CN109723027B - Method for designing rain intensity scale Sr in flood discharge atomization model test - Google Patents
Method for designing rain intensity scale Sr in flood discharge atomization model test Download PDFInfo
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Abstract
The invention discloses a method for designing a rain intensity scale Sr in a flood discharge atomization model test, which belongs to the field of hydraulic engineering and comprises the following steps: 1) energy dissipater classification; 2) conversion symbol of flood discharge atomization rain intensity scale Sr and model geometric scale Lr indexTotal Sr ═ LrnAnd respectively calculating the rain intensity scale of the gauge hole and the medium-hole deep hole. The invention has the advantages that: the invention provides a method for designing a rain intensity scale Sr in a flood discharge atomization model test; the relation between the scale effect of the flood discharge atomization model and the geometric scale of the model is provided, the relation between the index n and the geometric scale Lr of the model is established, the rain strength scale Sr of the atomization model under different flood discharge modes and energy dissipater types can be reasonably determined, and the accuracy of the rain strength scale of the flood discharge atomization model is improved.
Description
Technical Field
The invention relates to a design of a rain intensity scale in a hydraulic model test, in particular to a method for designing the rain intensity scale in a flood discharge atomization model test, and belongs to the field of hydraulic engineering.
Background
Along with the construction of a large number of high dam projects with high water heads, large discharge capacity and high power in China, the problem of discharge atomization becomes one of the key technical problems which are urgently needed to be solved in the construction and operation of the water conservancy and hydropower projects in China. The leakage atomization shows that ultra-strong rainfall and fog flow diffusion phenomena are formed in a local range at the downstream of a dam, the intensity of the generated heavy rain and rain often exceeds the extreme value of atmospheric rainfall, slope landslides of both bank slopes can be induced, the safe operation of a hydropower station transmission system is threatened, the road traffic interruption of a plant area is caused, and the normal life of workers and residents is influenced. Therefore, for high dam engineering, accurate assessment of flood discharge atomization rainfall intensity has extremely important engineering significance for guaranteeing hub safety.
The method for evaluating the flood discharge atomization rainfall intensity mainly comprises prototype observation, physical model test and numerical simulation calculation. Prototype observation is the most intuitive and reliable method for researching the flood discharge atomization problem, but needs to be implemented after engineering construction, cannot play a prediction role, and has poor data integrity due to wide related range and large observation workload. The numerical simulation method is influenced by factors such as fuzzy flood discharge atomization mechanism, parameter uncertainty and the like, particularly the amount of the fog source cannot be accurately given, and the accuracy and the reliability of the numerical simulation method cannot meet the requirements of engineering design. At present, a physical model test method is still a relatively successful method for researching the flood discharge atomization problem. The flood discharge atomization relates to a plurality of physical processes of air crushing, air entrainment, diffusion, collision, water entering splash and the like of a water tongue, belongs to the category of gas-liquid two-phase flow, and a flood discharge atomization physical model needs to follow both the similarity of gravity and the similarity of surface tension. However, in the flood discharge atomization model test, only major factors can be grasped, the gravity similarity criterion is followed, the similarity of the main physical quantities of the water flows is ensured, some minor factors are ignored, the flood discharge atomization physical model has an obvious scale reduction effect, and the rain intensity obtained by the model test is converted into a prototype and does not follow the gravity similarity criterion.
In the past, the flood discharge atomization rain intensity scale Sr and the geometric scale Lr are generally considered to be in an exponential relationship: sr ═ LrnIn physical model experiments, Sr ═ Lr is often used1.53Namely, the index n is 1.53, and is used as an outer envelope control value of the discharge atomization rain intensity. However, according to the atomization prototype observation result, the atomization rain intensity similarity scale of different scale models of each project has great discreteness which can be 10-100 times different, the control value has great difference with the actual prototype observation result, and especially when the geometric scale Lr is large, the change of n value can directly cause the change of the rain intensity scale of dozens of times or even hundreds of times. In order to improve the accuracy of the rain intensity scale in the flood discharge atomization model and control the test cost of the model, a new method for designing the rain intensity scale Sr needs to be provided.
Disclosure of Invention
The invention aims to provide a method for designing a rain intensity scale Sr so as to reduce test errors caused by a scale reduction effect of a model and improve the precision of the flood discharge atomization model rain intensity scale.
For this reason, the above object of the present invention is achieved by adopting the following technical solutions:
the method for designing the rain intensity scale Sr in the flood discharge atomization model test sequentially comprises the following steps of:
1) energy dissipater classification;
dividing the energy dissipater into a surface hole flood discharge and b middle-hole deep hole and flood discharge hole flood discharge according to the flood discharge mode and the energy dissipater body type;
the surface hole flood discharge is further divided into surface hole flaring pier of a1 and surface hole trajectory energy dissipation of a 2.
2) The inventor obtains through creative tests and analysis: the conversion of the flood discharge atomization rain intensity scale Sr and the model geometric scale Lr index is in accordance with Sr-LrnA relationship;
for a1 pilot hole flaring pier:
n＝0.5 (1)
Sr＝Lr0.5(2)
for a2 surface hole trajectory energy dissipation:
n＝0.43Lr0.33(3)
for b, flood discharge of medium and deep holes and flood discharge holes:
n＝0.04Lr0.82(5)
the invention has the following beneficial effects:
1. the invention provides a method for designing a rain intensity scale Sr, which solves the problem that the difference between the rain intensities of an original model and a model is large due to the scale effect of a flood discharge atomization model.
2. The invention provides the relation between the scale effect of the flood discharge atomization model and the geometric scale of the model, establishes the relation between the index n and the geometric scale Lr of the model, can reasonably determine the rain strength scale Sr of the atomization model under different flood discharge modes and energy dissipater types, and improves the accuracy of the rain strength scale of the flood discharge atomization model.
Drawings
FIG. 1 is a schematic diagram of the relationship between index n and Lr when energy dissipation is performed by a surface hole flaring pier;
FIG. 2 is a schematic diagram showing the relationship between the index n and Lr when the surface hole trajectory energy dissipation is performed;
fig. 3 is a diagram illustrating the relationship between the indexes n and Lr when the medium (deep) hole and the flood discharging hole discharge flood.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The present embodiment is developed based on the technical solutions of the present invention, and is only used for more clearly illustrating the technical solutions of the present invention, and the protection scope of the present invention is not limited thereby.
Example one
An engineering book comprising: 4 surface holes and 5 deep holes of the dam body, and 1 flood discharge hole of the right bank, wherein the surface holes are subjected to slip flood discharge and energy dissipation. The geometric scale Lr of the flood discharge atomization model is 50.
1) Taking 4 surface holes of the dam body as surface hole flood discharge according to a flood discharge mode and energy dissipater body types, and taking 5 deep holes and 1 flood discharge hole of the right bank as middle and deep holes and flood discharge holes; wherein 4 surface holes are 'a 2 surface hole trajectory energy dissipation'.
2) The inventor obtains through creative tests and analysis: the conversion of the flood discharge atomization rain intensity scale Sr and the model geometric scale Lr index is in accordance with Sr-LrnA relationship;
for a1 pilot hole flaring pier:
n＝0.5 (1)
Sr＝Lr0.5(2)
for a2 surface hole trajectory energy dissipation, 4 surface hole flood discharge indexes n and a model geometric scale Lr satisfy a formula 3, and a rain intensity scale is calculated according to a formula 4:
n＝0.43Lr0.33(3)
calculated as Sr 453
For flood discharge of medium and deep holes and flood discharge holes b, index n and model geometric scale Lr satisfy formula 5 when flood discharge occurs in 5 deep holes and 1 flood discharge hole, and the rain intensity scale is calculated according to formula 6:
n＝0.04Lr0.82(5)
calculated Sr is 48
The inventor refers to the following through creative analysis: the inventor introduces the Weber number We, so that the influence of a model geometric scale and water flow can be comprehensively considered when designing the rain intensity scale Sr in the flood discharge atomization model test.
For the a1 case wide tail pier, the water flow surface tension effect can be ignored, and the gravity similarity criterion is approximately satisfied:
n＝0.5 (7)
Sr＝Lr0.5(8)
for a2 surface hole trajectory entry, 4 surface hole trajectory entry energy dissipation time indexes n and water flow Weber numbers We satisfy formula 9, and the rain intensity scale is calculated according to formula 10:
n＝13.537We-0.362(9)
calculated Sr 476
Therefore, when the surface hole is simulated and the rain intensity scale Sr is designed in the flood atomization model test, Sr 453-476 can be determined according to the calculation results of the formulas 3, 4, 9 and 10.
For flood discharge of medium and deep holes and flood discharge holes b, index n and model geometric scale We satisfy formula 11 when 5 deep holes and 1 flood discharge hole discharge floodwaters, and the rain intensity scale is calculated according to formula 12:
n＝103.22We-0.751(11)
calculated Sr is 53
Therefore, when the engineering simulates middle and deep holes in a flood atomization model test, the Sr (48-53) can be determined according to the calculation results of the formulas 5, 6, 11 and 12 when the rain intensity scale Sr is designed.
Example two
The water outlet structure of some engineering is composed of 7 overflow surface holes, all the surface holes adopt energy dissipators of wide tail piers, and the geometric scale Lr of flood discharge atomization model is 36.
1) Taking 7 surface holes of the dam body as surface holes a to discharge flood according to a flood discharge mode and an energy dissipater body type, and enabling the 7 surface holes to dissipate energy for surface hole flaring piers a 2;
2) the inventor obtains through creative tests and analysis: the conversion of the flood discharge atomization rain intensity scale Sr and the model geometric scale Lr index is in accordance with Sr-LrnA relationship;
for a1 surface hole flaring pier energy dissipation 7 surface holes flood discharge, the index n and the model geometric scale Lr satisfy the formula 1, and the rain intensity scale is calculated according to the formula 2:
n＝0.5 (1)
Sr＝Lr0.5(2)
calculated Sr is 6
For a2 surface hole trajectory energy dissipation:
n＝0.43Lr0.33(3)
for b, flood discharge of medium and deep holes and flood discharge holes:
n＝0.04Lr0.82(5)
the above-described embodiments are intended to illustrate the present invention, but not to limit the present invention, and any modifications, equivalents, improvements, etc. made within the scope of the claims of the present invention are included in the present invention.
Claims (1)
1. A method for designing a rain intensity scale Sr in a flood discharge atomization model test is characterized by comprising the following steps: comprises thatThe method comprises the following steps: (A1) energy dissipater classification; (A2) the conversion of the flood discharge atomization rain intensity scale Sr and the model geometric scale Lr index is in accordance with Sr-LrnCalculating rain intensity scales of the gauge hole and the middle-hole deep hole respectively by using a formula; the step (A1), energy dissipater classification, comprises the following steps:
dividing the energy dissipater into a surface hole flood discharge and b middle and deep holes and flood discharge holes according to a flood discharge mode and the energy dissipater body type;
dividing flood discharge of surface holes a into surface hole flaring piers a1 and surface hole trajectory jet energy dissipation a 2; in the step (a2), the flood discharge atomizing rain intensity scale Sr and the model geometric scale Lr are exponentially converted to conform to Sr ═ LrnA relationship; the rain intensity scale for respectively calculating the surface hole and the middle hole deep hole by using a formula comprises the following contents:
for a1 pilot hole flaring pier:
n＝0.5 (1)
Sr＝Lr0.5(2)
for a2 surface hole trajectory energy dissipation:
n＝0.43Lr0.33(3)
for b, flood discharge of medium and deep holes and flood discharge holes:
n＝0.04Lr0.82(5)
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