AERODYNAMIC NOISES RADIATING FROM SURFACE IRREGULARITIES OF HIGH SPEED CARBODY

摘要

(1) At lower frequency the directivity of scattering of quadrupole sounds from surface irregularities tends to be a dipole type whose axis is tangent to the base plane.(2) At higher frequency aerodynamic sounds scattered from a surface irregularity with height or depth h and with the wave number k and radiated in the direction normal to a base plane are characterized by an acoustic filter like sin~2(kh) caused by dipole sound pairs that are coherent.(3) Aerodynamic sounds generating at window rims are strong at the leeward rim of the window and efficiently radiated windward. The sounds are drastically lowered under an acoustic effect if the step of the rim has a gentle slope or a rounded edge.(4) Aerodynamic sounds generating at a louver were reduced under an aerodynamic effect when the configuration of the strip plates of the louver was changed from right angles to parallel to the direction of an airflow.