CN114674529A - Small circulating water tank for streaming simulation under medium and high Reynolds numbers and test method - Google Patents

Small circulating water tank for streaming simulation under medium and high Reynolds numbers and test method Download PDF

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Publication number
CN114674529A
CN114674529A CN202210408031.5A CN202210408031A CN114674529A CN 114674529 A CN114674529 A CN 114674529A CN 202210408031 A CN202210408031 A CN 202210408031A CN 114674529 A CN114674529 A CN 114674529A
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section
water tank
test piece
streaming
working
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CN202210408031.5A
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Inventor
何霞
王杰
钟林
王国荣
杨成宇
胡刚
王川
敬佳佳
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Southwest Petroleum University
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Southwest Petroleum University
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01MTESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M10/00Hydrodynamic testing; Arrangements in or on ship-testing tanks or water tunnels

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  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Aerodynamic Tests, Hydrodynamic Tests, Wind Tunnels, And Water Tanks (AREA)

Abstract

The invention relates to a small circulating water tank for simulating streaming under medium and high Reynolds numbers and a test method, wherein the circulating water tank mainly comprises three parts, the first part is a working part and comprises a working section, a contraction section and a rectification section; the second part is a backflow part which comprises an expansion section, a corner section, a straight pipe section, a power system and a water tank; the third part is a test part and mainly comprises a test piece, a sensor, an LDV velocimeter, a PIV camera, a laser instrument and the like. The power system is connected with the working part through an expansion section, a straight pipe section, a corner section, a water tank and the like, a rectifying grid and a damping net are installed in the rectifying section, and a flow deflector is installed in the corner section. In the test process, a multi-axis force sensor is used for measuring the flow-around resistance of the test piece, LDV is used for measuring the flow velocity, and PIV is used for shooting the flow field. The invention has small structure occupation area, can simulate high Reynolds number working conditions and can be widely applied to the experimental research in the hydraulic fields of pipe column streaming simulation, vortex-induced vibration and the like.

Description

Small circulating water tank for streaming simulation under medium and high Reynolds numbers and test method
Technical Field
The invention relates to a small circulating water tank for simulating streaming under medium and high Reynolds numbers and a test method, in particular to a circulating water tank test platform for testing streaming performance of a tubular column under medium and high Reynolds numbers, and belongs to the field of test equipment.
Background
The performance of the circulating water tank serving as a water circulation test device is reflected in the four aspects of the uniformity of cross-sectional flow velocity distribution, the inclination of the water surface and the conditions of waves, the turbulence of working fluid and the content and transparency of bubbles.
The development of domestic and foreign circulating water tank experimental devices is very rapid, and the past large-scale is changed into the present small-scale; meanwhile, the precision degree of the circulating water tank experimental device is also continuously improved. At present, the development of the construction technology of the circulating water tank is mature, the types of experiments which can be completed are increased gradually, the accuracy of experimental data is further improved due to the introduction of a modern advanced testing technology, but the existing circulating water tank is mainly used for carrying out relevant experimental researches such as a ship model resistance test, a propeller open water test, an maneuverability test and the like, and a circulating water tank experimental platform for testing the streaming performance of a tubular column under the condition of medium and high Reynolds numbers is lacked. Therefore, the device aims to simulate the working condition of medium and high Reynolds numbers by using the characteristic that the circulating water tank is used for manufacturing a continuous and stable flow field, and invents a small circulating water tank experimental device for simulating the streaming under the medium and high Reynolds numbers.
Disclosure of Invention
Aiming at the structural characteristics, applicable occasions and realized functions of the current circulating water tank, the invention provides a small circulating water tank for the streaming simulation under medium and high Reynolds numbers and a test method.
In order to achieve the purpose, the invention adopts the following technical scheme:
a small circulating water tank for simulating streaming under medium and high Reynolds numbers mainly comprises three parts: a working section, a reflux section, and a test section. The water tank is connected with the working part by an expansion section, a straight pipe section, a corner section and a rectification section. Under the action of the power system, water flows out of the water outlet of the water tank, sequentially flows through the backflow part, the working part and the backflow part, and finally returns to the water inlet of the water tank, so that water circulation is realized.
The working principle is as follows: according to the small circulating water tank for simulating streaming under high Reynolds number and the test method, the test simplifies the marine riser into a rigid cylindrical model, simulates an experimental environment with high flow velocity and high Reynolds number in the working section of the water tank, measures streaming resistance and lift force of a cylindrical test piece by using the multi-axis force sensor, and observes a flow field by using LDV (laser direct potential) velocity measurement and PIV (particle image velocimetry).
An internal thread is processed in the cylindrical hole above the sealing cover; a square hole is designed below the sealing cover; the closing cover is connected with the working section by bolts. The sealing cover can be conveniently connected with the test piece connecting rod; the sensor can be placed in static clear water, so that the measurement error is reduced; the test requirement is convenient to meet, and the closing cover can be detached.
The test piece and the test piece connecting rod are in threaded connection; a waterproof protective shell is arranged outside the sensor, and the sensor is connected with an external computer through a central hole of a sensor connecting rod; the sensor connecting rod can be adjusted in height and is connected with the test piece connecting rod through a bearing. The test piece and the sensor can be conveniently mounted and dismounted in the test, and the service life of the sensor is prolonged.
The working section is made of toughened glass, so that the working section is transparent, and the experimental observation and the processing and manufacturing are convenient; the working section adopts a detachable semi-closed structure, and can realize the switching between the closed state and the non-closed state of the working section.
The contraction section adopts a centrosymmetric contraction mode to improve the flow field quality of the working section; meanwhile, the axial length of the contraction section is 450-500mm, the contraction ratio is 7-10, and a Vickers curve is selected as the contraction curve, so that the integral volume of the water tank and the economical efficiency of processing are considered, and the uniformity of the water flow speed is improved.
The length ratio of the rectifying section to the length ratio of the working section is designed to be 1:1, so that the working section is ensured to have better flow field uniformity; the rectifying grids are arranged in the rectifying section to cut large vortexes existing in water flow into small vortexes, reduce rotation and transverse flow in the water flow, straighten the direction of the incoming flow velocity, and further enable the direction of the incoming flow streamline in the rectifying section to be consistent with the direction of the central axis of the working section; the damping net is arranged to eliminate air bubbles in the water flow.
The corner section adopts a semicircular bent pipe form, so that the stability of a flow field is improved; the guide vanes are arranged at equal intervals on the corner sections so as to reduce resistance loss caused by circular motion when water flows pass through the corner sections.
The first expansion section and the second expansion section adopt different expansion forms so as to promote the backflow of fluid in the water tank and improve the backflow efficiency.
The experimental method comprises the following steps:
before the experiment starts, the test piece needs to be reasonably installed. Firstly, the water tank is mainly used for the research on the streaming drag reduction performance of a marine riser, and aims at the marine riser test piece with different textures arranged on the surface, so that the quick-disassembly factor needs to be considered in the design of the installation mode so as to facilitate the replacement of the test piece; secondly, the water tank is in a fully closed state when completely working, the connection mode of a sensor connected with a test piece needs to be considered, and errors are reduced on the premise of ensuring the reliability of measured data; and finally, the application range of the designed water tank is expanded, and the installation of models with different dimensions and specifications is required to be considered when other hydrodynamic tests are carried out.
When the experiment is started, the flow pump is started, water flows out from the water outlet of the water tank, and after a period of time, the water flows through the working section stably at a high speed under the action of the flow deflectors, the rectifying grids, the damping net and other accessories. Under the current Reynolds similar simulation working condition, firstly, measuring the streaming resistance and the lift force of a cylindrical test piece with different textures by using a multi-axis force sensor, and then, carrying out data processing by using a computer for receiving output signals of the sensor to finally obtain texture parameters with the best resistance reduction effect; meanwhile, the installed LDV velocimeter is used for adjusting the height of the supporting rod to measure the flow velocity of different sections of the working section; capturing flow field characteristics by using a PIV laser instrument and a PIV camera arranged right below the test piece to realize shooting of the flow field; and finally, evaluating the resistance reduction effect of the cylindrical flow by comparing and analyzing the flow velocity and the flow field data measured by different groups.
The invention has the beneficial effects that:
(1) the small circulating water tank for simulating streaming under medium and high Reynolds numbers occupies small area and can simulate the working conditions of high flow speed and high Reynolds numbers.
(2) The water tank can provide an effective indoor experimental test evaluation platform for a cylindrical streaming simulation test in a medium and high Reynolds number environment, and has important significance for improving the resistance reduction and vibration suppression performance of the cylinder, optimizing the structure and researching the vortex-induced vibration characteristics of the cylinder structure.
(3) The water tank can realize the measurement of the streaming lift resistance, and LDV speed measurement and PIV flow field measurement.
(4) A square hole is designed below the water tank sealing cover, and the sensor is placed in static clear water, so that the measurement error is reduced; the working section adopts a detachable semi-closed structure, so that the test piece can be conveniently mounted and dismounted under the multi-group test.
Drawings
FIG. 1 is a schematic view of the overall structure of a sink
FIG. 2 is a schematic view of the connection and installation of the test part
FIG. 3 is a schematic view of the structure of the working section still water area
FIG. 4 is a schematic view of a specimen attachment mechanism
FIG. 5 is a schematic diagram of a rectification grid of a rectification section
FIG. 6 is a schematic view of the arrangement of corner segments
FIG. 7 is a schematic view of a damping net with uniformly arranged meshes
The device comprises a water tank, a pump, a contraction, a working section support, a working section, a pressure meter, a PIV, a pressure meter, a pressure meters, a pressure meter, a PIV, a pressure meters, a pressure meter and a pressure meter.
Detailed Description
For a better understanding of the present invention, reference is made to the following description taken in conjunction with the accompanying drawings and examples.
The integral structure of the circulating water tank consists of three parts, wherein the first part is a working part and comprises a working section, a contraction section and a rectification section; the second part is a backflow part which comprises an expansion section, a corner section, a straight pipe section, a power system and a water tank; the third part is a test part and mainly comprises a test piece, a test piece connecting rod, a sensor connecting rod, an LDV velocimeter, a PIV camera, a laser instrument, a sealing cover and the like, wherein the sealing cover is in threaded connection with the test piece connecting rod; the LDV velocimeter is arranged at the upstream of the test piece, the PIV camera is arranged under the test piece, and the laser instrument is arranged in front of the test piece.
Referring to fig. 1 to 7, the test water tank includes a water tank 1, a pump 2, a first expansion section 3, a first corner section 4, a first direct current section 5, a second corner section 6, a rectification section 7, a contraction section 8, a working section support frame 9, a working section 10, an LDV velocimeter 11, a PIV12, a test piece connecting rod 13, a sensor connecting rod 14, a second expansion section 15, a third corner section 16, a second direct current section 17, and a fourth corner section 18.
Under the action of a power system, water flows out of a water outlet of the water tank, sequentially flows through the backflow part, the working part and the backflow part, and finally flows back to a water inlet of the water tank, so that water flow circulation is realized.
After a period of time, the working section realizes the simulation working condition, and the observation of the phenomenon of the cylindrical streaming experiment and the data measurement are carried out in the working section, wherein the data measurement of the lift drag force of the test piece under the impact of water flow, the measurement of the flow velocity of the water flow in the working section and the observation of the flow field of the test piece when the cylindrical streaming phenomenon occurs are included.
The experimental method comprises the following steps:
after the experiment begins, the pump 2 is started, water flows out of the water tank 1, sequentially flows through the first expansion section 3, the first corner section 4, the first transition direct-current section 5, the second corner section 13, the rectification section 7 and the contraction section 8, then flows into the working section 10, finally flows through the second expansion section 15, the third corner section 16, the second transition direct-current section 17 and the fourth corner section 18, and flows back to the water tank 1, so that water circulation is realized.
In the whole water flow circulation, a working section realizes a Reynolds similar simulation working condition with high flow speed and high Reynolds number, under the simulation working condition, a multi-axis force sensor is used for measuring the streaming resistance and the lift force of a cylindrical test piece with different textures, and then a computer receiving output signals of the sensor is used for carrying out data processing analysis, so that texture parameters with the best resistance reduction effect are obtained finally; meanwhile, the installed LDV velocimeter is used, the height of the supporting rod is adjusted to measure the flow velocity of different sections of the working section, and the PIV laser and a PIV camera arranged right below the test piece are used for capturing the characteristics of the flow field, so that the shooting of the flow field is realized; and finally, evaluating the resistance reduction effect of the cylindrical flow by comparing and analyzing the flow velocity and the flow field data measured by different groups.

Claims (10)

1. The small circulating water tank for the streaming simulation under the medium and high Reynolds numbers is characterized in that: the device comprises a water tank, a power system, an expansion section, a corner section, a transition straight pipe section, a rectification section, a contraction section and a working section; the test part comprises a test piece, a test piece connecting rod, a sensor connecting rod, an LDV velocimeter, a PIV camera and laser instrument, a sealing cover and the like; the sealing cover is in threaded connection with the test piece connecting rod, the test piece connecting rod is in threaded connection with the test piece, the sensor connecting rod is in bearing connection with the test piece connecting rod, and the sensor is connected with an external computer through a central hole of the sensor connecting rod; the LDV velocimeter is placed at the upstream of the test piece, the PIV camera is arranged right below the test piece, and the laser instrument is arranged right in front of the test piece; in the test, a multi-axis force sensor is used for measuring the streaming lift resistance of a test piece, an LDV velocimeter is used for measuring the flow velocity of a working section, and a PIV is used for shooting a cylindrical streaming flow field.
2. The small circulation water tank for simulating medium and high Reynolds number downward flow according to claim 1, wherein: the cylinder hole processing of closing cap top has the internal thread, and the design of closing cap below has the quad slit, adopts bolted connection between closing cap and the working section.
3. The small-sized circulating water tank for simulating the streaming under the medium-high reynolds number according to claim 1, wherein: the test piece and the test piece connecting rod are in threaded connection; a waterproof protective shell is arranged outside the sensor, and the sensor is connected with an external computer through a central hole of a sensor connecting rod; the sensor connecting rod can be adjusted in height and is connected with the test piece connecting rod through a bearing.
4. The small-sized circulating water tank for simulating the streaming under the medium-high reynolds number according to claim 1, wherein: the diameter and the length-diameter ratio of the test piece are between 2 and pi, and the streaming resistance and the lift force of the test piece are measured by adopting a multi-axis force sensor.
5. The small-sized circulating water tank for simulating the streaming under the medium-high reynolds number according to claim 1, wherein: the working section material adopts detachable semi-enclosed construction for toughened glass, and is provided with the support frame below the working section.
6. The small-sized circulating water tank for simulating the streaming under the medium-high reynolds number according to claim 1, wherein: the shrinkage section is designed by a Vickers shrinkage curve, the shrinkage ratio is between 7 and 10, and the axial length of the shrinkage section is 450-500 mm; meanwhile, the contraction section adopts a centrosymmetric contraction mode.
7. The small-sized circulating water tank for simulating the streaming under the medium-high reynolds number according to claim 1, wherein: the length ratio of the rectifying section to the length ratio of the working section is designed to be 1: 1; the square rectifying grids are arranged in the rectifying section, the material of the square rectifying grids is an epoxy resin plate with the thickness of 1mm, and meanwhile, a damping net with the aperture ratio of 0.62, the mesh diameter of 0.425mm and the mesh number of 40 is selected.
8. The small-sized circulating water tank for simulating the streaming under the medium-high reynolds number according to claim 1, wherein: the corner section adopts a semicircular bent pipe structure, the first corner section and the second corner section have the same size, and 5 flow deflectors are arranged at equal intervals; the third corner section is equal to the fourth corner section in size, and 4 flow deflectors are arranged at equal intervals.
9. The small-sized circulating water tank for simulating the streaming under the medium-high reynolds number according to claim 1, wherein: the expansion section comprises a first expansion section and a second expansion section; the expansion angles of the first expansion section and the second expansion section are equal, the second expansion section adopts a left-right and lower-left simultaneous expansion form, and the first expansion section adopts an upper-lower left-right complete expansion form.
10. The test method for testing a circulation tank according to any one of claims 1 to 9, characterized in that: the method comprises the following steps:
(1) after the experiment begins, a pump (2) is started, water flows out from a water tank (1), sequentially flows through a first expansion section (3), a first corner section (4), a first transition straight pipe section (5), a second corner section (6), a rectifying section (7) and a contraction section (8), then flows into a working section (10), finally flows through a second expansion section (15), a third corner section (16), a second transition straight pipe section (17) and a fourth corner section (18), and flows back to the water tank (1), so that water flow circulation is realized;
(2) in the whole water flow circulation, the working section realizes the Reynolds similar simulation working condition with high flow speed and high Reynolds number; under the simulation working condition, measuring the streaming resistance and the lift force of the cylindrical test piece by using a multi-axis force sensor; adjusting the height of the supporting rod to measure the flow velocity of different sections of the working section by using the installed LDV velocimeter; and capturing the characteristics of the flow field by using a PIV laser instrument and a PIV camera arranged right below the test piece, thereby realizing the shooting of the flow field.
CN202210408031.5A 2022-04-18 2022-04-18 Small circulating water tank for streaming simulation under medium and high Reynolds numbers and test method Pending CN114674529A (en)

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CN116858492A (en) * 2023-09-05 2023-10-10 浙江省水利河口研究院(浙江省海洋规划设计研究院) Reciprocating flow sand conveying self-adaptive moving bed test water tank

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CN116858492A (en) * 2023-09-05 2023-10-10 浙江省水利河口研究院(浙江省海洋规划设计研究院) Reciprocating flow sand conveying self-adaptive moving bed test water tank
CN116858492B (en) * 2023-09-05 2024-02-13 浙江省水利河口研究院(浙江省海洋规划设计研究院) Reciprocating flow sand conveying self-adaptive moving bed test water tank

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