first and second substances,
by penetration depth is meant the relative distance between the master node of a domain unit in the first fluid domain and the slave node of a domain unit in the parafoil structure,
for the relative velocity of the master node of a domain unit in the first fluid domain and the slave node of a domain unit in the parafoil structure at an intermediate time,
the relative speed of the master node and the slave node at the intermediate time, that is, the speed of the slave node, that is, the speed of the structural node, and the speed of the master node can be regarded as the speed of a certain fluid point obtained by the change of the isoparametric coordinates of the fluid unit node, then:
wherein the content of the first and second substances,
for the node velocities of the domain units in the parafoil structure at intermediate times,
the velocity of a fluid domain unit node in the first fluid domain at an intermediate time; if and only if
When the penetration is generated,
is the number of integration time steps. The parafoil knotThe coupling force between the nodes of the structural domain units and the nodes of the fluid domain units in the first fluid domain is
：
Wherein
And representing the stiffness coefficient, corresponding to the stiffness coefficient in the fluid-solid coupling control parameter.
Applying a balanced force between a master node of a fluid domain unit in the first fluid domain and a slave node of a domain unit in the parafoil structure
:
Passing the force experienced by the fluid domain elements in the first fluid domain through a shape function
Nodes distributed to domain units in the parafoil structureiEach of said parafoil structure nodes of domain units being subjected to a fluid domain force of
：
Wherein the content of the first and second substances,
is the firstA master node of a fluid domain unit in the fluid domain,
is a slave node of a domain unit in the parafoil structure,
is a coupling interface;
for block unit
The force interaction criterion is satisfied at the coupling interface.
The specific simulation process is as follows;
obtaining a parafoil air chamber full bulge state model through finite element modeling;
applying boundary condition constraint and a trailing edge deflection load curve to the parafoil structure in the bulge state;
setting fluid domain grid node parameters for automatically generating grids;
setting coupling to solve related parameters and developing simulation calculation;
and generating a flow field and structural field data file according to the simulation result, and analyzing fluid-solid coupling performance parameters.
And analyzing the dynamic characteristics and structural response of the flow field around the parafoil according to the performance parameters, and guiding the design and task planning of the parafoil recovery system.
Example two
On the basis of the first embodiment, the second embodiment of the invention provides a method for simulating a flow fixed coupling trailing edge in a parafoil deflection process, which comprises the following steps:
carrying out parametric modeling according to the geometric parameters of the specific parafoil to generate a parafoil structure model, and dividing finite element grids for structure simulation calculation;
carrying out fluid-solid coupling simulation in the inflation process to obtain a parafoil structure diagram in a full-bulge state;
deriving a parafoil structure chart, using the parafoil structure chart for trailing edge deflection process fluid-solid coupling simulation, and loading a deflection load curve;
obtaining a flow field characteristic velocity vector cloud picture in the trailing edge deflection process of the parafoil, and obtaining a stress cloud picture and a surface pressure cloud picture of parafoil structure response;
analyzing the inflating performance of the parafoil according to the simulation result, and checking the geometric state and structural stress distribution of the parafoil bulge; analyzing the fluid-solid coupling performance of the trailing edge deflection process of the parafoil, checking the fluid change process around the parafoil, analyzing the evolution of vortex and flow separation phenomena, and evaluating the stress concentration high-risk easy-to-tear damage area on the structure surface of the parafoil.
EXAMPLE III
Referring to fig. 3, fig. 3 is a schematic composition diagram of a ram parafoil trailing edge deflection process fluid-solid coupling simulation system, a third embodiment of the present invention provides a ram parafoil trailing edge deflection process fluid-solid coupling simulation system, which includes:
the device comprises a geometric modeling unit, a data processing unit and a data processing unit, wherein the geometric modeling unit is used for performing geometric modeling on a parafoil structure to obtain a three-dimensional geometric shape of the parafoil structure, the parafoil structure is in an unfolded state, and an air chamber of the parafoil structure is in a bulge state;
a first mesh model obtaining unit, configured to perform mesh division on the three-dimensional geometric shape to obtain a mesh division result, and obtain a first mesh model of the parafoil structure based on the mesh division result and material parameters of the canopy fabric;
a first fluid field geometric parameter determination unit, configured to determine a geometric parameter of a first fluid field enclosing the first mesh model based on a geometric parameter of the parafoil structure;
a second mesh model generating unit, configured to set a first characteristic parameter of the first fluid domain edge mesh point based on a shell cell mesh size of the first mesh model, and generate a second mesh model of the first fluid domain based on the first characteristic parameter;
a fluid-solid coupling mesh model generating unit, configured to generate a fluid-solid coupling mesh model based on the first mesh model and the second mesh model;
and the fluid-solid coupling simulation unit is used for carrying out fluid-solid coupling simulation on the surrounding air field of the parafoil structure and the parafoil structure based on the fluid-solid coupling grid model, the material parameters, the boundary conditions of the first fluid domain, the constraint parameters of the parafoil structure, the load conditions of the parafoil structure and fluid-solid coupling solving related parameters.
Example four
The fourth embodiment of the invention provides a fluid-solid coupling simulation device in a trailing edge deflection process of a ram parachute, which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor realizes the steps of the fluid-solid coupling simulation method in the trailing edge deflection process of the ram parachute when executing the computer program.
The processor may be a Central Processing Unit (CPU), or other general-purpose processor, a digital signal processor (digital signal processor), an Application Specific Integrated Circuit (Application Specific Integrated Circuit), an off-the-shelf programmable gate array (field programmable gate array) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory can be used for storing the computer program and/or the module, and the processor realizes various functions of the trailing edge deflection process fluid-solid coupling simulation device of the ram parachute by operating or executing the data stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function (such as a sound playing function, an image playing function, etc.), and the like. Further, the memory may include high speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card, a secure digital card, a flash memory card, at least one magnetic disk storage device, a flash memory device, or other volatile solid state storage device.
EXAMPLE five
An embodiment of the invention provides a computer-readable storage medium, which stores a computer program, and when the computer program is executed by a processor, the method for simulating the fluid-solid coupling in the trailing edge deflection process of the ram parachute is implemented.
The ram parachute trailing edge deflection process fluid-solid coupling simulation device can be stored in a computer readable storage medium if the device is realized in the form of a software functional unit and sold or used as a stand-alone product. Based on such understanding, all or part of the flow in the method of implementing the embodiments of the present invention may also be stored in a computer readable storage medium through a computer program, and when the computer program is executed by a processor, the computer program may implement the steps of the above-described method embodiments. Wherein the computer program comprises computer program code, an object code form, an executable file or some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying said computer program code, a recording medium, a usb-disk, a removable hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory, a random access memory, a point carrier signal, a telecommunications signal, a software distribution medium, etc. It should be noted that the computer readable medium may contain content that is appropriately increased or decreased as required by legislation and patent practice in the jurisdiction.
While the invention has been described with respect to the basic concepts, it will be apparent to those skilled in the art that the foregoing detailed disclosure is only by way of example and not intended to limit the invention. Various modifications, improvements and adaptations to the present description may occur to those skilled in the art, although not explicitly described herein. Such modifications, improvements and adaptations are proposed in the present specification and thus fall within the spirit and scope of the exemplary embodiments of the present specification.
Also, the description uses specific words to describe embodiments of the description. Reference throughout this specification to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic described in connection with at least one embodiment of the specification is included. Therefore, it is emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, some features, structures, or characteristics of one or more embodiments of the specification may be combined as appropriate.
Moreover, those skilled in the art will appreciate that aspects of the present description may be illustrated and described in terms of several patentable species or situations, including any new and useful combination of processes, machines, manufacture, or materials, or any new and useful improvement thereof. Accordingly, aspects of this description may be performed entirely by hardware, entirely by software (including firmware, resident software, micro-code, etc.), or by a combination of hardware and software. The above hardware or software may be referred to as "data block," module, "" engine, "" unit, "" component, "or" system. Furthermore, aspects of the present description may be represented as a computer product, including computer readable program code, embodied in one or more computer readable media.
The computer storage medium may comprise a propagated data signal with the computer program code embodied therewith, for example, on baseband or as part of a carrier wave. The propagated signal may take any of a variety of forms, including electromagnetic, optical, etc., or any suitable combination. A computer storage medium may be any computer-readable medium that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code located on a computer storage medium may be propagated over any suitable medium, including radio, cable, fiber optic cable, RF, or the like, or any combination of the preceding.
Computer program code required for the operation of various portions of this specification may be written in any one or more programming languages, including an object oriented programming language such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C + +, C #, VB.NET, Python, and the like, a conventional programming language such as C, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, a dynamic programming language such as Python, Ruby, and Groovy, or other programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any network format, such as a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet), or in a cloud computing environment, or as a service, such as a software as a service (SaaS).
Additionally, the order in which the elements and sequences of the process are recited in the specification, the use of alphanumeric characters, or other designations, is not intended to limit the order in which the processes and methods of the specification occur, unless otherwise specified in the claims. While various presently contemplated embodiments of the invention have been discussed in the foregoing disclosure by way of example, it is to be understood that such detail is solely for that purpose and that the appended claims are not limited to the disclosed embodiments, but, on the contrary, are intended to cover all modifications and equivalent arrangements that are within the spirit and scope of the embodiments herein. For example, although the system components described above may be implemented by hardware devices, they may also be implemented by software-only solutions, such as installing the described system on an existing server or mobile device.
Similarly, it should be noted that in the preceding description of embodiments of the present specification, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the embodiments. This method of disclosure, however, is not intended to imply that more features than are expressly recited in a claim. Indeed, the embodiments may be characterized as having less than all of the features of a single embodiment disclosed above.
For each patent, patent application publication, and other material, such as articles, books, specifications, publications, documents, etc., cited in this specification, the entire contents of each are hereby incorporated by reference into this specification. Except where the application history document does not conform to or conflict with the contents of the present specification, it is to be understood that the application history document, as used herein in the present specification or appended claims, is intended to define the broadest scope of the present specification (whether presently or later in the specification) rather than the broadest scope of the present specification. It is to be understood that the descriptions, definitions and/or uses of terms in the accompanying materials of this specification shall control if they are inconsistent or contrary to the descriptions and/or uses of terms in this specification.
Finally, it should be understood that the embodiments described herein are merely illustrative of the principles of the embodiments of the present disclosure. Other variations are also possible within the scope of the present description. Thus, by way of example, and not limitation, alternative configurations of the embodiments of the specification can be considered consistent with the teachings of the specification. Accordingly, the embodiments of the present description are not limited to only those embodiments explicitly described and depicted herein.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A method for simulating the fluid-solid coupling in the trailing edge deflection process of a ram parafoil is characterized by comprising the following steps:
carrying out geometric modeling on a parafoil structure to obtain a three-dimensional geometric shape of the parafoil structure, wherein the parafoil structure is in an unfolded state, and an air chamber of the parafoil structure is in a bulge state;
meshing the three-dimensional geometric shape to obtain a meshing result, and obtaining a first mesh model of the parafoil structure based on the meshing result and the material parameters of the canopy fabric;
determining a geometric parameter of a first fluid domain that encloses the first mesh model based on a geometric parameter of the parafoil structure;
setting a first characteristic parameter of the first fluid domain boundary grid points based on the shell cell grid size of the first grid model, and generating a second grid model of the first fluid domain based on the first characteristic parameter;
generating a fluid-solid coupled mesh model based on the first mesh model and the second mesh model;
and performing fluid-solid coupling simulation on the surrounding air field of the parafoil structure and the parafoil structure based on the fluid-solid coupling grid model, the material parameters, the boundary conditions of the first fluid domain, the constraint parameters of the parafoil structure, the load conditions of the parafoil structure and fluid-solid coupling solving related parameters.
2. The method for simulating the fluid-solid coupling of the trailing edge deflection process of the ram parachute as recited in claim 1, wherein the fluid-solid coupling simulation comprises:
a first simulation stage: simulating and simulating the fluid-solid coupling dynamic performance of the surrounding air field of the parafoil structure and the parafoil structure, wherein the load condition is that the load curve parameter value is 0;
and a second simulation stage: and applying a deflected load curve to the rear edge part of the parafoil structure to carry out the fluid-solid coupling dynamic simulation of the rear edge deflection state, wherein the load condition is that the parameter value of the load curve is greater than 0.
3. The method for simulating the fluid-solid coupling in the trailing edge deflection process of the ram parafoil according to claim 1, wherein the dynamic control equation of the parafoil structure in the method is as follows:
wherein the content of the first and second substances,
is the material density of the parafoil structure,
is the tension of the Coriolis stress,
for external forces acting on the parafoil structure,
is the velocity vector of the structural particle of the parafoil,
in order to calculate the time of day,
is the sign of partial differential operation.
4. The method for simulating the fluid-solid coupling in the trailing edge deflection process of the ram parafoil according to claim 1, wherein the method adopts film units to grid the three-dimensional geometric shape, and the constitutive equation of the film units is as follows:
wherein the content of the first and second substances,
longitudinal strain of the membrane unit in the parafoil structure,
is the longitudinal stress of the parafoil structural film unit,
is the longitudinal Poisson ratio of the parafoil structural membrane unit,
is the longitudinal elastic modulus of the parafoil structural film unit,
is the transverse strain of the parafoil structural membrane unit,
is the transverse stress of the parafoil structural membrane unit,
is the transverse Poisson ratio of the parafoil structure membrane unit,
is the transverse elastic modulus of the parafoil structural film unit,
is the tangential strain of the parafoil structural membrane unit,
is the shear stress of the parafoil structural film unit,
is the shear modulus of the parafoil structural membrane unit,
is the nonlinear coefficient of the parafoil structural film unit.
5. The method for simulating the fluid-solid coupling in the trailing edge deflection process of the ram parachute as claimed in claim 1, wherein the dynamic equation of the first fluid domain in the method is as follows:
wherein the content of the first and second substances,
is the density of the fluid domain units in the first fluid domain gas,
is the velocity vector of the fluid domain unit in the first fluid domain,
for external forces acting on the fluid domain unit in said first fluid domain,
being the stress tensor of the fluid domain element in the first fluid domain,
in the form of a Hamiltonian operator,
to obtain the divergence of the velocity tensor for the fluid domain elements in the first fluid domain,
in order to be a sign of the partial differential operation,
to calculate the time.
6. The method for simulating the fluid-solid coupling in the trailing edge deflection process of the ram parachute according to claim 1, wherein in the method, the lagrangian euler-formatted control equation of the first fluid domain is as follows:
wherein the content of the first and second substances,
is the density of the fluid domain units in the first fluid domain gas,vandwthe first fluid domain unit particle velocity and the first fluid domain unit material grid point velocity are respectively the fluid domain unit particle velocity and the fluid domain unit material grid point velocity;u f is the velocity of the fluid domain unit in the first fluid domain,u f =v-w，
in order to be a sign of the partial differential operation,
to resolve the divergence of the fluid domain units in the first fluid domain,
to calculate the time;
being the stress tensor of the fluid domain element in the first fluid domain,
is the external normal force tensor to which the fluid domain elements are subjected in the first fluid domain.
7. The method for simulating the fluid-solid coupling of the trailing edge deflection process of the ram parachute according to claim 1, wherein the method is based on a penalty function method for the transmission calculation of the node force information between the fluid domain unit in the first fluid domain and the domain unit in the parafoil structure.
8. The method of claim 7, wherein the step of time is defined as
When the penetration depth of the structure domain unit node in the parafoil structure isd n Then the penetration depth of the domain unit node in the parafoil structure of the next moment iteration isd n+1：
Wherein the content of the first and second substances,
by penetration depth is meant the relative distance between the master node of a domain unit in the first fluid domain and the slave node of a domain unit in the parafoil structure,
in order to integrate the number of time steps,
the relative velocity of the master node of a domain unit in the first fluid domain and the slave node of a domain unit in the parafoil structure for an intermediate time instant is:
wherein the content of the first and second substances,
for the node velocities of the domain units in the parafoil structure at intermediate times,
the velocity of a fluid domain unit node in the first fluid domain at an intermediate time;
the coupling force between the nodes of the domain units in the parafoil structure and the nodes of the fluid domain units in the first fluid domain is
：
Wherein the content of the first and second substances,
is the stiffness coefficient;
applying a balanced force between a master node of a fluid domain unit in the first fluid domain and a slave node of a domain unit in the parafoil structure
：
Passing the force experienced by the fluid domain elements in the first fluid domain through a shape function
Nodes distributed to domain units in the parafoil structureiEach of the parafoil knotsThe nodes of the structural domain units are subjected to a fluid domain force of
：
Wherein the content of the first and second substances,
a master node being a fluid domain unit in the first fluid domain,
is a slave node of a domain unit in the parafoil structure,
is a coupling interface.
9. The ram parafoil trailing edge deflection process fluid-solid coupling simulation method of claim 1, wherein the method applies full constraint at a node at the parafoil leading edge notch of the parafoil structure and applies a pull-down load curve at the parafoil trailing edge of the parafoil structure.
10. A ram parafoil trailing edge deflection process fluid-solid coupling simulation system, characterized in that the system comprises:
the device comprises a geometric modeling unit, a data processing unit and a data processing unit, wherein the geometric modeling unit is used for performing geometric modeling on a parafoil structure to obtain a three-dimensional geometric shape of the parafoil structure, the parafoil structure is in an unfolded state, and an air chamber of the parafoil structure is in a bulge state;
a first mesh model obtaining unit, configured to perform mesh division on the three-dimensional geometric shape to obtain a mesh division result, and obtain a first mesh model of the parafoil structure based on the mesh division result and material parameters of the canopy fabric;
a first fluid field geometric parameter determination unit, configured to determine a geometric parameter of a first fluid field enclosing the first mesh model based on a geometric parameter of the parafoil structure;
a second mesh model generating unit, configured to set a first characteristic parameter of the first fluid domain edge mesh point based on a shell cell mesh size of the first mesh model, and generate a second mesh model of the first fluid domain based on the first characteristic parameter;
a fluid-solid coupling mesh model generating unit, configured to generate a fluid-solid coupling mesh model based on the first mesh model and the second mesh model;
and the fluid-solid coupling simulation unit is used for carrying out fluid-solid coupling simulation on the surrounding air field of the parafoil structure and the parafoil structure based on the fluid-solid coupling grid model, the material parameters, the boundary conditions of the first fluid domain, the constraint parameters of the parafoil structure, the load conditions of the parafoil structure and fluid-solid coupling solving related parameters.
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