An efficient hydrodynamic simulation method for energy absorption / dissipation type ocean structures

Abstract

The present invention discloses an efficient hydrodynamic simulation method for an energy absorption / dissipation type marine structure, belonging to the technical field of ocean wave energy utilization. Instantaneous flow rate data is obtained, non-linear resistance is introduced, and a hydrodynamic simulation method is determined based on the Darcy-Forchheimer equation; the resistance coefficient of the perforated plate is calculated by combining the porosity and geometric characteristics of the perforated plate with empirical formulas; a reconstructed geometric model of the OWC device is established, meshed, a porous medium region and an inserted source term are set, and numerical simulation is carried out to obtain data and verify the efficiency of the dynamic behavior of the fluid. Taking the oscillating water column (OWC) wave energy device as an example, the present invention introduces a porous medium to replace the traditional small orifice and perforated plate damping methods, solves the problem of low calculation efficiency caused by small orifices, and at the same time calculates the non-linear resistance coefficient using the Darcy-Forchheimer formula. Finally, numerical simulation and verification are carried out to ensure the high precision of the simulation results, providing a scientific basis and technical support for subsequent hydrodynamic numerical simulation methods.

Description

Technical Field

[0001] The present invention belongs to the technical field of ocean wave energy utilization, and particularly relates to an efficient hydrodynamic simulation method for an energy absorption / dissipation type ocean structure. Background Art

[0002] With the increasing severity of environmental problems such as global warming, achieving low-carbon economy and sustainable development has become the focus of global attention. Among many renewable energy sources, wave energy has become an important research direction due to its rich reserves and convenient access. Among them, the oscillating water column (OWC) wave energy device has stood out among many wave energy technologies in recent years due to its unique advantages such as convenient installation, high safety, and strong ability to cope with extreme weather.

[0003] In academic research, using small air holes to replace the power take-off (PTO) damping in the OWC device is a relatively common research method at present. However, due to the small size of the air holes themselves, especially in two-dimensional conditions, in order to maintain similar damping effects, the opening size in the model often needs to be set extremely small. This brings significant problems in the numerical simulation process, that is, the air hole part needs to use very fine grids, which not only increases the total number of grids but also requires using extremely small time steps for simulation. The simulation time will increase exponentially, resulting in extremely low computational efficiency and being difficult to meet the requirements of actual engineering applications. And in the existing research in the application field of porous media that has been publicly disclosed, most of these studies focus on other fields, and there has not been extensive attention and a mature methodology for applying the porous media model to the simulation of air holes and perforated plates of OWC devices. Summary of the Invention

[0004] Aiming at the deficiencies in the background art, the purpose of the present invention is to propose an efficient hydrodynamic simulation method for an energy absorption / dissipation type ocean structure, including the following steps:

[0005] Step S1, obtain the instantaneous flow rate data in the air chamber, and based on the Darcy-Forchheimer equation, determine the hydrodynamic simulation method by combining linear resistance and nonlinear resistance;

[0006] Step S2, for the OWC device with a perforated plate, calculate the resistance coefficient of the perforated plate through the porosity and geometric characteristics of the perforated plate and in combination with empirical formulas;

[0007] Step S3, reconstruct the geometric model of the OWC device, perform mesh division on the geometric model, set the porous medium region and insert source terms, conduct numerical simulation, obtain the response data of the geometric model under different wave conditions, and finally verify the accuracy and efficiency of the fluid dynamic behavior in the numerical model.

[0008] Preferably, the specific process of determining the hydrodynamic simulation method in step S1 includes:

[0009] Step Sa1, obtain the experimental instantaneous flow rate and the simulated instantaneous flow rate in the air chamber through a wave height meter experiment and a numerical simulation method respectively;

[0010] Step Sa2, perform double verification and data fusion on the experimental instantaneous flow rate and the simulated instantaneous flow rate to obtain the instantaneous flow rate data;

[0011] Step Sa3, based on the Darcy-Forchheimer equation, determine the hydrodynamic simulation method by combining the instantaneous flow rate data and the corresponding local pressure drop data with linear resistance and nonlinear resistance.

[0012] Preferably, the specific process of obtaining the experimental instantaneous flow rate in step Sa1 is as follows:

[0013] Use a wave height meter to collect the wave height in the air chamber, and combine the liquid surface movement speed and the air chamber width to calculate the volume change rate of the gas to obtain the experimental instantaneous flow rate;

[0014] ① Set up the experimental device

[0015] Arrange a high-precision wave height meter, a flow velocity sensor and an air chamber width measuring device in the air chamber of the OWC device to ensure that the installation positions of the sensors accurately capture the instantaneous changes of the air chamber liquid surface;

[0016] ② Collect data

[0017] Assume that the fluid moves in a generally sinusoidal wave form, use a wave height meter to record the wave height data in the air chamber, and calculate the liquid surface movement speed by taking the derivative of the wave height data with respect to time , and its calculation formula is:

[0018]

[0019] In the formula represents the change amount of the wave height, and the difference calculation formula of the wave height change amount data is , represents the time interval, and the difference calculation formula of the time interval data is ;

[0020] In each time interval, calculate the experimental instantaneous flow rate according to the liquid surface movement speed and the air chamber width. The calculation formula of the experimental instantaneous flow rate is:

[0021]

[0022] In the formula represents the experimental instantaneous flow rate, v represents the liquid surface movement speed, that is, the instantaneous speed of the liquid surface movement,B Denote the width of the air chamber;

[0023] To ensure the stability and repeatability of the data, repeated experiments are carried out under multiple points and multiple working conditions;

[0024] ③ Preprocess the data

[0025] Filter and denoise the collected experimental instantaneous flow rate, and use statistical methods to average multiple experimental results to obtain a representative experimental instantaneous flow rate curve.

[0026] Preferably, the specific process of obtaining the simulated instantaneous flow rate in step Sa1 is as follows:

[0027] ① Construct the primary geometric model for simulation

[0028] Use CFD software to establish the primary geometric model of the OWC device, including the air chamber, opening, and bottom structure to reflect the physical characteristics of the actual device, set reasonable mesh division and boundary conditions, simulate the fluid motion in the air chamber under regular wave excitation conditions, and observe the complex phenomena of air flow velocity, pressure change, and vortex formation;

[0029] ② Calculate the simulated instantaneous flow rate

[0030] In the simulation of the primary geometric model of the OWC device established by CFD software, probe probes are arranged at key monitoring points in the air chamber to collect fluid velocity field and pressure field data in real time, and the instantaneous velocity of the air flow at the air hole is combined with the parameters of the primary geometric model of the air chamber opening to calculate the simulated instantaneous flow rate;

[0031] ③ Calibrate the preliminary parameters

[0032] Adjust the geometric model parameters according to the simulation results, and carry out corresponding calibration and verification to ensure the convergence of the numerical simulation and the matching with the actual flow field characteristics.

[0033] Preferably, the specific process of double verification and data fusion in step Sa2 is as follows:

[0034] ① Compare and analyze the data

[0035] Compare the experimental instantaneous flow rate and the simulated instantaneous flow rate, and use statistical methods, such as correlation coefficient and root mean square error, to display the comparison results and evaluate the consistency of the two groups of data;

[0036] ② Analyze the residuals and sensitivities of the data

[0037] Analyze the differences between the results of the two methods of experimental instantaneous flow rate and simulated instantaneous flow rate, find the possible reasons for the deviation, and adjust the parameters of the experiment or numerical simulation accordingly;

[0038] ③ Fuse and optimize the data

[0039] Verify the experimental instantaneous flow rate and the simulated instantaneous flow rate against each other to make up for the possible deficiencies of a single method; according to the comparison results, use weighted average or other data fusion techniques to optimize the accuracy and obtain the optimized instantaneous flow rate data, providing a more accurate basis for the subsequent solution of the linear resistance coefficient and the non-linear resistance coefficient.

[0040] Preferably, the specific process of determining the hydrodynamic simulation method based on the Darcy-Forchheimer equation in step Sa2 is as follows:

[0041] ① Data preparation

[0042] With the help of the instantaneous flow rate data and the corresponding local pressure drop data, perform preprocessing on them, including filtering and smoothing.

[0043] ② Establish a numerical model

[0044] Based on the Darcy-Forchheimer equation to describe the resistance characteristics of fluid flow in porous media, comprehensively consider the linear and non-linear flow effects, and establish a numerical model; calculate the Darcy-Forchheimer coefficient in porous media by writing a custom program, and calculate the local pressure drop with the help of the instantaneous flow rate data and relevant parameters. The calculation formula is:

[0045]

[0046]

[0047]

[0048] Where is the local pressure drop, q is the instantaneous flow rate data, is the cross-sectional area, is the hydrodynamic viscosity, is the fluid density, is the linear resistance caused by fluid viscosity, applicable to low-speed flow, is the linear resistance coefficient; is the non-linear resistance caused by inertial effects, applicable to high-speed flow, is the non-linear resistance coefficient;

[0049] For the numerical model of porous media containing only linear terms, let the resistance coefficient F = 0, and the simplified equation is:

[0050]

[0051] Further derivation gives the expression of the linear resistance coefficient D:

[0052]

[0053] For the numerical model of porous media considering the nonlinear term, a quadratic nonlinear term is introduced, and it is assumed that the resistance coefficient based on the nonlinear assumption D = 0, and the simplified equation is:

[0054]

[0055] Further derivation gives the expression of the nonlinear resistance coefficient F:

[0056]

[0057] By comparing the numerical model of porous media containing only the linear term coefficient D and the current numerical model of porous media considering the nonlinear term coefficient F to describe the resistance characteristics, and then confirming the hydrodynamic simulation method based on the Darcy - Forchheimer equation.

[0058] Preferably, the specific process of calculating the resistance coefficient of the perforated plate in step S2 is as follows:

[0059] Step Sb1, determine the porosity and geometric characteristics of the perforated plate

[0060] According to the design parameters of the perforated plate, measure or calculate the porosity and the geometric characteristics of the orifices, including the orifice diameter and orifice distribution, which determine the resistance characteristics of the fluid passing through the perforated plate and thus affect the effectiveness of the numerical model of porous media;

[0061] Step Sb2, calculate the resistance coefficient using Molin's empirical formula for porous structures

[0062] According to the porosity and geometric characteristics, use the empirical formula proposed by Molin for porous marine structures to calculate the resistance coefficient of the perforated plate ; this coefficient is used to describe the resistance of the perforated plate to the water flow and provides necessary and accurate parameters for subsequent numerical simulations to improve the reliability and accuracy of the simulation results;

[0063]

[0064]

[0065] Among them, is the local pressure drop, is the opening ratio of the perforated structure in the i - direction, is the empirical coefficient.

[0066] Preferably, the specific process of step S3 is as follows:

[0067] Step Sc1, Reconstructing the geometric model and meshing

[0068] According to the actual engineering requirements, use CFD software to establish a reconstructed geometric model of the OWC device. To reduce the computational burden in numerical simulation, magnify the small pore size, and adopt a 10-fold magnification strategy. , where is the original pore size, is the magnified pore size; use the meshing tool built into the hydrodynamic analysis software to perform preliminary meshing on the reconstructed geometric model; to capture key flow details, use local fine meshing for the porous medium region, and to reduce the computational amount, use coarse meshing for other regions;

[0069] Step Sc2, Wave generation module and constructing a numerical wave tank

[0070] Use the wave generation module in the hydrodynamic analysis software to construct a numerical wave tank and simulate the response of the reconstructed geometric model of the OWC device under different wave conditions; according to the set wave height, wave period, and water depth parameters, ensure that the numerical tank realistically reproduces the actual ocean wave action and provides reliable external wave excitation;

[0071] Step Sc3, Setting the porous medium region and inserting source terms

[0072] Through the previous meshing of the region containing small orifices and perforated plates, clearly determine the geometric range of the porous medium region; subsequently, create a new region named porousZone and set it to the explicitPorositySource type, so that it can be directly inserted into the hydrodynamic control equation as an external source term during the numerical simulation to reproduce the resistance effect when the fluid flows through this region; for the setting of physical properties, use the DarcyForchheimer model, where the Darcy linear resistance coefficient is uniformly set to (0, 0, 0), and the Forchheimer nonlinear resistance coefficient is assigned corresponding values in the X, Y, and Z directions according to the main flow direction of the fluid. Only the main flow direction component of the air flow is assigned non-zero values, and the remaining directions remain zero;

[0073] Step Sc4, Numerical simulation, obtaining data, and verification

[0074] Run the numerical simulation, iteratively solve the hydrodynamic control equation on the discrete grid; set multiple monitoring points to monitor the air pressure and flow velocity in the porous medium region in real time, obtain the response data of the OWC device under different wave conditions, compare the simulation data with the experimental data, and verify the accuracy of the numerical model through statistical indicators such as the correlation coefficient and root mean square error.

[0075] Compared with the prior art, the present invention proposes an efficient hydrodynamic simulation method for energy absorption / dissipation type ocean structures. The beneficial effects of this method are as follows:

[0076] 1. Significantly improve the numerical simulation efficiency

[0077] The hydrodynamic simulation method for the absorption / energy dissipation type ocean structure system proposed by the present invention can significantly improve the computational efficiency of numerical simulation; by using a porous medium model to replace the traditional small pore damping method, not only the required number of grids and time steps are reduced, but also the simulation speed is greatly improved by optimizing the calculation process; this makes the numerical simulation of the absorption / energy dissipation type ocean structure system more efficient and can efficiently meet the requirements of actual engineering design and optimization.

[0078] 2. Accurately estimate the non-linear damping coefficient to ensure high-precision simulation results

[0079] By introducing the Darcy-Forchheimer equation, the present invention accurately estimates the damping coefficient in the porous medium and can accurately depict the non-linear air pressure distribution characteristics at the pores and perforated plates of the absorption / energy dissipation type ocean structure system; this method effectively solves the accuracy problem caused by the complexity of hydrodynamics during the approximate simulation of small pores, ensuring that while significantly improving the simulation speed, the simulation results still maintain high precision and reliability, meeting the stringent engineering requirements.

[0080] 3. Wide applicability and simplified simulation process

[0081] The numerical simulation method of the present invention is not only applicable to the traditional OWC absorption / energy dissipation type ocean structure system, but also can effectively simulate the OWC structure with perforated plates, having wide applicability; by simplifying the numerical simulation process and parameter settings, the modeling complexity is reduced and the operability of the method is improved, enabling engineers to more conveniently design and optimize various forms of OWC devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 is the flowchart of the method of the present invention;

[0083] Figure 2 is the schematic diagram of the OWC wave energy device model with perforated plates of the present invention;

[0084] Figure 3 is the accuracy verification diagram of the current numerical model of the present invention;

[0085] Figure 4 is the comparison diagram of the grid encryption method at the pores, where (a) is the diagram of the conventional small hole grid encryption method and (b) is the encryption method diagram after enlarging the hole size. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0086] The following will further clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application. It should be noted that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0087] In order to make the invention purpose, technical solutions and advantages of the present application clearer, the following further details the embodiments of the present application in conjunction with the drawings of the specification: In order to better understand the above-mentioned purpose, features and advantages of the present invention, the following will further illustrate the advantages of the present invention through the comparison of embodiments in combination with the drawings and specific implementation manners.

[0088] The present invention proposes an efficient hydrodynamic simulation method for energy absorption / dissipation type ocean structures, mainly taking the oscillating water column (OWC) wave energy device as the research object, and studying the hydrodynamic numerical simulation situation on a porous ocean structure (porous medium model, such as an open-hole plate). The step process of this method is as Figure 1 shown, and the specific steps of this method are described in detail:

[0089] Step S1, obtain the instantaneous flow rate data in the air chamber, combine the linear resistance and the nonlinear resistance, and determine the hydrodynamic simulation method based on the Darcy-Forchheimer equation;

[0090] Step Sa1, obtain the experimental instantaneous flow rate and the simulated instantaneous flow rate in the air chamber through the wave height meter experiment and the numerical simulation method;

[0091] Specifically, the specific process of obtaining the experimental instantaneous flow rate in step Sa1 is as follows:

[0092] (1) Obtain the experimental instantaneous flow rate through the wave height meter experiment

[0093] Use a wave height meter to collect the wave height in the air chamber, combine the liquid surface movement speed and the air chamber width to calculate the volume change rate of the gas, and obtain the experimental instantaneous flow rate;

[0094] ① Set up the experimental device

[0095] Arrange a high-precision wave height meter, a flow velocity sensor and an air chamber width measuring device in the air chamber of the OWC device to ensure that the installation positions of the sensors accurately capture the instantaneous changes of the air chamber liquid surface;

[0096] ② Collect data

[0097] Assume that the fluid moves in a generally sinusoidal wave form, use a wave height meter to record the wave height data in the air chamber, and calculate the liquid surface movement speed by taking the derivative of the wave height data with respect to time , and its calculation formula is:

[0098]

[0099] In the formula It represents the change of wave height (unit: m). The differential calculation formula of wave height change data is: , Represents the time interval (unit: s). The differential calculation formula for the time interval data is: ;

[0100] In each time interval, the experimental instantaneous flow rate is calculated according to the liquid surface movement speed and the air chamber width. The calculation formula is:

[0101]

[0102] In the formula Indicates the instantaneous flow rate of the experiment (unit: m 3 / s), v Indicates the liquid surface movement speed, that is, the instantaneous speed of the liquid surface movement (unit: m / s), B Indicates the width of the air chamber (unit: m);

[0103] To ensure the stability and repeatability of the data, repeated experiments were conducted at multiple points and under multiple working conditions;

[0104] ③Preprocessing data

[0105] The collected experimental instantaneous flow is filtered and denoised, and multiple experimental results are averaged using statistical methods to obtain a representative experimental instantaneous flow curve;

[0106] (2) Numerical simulation method to obtain simulated instantaneous flow

[0107] ①Construction and simulation of geometric models

[0108] The primary geometric model of the OWC device is established using CFD software, such as Figure 2 As shown, it includes air chambers, openings, bottom structures, etc., to accurately reflect the physical characteristics of the actual device, set reasonable grid division and boundary conditions, simulate the fluid movement in the air chamber under regular wave excitation conditions, and observe complex phenomena such as air flow velocity, pressure changes and vortex formation;

[0109] ② Calculate and simulate instantaneous flow

[0110] In the simulation of the primary geometric model of the OWC device established by CFD software, probes are arranged at key monitoring points such as the interior of the air chamber and the orifice to collect fluid velocity field and pressure field data in real time, and the instantaneous velocity of the air flow at the orifice is combined with the primary geometric model parameters of the air chamber opening to calculate and simulate the instantaneous flow rate;

[0111] ③Calibrate preliminary parameters

[0112] Adjust the geometric model parameters according to the simulation results, and perform corresponding calibration and verification to ensure the convergence of numerical simulation and the matching with the actual flow field characteristics;

[0113] Step Sa2: Perform double verification and data fusion on the experimental instantaneous flow rate and the simulated instantaneous flow rate to obtain the instantaneous flow rate data;

[0114] Specifically, the specific process of the double verification and data fusion in the step Sa2 is as follows:

[0115] ①Compare and analyze the data

[0116] Compare the experimental instantaneous flow rate and the simulated instantaneous flow rate, and use statistical methods (such as correlation coefficient, root mean square error, etc.) to display the comparison results and evaluate the consistency of the two groups of data;

[0117] ②Analyze the residuals and sensitivity (i.e., the difference between the predicted value and the actual value)

[0118] Analyze the differences between the results of the two methods of the experimental instantaneous flow rate and the simulated instantaneous flow rate, find the possible reasons for the deviation, and adjust the parameters of the experiment or numerical simulation accordingly;

[0119] ③Fuse and optimize the data

[0120] Mutually verify the experimental instantaneous flow rate and the simulated instantaneous flow rate to make up for the possible deficiencies of a single method; according to the comparison results, use weighted average or other data fusion technologies to optimize the accuracy, obtain the optimized instantaneous flow rate data, improve the reliability and accuracy of the instantaneous flow rate data, and provide a more accurate basis for the subsequent solution of the resistance coefficient D and F of.

[0121] Step Sa3: Based on the Darcy-Forchheimer equation, determine the hydrodynamic simulation method by combining the instantaneous flow rate data and the corresponding local pressure drop data, together with the linear resistance and the nonlinear resistance.

[0122] Specifically, the specific process of determining the hydrodynamic simulation method based on the Darcy-Forchheimer equation in the step Sa3 is as follows:

[0123] ①Data preparation

[0124] With the help of the instantaneous flow rate data and the corresponding local pressure drop data, preprocess the original data (filtering, smoothing, etc.) to ensure the accuracy of the data;

[0125] ②Establish a numerical model

[0126] Based on the Darcy-Forchheimer equation to describe the resistance characteristics of fluid flow in porous media, integrating linear and nonlinear flow effects, a numerical model is established; by writing a custom program to calculate the Darcy-Forchheimer coefficient in porous media, and using the instantaneous flow rate data and relevant parameters to calculate the local pressure drop, and its calculation formula is:

[0127]

[0128]

[0129]

[0130] where is the local pressure drop, q is the instantaneous flow rate data, is the cross-sectional area, is the dynamic viscosity of the fluid, is the fluid density, is the linear resistance caused by fluid viscosity, applicable to low-speed flow, is the linear resistance coefficient; is the nonlinear resistance caused by inertial effects, applicable to high-speed flow, is the nonlinear resistance coefficient;

[0131] For the numerical model of porous media containing only linear terms, let the resistance coefficient F = 0, and the simplified equation is:

[0132]

[0133] Further derivation gives the expression of the linear resistance coefficient D:

[0134]

[0135] For the numerical model of porous media considering nonlinear terms, introduce the quadratic nonlinear term, and assume that the resistance coefficient D = 0, and the simplified equation is:

[0136]

[0137] Further derivation gives the expression of the nonlinear resistance coefficient F:

[0138]

[0139] By comparing the resistance characteristics described by the numerical model of porous media containing only the linear term coefficient D and the current numerical model of porous media considering the nonlinear term coefficient F such as Figure 3As shown, the accuracy of the current numerical model of the porous medium is further verified, and the hydrodynamic simulation method based on the Darcy-Forchheimer equation is further confirmed.

[0140] Step S2, for the OWC device with an orifice plate, based on the porosity and geometric characteristics of the orifice plate, the resistance coefficient of the orifice plate is calculated by combining empirical formulas, further improving the application of the numerical model of the porous medium under different structures;

[0141] Specifically, the specific process of calculating the resistance coefficient of the orifice plate in step S2 is as follows:

[0142] Step Sb1, determine the porosity and geometric characteristics of the orifice plate

[0143] According to the design parameters of the orifice plate, measure or calculate the porosity and geometric characteristics of the orifice (such as orifice diameter, orifice distribution, etc.), which determine the resistance characteristics of the fluid passing through the orifice plate and thus affect the effectiveness of the numerical model of the porous medium;

[0144] Step Sb2, calculate the resistance coefficient using Molin's empirical formula for porous structures

[0145] According to the porosity and geometric characteristics, use the empirical formula for porous marine structures proposed by Molin to calculate the resistance coefficient of the orifice plate ; This coefficient is used to describe the resistance of the orifice plate to the water flow, providing necessary and accurate parameters for subsequent numerical simulations to improve the reliability and accuracy of the simulation results;

[0146]

[0147]

[0148] where is the local pressure drop, is the orifice opening ratio of the orifice structure in the i direction, generally taking values such as 10%, 20%, 30%, etc., is the empirical coefficient, and when the orifice opening ratio is less than 50%, the value ranges between 0.3 and 0.4;

[0149] Reference: Molin, B., 2011. Hydrodynamic modeling of perforated structures. Appl. Ocean Res. 33(1), 1–11.

[0150] Step S3: Establish the reconstructed geometric model of the OWC device, perform mesh division on the reconstructed geometric model, set the porous medium region and insert source terms, conduct numerical simulations, obtain the response data of the reconstructed geometric model under different wave conditions, and finally verify the accuracy and efficiency of the fluid dynamic behavior in the numerical model.

[0151] Specifically, the specific process of step S3 is as follows:

[0152] Step Sc1: Reconstruct the geometric model and perform mesh division

[0153] Establish the reconstructed geometric model of the OWC device using CFD software according to the actual engineering requirements to ensure the accuracy of numerical simulations; to reduce the computational burden in numerical simulations, magnify the small air hole size using a 10-fold magnification strategy, , where is the original air hole size, is the magnified air hole size; when the small air hole size is too small, extremely fine grids are required to accurately capture the flow details, and this kind of high-density grid will greatly increase the computational amount; by appropriately magnifying the air hole size and defining this as the porous medium region, the accuracy requirements for local mesh division can be reduced, thereby improving the overall simulation efficiency;

[0154] Use the mesh division tool built into the hydrodynamic analysis software to perform preliminary mesh division on the reconstructed geometric model; use local fine mesh division for the porous medium region to capture key flow details; other regions can use coarse mesh division to reduce the overall computational amount, thus taking into account both accuracy and computational efficiency; the mesh division diagram is as Figure 4 shown;

[0155] Step Sc2: Wave generation module and construction of the flume

[0156] Use the wave generation module in the hydrodynamic analysis software to construct a numerical wave flume to simulate the response of the reconstructed geometric model of the OWC device under different wave conditions; according to the set parameters such as wave height, wave period, and water depth, ensure that the numerical flume can realistically reproduce the actual ocean wave action and provide reliable external wave excitation; different combinations of wave height, wave period, and water depth represent different sea conditions, and by simulating the response of the OWC device under these different sea conditions, the performance of the device can be comprehensively evaluated;

[0157] Step Sc3: Set the porous medium region and insert source terms

[0158] Through the previous meshing of the area containing the small orifice and the perforated plate, the geometric range of the porous medium area was clearly determined; subsequently, a new area named porousZone was created and set to the explicitPorositySource type, so that it could be directly inserted into the hydrodynamic control equation as an external source term during the numerical simulation to reproduce the resistance effect when the fluid flows through this area; for the setting of physical properties, the DarcyForchheimer model was adopted, where the Darcy linear resistance coefficient was uniformly set to (0, 0, 0), while the Forchheimer nonlinear resistance coefficient was assigned corresponding values in the X, Y, and Z directions according to the main flow direction of the fluid. Only the main direction component of the air flow was assigned non-zero values, and the remaining directions remained zero;

[0159] Step Sc4, numerical simulation, data acquisition, and verification

[0160] Run the numerical simulation, iteratively solve the control equation on the discrete grid, and then obtain the response of the internal fluid of the OWC device under different wave conditions; set multiple monitoring points to monitor key parameters such as air pressure and flow velocity in the porous medium area in real time, so as to obtain the response data of the OWC device under different wave conditions. Compare the simulation data with the experimental or reference data, and verify the accuracy of the numerical model through statistical indicators such as the correlation coefficient and root mean square error;

[0161] The data shows that the above numerical simulation strategy can improve the overall simulation speed by 3 - 10 times, while keeping the key flow characteristics within a reasonable error range, providing an accurate basis for the design and optimization of the OWC device; the comparison of relevant calculation speeds is shown in Table 1.

[0162] Table 1 Comparison of calculation speeds

[0163]

[0164] Table 1 compares the calculation speeds of the conventional small orifice simulation and the porous medium model under different calculation conditions. Both models use 520,000 grid cells and 128 computing cores, but the conventional small orifice simulation takes 36 hours, while the porous medium model only takes 10 hours, and the calculation speed is increased by about 3.6 times. Moreover, for the turbulence model, the conventional small orifice simulation takes 89 hours, while the porous medium model only takes 9 hours, and the calculation speed is increased by about 9.9 times; in summary, adopting the porous medium model can significantly improve the calculation speed while maintaining the accuracy of the key flow characteristics, which provides a powerful numerical simulation tool for the design and optimization of the OWC device.

[0165] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present application.

[0166] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

1. A highly efficient hydrodynamic simulation method for energy absorbing / dissipating marine structures, characterized in that: include: Step S1, obtaining instantaneous flow data in the air chamber, combining linear resistance and nonlinear resistance, and determining a hydrodynamic simulation method based on the Darcy-Forchheimer equation; Step Sa1, obtaining the experimental instantaneous flow rate and the simulated instantaneous flow rate in the air chamber by using a wave height meter experiment and a numerical simulation method respectively; Step Sa2, double verification and data fusion of the experimental instantaneous flow and the simulated instantaneous flow to obtain instantaneous flow data; Step Sa3, combining the instantaneous flow data and the corresponding local pressure drop data with the linear resistance and the nonlinear resistance, and determining the hydrodynamic simulation method based on the Darcy-Forchheimer equation; ①Data preparation With the help of instantaneous flow data and corresponding local pressure drop data, pre-processing is performed on them, including filtering and smoothing; ② Establish a numerical model Based on the Darcy-Forchheimer equation, the resistance characteristics of fluid flow in porous media are described, and the linear and nonlinear flow effects are integrated to establish a numerical model. The Darcy-Forchheimer coefficient in porous media is calculated by writing a custom program, and the local pressure drop is calculated with the help of instantaneous flow data and related parameters. The calculation formula is: ； ； ； In the formula is the local pressure drop, q is the instantaneous flow data, is the cross-sectional area, is the fluid dynamic viscosity, is the fluid density, It is the linear resistance caused by fluid viscosity and is applicable to low-speed flow. is the linear resistance coefficient; It is a nonlinear resistance caused by inertial effect and is suitable for high-speed flow. is the nonlinear resistance coefficient; For numerical models of porous media containing only linear terms, let the resistance coefficient based on the linear assumption be F = 0, the simplified equation is: ; The expression of linear resistance coefficient D is further derived: ; For the numerical model of porous media considering nonlinear terms, a quadratic nonlinear term is introduced and the resistance coefficient based on the nonlinear assumption is assumed to be D = 0, the simplified equation is: ； In the formula is the nonlinear resistance coefficient, is the fluid density, is the instantaneous flow data, is the cross-sectional area; The expression of the nonlinear resistance coefficient F is further derived: ; By comparing the linear coefficients D The numerical model of porous media and the coefficient of nonlinear term currently considered F The resistance characteristics of porous media described by numerical models are confirmed by the hydrodynamic simulation method based on the Darcy-Forchheimer equation; Step S2, for the OWC device with a perforated plate, the resistance coefficient of the perforated plate is calculated by combining the porosity and geometric characteristics of the perforated plate with an empirical formula; Step S3, establish a reconstructed geometric model of the OWC device, mesh the reconstructed geometric model, set the porous medium area and insert the source term, perform numerical simulation, obtain the response data of the reconstructed geometric model under different wave conditions, and finally verify the accuracy and efficiency of the fluid dynamic behavior in the numerical model.

2. The method for simulating high-efficiency hydrodynamics of an energy absorbing / dissipating marine structure according to claim 1, characterized in that: The specific process of obtaining the experimental instantaneous flow in step Sa1 is as follows: The wave height in the air chamber is collected using a wave height meter, and the volume change rate of the gas is calculated by combining the liquid surface movement speed and the width of the air chamber to obtain the experimental instantaneous flow rate; ① Set up the experimental device A high-precision wave height meter, flow velocity sensor and air chamber width measuring device are arranged in the air chamber of the OWC device, so that the sensor installation position can accurately capture the instantaneous changes of the air chamber liquid level; ② Collect data Assuming that the fluid moves in a sinusoidal form, the wave height data in the air chamber is recorded using a wave height meter, and the liquid surface movement speed is calculated by taking the derivative of the wave height data over time. , and its calculation formula is: ； In the formula It represents the change of wave height. The differential calculation formula of wave height change data is: , Represents the time interval. The differential calculation formula for the time interval data is: ; In each time interval, the experimental instantaneous flow rate is calculated according to the liquid surface movement speed and the air chamber width. The calculation formula is: ; In the formula represents the instantaneous flow rate of the experiment, It represents the liquid surface movement speed, that is, the instantaneous speed of the liquid surface movement. Indicates the width of the air chamber; To ensure the stability and repeatability of the data, repeated experiments were conducted at multiple points and under multiple working conditions; ③Preprocessing data The collected experimental instantaneous flow is filtered and denoised, and multiple experimental results are averaged using statistical methods to obtain a curve of representative experimental instantaneous flow.

3. The method for simulating high-efficiency hydrodynamics of energy absorbing / dissipating marine structures according to claim 1, characterized in that: In step Sa1, the specific process of obtaining the simulated instantaneous flow is as follows: ①Build and simulate primary geometric models Use CFD software to establish the primary geometric model of the OWC device, set reasonable meshing and boundary conditions, and simulate the fluid movement in the air chamber under regular wave excitation conditions; ② Calculate and simulate instantaneous flow In the simulation of the primary geometric model of the OWC device established by CFD software, probes are arranged at key monitoring points of the air chamber to collect fluid velocity field and pressure field data in real time, and the instantaneous velocity of the air flow at the pores is combined with the primary geometric model parameters of the air chamber opening to calculate and simulate the instantaneous flow rate; ③ Calibrate preliminary parameters The primary geometric model parameters are adjusted according to the simulated instantaneous flow, and corresponding calibration and verification are performed to ensure the convergence of the numerical simulation and the matching with the actual flow field characteristics.

4. The method for simulating high-efficiency hydrodynamics of energy absorbing / dissipating marine structures according to claim 1, characterized in that: In step Sa2, the specific process of double verification and data fusion of the experimental instantaneous flow and the simulated instantaneous flow is as follows: ①Comparative analysis data Compare the experimental instantaneous flow rate with the simulated instantaneous flow rate, use statistical methods to display the comparison results, and evaluate the consistency of the two sets of data; ②Analyze the residuals and sensitivity of the data Analyze the differences between the results of the experimental instantaneous flow and the simulated instantaneous flow, find possible causes of deviation, and adjust the parameters of the experiment or numerical simulation accordingly; ③Integrate and optimize data The experimental instantaneous flow rate and the simulated instantaneous flow rate are mutually verified to make up for the possible shortcomings of a single method; based on the comparison results, data fusion technology is used to optimize the accuracy and obtain optimized instantaneous flow data, providing a more accurate basis for the subsequent solution of the linear resistance coefficient and the nonlinear resistance coefficient.

5. The method for simulating high-efficiency hydrodynamics of energy absorbing / dissipating marine structures according to claim 1, characterized in that: The specific process of calculating the resistance coefficient of the perforated plate in step S2 is as follows: Step Sb1, determine the porosity and geometric characteristics of the perforated plate According to the design parameters of the perforated plate, the porosity and orifice geometric characteristics are measured or calculated, which determine the resistance characteristics of the fluid passing through the perforated plate; Step Sb2, calculating the resistance coefficient using Molin's empirical formula for porous structures Based on the porosity and geometric characteristics, the resistance coefficient of the perforated plate is calculated using the empirical formula for porous marine structures proposed by Molin. ; This coefficient is used to describe the resistance of the perforated plate to water flow and provide necessary and accurate parameters for subsequent numerical simulations; ; ； in, is the local pressure drop, is the porosity of the open-pore structure in the i direction, is the empirical coefficient, is the fluid density, is the nonlinear resistance coefficient, Indicates the speed of liquid surface movement.

6. A highly efficient hydrodynamic simulation method for energy absorbing / dissipating marine structures according to claim 1, characterized in that: The specific process of step S3 is as follows: Step Sc1: Reconstruct the geometry model and mesh division According to the actual engineering requirements, the CFD software was used to establish the reconstructed geometric model of the OWC device. In order to reduce the computational burden in the numerical simulation, the small pore size was enlarged and a 10-fold enlargement strategy was adopted. , where is the original pore size, The pore size after enlargement; The meshing tool built into the hydrodynamic analysis software is used to perform preliminary meshing on the reconstructed geometric model: local fine meshing is used for the porous medium area, and coarse meshing is used for other areas; Step Sc2, wave generation module and construction of numerical wave flume Use the wave generation module in the hydrodynamic analysis software to build a numerical wave tank to simulate the response of the reconstructed geometric model of the OWC device under different wave conditions; according to the set wave height, wave period and water depth parameters, ensure that the numerical wave tank realistically reproduces the actual ocean wave action and provides reliable wave external excitation; Step Sc3, setting the porous media region and inserting source terms Through the early meshing of the area containing small orifices and perforated plates, the geometric range of the porous medium area is clearly determined; then, a new area named porousZone is created and set to the explicitPorositySource type so that it can be directly inserted into the hydrodynamic control equation as an external source term during the numerical simulation process to reproduce the resistance effect of the fluid flowing through this area; for the setting of physical properties, the DarcyForchheimer model is adopted, in which the Darcy linear resistance coefficient is uniformly set to (0,0,0), and the Forchheimer nonlinear resistance coefficient is assigned corresponding values ​​in the X, Y, and Z directions according to the main flow direction of the fluid. Only the main direction component of the airflow is assigned a non-zero value, and the other directions remain zero; Step Sc4: numerical simulation, data acquisition and verification Numerical simulations were performed to iteratively solve the hydrodynamic control equations on discrete grids. Multiple monitoring points were set to monitor the air pressure and flow velocity in the porous medium area in real time, and the response data of the OWC device under different wave conditions were obtained. The numerical simulation data were compared with the experimental data, and statistical methods were used to verify the accuracy of the fluid dynamic behavior in the numerical model.

Images