A high-speed nappe diffusion similarity correction method

Abstract

The application discloses a high-speed pick-up flow water tongue diffusion similarity correction method, and belongs to the field of pick-up flow energy dissipation hydraulic model test of discharge structures. The application firstly defines a right water tongue transverse diffusion coefficient and a total transverse diffusion angle, obtains prototype observation data of a target project and test data of a corresponding hydraulic model; based on the model test data, a preliminary index calculation formula of the water tongue transverse diffusion coefficient is fitted, and a correction parameter greater than 1 fitted from the prototype observation data is introduced to obtain a corrected prototype diffusion coefficient calculation formula; for an outlet body modification scheme, a body correction parameter is introduced to construct a prediction formula, so that the water tongue transverse water entry position of different schemes can be quickly predicted. The application effectively corrects the diffusion deviation caused by the scale effect of the hydraulic model, significantly improves the prediction accuracy of the transverse diffusion characteristics of the pick-up flow water tongue, and can be directly used for safety review and outlet body optimization of the discharge structure, thereby providing reliable technical support for engineering design and safe operation.

Description

Technical Field

[0001] This invention relates to the field of hydraulic model tests for energy dissipation of spillway structures, and particularly to a method for correcting the similarity of high-speed spillway water tongue diffusion. Background Technology

[0002] In the design of high dam spillway energy dissipation, jet flow energy dissipation is one of the most widely used energy dissipation methods. Accurately predicting the trajectory of the jet flow in the air, especially its lateral diffusion range and entry point into the water, is crucial for assessing the energy dissipation effect, preventing downstream riverbed scouring, and ensuring the safety of the dam's key structures.

[0003] Currently, most hydraulic physical models of spillway structures are made of plexiglass. However, the bottom of actual engineering spillways is prone to the adhesion of moss and other deposits, resulting in a difference in roughness. This leads to deviations in the model's outlet velocity and water depth compared to the prototype, directly affecting the diffusion characteristics of the jet stream. Furthermore, the surface tension effects of the model and prototype water flows are different; the water body at the model scale is more affected by surface tension, easily causing the jet stream to contract and deform, resulting in a significantly smaller lateral diffusion angle for the model jet stream compared to the prototype. In addition, physical models cannot completely and accurately simulate the full aeration and expansion process of high-speed jet streams, further exacerbating the similarity deviation in diffusion characteristics. These scaling effects lead to significant deviations in the lateral entry position of the prototype jet stream predicted directly from model test results, potentially posing risks to engineering safety.

[0004] Therefore, it is urgent to propose a similarity correction method for high-speed jetting water tongue diffusion to correct the scaling effect deviation of hydraulic model tests, accurately predict the lateral water entry position of the prototype jetting water tongue, and provide a scientific basis for the optimization of the outlet shape and safety design of spillway structures. Summary of the Invention

[0005] The purpose of this invention is to overcome the inaccuracy of predicting the lateral diffusion of jet streams due to the scaling effect in existing hydraulic model tests. It provides a method for correcting the similarity of jet stream diffusion in high-speed jet streams. Through the technical approach of "building basic calculation relationships through model tests + correcting the correction coefficients using prototype observation data", it achieves high-precision prediction of the lateral diffusion characteristics of prototype jet streams, providing reliable support for the safe design and operation of spillway structures.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for correcting the similarity of high-speed jetting water tongue diffusion includes the following steps: S1, Parameter Definition: Define the transverse diffusion coefficient of the water tongue on the right as (B r -B 0r ) / B 0r Among them, B r B is the horizontal distance from the right inlet point of the water jet to the centerline of the outlet of the spillway structure. 0rThe horizontal distance from the centerline to the right sidewall of the spillway outlet; the total lateral diffusion angle θ of the jet stream is defined as the sidewall diffusion angle θ. b With the additional diffusion angle θ of the water tongue f sum; S2. Data Acquisition: Obtain prototype observation data on the diffusion pattern of the jet stream of the target project's spillway structure under different reservoir water levels and other operating conditions; simultaneously, construct a corresponding hydraulic physical model according to the geometric scale, reproduce the same operating conditions, and measure and obtain model test data.

[0007] S3. Deviation Analysis: By comparing the prototype observation data with the model test data, the deviation pattern between the lateral diffusion of the water tongue in the model and that of the prototype is clarified, and the systematic deviation characteristic that the diffusion degree of the water tongue in the model is generally less than that in the prototype is confirmed.

[0008] S4. Preliminary Model Construction: Based on the model test data obtained in step S2, analyze the transverse diffusion coefficient of the right-side water tongue and the dimensionless hydraulic parameter L / B. 0r • The correlation between tanθ and the initial calculation formula is constructed, where L is the water tongue distance; S5. Prototype Correction: Substitute the prototype observation data into the preliminary calculation formula. To address the systematic bias caused by the model data, introduce a correction parameter C′ greater than 1 through parameter fitting to correct the preliminary calculation formula, thus forming a corrected formula for calculating the transverse diffusion coefficient of the water tongue.

[0009] S6. Engineering Application: The corrected calculation formula is used to predict the lateral water inlet position of the original design scheme under various working conditions, and to assess the safety risks of the downstream structure; for the modified outlet shape scheme, shape correction parameters are introduced to construct the prediction formula for the modified scheme, and the optimal shape design is selected.

[0010] Furthermore, the preliminary calculation formula described in step 4 is an exponential relationship:

[0011] C1 and C2 are the water tongue diffusion parameters obtained by fitting model test data.

[0012] Furthermore, the revised calculation formula described in step 5 is as follows:

[0013] Among them, C′ comprehensively reflects the superimposed influence of multiple scaling factors such as roughness dissimilarity, surface tension effect, and insufficient aeration on the lateral diffusion of water tongue, and realizes the amplitude correction from model to prototype.

[0014] Furthermore, the prediction formula constructed for the modified export size scheme is as follows:

[0015] K1 and K2 are diffusion correction parameters determined through model experiments for a specific body shape modification scheme. They can quickly predict the prototype water tongue diffusion effect of the modification scheme based on a small number of model experiments.

[0016] The application of the high-speed jet flow tongue diffusion similarity correction method in the jet flow energy dissipation hydraulic model test of the spillway structure.

[0017] Furthermore, the lateral diffusion coefficient of the jetting water tongue is calculated using the aforementioned correction method to predict the lateral water entry position of the jetting water tongue under different design schemes in actual engineering projects.

[0018] Compared with the prior art, the present invention has the following advantages by adopting the above technical solution: 1. Significantly improved prediction accuracy: This invention breaks through the limitation of the scaling effect in traditional hydraulic model tests. It adopts a two-step correction method of "model fitting basic law + prototype data correction deviation", which comprehensively corrects the diffusion deviation caused by multiple factors such as roughness dissimilarity, surface tension, and insufficient aeration. This greatly improves the prediction accuracy of the lateral diffusion position of the prototype water tongue. In the example, the corrected results are in high agreement with the prototype observation values.

[0019] 2. Comprehensive applicability: This invention can not only perform safety verification of the water tongue diffusion of the original design scheme, but also quickly predict the prototype diffusion effect of different outlet shape modification schemes by introducing shape correction parameters. There is no need to carry out complete prototype observation and verification for each scheme, which greatly reduces the design cost and shortens the shape optimization cycle.

[0020] 3. Strong engineering applicability: The method of this invention has a clear logic and convenient parameter acquisition. Model calibration can be completed based on conventional hydraulic model tests and limited prototype observation data. There is no need to build additional complex test equipment. It can be directly applied to the flow dissipation model test and engineering design of various spillway structures, and is easy to promote and use. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall process of the method of the present invention; Figure 2 This is a schematic diagram of the diffusion plane of the outlet jet water tongue in the embodiment; Figure 3 This is a graph showing the variation of the lateral diffusion coefficient of the water tongue on the right side with dimensionless parameters in the embodiment. Figure 4 This is a graph showing the correlation between the calculated and experimental values ​​of the lateral diffusion coefficient of the water tongue on the right side in the example. Figure 5 This is a schematic diagram of the partial shape modification scheme for the outlet in the embodiment; Figure 6This is a graph showing the correlation between the lateral diffusion coefficients of the water tongue on the right side of the original and modified designs in the embodiments. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0023] This embodiment uses the No. 3 open-flow tunnel of XLD Reservoir as the engineering object to provide a detailed description of the high-speed jet flow tongue diffusion similarity correction method of the present invention.

[0024] Step S1: Parameter Definition Define the lateral diffusion coefficient of the water tongue on the right as (B r -B 0r ) / B 0r Among them, B r B is the horizontal distance from the right inlet point of the water jet to the centerline of the outlet of the spillway structure. 0r The horizontal distance from the centerline to the right sidewall of the spillway outlet; the total lateral diffusion angle θ of the jet stream is defined as the sidewall diffusion angle θ. b With the additional diffusion angle θ of the water tongue f sum In this embodiment, the left edge of the top of pier No. 2 is taken as the coordinate zero point. When the water inlet point on the right side of the water tongue is located to its right, the distance S is negative; when it is located to its left, S is positive. The water tongue diffusion pattern is as follows: Figure 2 As shown.

[0025] Step S2: Prototype observation and model test data acquisition Eight sets of prototype observation data were obtained from the No. 3 open channel of XLD Reservoir under typical operating conditions at water levels ranging from 250.00m to 275.00m. The focus was on collecting data on the horizontal distance B from the right inlet point of the water jet to the outlet centerline. r The distance B from the centerline of the right side wall of the exit 0r Water tongue distance L, water tongue additional diffusion angle θ f Parameters such as the reservoir water level of 266.31m and the additional lateral diffusion angle θ of the water tongue observed by the prototype. f The angle is 3.38°, and the distance S from the right side of the water inlet point to the left edge of the top of the No. 2 pier is -5m.

[0026] A hydraulic physical model of the open channel was constructed according to a 1:60 geometric scale. The above 8 sets of operating conditions were reproduced, and the model test data obtained are shown in Table 1.

[0027] Table 1 Results of hydraulic model test for jet propagation of water tongue

[0028] Step S3: Deviation Pattern Analysis Comparison of prototype observation data and model test data reveals that the jet flow diffusion of the 1:60 hydraulic model exhibits significant similarity deviations. The lateral diffusion coefficient of the jet flow measured by the model is generally smaller than the prototype observation value, which is a systematic underestimation of the deviation. The influence of the scaling effect needs to be eliminated through correction methods.

[0029] Step S4: Construct the preliminary calculation formula Based on the model test data in Table 1, the relationship between the transverse diffusion coefficient of the right-side water tongue and the dimensionless hydraulic parameter L / B is analyzed. 0r • The correlation between tanθ and the curves showing their variation are as follows: Figure 3 As shown. Through exponential function fitting, a preliminary calculation formula based on the model data is obtained:

[0030] In the formula, C1=0.5954 and C2=0.3492 are the water tongue diffusion parameters obtained by fitting the model test data.

[0031] Upon testing, the preliminary calculation formula showed excellent fitting accuracy with the model test data and consistent trends with the prototype observation data, although a small systematic deviation was observed. The correlation coefficient between the two was 0.984, and the correlation relationship is as follows: Figure 4 As shown.

[0032] Step S5: Prototype Data Correction Substituting the prototype observation data into the above preliminary calculation formula, and introducing the water tongue diffusion correction parameter C′ through parameter fitting, we obtain the final calculation formula after correction by the prototype data: In the formula, the correction parameter C′=1.310, which is greater than 1, is used to correct the problem of the water tongue being too small in lateral diffusion caused by the model scaling effect.

[0034] Table 2 shows a comparison of the lateral diffusion results of the jet stream before and after the correction. As can be seen from Table 2, the corrected calculation results are in high agreement with the prototype observations, verifying the accuracy of this correction method.

[0035] Table 2 Comparison of the lateral diffusion results of the jetting water tongue

[0036] Step S6: Engineering Applications and Body Shape Optimization (1) Safety review of the original design scheme The original design scheme was re-evaluated using the corrected calculation formula. The prediction results show that when the reservoir water level is higher than 260m, the water jet will impact the No. 2 pier of the stilling basin; at a water level of 275m, the water jet's right entry point will extend approximately 10.50m beyond the left edge of the pier, indicating a clear safety hazard in the original design scheme.

[0037] (2) Forecast of export body shape modification scheme To eliminate the risk of water jets impacting the downstream stilling basin piers, a modified scheme is proposed to offset the right wall at the end of the cantilever sill inward. Three offset values ​​are set: 1.5m, 1.7m, and 2.0m. The modified scheme is illustrated below. Figure 5 As shown.

[0038] The water tongue diffusion data of the three modified schemes at different reservoir water levels were obtained through model experiments, as shown in Table 3.

[0039] Table 3. Test results of the modified scheme's jet stream diffusion model.

[0040] Analyze the correlation between the lateral diffusion coefficient of the right-side water tongue of the original design scheme and the modified design scheme under the same working conditions, such as... Figure 6 As shown. Based on the correction calculation formula of the original scheme, the prediction formula of the modified scheme is derived through parameter fitting:

[0041] By fitting the model experiment data, the diffusion correction parameters corresponding to different migration schemes were obtained: Modified scheme 1 (offset 1.5m): K1=0.9909, K2=0.8281; Modified scheme 2 (offset 1.7m): K1=0.8652, K2=0.9195; Modified scheme 3 (offset 2.0m): K1=0.7313, K2=1.0767.

[0042] The above formula was used to predict the prototype water jet diffusion of the three modified schemes, and the results are shown in Table 4. The prediction results show that at a water level of 275m, all three modified schemes can ensure that the water jet safely falls into the stilling basin and will not impact the piers.

[0043] Table 4 Comparison of the results of the modified scheme for correcting the diffusion of the jet stream.

[0044] Considering both safety margin and engineering economy, the optimized scheme with a 1.7m offset from the right wall is recommended. This scheme predicts the water jet entry point to be 5.72m from the pier at a water level of 275m, meeting safety requirements while avoiding loss of discharge capacity due to excessive adjustment. Engineering flow testing showed that the water jet falls within the predetermined area under this scheme, demonstrating good energy dissipation.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention; any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for correcting the similarity of high-speed jetting water tongue diffusion, characterized in that: Includes the following steps: S1, Define the transverse diffusion coefficient of the water tongue on the right as (B r -B 0r ) / B 0r Among them, B r B is the horizontal distance from the right inlet point of the water jet to the centerline of the outlet of the spillway structure. 0r The horizontal distance from the centerline to the right sidewall of the spillway outlet; the total lateral diffusion angle θ of the jet stream is defined as the sidewall diffusion angle θ. b With the additional diffusion angle θ of the water tongue f sum; S2. Obtain prototype observation data of the lateral diffusion width and displacement of the spillway tongue of the target project's spillway structure under different operating conditions, and reproduce the corresponding operating conditions on a hydraulic physical model scaled down to a geometric scale, and measure and obtain model test data. S3. Compare the observation data of the prototype water tongue and the model test data to determine the deviation pattern of the lateral diffusion of the water tongue between the model and the prototype. S4. Based on the model test data obtained in step S2, analyze the transverse diffusion coefficient of the right-side water tongue and the dimensionless hydraulic parameter L / B. 0r • The correlation between tanθ and the initial calculation formula is constructed, where L is the water tongue distance; S5. Substitute the prototype observation data obtained in step S2 into the preliminary calculation formula obtained in step S4, and introduce the water tongue diffusion correction parameter through parameter fitting to obtain the corrected water tongue transverse diffusion coefficient calculation formula. S6. Using the corrected calculation formula obtained in step S5, predict the lateral water entry position of the spillway tongue under the original design scheme or different modified schemes, assess its safety impact on downstream structures, and provide a basis for optimizing the shape of the spillway structure.

2. The method for correcting the similarity of high-speed jetting water tongue diffusion according to claim 1, characterized in that: In step S4, the preliminary calculation formula is an exponential relationship: C1 and C2 are the water tongue diffusion parameters obtained by fitting model test data.

3. The method for correcting the similarity of high-speed jetting water tongue diffusion according to claim 2, characterized in that: In step S5, the corrected calculation formula is: Wherein, C′ is a water tongue diffusion correction parameter greater than 1 obtained by fitting the prototype observation data, which is used to correct the diffusion similarity deviation between the model and the prototype.

4. The method for correcting the similarity of high-speed jetting water tongue diffusion according to claim 3, characterized in that: In step S6, for the prediction of water tongue diffusion under the modified outlet shape scheme, a prediction formula is constructed based on the modified calculation formula of the original design scheme: Wherein, K1 and K2 are diffusion correction parameters determined through model experiments for a specific modification scheme; By comparing the prediction results of different modification schemes, the optimal body shape that ensures the water tongue falls into the safe zone can be selected.

5. The application of the high-speed jet flow tongue diffusion similarity correction method according to any one of claims 1 to 4 in the jet flow energy dissipation hydraulic model test of the spillway structure.

6. The application according to claim 5, characterized in that: The lateral diffusion coefficient of the jet stream is calculated using the aforementioned correction method, and the lateral water entry position of the jet stream is predicted under different design schemes in actual engineering projects.

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