| Aimed at introducing computational fluid dynamics (CFD) technique into the computation for the wind loads on radar antennas, the numerically computational method for wind loads on antennas is researched based on CFD technique and the theory of stationary random process. Adopting Reynolds Averaged Navier-Stokes equations, a computational method of mean wind loads on antennas is proposed in this thesis. In view of the difference inlet airflow in the industrial wind tunnel and the atmospheric boundary layer wind tunnel, the characteristics of wind loads on antennas placed in the two kinds of wind tunnel are simulated by numerical wind tunnel. Combining CFD technique and potential flow theory, a method to eliminate the interference to the mean wind loads on antennas resulted by the walls of the industrial wind tunnel is presented. In addition, according to the quasi-steady theory, a method to compute the histories of the wind loads on antennas in atmospheric boundary layer is obtained from the steadily numerical model. Furthermore, this thesis also puts forword a computational method to obtain the histories of the wind pressure and wind loads on antennas in atmospheric boundary layer using large eddy simulation. Then, all researches are helpful to guide the optimized design of antenna structure.To sum up, the following works are carried out:1. Research on numerical computation method of the mean wind loads on antennas in industrial wind tunnelAccording to the previous achievements of the research topic group, a geometric model for wind loads on the antenna is built, and its computational grids are generated. After the boundary conditions and wall function have been determined, the turbulent model and the solving method has been choosen, the numerical computation for mean wind loads on the antenna is put up under the control of the computational parameters. Moreover, the computational results are compared with the experimental results. Then, the numerically computational method for mean wind loads on antennas is presented.2. Research on the numerical simulation for the characteristics of mean wind loads on antennas in industrial wind tunnel and atmospheric boundary layer wind tunnelAccording to the testing conditions in different wind tunnels, the relevant parameters including the profile of mean wind velocity and turbulent intensity are determined. Then, the inlet conditions of the wind tunnel can be obtained, and the characteristics of wind loads on the antenna in different wind tunnels can be numerically computed. Furthermore, the computational results tested by different wind tunnels are compared, and it can supply some suggestions for the structural design of the antenna.3. Research on the corrected method of the blockage effect for mean wind loads on antennas in industrial wind tunnelAs the influence on experimental data resulted by the walls of the industrial wind tunnel test, there are some deviations between the wind pressure distributions derived from test and the actual wind pressure distributions. According to the law of wind pressure distribution and the empirical formula to base pressure coefficient, taking the potential flow model into account, the actual drag coefficient of the antenna without blockage is obtained. After re-normalizing wind pressure coefficient, the interference to the wind pressures on the antenna by walls is eliminated, and the wind pressure coefficient distributions on antenna without blockage are obtained.4. Research on numerical simulation of wind pressure and wind loads on antennas in atmospheric boundary layer based on quasi-steady assumptionAdopting the wind velocity spectrum proposed by Kaimal, the wind velocity of the surface on the antenna is simulated. Based on quasi-steady assumption, and the simulated results for mean wind pressure on the antenna, the histories of wind pressure and wind loads on the antenna are obtained, and they are in agreement with the experimental data.5. Research on large eddy simulation for histories of the wind pressure and wind loads on antennas in atmospheric boundary layer based on synthetical turbulent flowThe inlet conditions for large eddy simulation are simulated, and the histories of wind pressure and wind loads on an antenna are obtained. Furthermore, the computed results are compared with the data of a standard model tested by wind tunnels. According to the above researches mentioned, the numerical model for wind loads on antennas is built, and the effects of wall interference on mean wind pressure and wind loads on antennas are removed. Moreover, the computational method for histories of wind loads on antennas has been explored by steadily and unsteadily numerical computation and the research results have been meaningful to vibration analysis of the antenna in time domain.The originalities in this thesis can be summarized as follows:1. The numerically computational models of mean wind loads on antenna in industrial wind tunnel are builtBased on Finite Volume Method (FVM), adopted suited turbulent model and wall function, the computational model of wind load characteristics of antennas is built, and the wind pressure distributions on antennas are computed. Compared with the test data, the numerical results are in good agreement with those tested by wind tunnel. This study extends the wind loads characteristic of antennas from wind tunnel to numerical wind tunnel, and improves the research method to wind loads on antennas further.2. The method to correct the blockage effect on the mean wind loads of antennas resulted by the industrial wind tunnel walls is presentedAfter the law of base pressure coefficient of an antenna in changing blockage ratios has been obtained by steadily numerical computation, a method to correct the wind pressure and wind loads is presented from the base pressure and potential flow theory based on the tested data. Comparing the simulation results with the experimental results, the method is validated to be feasible and correct.3. The numerical method to compute the histories of the wind loads on antennas in atmospheric boundary layer based on RANS model is proposedAccording to the power spectral density of wind velocity proposed by Kaimal, the histories of wind velocity in atmospheric boundary layer are simulated. Based on the squasi-steady assumption, the histories of wind loads on the antenna are derived from the mean wind pressures which are computed by steadily numerical computation. In view of the isotropic characteristics of the wind field, the wind loads on the antenna in transverse direction are obtained accordingly. The validity of the computational method is verified by test, and its limitation also is revealed.4. The numerical method to compute the histories of the wind loads on antennas in atmospheric boundary layer based on large eddy simulation is presentedIn view of the power spectral density of wind velocity and spatial correlation, the velocities of these points distributed by different schemes are simulated in along-wind and cross-wind direction, and take them into the inlet of computational domain. Using the dynamic subgrid-scale eddy viscosity model, the histories of wind pressure and wind loads on antennas are obtained by larege eddy simulation, and are in good agreement with the experimental data. |
PDF Full Text Request