2015 年 81 巻 825 号 p. 14-00467
We studied sound generated by a diagonally arranged fin in a uniform flow. We set 2-dimensional computational model which neglected spanwise effect of the fins, and performed direct simulation of aerodynamic sound for two types of fins whose difference is the width of the back section with the finite-difference lattice Boltzmann method. Conditions of numerical results in which strong resonance occurred consisted with experimental results and Parker type resonance appeared. When the resonance occurred, the frequency of Kármán vortex shedding from the trailing edges of the fins agreed with the natural frequency of air columns which correspond the space between neighbouring fins. The phase differences between the neighbouring columns were completely “anti-phase” and the same was true for the vortex shedding. We also show the temporal and spacial variations in far sound field which are caused by the asymmetric arrangement of the fins. We also noted that the radiations of sounds of two different frequency existed for high speed flow range.
