CFD-based wet spraying machine conveying pipe structure optimization design method

Abstract

The invention discloses a CFD (computational fluid dynamics)-based wet spraying machine conveying pipe structure optimization design method, which belongs to the field of computational fluid mechanics and comprises the following steps: step 1, acquiring characteristic parameters of a mixed concrete material; 2, according to the actual working condition of the conveying pipe of the wet spraying machine, the geometric dimension parameters of the pipeline are determined, a three-dimensional model of the pipeline is established, and unstructured grid division is carried out; 3, setting a physical model, selecting a turbulence model, and setting concrete as a non-Newtonian fluid model; 4, defining boundary conditions, solving through an algorithm, and completing numerical calculation of pressure loss; 5, linearly fitting a relation equation of the pressure loss and the geometric parameters of the pipeline based on a least square method; and 6, optimizing the geometric parameters of the conveying pipe of the wet spraying machine by using a single-target optimization algorithm. According to the method, numerical simulation is combined with parameter optimization, the influence of the structural parameters of the straight pipe, the bent pipe and the taper pipe on the pressure loss of concrete flowing is systematically studied, and optimization of pipeline design is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of computational fluid dynamics, and particularly to an optimized design method for the conveying pipe structure of a wet shotcreting machine based on CFD. Background Art

[0002] Computational Fluid Dynamics (CFD) is an interdisciplinary subject between mathematics, fluid mechanics, and computers. Its main research content is to solve the control equations of fluid mechanics through computers and numerical methods, and to simulate and analyze fluid mechanics problems.

[0003] A wet shotcreting machine is a concrete spraying device widely used in construction. Its conveying pipeline is a key component for efficient concrete conveying. In traditional design methods, the parameter selection of the conveying pipe structure mostly relies on experience and lacks scientific theoretical support. In particular, the influence of the geometric dimensions of pipe sections such as straight pipes, elbows, and taper pipes on the pressure loss of concrete has not been fully studied. In addition, as a non-Newtonian fluid, the complex flow behavior of concrete, such as its yield stress and plastic viscosity, in the pipeline is difficult to accurately describe by simple formulas. Summary of the Invention

[0004] The purpose of the present invention is to provide an optimized design method for the conveying pipe structure of a wet shotcreting machine based on CFD. Through numerical simulation combined with parameter optimization, the influence of the structural parameters of straight pipes, elbows, and taper pipes on the pressure loss of concrete flow is systematically studied, so as to achieve the optimization of pipeline design.

[0005] To achieve the above purpose, the present invention provides an optimized design method for the conveying pipe structure of a wet shotcreting machine based on CFD, including the following steps:

[0006] Step 1: Obtain the characteristic parameters of the mixed concrete material, including density, yield stress, and plastic viscosity;

[0007] Step 2: According to the actual working conditions of the conveying pipe of the wet shotcreting machine, determine the geometric dimension parameters of the straight pipe, elbow, and taper pipe, establish a three-dimensional model of the pipeline, and import the three-dimensional model into the Fluent module of ANSYS software for unstructured grid division;

[0008] Step 3: Set the physical model, select the Stand k-epsilon model for the turbulence model, set the concrete as the Bingham non-Newtonian fluid model, and define the density, yield stress, and viscosity parameters;

[0009] Step 4: Define the boundary conditions. Set the inlet boundary condition of the conveying pipe of the wet shotcreting machine as a velocity inlet, and set the outlet boundary condition as a pressure outlet. Use the SIMPLE algorithm to solve and complete the numerical calculation of the pressure loss;

[0010] Step 5: Based on the least squares method, linearly fit the relationship equation between the pressure loss and the geometric parameters of the wet shotcreting machine's conveying pipe;

[0011] Step 6: Use a single-objective optimization algorithm to optimize the geometric parameters of the wet shotcreting machine's conveying pipe.

[0012] Preferably, in Step 2, the modeling of the wet shotcreting machine's conveying pipe is drawn using SolidWorks software and saved in Parasolid format.

[0013] Preferably, in Step 2, the parameters of the straight pipe include the length L 1 , the parameters of the elbow pipe include the curvature radius R and the bending angle α, and the parameters of the tapered pipe include the length L 2 ;

[0014] Preferably, in Step 2, using the Fluent module in ANSYS, import the three-dimensional model of the wet shotcreting machine's conveying pipe into the Geometry module in Fluent.

[0015] Preferably, for the model mesh division of the wet shotcreting machine's conveying pipe, tetrahedral unstructured meshes are used. Import the three-dimensional model of the wet shotcreting machine's conveying pipe into the FLUENT mesh module, define the inlet and outlet of the wet shotcreting machine's conveying pipe, and the corresponding names of the inlet and outlet of the wet shotcreting machine's conveying pipe are inlet and outlet.

[0016] Preferably, in Step 4, for the solution settings: Select SIMPLE in the calculation method in solution methods, click Initialize for initialization, click Run calculation to set the number of iteration steps, and click Calculate for calculation simulation; for the post-processing analysis: Analyze the pressure field of the fluid in the Result module and calculate the pressure loss in different regions inside the wet shotcreting machine's conveying pipe.

[0017] Preferably, in Step 5, for the fitting of the pressure loss equation: According to the simulation results, establish a linear relationship equation between the structural parameters of the straight pipe, elbow pipe, and tapered pipe and the pressure loss.

[0018] Preferably, the pipeline parameters L 1 , R, α, L 2 are set in 5 groups for simulation;

[0019] The relationship equation between the pressure loss and the pipeline structure parameters is obtained by linear fitting using the least squares method based on the pressure calculation results of 5 groups of pipeline parameters, and the formula is as follows:

[0020] △P 直 = f(L 1 ) = a + k 1 L 1;

[0021] △P 弯 = f(R, α) = b + K 2 R + K 3 α;

[0022] △P 锥 = f(L 2 ) = c + K 3 L 2 ;

[0023] △P 总 = f(L 1 ) + f(R, α) + f(L 2 );

[0024] In the formula:

[0025] △P 直 —— Pressure loss of the straight pipe section, Pa;

[0026] △P 弯 —— Pressure loss of the elbow pipe section, Pa;

[0027] △P 锥 —— Pressure loss of the tapered pipe section, Pa;

[0028] △P 总 —— Pressure loss of the entire pipeline, Pa;

[0029] L 1 —— Length of the straight pipe section, m;

[0030] L 2 —— Length of the tapered pipe section, m;

[0031] R—— Bending radius of the elbow pipe section, m;

[0032] α—— Bending angle of the elbow pipe section, °;

[0033] K 1 , K 2 , K 3 are the constant terms of the pressure loss models for the straight pipe section, elbow pipe section, and tapered pipe section, respectively, and are obtained by fitting through the least squares method.

[0034] Preferably, in step six, the pressure loss equation is optimized: parameter optimization is carried out with the lowest pressure loss equation as the goal to determine the pipeline geometric structure parameters that minimize the pressure loss.

[0035] Therefore, the present invention adopts the above-mentioned method for optimizing the structure of the conveying pipe of a wet shotcreting machine based on CFD, and has the following beneficial effects:

[0036] The method of the present invention combines numerical simulation with parameter optimization to systematically study the influence of the structural parameters of straight pipes, bent pipes, and tapered pipes on the pressure loss of concrete flow, thereby achieving the optimization of pipeline design, effectively reducing the pressure loss during concrete transportation, improving the transportation efficiency of wet shotcreters, and having important engineering value.

[0037] The following further describes the technical solutions of the present invention in detail through the accompanying drawings and embodiments. Description of the Drawings

[0038] Figure 1 It is a schematic flow chart of the method of the embodiment of the present invention. Specific Embodiments

[0039] In order to make the objectives, technical solutions, and advantages of the embodiments disclosed in the present invention clearer, the following further elaborates on the embodiments of the present invention in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts fall within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout.

[0040] It should be noted that the terms "comprising" and "having", and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or server that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0041] Similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0042] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is customarily placed during use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0043] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "arrangement", "installation", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] Embodiment

[0045] As Figure 1 shown, a method for optimizing the design of the conveying pipe structure of a wet shotcreting machine based on CFD according to the present invention includes the following steps:

[0046] Step 1: Obtain the characteristic parameters of the mixed concrete material, including density, yield stress, and plastic viscosity.

[0047] Step 2: According to the actual working conditions of the conveying pipe of the wet shotcreting machine, determine the geometric dimension parameters of the straight pipe, elbow pipe, and taper pipe, establish a three-dimensional model of the pipeline, use the Fluent module in ANSYS, import the three-dimensional model of the conveying pipe of the wet shotcreting machine into the Geometry module in Fluent, and perform unstructured grid division.

[0048] The conveying pipe of the wet shotcreting machine mainly consists of a straight pipe, an elbow pipe, and a taper pipe. There are 5 groups each of the straight pipe radius, straight pipe length, elbow pipe curvature radius, elbow pipe bending angle, taper pipe length, taper pipe inlet radius, and taper pipe outlet radius. The parameters are shown in Table 1. The pipeline modeling is drawn using SolidWorks software. First, select the right view reference plane and establish a sketch Figure 1 Use the sketch drawing command to draw a line segment connecting an arc with a certain curvature radius; select the front view reference plane, establish Sketch 2, and use the sketch drawing command to draw a circle with the end point of the line segment as the center; use the sweep command to set the sketch Figure 1 as the path and Sketch 2 as the profile for sweeping to form a section of straight pipe and a section of elbow pipe; select the front view reference plane, establish Sketch 3, use the sketch drawing command to draw a trapezoid at the end of the elbow pipe, with its radius as the long base and the center as the right-angle vertex; use the revolve command to revolve Sketch 3 to obtain the taper pipe, and finally save it in Parasolid format.

[0049] The parameters of the straight pipe include the length L 1 ; the parameters of the elbow pipe include the curvature radius R and the bending angle α; the parameters of the taper pipe include the length L 2 .

[0050] Table 1

[0051]

[0052] The model mesh division of the pipeline adopts tetrahedral unstructured mesh. Using the Fluent module in ANSYS, import the drawn model in Parasolid format in the Geometry module.

[0053] Using the Mesh module in ANSYS, define the inlet and outlet. The corresponding names of the inlet and outlet of the pipeline are inlet and outlet. Click Body Sizing in Mesh, and set the Element Size of Definition to 3mm; click Generate Mesh to generate the mesh.

[0054] Step 3: Set the physical model. Select the Standard k-epsilon model (Standard k-∈ turbulence model) for the turbulence model, set the concrete as the Bingham non-Newtonian fluid model, and define the density, yield stress, and viscosity parameters. Specifically:

[0055] Enter the Setup module in Fluent, enter the following command in the window to open the non-Newtonian fluid "define / models / viscous / turbulence-expert / turb-non-newtonian", then press Enter, enter y, and then press Enter.

[0056] Enter the Materials module in Fluent, create a new fluid material concrete, select the non-Newtonian fluid for the viscosity model, set the density as ρ, the plastic viscosity as η, and the yield stress as σ y .

[0057] Select the fluid material as concrete in Cell Zone Conditions.

[0058] Step 4: Define the boundary conditions. Set the inlet boundary condition of the wet shotcreting machine delivery pipe as the velocity inlet, and set the outlet boundary condition of the wet shotcreting machine delivery pipe as the pressure outlet. Use the SIMPLE algorithm to solve and complete the numerical calculation of the pressure loss. Specifically:

[0059] In the Boundary Condition, set the inlet boundary inlet as the velocity inlet, define it as v, set the outlet boundary outlet as the free out flow, the pipe wall as the non-slip rough wall, and the gravitational acceleration as g.

[0060] Select SIMPLE in the calculation method of solution methods, click Initialize for initialization. Click Run calculation, set the number of iteration steps to n, click Calculate for calculation simulation. The simulation process can be judged according to the residual curve graphs of various parameters shown and the calculation status and calculation steps displayed in the information bar. Wait until all residuals are less than 10 -6 magnitude, then the software automatically stops iteration. After the simulation is completed, save the case and date files.

[0061] Use the CFD-post section in ANSYS for post-processing. Open the case and date files of the simulation results, import the calculation data, and obtain the pressure losses of the straight pipe section, elbow section, and tapered pipe section.

[0062] Step five, based on the least squares method, linearly fit the relationship equation between the pressure loss and the geometric parameters of the wet spraying machine conveying pipe: establish a pressure loss equation for fitting. According to the simulation results, establish a linear relationship equation between the structural parameters of the straight pipe, elbow, and tapered pipe and the pressure loss.

[0063] Pipe parameter L 1 , R, α, L 2 Set 5 groups for simulation;

[0064] The relationship equation between the pressure loss and the pipeline structure parameters is obtained by linear fitting through the least squares method according to the pressure calculation results of 5 groups of pipeline parameters. The formula is as follows:

[0065] △P 直 =f(L 1 )=a + k 1 L 1 ;

[0066] △P 弯 =f(R, α)=b + K 2 R + K 3 α;

[0067] △P 锥 =f(L 2 )=c + K 3 L 2 ;

[0068] △P 总 =f(L 1 ) + f(R, α) + f(L 2 );

[0069] In the formula:

[0070] △P 直 —— The pressure loss of the straight pipe section, Pa;

[0071] △P 弯 —— Pressure loss of the elbow section, Pa;

[0072] △P 锥 —— Pressure loss of the conical section, Pa;

[0073] △P 总 —— Pressure loss of the entire pipeline, Pa;

[0074] L 1 —— Length of the straight pipe section, m;

[0075] L 2 —— Length of the conical section, m;

[0076] R —— Bending radius of the elbow section, m;

[0077] α —— Bending angle of the elbow section, °;

[0078] K 1 、K 2 、K 3 Are the constant terms of the pressure loss models for the straight pipe section, elbow section, and conical section respectively, and are obtained by least squares fitting.

[0079] Step six, use the single-objective optimization algorithm to optimize the geometric parameters of the conveying pipe of the wet shotcrete machine. Optimize the pressure loss equation, and perform parameter optimization with the lowest pressure loss equation as the goal to determine the pipeline geometric structure parameters that minimize the pressure loss.

[0080] Adopt the single-objective optimization algorithm with △P 总 = f(L 1 ) + f(R, α) + f(L 2 ) as the objective function, and L 1 (L 1min , L 1max ), L 2 (L 2min , L 2max ), α(α min , α max ), R(R min , R max ) as the constraint conditions for analysis, and obtain the structural parameters of each section of the conveying pipe when the pressure loss is minimized.

[0081] Therefore, the present invention adopts the above-mentioned structural optimization design method for the conveying pipe of the wet shotcrete machine based on CFD. Through numerical simulation combined with parameter optimization, it systematically studies the influence of the structural parameters of the straight pipe, elbow, and cone on the pressure loss of concrete flow, thereby realizing the optimization of pipeline design, effectively reducing the pressure loss during concrete conveying, and thus improving the conveying efficiency of the wet shotcrete machine, which has important engineering value.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A CFD-based wet spraying machine conveying pipe structure optimization design method, characterized by: The following steps are involved: Step 1, obtaining the material characteristic parameters of the mixed concrete, including density, yield stress and plastic viscosity; Step 2: According to the actual working conditions of the wet spraying machine delivery pipe, the geometric size parameters of the straight pipe, the curved pipe and the tapered pipe are determined, a three-dimensional model of the pipeline is established, and the three-dimensional model is imported into the Fluent module of the ANSYS software for unstructured mesh division; Step 3: Set the physical model, select the Stand k-epsilon model for the turbulence model, set the concrete to the Bingham non-Newtonian fluid model, and define the density, yield stress, and viscosity parameters; Step 4: Define boundary conditions. The boundary condition of the wet spraying machine delivery pipe inlet is set as the velocity inlet, and the boundary condition of the wet spraying machine delivery pipe outlet is set as the pressure outlet. The SIMPLE algorithm is used to solve and complete the numerical calculation of pressure loss. Step 5: linearly fit the relationship equation between pressure loss and geometric parameters of the wet spraying machine delivery pipe based on the least square method; Step six: Use the single-objective optimization algorithm to optimize the geometric parameters of the wet spraying machine delivery pipe.

2. The CFD-based wet spraying machine conveying pipe structure optimization design method according to claim 1 is characterized in that: In step 2, the wet shotcrete delivery pipe modeling was drawn using SolidWorks software and saved in Parasolid format.

3. The CFD-based wet spraying machine delivery pipe structure optimization design method according to claim 2 is characterized by: In step 2, the straight tube parameters include the length L1, the curved tube parameters include the curvature radius R and the bending angle α, and the tapered tube parameters include the length L 2。 4. The CFD-based wet spraying machine conveying pipe structure optimization design method according to claim 3 is characterized by: In step 2, the Fluent module in ANSYS is used to import the three-dimensional model of the wet spraying machine conveying pipe into the Geometry module in Fluent.

5. The CFD-based wet spraying machine delivery pipe structure optimization design method according to claim 4 is characterized in that: The model mesh of the wet shotcrete conveying pipe adopts tetrahedral unstructured mesh. The three-dimensional model of the wet shotcrete conveying pipe is imported into the FLUENT mesh module, and the inlet and outlet of the wet shotcrete conveying pipe are defined. The corresponding names of the inlet and outlet of the wet shotcrete conveying pipe are inlet and outlet.

6. The CFD-based wet spraying machine conveying pipe structure optimization design method according to claim 5 is characterized in that: In step 4, solution settings: select SIMPLE in the calculation method in solution methods, click Initialize to initialize, click Run calculation to set the number of iterations, and click Calculate to perform calculation simulation; post-processing analysis: analyze the pressure field of the fluid in the Result module and calculate the pressure loss in different areas of the wet spraying machine delivery pipe.

7. The CFD-based wet spraying machine conveying pipe structure optimization design method according to claim 6 is characterized by: In step five, pressure loss equation fitting: according to the simulation results, the linear relationship equation between the structural parameters of the straight pipe, curved pipe and tapered pipe and the pressure loss is established.

8. The CFD-based wet spraying machine conveying pipe structure optimization design method according to claim 7 is characterized by: The pipeline parameters L1, R, α, and L2 were set to 5 groups for simulation; The relationship equation between pressure loss and pipeline structural parameters is obtained by least squares linear fitting based on the pressure calculation results of 5 sets of pipeline parameters. The formula is as follows: △P 直 =f(L1)=a+k1L1; △P 弯 =f(R,α)=b+K2R+K3α; <h2 style=";text-align:left;direction:ltr">△P<h2 style=";text-align:left;direction:ltr"> 锥 <h2 style=";text-align:left;direction:ltr"> (f(L2)=c+K3L2) △P 总 =f(L1)+f(R,α)+f(L2); Where: △P 直 ——pressure loss in straight pipe section, Pa; △P 弯 ——Pressure loss in the bend section, Pa; △P 锥 ——Pressure loss of the tapered pipe section, Pa; △P 总 ——pressure loss of the entire pipeline, Pa; L1——the length of the straight pipe section, m; L2——the length of the tapered pipe section, m; R——bending radius of the curved pipe section, m; α——bending angle of the elbow section, °; K1, K2, and K3 are the constant terms of the pressure loss models of the straight pipe section, the curved pipe section, and the tapered pipe section, respectively, and are obtained by fitting using the least squares method.

9. The CFD-based wet spraying machine delivery pipe structure optimization design method according to claim 8 is characterized by: In step six, pressure loss equation optimization: parameter optimization is performed with the minimum pressure loss equation as the goal to determine the pipeline geometric structure parameters that minimize the pressure loss.

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