A method for calculating water flow resistance of a through-type frame pier type wharf structure

Abstract

The application discloses a kind of water flow resistance calculation methods of open-type frame pier structure, structure is generalized as rigid vegetation group, submergence and non-submergence case are divided, consider the water-blocking effect of diameter, height, density and transverse contact support of column, steps include: S1, determine the drag coefficient of single column of wharf structure;S2, determine the comprehensive drag coefficient of single column of wharf structure;S3, calculate the overall drag coefficient of wharf structure, in submergence case, the overall drag coefficient is calculated after modification to Baptist (2005) formula;In non-submergence case, the overall drag coefficient is calculated using Baptist (2005) formula;S4, calculate flow field.The application can accurately calculate the overall water flow resistance of open-type frame pier structure, has the advantages of clear physical mechanism, high calculation precision, etc., combined with hydrodynamic simulation software, can provide more accurate and reliable technical support for wharf structure optimization design, navigation condition analysis and flood control influence evaluation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical fields of port and shipping engineering, water conservancy engineering, and the like, and particularly relates to a water flow resistance calculation method for a frame pier type wharf structure. BACKGROUND

[0002] A high mountain and canyon type river reservoir has a large water level amplitude under flood control and power generation dispatching, and a frame pier type permeable structure (as shown in the figure) is usually used for the port wharf constructed in the reservoir area. Figure 1 The wharf structure is complex in composition: a pile cap structure is used at the bottom, which is supported by a plurality of rock-embedded bored cement injection piles; a multi-layer reinforced concrete permeable frame structure is provided on the pile cap, with a vertical column as the main support structure, and a plurality of horizontal and vertical contact braces and face plates are provided. This type of structure has a strong water-blocking effect on the water flow, which can significantly change the local flow field and flow state.

[0003] The existing hydrodynamic numerical simulation technology is mainly aimed at relatively simple permeable high-pile wharfs (mostly located in estuary and coastal areas), which lack multi-layer horizontal and vertical contact braces and face plates, and only have a single-layer ship berthing platform. One existing technical solution is to generalize the high-pile wharf as a non-permeable gravity wharf, which has a small impact on the overall flow field calculation error, but can lead to distortion of the local flow field simulation in front of the wharf, thereby affecting the safety analysis of ship berthing and unberthing and the water-logging effect analysis of the structure. Tang Shifang proposed in his doctoral dissertation "Water flow resistance of piles and pile groups and its application in tidal flow numerical simulation" in 2002 that the water flow resistance of a non-flooded permeable high-pile wharf can be simulated by adding the additional roughness of the pile group to the roughness of the original riverbed without the pile group. The specific method is to divide the resistance coefficient (Manning roughness coefficient) of a single pile by the pile spacing of the pile group to obtain the additional roughness of the pile group, and then add it to the roughness of the original riverbed without the pile group to obtain the comprehensive roughness. In addition, this technical solution also requires additional correction of the water depth in the pile group area to improve the simulation accuracy, but the physical mechanism of this technical step is not clear.

[0004] In contrast, the permeable frame pier type wharf of the high mountain and canyon type river reservoir adopts a multi-layer longitudinal and horizontal contact brace and face plate structure to adapt to the large water level amplitude, and has a multi-layer berthing platform, which has a significantly higher structural complexity than the high-pile wharf. However, the existing technology does not consider the water-blocking effect of the horizontal and vertical contact braces in the frame pier type wharf and the water-blocking effect under the submerged condition of the structure, and also lacks a resistance coefficient calculation method that considers the permeable frame pier type structure as a whole, making it difficult to accurately simulate its water flow resistance characteristics.

[0005] Liu Qibing et al. "Numerical simulation of flow around frame pier wharf structure" (Journal of Hydraulic Engineering and Water Transport, 2014.6, 23-29.) carried out numerical simulation of flow around different square column arrangement combinations based on FLUENT software, and discussed the flow around effect of simple square column arrangement and spacing and the water blocking effect of transverse connection support, but it cannot be applied to the flow blocking simulation calculation of actual open-type frame pier wharf structure.

[0006] So far, the technical scheme which can consider the water blocking influence of the diameter, height and density of the vertical column in the prototype open-type frame pier wharf structure and the water blocking effect of the transverse connection support and fully reflects the overall water blocking characteristics of the frame pier wharf structure is still blank. SUMMARY

[0007] In view of the above problems, the present application provides an open-type frame pier wharf structure water flow resistance calculation method, which generalizes the open-type frame pier wharf structure as a rigid vegetation group, and proposes a calculation method of overall resistance coefficient under non-submerged and submerged conditions, which can more accurately reflect the water blocking effect of the open-type frame pier wharf structure.

[0008] The present application is implemented as follows:

[0009] An open-type frame pier wharf structure water flow resistance calculation method generalizes the open-type frame pier wharf structure as a rigid vegetation group, and divides it into submerged and non-submerged conditions, considers the water blocking effect of the diameter, height, density of the vertical column and the transverse connection support, and includes the following steps:

[0010] S1, determining the drag coefficient of a single vertical column of the open-type frame pier wharf structure: obtaining the respective drag coefficients of the single vertical column and the transverse connection support of the open-type frame pier wharf structure according to physical model test measurement or computational fluid dynamics (CFD) or existing research results;

[0011] S2, determining the comprehensive drag coefficient of the single vertical column of the open-type frame pier wharf structure: the comprehensive drag coefficient of the single vertical column is the superposition of the drag coefficient of the vertical column and the drag coefficient of the transverse connection support;

[0012] S3, calculating the overall drag coefficient of the open-type frame pier wharf structure: generalizing the open-type frame pier wharf structure as a rigid vegetation group, dividing it into submerged and non-submerged conditions, under the submerged condition, calculating the overall drag coefficient after modifying the Baptist (2005) formula; under the non-submerged condition, calculating the overall drag coefficient by using the Baptist (2005) formula;

[0013] S4, calculating flow field: a large range of hydrodynamic simulation software is used, the overall drag coefficient of the open-frame pier structure under different submergence conditions is given to the numerical grid nodes in the region according to the change of water level, and the hydrodynamic field is simulated and calculated.

[0014] Further, in step S2, the calculation of the comprehensive drag coefficient, the mutual influence between the columns can be ignored under the condition that the distance between the columns is greater than 3 times the diameter of the column.

[0015] Further, in step S2, the mutual influence between the transverse contact supports can be ignored under the condition that the distance between the transverse contact supports is greater than 3 times the width of the transverse contact support.

[0016] Further, the drag coefficient calculation method of the non-submergence condition in step S3 is that Baptist (2005) formula is used to calculate the overall Chezy coefficient of the open-frame pier structure:

[0017]

[0018] In the formula, C D is the comprehensive drag coefficient of a single column, C z is the Chezy coefficient of the riverbed without the column, D is the diameter of the column, k is the height of the column, m is the density of the column, that is, the number of columns per unit area, h is the water depth, and g is the acceleration of gravity.

[0019] The overall Chezy coefficient of the open-frame pier structure is converted into a drag coefficient or a Manning roughness coefficient, and the calculation formula is:

[0020]

[0021] In the formula, C D，bulk is the overall drag coefficient, and n is the Manning roughness coefficient.

[0022] Further, in step S3, the drag coefficient calculation method of the open-frame pier structure under the submergence condition is:

[0023] The overall Chezy coefficient of the open-frame pier structure is calculated, Baptist (2005) formula is modified, and the modified Chezy coefficient formula is:

[0024]

[0025] The overall drag coefficient or the Manning roughness coefficient of the frame pier structure is calculated by using formula (4).

[0026] The beneficial effects of the present application are:

[0027] The open-frame pier structure is divided into non-submerged and submerged cases, and a calculation method of the overall resistance coefficient of the open-frame pier structure is proposed.

[0028] The open-frame pier structure is generalized as the water-blocking effect of rigid vegetation groups, considering the water-blocking effect of the diameter, height and density of the vertical columns and the water-blocking effect of the transverse contact supports, so that the water-blocking characteristics of the open-frame pier structure as a whole are fully reflected, and the water-blocking effect of the open-frame pier structure can be more accurately calculated.

[0029] The complete technical steps for calculating the water-blocking effect of the open-frame pier structure in the submerged and non-submerged cases are innovatively proposed by referring to and modifying the existing research results, and the method has the advantages of clear physical mechanism and high calculation accuracy.

[0030] The present application is described in detail in combination with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a schematic diagram of the frame of the open-frame pier structure;

[0032] Figure 2 is Figure 1 a schematic diagram of the local structure of the A-A section;

[0033] Figure 3 is the simulation result of the flow resistance effect of the calculation method of the present application in each scene.

[0034] In the figure: 1-vertical column, 2-transverse contact support, 3-longitudinal contact support. DETAILED DESCRIPTION

[0035] Example 1:

[0036] The present embodiment is a calculation method of the water flow resistance of an open-frame pier structure, which generalizes the open-frame pier structure as rigid vegetation groups, divides it into submerged and non-submerged cases, considers the water-blocking effect of the diameter, height and density of the vertical columns and the transverse contact supports, and the open-frame pier structure is as shown in Figures 1-2 .

[0037] The method comprises the following steps:

[0038] S1, determine the drag coefficient of a single vertical column 1 of the open-frame pier structure:

[0039] The drag coefficient is a dimensionless parameter in fluid mechanics that describes the resistance experienced by an object moving through a fluid, such as water. It takes into account the shape of the structure, the roughness of the surface, the characteristics of the water flow (such as velocity and viscosity), and the flow regime (laminar or turbulent). It is a key parameter for analyzing the water flow conditions around a framed-pier wharf and evaluating the forces exerted on the structure.

[0040] The drag coefficients of the individual columns and cross ties of the open-frame pier wharf structure are obtained through physical model tests, computational fluid dynamics (CFD) simulations, or existing research results.

[0041] (1) Method for obtaining the drag coefficient of a single component:

[0042] The drag coefficients of the individual columns and cross ties of the open-frame pier wharf structure can be obtained through three methods.

[0043] The first method is to measure the water flow forces on the columns and cross ties through physical model tests in a laboratory that simulates the actual water flow environment. Then, the corresponding drag coefficients are obtained based on the water flow drag force calculation formula.

[0044] The second method is to use computational fluid dynamics (CFD) to establish a numerical model, input the parameters of the single component and the water flow conditions, and simulate the calculation of the drag coefficient of the single component.

[0045] The third method is to refer to existing research results, such as relevant academic papers and engineering reports, to obtain drag coefficient data for similar components and working conditions.

[0046] S2, determining the comprehensive drag coefficient of the individual columns of the open-frame pier wharf structure:

[0047] The drag coefficient of the individual columns is added to the drag coefficient of the cross ties to obtain the comprehensive drag coefficient.

[0048] The arrangement of multiple columns or components in the framed pier can cause mutual interference of water flow (pile group effect). In this case, the comprehensive drag coefficient needs to consider the influence of the component spacing (such as the pile diameter ratio). When the spacing is small, the water flow blocking and flow around the superposition will increase the total resistance. For columns, when the distance between columns 1 is greater than 3 times the diameter of column 1, or the distance between cross ties 2 is greater than 3 times the width of cross tie 2, the mutual influence between columns and cross ties is considered to be small and can be ignored.

[0049] This is because when the component spacing is large, the flow field disturbance generated by each component will fully diffuse and decay before interacting with each other, and will not significantly change the flow field characteristics and force state around other components.

[0050] For longitudinal contact support, longitudinal contact support 3 parallel to water flow, because it is parallel to the direction of water flow, the area of the flow is very small, the resistance of water flow is weak, the resistance effect is negligible, and the influence of longitudinal contact support 3 is not considered in calculating the comprehensive drag coefficient.

[0051] S3, calculate the overall drag coefficient of the open-frame pier structure:

[0052] Both the water resistance of the diameter, height, density and other factors of the vertical column in the open-frame pier structure and the water resistance of the horizontal contact support are considered, and the open-frame pier structure is generalized as a rigid vegetation group to calculate the overall water resistance. This step is divided into two cases of non-submergence and submergence, each case consisting of two calculation steps.

[0053] a) Non-submergence case

[0054] First, Baptist (2005) formula is used to calculate the overall Chezy coefficient of the open-frame pier structure in the non-submergence case, and the calculation formula is:

[0055]

[0056] In the formula, C D is the overall drag coefficient of a single column, C z is the Chezy coefficient of the riverbed without columns, D is the diameter of the column, k is the height of the column, m is the density of the column, i.e. the number of columns per unit area, h is the water depth, and g is the acceleration of gravity.

[0057] Secondly, after obtaining the overall Chezy coefficient of the non-submergence open-frame pier structure, it is converted into drag coefficient or Manning roughness using the following formula:

[0058]

[0059] In the formula, C D，bulk is the overall drag coefficient, n is the Manning roughness coefficient, and the meanings of the remaining letters are the same as above.

[0060] b) Submergence case

[0061] In the submergence case, considering the influence of the pier structure on water resistance, Baptist (2005) formula is modified, i.e. the Nikuradse roughness height parameter in the original formula is uniformly taken as 0.1 times the height of the column (0.1k); At the same time, multiply the formula by 0.5 times, and the modified overall Chezy coefficient calculation formula is:

[0062]

[0063] In the formula, each letter has the same meaning as in formula (1) and (2), and the overall drag coefficient or Manning roughness coefficient of the frame pier wharf structure is calculated by using formula (4).

[0064]

[0065] S4, calculating the flow field:

[0066] By using 2D or 3D large-scale hydrodynamic simulation software, the overall drag coefficient of the permeable frame pier wharf structure under different submergence conditions is assigned to the numerical grid nodes in the region according to the change of the water level, the hydrodynamic field is simulated and calculated, and the influence degree and range of the wharf structure on the water level, flow velocity, flow direction and other elements are analyzed.

[0067] The calculation method of the present application has the following improvements compared with the existing technical solutions:

[0068] 1. Distinguish between submergence and non-submergence:

[0069] The existing technical solutions all treat the permeable high-pile wharf as a non-submergence condition, without considering the resistance problem under the submergence condition. Due to the large water level fluctuation characteristics of the high mountain and valley type river channel reservoir, the frame pier wharf structure may also be submerged by the flow as a whole or partially. The present application divides the frame pier wharf structure into non-submergence and submergence conditions, and considers the resistance problem under the two conditions, which is more accurate for calculating the flow resistance effect of the wharf.

[0070] 2. Calculate the overall drag coefficient of a single column:

[0071] The present application adds the drag coefficient of the transverse connecting strut to the drag coefficient of the single column as the overall drag coefficient of the column.

[0072] 3. Calculate the overall drag coefficient of the permeable frame pier wharf structure:

[0073] The present application generalizes the permeable frame pier wharf structure as a rigid vegetation group to calculate its water resistance effect, which can consider the water resistance effect of the diameter, height and density of the column 1 in the permeable frame pier wharf structure, and also consider the water resistance effect of the transverse connecting strut 2, fully reflecting the overall water resistance characteristics of the frame pier wharf structure.

[0074] 4. Calculate the overall Chezy coefficient of the permeable frame pier wharf structure by using Baptist (2005) formula:

[0075] The present application adopts Baptist (2005) formula to calculate the overall drag coefficient of the open-frame pier structure in the non-submerged condition, and modifies the Baptist (2005) formula for the submerged condition (formula 3), which is more reasonable in physical mechanism and improves the calculation accuracy.

[0076] Embodiment 2:

[0077] This embodiment is based on the calculation example of embodiment 1.

[0078] A certain mountainous reservoir is constructed with an open-frame pier structure as shown in the drawing. Figure 1 The column 1 is square with a side length of 1.2 m, and the height is designed to be 12 m and 20 m. The longitudinal row number of the column 1 is 7, and the lateral row number is 3. The longitudinal and lateral spacing of the column 1 is 10 m. The width of the lateral contact support 2 is 0.5 m, and the spacing between the upper and lower lateral contact supports 2 is 4.0 m. It is assumed that the river width is 100 m, the water depth is 15 m, and the upstream flow of the river is 1000 m 3 / s.

[0079] S1, determine the drag coefficient of a single column of the open-frame pier structure:

[0080] Since the spacing of the column 1 and the spacing of the lateral contact support 2 are both greater than 3 times the diameter of the column 1 and 3 times the width of the contact support 2, respectively, the mutual influence between the square columns and the lateral contact supports 2 can be ignored.

[0081] S2, according to the existing research results, the drag coefficient of a single square column is 2.05, and the drag coefficient of the lateral contact support 2 is 2.0, so the comprehensive drag coefficient of a single square column is 4.05.

[0082] S3, calculate the overall drag coefficient of the open-frame pier structure:

[0083] According to the relationship between the water depth and the column height, the overall drag coefficient of the open-frame pier structure in the non-submerged condition and the submerged condition is calculated by formula (1) or formula (3), respectively, and the drag coefficient is assigned to the numerical grid nodes in the area where the frame pier structure is located.

[0084] S4, calculate the large-scale flow field:

[0085] After the mesh partitioning and the aforementioned steps 1-3, the large-scale flow field simulation is performed by using the finite volume method, triangular unstructured mesh, and parallel computing hydrodynamic numerical simulation software FVCOM.

[0086] Figure 3It is shown that, under the conditions of no construction of wharf, construction of water-permeable frame pier wharf (including non-submerged and submerged conditions) and non-water-permeable generalized wharf, the local flow field conditions of the simulated flow field (the longitudinal coordinate is enlarged by 10 times to improve the display effect) are collected. In the condition of no wharf, the flow velocity of water at point A is 0.99 meters per second; in the condition of submerged water-permeable frame wharf, the flow velocity at the point is 0.32 meters per second; in the condition of non-submerged water-permeable frame wharf, the flow velocity is 0.28 meters per second; and in the condition of non-water-permeable generalized wharf, the flow velocity is 0.04 meters per second.

[0087] The obvious differences between the local flow field flow states under the conditions of no wharf, construction of water-permeable frame pier wharf (including non-submerged and submerged conditions) and non-water-permeable generalized wharf, especially the use of traditional non-water-permeable generalized wharf scheme significantly exaggerates the water-blocking effect of the wharf structure, resulting in a significant decrease in the calculated flow velocity in front of the wharf, which is almost zero, thus causing serious distortion. The water-blocking effect calculated by the technical scheme of the present application is more accurate and reasonable, and the water-blocking effect is larger in the non-submerged condition and smaller in the submerged condition.

[0088] This shows that the water flow resistance calculation method of the water-permeable frame pier wharf structure of the present application can truly reflect the water-blocking effect under different states (submerged and non-submerged), avoid the distortion of the flow field caused by excessive water-blocking using the traditional non-water-permeable generalized wharf as the calculation basis, and provide more reliable flow field data for related engineering analysis. The water-blocking effect changes with the submerged state, which is more in line with the interaction rules of natural water flow and wharf structure, can accurately reflect the influence of the structure on the water flow, and can provide more accurate and reliable technical support for wharf structure optimization design, navigation condition analysis and flood control impact evaluation.

[0089] Finally, it should be noted that the above is only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that the technical solutions of the present application (such as the use of various formulas, the order of steps, etc.) can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for calculating the water flow resistance of a permeable frame pier-type wharf structure, characterized in that, The open-frame pier-type wharf structure is generalized as a rigid vegetation community, divided into submerged and non-submerged cases. Considering the diameter, height, density of the columns and the water-blocking effect of the lateral bracing, the following steps are included: S1, Determine the drag coefficient of a single column of a permeable frame pier wharf structure: Obtain the drag coefficients of a single column and a transverse connecting brace of a permeable frame pier wharf structure based on physical model test measurement, computational fluid simulation technology, or existing research results. S2, Determine the comprehensive drag coefficient of a single column of a transparent frame pier wharf structure: The comprehensive drag coefficient of a single column is the sum of the column drag coefficient and the drag coefficient of the transverse connecting brace. S3, Calculate the overall drag coefficient of the open frame pier wharf structure: The open frame pier wharf structure is generalized as a rigid vegetation group and divided into two cases: submerged and non-submerged. In the submerged case, the Baptist 2005 formula is modified to calculate the overall drag coefficient; in the non-submerged case, the Baptist 2005 formula is used to calculate the overall drag coefficient. The method for calculating the drag coefficient in the non-submerged case is as follows: The integrity coefficient of the open frame pier wharf structure was calculated using the Baptist 2005 formula, as follows: （1） In the formula, It is the overall drag coefficient of a single column. It is the Chezy coefficient of the riverbed when no pillars are present. It is the diameter of the column. It is the height of the column. It refers to the column density, that is, the number of columns per unit area. It's the water depth. It is gravitational acceleration; The Chezy coefficient of the permeable frame pier wharf structure under non-submerged conditions is converted into the towing coefficient or Manning roughness coefficient, and the calculation formula is as follows: （2） In the formula, It is the overall drag coefficient. It is the Manning roughness coefficient; The method for calculating the drag coefficient under the flooding scenario is as follows: The Chezy coefficient for the overall integrity of open-frame pier-type wharf structures is calculated by modifying the Baptist 2005 formula. The modified Chezy coefficient calculation formula is as follows: ； In the formula, It is the overall drag coefficient of a single column. It is the Chezy coefficient of the riverbed when no pillars are present. It is the diameter of the column. It is the height of the column. It refers to the column density, that is, the number of columns per unit area. It's the water depth. It is gravitational acceleration; （4） In the formula, It is the overall drag coefficient. It is the Manning roughness coefficient; The drag coefficient or Manning roughness coefficient of the overall integrity of the open frame pier wharf structure under flood conditions is calculated using formula (4). S4, Calculate the flow field: Using large-scale hydrodynamic simulation software, the overall drag coefficient of the open frame pier wharf structure under different flooding conditions is assigned to the numerical grid nodes of its region according to the changes in water level, and the hydrodynamic field is simulated and calculated.

2. The method for calculating the water flow resistance of a permeable frame pier wharf structure according to claim 1, characterized in that, In step S2, the calculation of the comprehensive drag coefficient is based on the condition that the mutual influence between the columns can be ignored: the distance between the columns is greater than 3 times the column diameter.

3. The method for calculating the water flow resistance of a permeable frame pier wharf structure according to claim 1, characterized in that, In step S2, the condition under which the mutual influence between the transverse connecting braces can be ignored is that the distance between the transverse connecting braces is greater than 3 times the width of the transverse connecting brace.

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