Application And Research On Cavity Flow And Aero-acoustic Based On LBM

Aerodynamic is a common phenomenon in daily life and engineeringapplications, the control of noise has a great significance on the two aspects, and thenumerical research on it has developed rapidly in recent years. The Lattice BoltzmannMethod is one of the method that could simulate the sound wave generation andpropagation accurately. That fluid is deemed to be slightly compressible by model D2Q9which is based on adiabatic and isentropic assumptions makes the sound simulation to bepossible. The investigation is carried out as follows:First of all, that is the simulation of types of cavities, which includes squarecavity, triangular cavity, semicircular cavity and trapezoidal cavity. The boundaryconditions that are suitable for the cavities whose boundary could be complicated is theinterpolated oblique boundary extrapolation. Then we explore the impact on cavity fieldbrought by the different inflow velocity. The changes lie in vortex intensity, vortex centerposition and the number of vortex in cavity. Generally the cavity flow becomes complexand unstable with the increase of inflow velocity. Small eddys will spilt from the centralvortex at the bottom of cavity when wall shear flow reaches a certain level.Secondly, we simulate some cases to understand the acoustic wavepropagation characteristics. The cases include the propagation of point source and linesource, synthesis of point sources whose frequency could be the same or different, theinfluence of relaxation time to sound wave and the doppler effect. By comparing theresults of simulation on point source and line source, the interference phenomenon anddoppler effect. The LBM is a feasible method for CFD, and the relaxation time and flowfield damp is positive correlated.Finally, this paper investigates the flow field of rectangle cavity by changingdepth/length ratio, inflow velocity and viscosity. After that, the traditional CFD resultsbring in to verify the LBM simulation results. From the results of the two could we findthat the error between the two minimized when the depth/length ratio is at a higher levelor a lower case, and the error decreases with the decreasing of inflow rates. At the sametime, the simulation of different grid shows the reduction of computational time could be done by proper grid.In addition, this paper monitors the acoustic pressure variation ofcavity and obtains the accuracy of LBM in calculation of acoustic pressure by comparingthe result with thesis.