A method and system for calculating the laying length of the protection in front of the pier

Abstract

The present invention relates to a method and system for calculating the laying length of the protection in front of a pier, belonging to the technical field of bridge scour prevention structures, including respectively simulating the vortex rollers in front of the pier under different working conditions to collect the separation distance, and obtaining the theoretical vortex roller length according to the processing of the separation distance. The first dimensionless parameter is obtained from the ratio of the theoretical vortex roller length to the pier width, the second dimensionless parameter is obtained from the ratio of the water depth to the pier width, the Froude number is obtained by processing the water body flow velocity and the water depth, and a calculation model of the actual vortex roller length is obtained through fitting processing according to the first dimensionless parameter, the second dimensionless parameter, and the Froude number, and the output of this calculation model is used as the laying length of the protection in front of the pier. This application can...

Description

Technical Field

[0001] The present invention relates to the technical field of bridge scour prevention structures, and particularly relates to a method and system for calculating the laying length of the front pier protection. Background Art

[0002] The swirling roll range is a concept proposed for the local protection technology of bridge foundations. Since the local protection measures are closely related to the water flow conditions in front of the pier and the generation of local scour, it is necessary to deeply study the characteristics of the water flow structure around the pier.

[0003] As Figure 1 shown in the figure, when the water approaches the pier 1, due to the obstruction of the pier 1, part of the obstructed water flows around the pier, and the other part impacts the pier 1, converting kinetic energy into potential energy. The impact water flow in front of the pier forms a downward subsurface flow that impacts the riverbed and constitutes a clockwise downward swirling roll at the bottom with the horizontally flowing water in the lower layer. The main function of the local protection measures is to prevent or reduce the scour of the sediment around the pier caused by the downward swirling roll in front of the pier. Therefore, the local protection measures should aim to eliminate the downward swirling roll in front of the pier and prevent it from scouring the sediment around the pier.

[0004] The local protection measures should be laid in front of or around the pier. The so-called front of the pier refers to the direction opposite to the direction of the water flow in front of the pier. The laying length of the local protection measures (also called the front pier protection) is closely related to the swirling roll range (also called the swirling roll length). Generally, its laying length is the same as the swirling roll length, and the swirling roll length is the distance between the center of the swirling roll and the pier.

[0005] The existing formula for calculating the swirling roll length is where L represents the front pier protection length (m), K represents the safety factor, g represents the acceleration due to gravity (m / s 2 ), h represents the average water depth of the water area where the pier is located (m), h ′ represents the effective water depth, h ′ ≈h / 2, and v represents the average flow velocity of the water area where the pier is located (m / s).

[0006] However, the above calculation formula is not applicable to the situation. How to calculate the swirling roll range for this situation and then obtain the laying length of the front pier protection is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0007] In order to solve the problems existing in the prior art, the embodiments of the present application provide a method and system for calculating the laying length of the front pier protection, which can obtain the theoretical swirling roll length by simulating the swirling roll in front of the pier, and further fit according to the first dimensionless parameter and the second dimensionless parameter to obtain a calculation model that can be used to calculate the laying length of the front pier protection. This model can solve the problem that the existing formula is not applicable to the working condition of Fr<0.135.

[0008] In a first aspect, a method for calculating the laying length of the protection in front of the pier is provided, including:

[0009] Simulate the swirl rollers in front of the pier under different working conditions respectively to collect the separation distance, and obtain the theoretical swirl roller length according to the processing of the separation distance; each of the said working conditions has corresponding water depth, pier width, and water body flow velocity, and the separation distance is the distance between the bed separation point of the swirl roller and the center of the pier;

[0010] Obtain the first dimensionless parameter from the ratio of the theoretical swirl roller length to the pier width, obtain the second dimensionless parameter from the ratio of the water depth to the pier width, obtain the Froude number by processing the water body flow velocity and the water depth, perform fitting processing according to the first dimensionless parameter, the second dimensionless parameter, and the Froude number to obtain the calculation model of the actual swirl roller length, and use the output of this calculation model as the laying length of the protection in front of the pier.

[0011] In some embodiments, the calculation model calculates the actual swirl roller length based on the following formula:

[0012]

[0013] Wherein,

[0014] L x represents the actual swirl roller length;

[0015] D represents the pier width;

[0016] h represents the water depth;

[0017] F r represents the Froude number.

[0018] In some embodiments, the Reynolds number of each of the said working conditions is greater than 10 4 .

[0019] In some embodiments, the Froude number of each of the said working conditions is not greater than 0.135.

[0020] In some embodiments, the large eddy simulation technology is used to perform the said simulation on the swirl rollers in front of the pier under different working conditions respectively.

[0021] In some embodiments, the theoretical swirl roller length is calculated using the following formula:

[0022] L x ′ = X s - 0.5D

[0023] Wherein,

[0024] L x ′ represents the theoretical swirl roller length;

[0025] Xs denotes the separation distance;

[0026] D denotes the pier width.

[0027] In some embodiments, the Froude number is calculated using the following formula:

[0028]

[0029] where,

[0030] F r denotes the Froude number;

[0031] v denotes the water body flow velocity;

[0032] g denotes the acceleration due to gravity;

[0033] h denotes the water depth.

[0034] In some embodiments, the calculation model for the actual vortex roller length obtained by fitting based on the first dimensionless parameter, the second dimensionless parameter, and the Froude number specifically includes:

[0035] Performing mathematical fitting on the variation laws of the first dimensionless parameter and the second dimensionless parameter with time in combination with the Froude number to obtain the calculation model for the actual vortex roller length.

[0036] In a second aspect, a system for calculating the laying length of the protection in front of the pier is provided, and the system includes:

[0037] A simulation module, which is used to simulate the vortex rollers in front of the pier under different working conditions respectively to collect the separation distance, and process the separation distance to obtain the theoretical vortex roller length; each of the working conditions has corresponding water depth, pier width, and water body flow velocity, and the separation distance is the distance between the bed separation point of the vortex roller and the center of the pier;

[0038] A model processing module, which is used to obtain the first dimensionless parameter according to the ratio of the theoretical vortex roller length to the pier width, obtain the second dimensionless parameter according to the ratio of the water depth to the pier width, obtain the Froude number according to the water body flow velocity and the water depth, perform fitting processing according to the first dimensionless parameter, the second dimensionless parameter, and the Froude number to obtain the calculation model for the actual vortex roller length, and use the output of this calculation model as the laying length of the protection in front of the pier.

[0039] In some embodiments, the first dimensionless parameter increases as the second dimensionless parameter increases and finally tends to a fixed value.

[0040] The beneficial effects brought by the technical solution provided in this application include:

[0041] The theoretical vortex roller length is obtained by simulating the vortex roller in front of the pier, and further a calculation model for calculating the laying length of the protection in front of the pier is obtained by fitting according to the first dimensionless parameter and the second dimensionless parameter. This model can solve the problem that the existing formula is not applicable to the working condition of Fr < 0.135. Brief Description of the Drawings

[0042] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for describing the invention content will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0043] Figure 1 It is a schematic flowchart of the method for calculating the laying length of the protection in front of the pier in the embodiment of the present invention.

[0044] Figure 2 It is a schematic system diagram of the system for calculating the laying length of the protection in front of the pier in the embodiment of the present invention. Detailed Embodiments

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the drawings described are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0046] Based on the problems existing in the prior art, the present invention proposes a method for calculating the laying length of the protection in front of the pier, simulating the vortex rollers in front of the pier under different working conditions respectively to collect the separation distance X s , and processing according to the separation distance X s to obtain the theoretical vortex roller length L x ′. The ratio of the theoretical vortex roller length L x ′ to the pier width D gives the first dimensionless parameter The ratio of the water depth h to the pier width D gives the second dimensionless parameter The Froude number F is obtained by processing the water body flow velocity v and the water depth h r , according to the first dimensionless parameter the second dimensionless parameter and the Froude number F are subjected to fitting processing to obtain the calculation model of the actual vortex roller length L x , and the output of this calculation model is used as the laying length of the protection in front of the pier.

[0047] In this embodiment, the theoretical roller length is obtained by simulating the roller in front of the pier, and a calculation model for calculating the laying length of the protection in front of the pier is obtained by further fitting according to the first dimensionless parameter and the second dimensionless parameter. This model can solve the problem that the existing formula is not applicable to the working condition of Fr < 0.135.

[0048] Specifically, as Figure 1 shown, the method includes:

[0049] Step S1: Simulate the rollers in front of the pier under different working conditions respectively to collect the separation distance, and obtain the theoretical roller length according to the separation distance.

[0050] Step S2: Obtain the first dimensionless parameter from the ratio of the theoretical roller length to the pier width, obtain the second dimensionless parameter from the ratio of the water depth to the pier width, obtain the Froude number by processing the water body flow velocity and the water depth, perform fitting processing according to the first dimensionless parameter, the second dimensionless parameter, and the Froude number to obtain a calculation model for the actual roller length, and use the output of this calculation model as the laying length of the protection in front of the pier.

[0051] Each of the said working conditions has corresponding water depth, pier width, and water body flow velocity. The separation distance is the distance between the bed separation point of the roller and the center of the bridge pier.

[0052] In a preferred embodiment, the calculation model calculates the actual roller length based on the following formula (1):

[0053]

[0054] Where, L x represents the actual roller length. D represents the pier width. H represents the water depth. F r represents the Froude number.

[0055] In a preferred embodiment, the Reynolds number of each of the said working conditions is greater than 10 4 .

[0056] The Froude number of each of the said working conditions is not greater than 0.135.

[0057] Use large eddy simulation technology to perform the said simulation on the rollers in front of the pier under different working conditions respectively.

[0058] In this embodiment, after the body Reynolds number increases to a certain extent, the relative distance (X s ) between the flow separation point of the main (horseshoe) vortex in front of the pier and the central axis of the cylinder basically remains stable, and then the corresponding basically remains stable, but its size is related to dimensionless numbers such as F r etc.

[0059] Using large eddy simulation technology to simulate the vortex roller in front of the pier. Since the length of the vortex roller changes with time, using statistical methods to statistically analyze the dynamic change of the separation distance of the vortex roller in front of the pier over time can more simply calculate the length of the vortex roller in front of the pier of the super-large deep-water bridge foundation, solving the technical problem that the existing calculation formula is not applicable to the working condition of Fr < 0.135, and providing key technical support for the scour protection design of the super-large deep-water bridge foundation.

[0060] In a preferred embodiment, the theoretical vortex roller length is calculated using the following formula (2):

[0061] L x ′ = X s -0.5D (2)

[0062] Wherein, L x ′ represents the theoretical vortex roller length. X s represents the separation distance. D represents the pier width.

[0063] In this embodiment, the vortex roller range is characterized by the position of the main vortex separation point. The distance from the bed separation point of the retrograde flow in front of the pier to the center of the cylinder is called the separation distance. The separation distance is represented by X s This study gives the variation law of the separation distance X s with the dimensionless parameter through numerical simulation. Increases with and gradually increases, and finally tends to a certain value.

[0064] In a preferred embodiment, the Froude number is calculated using the following formula (3):

[0065]

[0066] Wherein, F r represents the Froude number. v represents the water body flow velocity. g represents the acceleration due to gravity. h represents the water depth.

[0067] In a preferred embodiment, the calculation model for the actual vortex roller length obtained by fitting the first dimensionless parameter, the second dimensionless parameter, and the Froude number specifically includes:

[0068] Mathematically fitting the variation laws of the first dimensionless parameter and the second dimensionless parameter with time in combination with the Froude number to obtain the calculation model for the actual vortex roller length.

[0069] Such as Figure 2As shown in the figure, the present invention also provides a calculation system for the laying length of the protection in front of the pier, which includes a simulation module 1 and a model processing module 2. The simulation module 1 is used to simulate the swirl rollers in front of the pier under different working conditions respectively to collect the separation distance, and process the separation distance to obtain the theoretical length of the swirl roller. The model processing module 2 is used to obtain the first dimensionless parameter according to the ratio of the theoretical length of the swirl roller to the pier width, obtain the second dimensionless parameter according to the ratio of the water depth to the pier width, obtain the Froude number according to the water flow velocity and the water depth, perform fitting processing according to the first dimensionless parameter, the second dimensionless parameter, and the Froude number to obtain a calculation model for the actual length of the swirl roller, and use the output of this calculation model as the laying length of the protection in front of the pier.

[0070] In this embodiment, the theoretical length of the swirl roller is obtained by simulating the swirl roller in front of the pier, and further fitting is performed according to the first dimensionless parameter and the second dimensionless parameter to obtain a calculation model that can be used to calculate the laying length of the protection in front of the pier. This model can solve the problem that the existing formula is not applicable to the working conditions with Fr < 0.135.

[0071] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for calculating the laying length of the protection in front of the pier, characterized in that, The method includes: Simulating the vortex rollers in front of the pier under different working conditions respectively to collect the separation distance, and obtaining the theoretical vortex roller length according to the processing of the separation distance; each of the working conditions has corresponding water depth, pier width and water body flow velocity, and the separation distance is the distance between the bed separation point of the vortex roller and the center of the pier; Obtaining a first dimensionless parameter from the ratio of the theoretical vortex roller length to the pier width, obtaining a second dimensionless parameter from the ratio of the water depth to the pier width, obtaining the Froude number by processing the water body flow velocity and the water depth, and performing fitting processing according to the first dimensionless parameter, the second dimensionless parameter, and the Froude number of all working conditions to obtain a calculation model of the actual vortex roller length, and using the output of this calculation model as the laying length of the protection in front of the pier; The calculation model calculates the actual vortex roller length based on the following formula: Wherein, Indicates the actual length of the swirling roller; Indicates the pier width; Indicates water depth; represents the Froude number.

2. The method for calculating the laying length of the protection in front of the pier according to claim 1, wherein, The Reynolds number of each working condition is greater than .

3. The method for calculating the laying length of the protection in front of the pier according to claim 1, wherein, The Froude number of each of the working conditions is not greater than 0.

135.

4. The method for calculating the laying length of the front protection of the pier according to claim 1, wherein, Using large eddy simulation technology to perform the above simulations on the vortex rollers in front of the pier under different working conditions respectively.

5. The method for calculating the laying length of the protection in front of the pier according to claim 1, characterized in that, The theoretical vortex roller length is calculated using the following formula: Wherein, Represents the theoretical roll length of the vortex; Indicates the separation distance; Indicates the pier width.

6. The method for calculating the laying length of the front protection of the pier according to claim 1, characterized in that, The Froude number is calculated using the following formula: Wherein, represents the Froude number; represents the water body flow velocity; represents the acceleration due to gravity; Indicates water depth.

7. The method for calculating the laying length of the protection in front of the pier according to claim 1, wherein, The performing fitting processing according to the first dimensionless parameter, the second dimensionless parameter, and the Froude number of all working conditions to obtain a calculation model of the actual vortex roller length specifically includes: Performing mathematical fitting in combination with the Froude number according to the variation laws of the first dimensionless parameter and the second dimensionless parameter of all working conditions with time to obtain the calculation model of the actual vortex roller length.

8. A calculation system for the laying length of the protection in front of the pier, characterized in that Based on the method for calculating the laying length of the protection in front of the pier according to any one of claims 1-7, the system includes: A simulation module, which is used to simulate the vortex rollers in front of the pier under different working conditions respectively to collect the separation distance, and obtain the theoretical vortex roller length according to the processing of the separation distance; each of the working conditions has corresponding water depth, pier width and water body flow velocity, and the separation distance is the distance between the bed separation point of the vortex roller and the center of the pier; A model processing module, which is used to obtain a first dimensionless parameter from the ratio of the theoretical vortex roller length to the pier width, obtain a second dimensionless parameter from the ratio of the water depth to the pier width, obtain the Froude number by processing the water body flow velocity and the water depth, perform fitting processing according to the first dimensionless parameter, the second dimensionless parameter, and the Froude number of all working conditions to obtain a calculation model of the actual vortex roller length, and use the output of this calculation model as the laying length of the protection in front of the pier.

9. The pier front protection laying length calculation system according to claim 8, wherein, The first dimensionless parameter increases as the second dimensionless parameter increases and finally tends to a fixed value.

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