Method for reconstructing air flow field above ship based on analogue simulation

Abstract

The invention discloses a method for reconstructing an air flow field over a ship based on analogue simulation, a laser wind finding radar is installed on the ship, and the method specifically comprises the following steps: S1, determining a reconstruction type of the air flow field over the ship; s2, when the distance between the ship and the laser wind finding radar is 0-20 m, reconstructing an air flow field above the ship through a simulation data result of CFD simulation; s3, when the distance from the laser wind finding radar is 50-200m, reconstructing an air flow field above the ship through an actual measurement data result of the laser wind finding radar; s4, when the distance is 20-50m from the laser wind finding radar, performing data fusion on a simulation data result of CFD analogue simulation and an actual measurement data result of the laser wind finding radar to reconstruct an air flow field above the ship; and S5, performing data correction on the fused data to complete reconstruction of the air flow field above the ship. According to the method, the ship body model is established, grid division is carried out on the air flow field near the ship body to finish simulation of the air flow field above the ship body, and the precision and efficiency of reconstruction of the air flow field above the ship are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of ship air flow fields, and in particular relates to a method for reconstructing the air flow field on a ship based on simulation. Background Art

[0002] In order to meet the needs of detecting three-dimensional wind fields above ships, the first is to use the ship-borne meteorological observation equipment equipped on the ship. The wind measurement data of the ship-borne automatic weather station needs to be corrected by the ship's speed and direction to obtain the real wind direction and speed data. The second is to use ship-borne laser wind measurement radar, which can realize the three-dimensional space atmospheric wind field measurement in the range of 6 to 500m. The third is that the research on the characteristics of the airflow field mainly uses wind tunnel scaled models, multi-sensor point source detection and CFD simulation analysis methods.

[0003] However, the atmospheric wind field above the ship deck is complex and changeable, and there is a lack of wind field detection means. The fixed-position shipborne meteorological observation equipment cannot effectively reflect the wind field distribution in the three-dimensional space above the deck. The shipborne laser wind radar has a high blind spot and a large inversion error, which cannot well reflect the actual three-dimensional wind field situation. In addition, the shipborne laser wind radar and wind field sensor's three-dimensional wind field data comprehensive reconstruction technology capabilities are insufficient. There is an urgent need for a fusion reconstruction method of the three-dimensional wind field above the ship deck that can comprehensively use simulation, laser wind radar and shipborne meteorological observation equipment. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and to provide a method for reconstructing the air flow field over a ship based on simulation. The present invention establishes a mathematical and physical model of the hull, adopts a deviation elimination averaging method, grids the airflow field near the hull, uses relevant calculation software of computational fluid dynamics (CFD), and adopts a computer numerical simulation method to complete the simulation of the air flow field over the hull.

[0005] In order to achieve the above invention purpose, the technical solution provided by the present invention is as follows:

[0006] A method for reconstructing air flow field on a ship based on simulation, wherein a laser wind radar is installed on the ship, and the method specifically comprises the following steps:

[0007] S1, determine the type of air flow field reconstruction on the ship, and select different air flow field reconstruction methods according to different distance ranges from the laser wind radar;

[0008] S2, when the distance from the laser wind radar is 0-20m, the air flow field over the ship is reconstructed through the simulation data results of CFD simulation;

[0009] S3, when the distance from the laser wind radar is 50-200m, the air flow field over the ship is reconstructed based on the measured data of the laser wind radar;

[0010] S4, when the distance from the laser wind radar is 20-50m, the simulated data results of the CFD simulation and the measured data results of the laser wind radar are fused to reconstruct the air flow field over the ship;

[0011] S5, performing data correction on the fused data of the simulated data results of the CFD simulation and the measured data results of the laser wind radar to complete the reconstruction of the air flow field over the ship.

[0012] Furthermore, the specific steps of the CFD simulation are:

[0013] S11, establish the hull structure model, and establish the ship structure model according to the ship data drawings; and use the wind environment numerical model of the ship data drawings to perform unstructured grid division inside the wind environment numerical model using ANSYS ICEM 2019;

[0014] S12, using ANSYS Fluent software to simulate and analyze the air flow field on the ship, according to the mass conservation equation, momentum conservation equation, general control equation, and opening the RNG k-ε model to obtain CFD simulation results.

[0015] Furthermore, the mass conservation equation is specifically:

[0016]

[0017] Where, is the fluid density, ρ is in kg / m 3 ; t is time, unit is s; u is the velocity component of the ship's speed in the x direction, v is the velocity component of the ship's speed in the y direction, w is the velocity component of the ship's speed in the z direction, and the speed unit is m / s.

[0018] Furthermore, the momentum equation includes a u momentum equation, a v momentum equation and a w momentum equation, and the u momentum equation is:

[0019]

[0020] The v-momentum equation is:

[0021]

[0022] The w-momentum equation is:

[0023]

[0024] Where η is the dynamic viscosity of the fluid; is the second molecular viscosity;

[0025] According to the calculation results of the mass conservation equation, the fluid vector equation is obtained by substituting it into the momentum conservation equation:

[0026]

[0027]

[0028]

[0029] Arranged:

[0030]

[0031]

[0032]

[0033] in,

[0034] Furthermore, the general control equation is obtained according to the mass conservation equation and the momentum conservation equation as follows:

[0035]

[0036] Among them, φ is a universal variable, which is the solution variable for velocity and temperature; Γ is the generalized diffusion coefficient; S is the generalized source term.

[0037] Furthermore, the RNG k-ε model obtains the RNG k-ε model through the mass conservation equation, the momentum conservation equation, and the general control equation, and obtains the CFD simulation results; the RNG k-ε model is specifically considered to be:

[0038]

[0039]

[0040]

[0041]

[0042] Wherein, u is the vector velocity component of the ship speed in the x direction, v is the vector velocity component of the ship speed in the y direction, w is the vector velocity component of the ship speed in the z direction, and the speed unit is m / s; u', v', w' are the pulsating speeds, in m / s.

[0043] Furthermore, the data fusion of the simulated data results of the CFD simulation and the measured data results of the laser wind radar is specifically as follows:

[0044]

[0045] Among them, U is the fused wind speed value; w1 is the fused wind field weight of the laser wind radar and ultrasonic wind observation instrument; U1 is the fused wind speed value of the optical wind radar and ultrasonic wind observation instrument; w2 is the CDF simulation weight; U2 is the CDF simulation wind speed value;

[0046] Among them, w1 and w2 are specifically:

[0047]

[0048] Among them, σ is the relative distance to the hull boundary; L is the length of the hull boundary.

[0049] Furthermore, the fused data of the simulated data results of the CFD simulation and the measured data results of the laser wind radar are corrected by the wind field data observed by the ship meteorological observation equipment; the fused data is corrected as follows:

[0050]

[0051] Among them, F(x, y, z) is the corrected air flow field simulation result at the x, y, z position; F0(x, y, z) is the original simulation result at the x, y, z position; W0 is the weight of the original simulation result, where W0 is 0.9; F1~F n It is the measured data of multiple ship meteorological equipment; W1~W n The weights corresponding to the observation data of multiple ship meteorological equipment;

[0052] The weight of each observation device is allocated according to the inverse distance weight method, and the formula is:

[0053]

[0054] Wherein, P is a positive integer, P=2; d is the distance from different observation devices to one of the devices;

[0055] The specific weight coefficient is:

[0056]

[0057] x a (j) = x b (j)+Δx(i,j)

[0058]

[0059] Among them, x a (j) is the analytical value at grid point j; x b(j) is the initial estimate of grid point j; x b (i) is the initial estimated field information interpolated to observation point i; y(i) is the corresponding observation value; w(i, j) is the weight coefficient.

[0060] Based on the above technical solution, the method of reconstructing the air flow field on a ship based on simulation in the present invention has achieved the following technical advantages through practical application:

[0061] 1. The method of reconstructing the air flow field on a ship based on simulation of the present invention establishes a mathematical and physical model of the hull, adopts a differential method to grid the airflow field near the hull, uses relevant calculation software of computational fluid dynamics (CFD), and adopts a computer numerical simulation method to complete the simulation of the air flow field over the hull, thereby improving the accuracy and efficiency of the reconstruction of the air flow field on the ship.

[0062] 2. The method of reconstructing the air flow field on a ship based on simulation in the present invention improves the accuracy of reconstructing the air flow field on the ship by selecting different airflow field reconstruction methods according to different distances from the ship, thereby forming high-resolution, low-blind-spot three-dimensional wind field data for the ship. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific examples shown. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0064] The present invention relates to a method for reconstructing an air flow field on a ship based on simulation. A laser wind radar is installed on the ship. The method specifically comprises the following steps:

[0065] S1, determine the type of air flow field reconstruction on the ship, and select different air flow field reconstruction methods according to different distance ranges from the laser wind radar;

[0066] S2, when the distance from the laser wind radar is 0-20m, the air flow field over the ship is reconstructed through the simulation data results of CFD simulation;

[0067] S3, when the distance from the laser wind radar is 50-200m, the air flow field over the ship is reconstructed based on the measured data of the laser wind radar;

[0068] S4, when the distance from the laser wind radar is 20-50m, the simulated data results of the CFD simulation and the measured data results of the laser wind radar are fused to reconstruct the air flow field over the ship;

[0069] S5, performing data correction on the fused data of the simulated data results of the CFD simulation and the measured data results of the laser wind radar to complete the reconstruction of the air flow field over the ship.

[0070] Furthermore, the specific steps of the CFD simulation are:

[0071] S11, establish the hull structure model, and establish the ship structure model according to the ship data drawings; and use the wind environment numerical model of the ship data drawings to perform unstructured grid division inside the wind environment numerical model using ANSYS ICEM 2019;

[0072] S12, using ANSYS Fluent software to simulate and analyze the air flow field on the ship, according to the mass conservation equation, momentum conservation equation, general control equation, and opening the RNG k-ε model to obtain CFD simulation results.

[0073] When calculating the mass of a fluid, it is necessary to follow the law of conservation of mass. The law of conservation of mass can be used to perform relevant calculations. The law of conservation of mass is expressed in fluid dynamics as follows: the increase in mass in a fluid microelement per unit time is equal to the net mass flowing into the microelement in the same time interval.

[0074] The mass conservation equation is specifically:

[0075]

[0076] Where, is the fluid density, ρ is in kg / m 3 ; t is time, unit is s; u is the speed component of the ship's speed in the x direction, v is the speed component of the ship's speed in the y direction, w is the speed component of the ship's speed in the z direction, the speed unit is m / s;

[0077] The above formula can be simplified and becomes:

[0078]

[0079] For incompressible fluids, the density is constant, which can be further simplified:

[0080] div(ρU)=0

[0081] The law of conservation of momentum is expressed in fluid dynamics as follows: the rate of change of momentum of the fluid in a microelement over time is equal to the sum of the various forces acting on the microelement from the outside. The momentum conservation equations in the x, y, and z directions are derived from this. It is studied using the property of conservation of momentum, by using Newton's second law to calculate in multiple coordinates and then combining them;

[0082] The momentum equation includes a u momentum equation, a v momentum equation and a w momentum equation, and the u momentum equation is:

[0083]

[0084] The v-momentum equation is:

[0085]

[0086] The w-momentum equation is:

[0087]

[0088] Where η is the dynamic viscosity of the fluid; is the second molecular viscosity;

[0089] According to the calculation results of the mass conservation equation, the fluid vector equation is obtained by substituting it into the momentum conservation equation:

[0090]

[0091]

[0092]

[0093] Arranged:

[0094]

[0095]

[0096]

[0097] in, is the vector velocity of the fluid, m / s;

[0098] S u , S v , S w is the generalized source term;

[0099] Incompressible flow with constant viscosity, S u =0, S v =0, S w =0, the momentum equation can be simplified to:

[0100]

[0101]

[0102]

[0103] The general control equation is obtained according to the mass conservation equation and the momentum conservation equation as follows:

[0104]

[0105]

[0106] Among them, φ is a universal variable, which is the solution variable of velocity and temperature; Γ is the generalized diffusion coefficient; S is the generalized source term;

[0107] The terms in the formula are transient term, convection term, diffusion term and source term respectively; for a specific equation, φ, Γ and S have a specific form,

[0108] Table 1 shows the specific values ​​of each symbol in the general control equation

[0109]

[0110] In this study, a pressure-based solver was used. In the solution, the velocity field is derived from solving the momentum equation. The pressure field is obtained by solving the pressure correction equation. The pressure correction equation is formulated by associating the continuity equation and the momentum equation. In the calculation method, a control volume-based treatment method is necessary. The control volume theory includes at least the following three aspects:

[0111] 1. Divide the computational domain into discrete control volumes through computational grids;

[0112] 2. Integrate the control equations over the control volumes to construct algebraic equations for solving discrete unknown independent variables;

[0113] 3. Linearize the discrete equations and solve them, continuously updating the values ​​of independent variables until convergence.

[0114] In the separated solution method of pressure-based solution, each control equation is independent, uncoupled and separated when solving. The required variables are solved in order on all grids. At any time, the system will only solve one discrete equation, and the next variable will be solved after all equations are solved on all grids. After all variables are completed, the new pressure field is obtained through the pressure correction equation, and the velocity field is updated. If there are other scalars, all scalar values, working fluid physical properties and various parameter values ​​related to the solution are updated.

[0115] The standard k-ε model is the most widely used turbulence model among the models using the Reynolds averaging method. The RNG k-ε model used in this paper is an improved model of the standard k-ε model, which is derived based on the renormalization group theory.

[0116] The equations of the RNG k-ε model are very similar to those of the standard k-ε model, but the RNG k-ε model has the following improvements:

[0117] First, the RNG k-ε model automatically limits the turbulent viscosity at high strain rates, preventing distortion when flowing over curved walls or curved streamlines.

[0118] Second, an additional term is added to the ε equation of the RNG k-ε model, which makes the strain rate a function of the flow conditions and spatial coordinates, thereby increasing the calculation accuracy of fast strain flows.

[0119] Third, the RNG k-ε model takes into account the rotation and swirl flow in the mean flow.

[0120] The above improvements make the RNG k-ε model more suitable for CFD numerical simulation of airflow organization in underground hydropower plant buildings with large space, strong heat source intensity and complex ventilation paths than the standard k-ε model. The CFD simulation results are fused with the laser wind radar data.

[0121] The RNG k-ε model obtains the RNG k-ε model through the mass conservation equation, momentum conservation equation, and general control equation, and obtains the CFD simulation results; the RNG k-ε model specifically considers:

[0122]

[0123]

[0124]

[0125]

[0126] Wherein, u is the vector velocity component of the ship speed in the x direction, v is the vector velocity component of the ship speed in the y direction, w is the vector velocity component of the ship speed in the z direction, and the speed unit is m / s; u', v', w' are the pulsating speeds, in m / s.

[0127] The main idea of ​​fusion of CFD simulation results and laser wind radar data: The laser wind radar deployed on the ship generally has a blind spot of 30 to 40 meters, that is, there is no data within 30 to 40 meters around the radar. When far away from the ship, the wind field is less affected by the hull structure, and the laser wind radar observation data can cover a range of 50 to 200 meters centered on the laser wind radar, so the laser wind radar measured data is mainly used in this range; and affected by the radar blind spot, and when inside the ship, the wind field is greatly affected by the hull structure, so the CFD simulation data is mainly used within the range of 0 to 20 meters centered on the laser wind radar; the two data are fused within the range of 20 to 50 meters, and the fusion method uses the deviation elimination average method;

[0128] The data fusion of the simulated data results of the CFD simulation and the measured data results of the laser wind radar is specifically as follows:

[0129]

[0130] Among them, U is the fused wind speed value; w1 is the fused wind field weight of the laser wind radar and ultrasonic wind observation instrument; U1 is the fused wind speed value of the optical wind radar and ultrasonic wind observation instrument; w2 is the CDF simulation weight; U2 is the CDF simulation wind speed value;

[0131] Among them, w1 and w2 are specifically:

[0132]

[0133] Among them, σ is the relative distance to the hull boundary; L is the length of the hull boundary.

[0134] Furthermore, the fused data of the simulated data results of the CFD simulation and the measured data results of the laser wind radar are corrected by the wind field data observed by the ship meteorological observation equipment; the fused data is corrected as follows:

[0135]

[0136] Among them, F(x, y, z) is the corrected air flow field simulation result at the x, y, z position; F0(x, y, z) is the original simulation result at the x, y, z position; W0 is the weight of the original simulation result, where W0 is 0.9; F1~F n It is the measured data of multiple ship meteorological equipment; W1~W n The weights corresponding to the observation data of multiple ship meteorological equipment;

[0137] The weight of each observation device is allocated according to the inverse distance weight method, and the formula is:

[0138]

[0139] Wherein, P is a positive integer, P=2; d is the distance from different observation devices to one of the devices;

[0140] The fused data is corrected with the actual measured data of the ship. When the wind force is small, turbulence with irregular wind direction is easy to form, which can easily reduce the accuracy of fusion. Therefore, a larger weight is given to the original simulation data during correction.

[0141] This patent uses the step-by-step correction method to fuse CFD simulation results with laser wind radar data. The basic principle is that the analysis field is obtained by adding the analysis increment to the initial estimated background field. The analysis increment on each analysis grid point is the deviation between the observation value and the initial value at each station within its influence radius, that is, the weighted average of the observation increment. Generally, the observation weight is inversely proportional to the distance between the observation position and the grid point. The influence radius is continuously reduced and corrections are made successively until the analysis field approaches the actual data.

[0142] The specific weight coefficient is:

[0143]

[0144] x a (j) = x b (j)+Δx(i,j)

[0145]

[0146] Among them, x a (j) is the analytical value at grid point j; x b (j) is the initial estimate of grid point j; x b (i) is the initial estimated field information interpolated to observation point i; y(i) is the corresponding observation value; w(i, j) is the weight coefficient.

[0147] The specific implementation steps are as follows:

[0148] 1. Model building

[0149] Using Solidworks2018 as the modeling software, the model building should be stacked in order from bottom to top. After the hull model is built, a fluid calculation area is established around the hull, and the model is saved as an IGES format file.

[0150] 2. Grid division

[0151] The file format of the exported model is IGES format. After importing the model, the topology check should be performed first to ensure that there are no loopholes in the model. Since this model is relatively complex, in order to better fit the geometric model, tetrahedral unstructured grid is selected for meshing.

[0152] 3. Simulation

[0153] After starting Fluent 2019, set the boundary conditions, initial conditions and other information, and then you can perform calculations and export results.

[0154] 4. Data Fusion

[0155] The fusion script was written in Python, and the deviation elimination method was used.

[0156] 5. Measured data quality control

[0157] In order to ensure that the wind field observation data accessed in wind field fusion is authentic and valid, it is necessary to perform quality control on the shipborne meteorological observation data.

[0158] 6. Fusion data correction

[0159] A step-by-step correction program is written in Python, observation data and fusion data are input, and the correction results are finally output.

[0160] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for reconstructing air flow field on a ship based on simulation, wherein a laser wind radar is installed on the ship, characterized in that: The method specifically comprises the following steps: S1, determine the type of air flow field reconstruction on the ship, and select different air flow field reconstruction methods according to different distance ranges from the laser wind radar; S2, when the distance from the laser wind radar is 0-20m, the air flow field over the ship is reconstructed through the simulation data results of CFD simulation; S3, when the distance from the laser wind radar is 50-200m, the air flow field over the ship is reconstructed based on the measured data of the laser wind radar; S4, when the distance from the laser wind radar is 20-50m, the simulated data results of the CFD simulation and the measured data results of the laser wind radar are fused to reconstruct the air flow field over the ship; S5, performing data correction on the fused data of the simulated data results of the CFD simulation and the measured data results of the laser wind radar to complete the reconstruction of the air flow field over the ship.

2. A method for reconstructing the air flow field on a ship based on simulation according to claim 1, characterized in that: The specific steps of the CFD simulation are as follows: S11, establish the hull structure model, and establish the ship structure model according to the ship data drawings; and use the wind environment numerical model of the ship data drawings to perform unstructured grid division inside the wind environment numerical model using ANSYS ICEM 2019; S12, using ANSYS Fluent software to simulate and analyze the air flow field on the ship, according to the mass conservation equation, momentum conservation equation, general control equation, and opening the RNG k-ε model to obtain CFD simulation results.

3. The method for reconstructing the air flow field on a ship based on simulation according to claim 2, characterized in that: The mass conservation equation is specifically: Where, is the fluid density, ρ is in kg / m 3 ; t is time, unit is s; u is the velocity component of the ship's speed in the x direction, v is the velocity component of the ship's speed in the y direction, w is the velocity component of the ship's speed in the z direction, and the speed unit is m / s.

4. The method for reconstructing the air flow field on a ship based on simulation according to claim 3 is characterized in that: The momentum equation includes a u momentum equation, a v momentum equation and a w momentum equation, and the u momentum equation is: The v-momentum equation is: The w-momentum equation is: Where η is the dynamic viscosity of the fluid; is the second molecular viscosity; According to the calculation results of the mass conservation equation, the fluid vector equation is obtained by substituting it into the momentum conservation equation: Arranged: in, 5. The method for reconstructing the air flow field on a ship based on simulation according to claim 4, characterized in that: The general control equation is obtained according to the mass conservation equation and the momentum conservation equation as follows: Among them, φ is a universal variable, which is the solution variable for velocity and temperature; Γ is the generalized diffusion coefficient; S is the generalized source term.

6. The method for reconstructing the air flow field on a ship based on simulation according to claim 5, characterized in that: The RNG k-ε model obtains the RNG k-ε model through the mass conservation equation, momentum conservation equation, and general control equation, and obtains the CFD simulation results; the RNG k-ε model specifically considers: Wherein, u is the vector velocity component of the ship speed in the x direction, v is the vector velocity component of the ship speed in the y direction, w is the vector velocity component of the ship speed in the z direction, and the speed unit is m / s; u', v', w' are the pulsating speeds, in m / s.

7. The method for reconstructing the air flow field on a ship based on simulation according to claim 1, characterized in that: The data fusion of the simulated data results of the CFD simulation and the measured data results of the laser wind radar is specifically as follows: Among them, U is the fused wind speed value; w1 is the fused wind field weight of the laser wind radar and ultrasonic wind observation instrument; U1 is the fused wind speed value of the optical wind radar and ultrasonic wind observation instrument; w2 is the CDF simulation weight; U2 is the CDF simulation wind speed value; Among them, w1 and w2 are specifically: Among them, σ is the relative distance to the hull boundary; L is the length of the hull boundary.

8. The method for reconstructing the air flow field on a ship based on simulation according to claim 1, characterized in that: The fused data of the simulated data results of the CFD simulation and the measured data results of the laser wind radar are corrected to the wind field data observed by the ship meteorological observation equipment; the fused data is corrected as follows: Among them, F(x,y,z) is the corrected air flow field simulation result at the x,y,z position; F0(x,y,z) is the original simulation result at the x,y,z position; W0 is the weight of the original simulation result, where W0 is 0.9; F1~F are the measured data of multiple ship meteorological equipment; W1~W n The weights corresponding to the observation data of multiple ship meteorological equipment; And the weight of each observation device is allocated according to the inverse distance weight method, the formula is Wherein, P is a positive integer, P=2; d is the distance from different observation devices to one of the devices; The specific weight coefficient is: x a (j)=x b (j)+Δx(i,j) Among them, x a (j) is the analytical value at grid point j; x b (j) is the initial estimate of grid point j; x b (i) is the initial estimated field information interpolated to observation point i; y(i) is the corresponding observation value; w(i,j) is the weight coefficient.

Images