A nondisturbance technique of measuring turbulent velocity spectra was studied to clarify the source of aerodynamic noise. In an anechoic wind tunnel, the continuous spectra of turbulent velocity in the wake of a cylinder of 10 mm diameter was measured over a range of mean velocity 30-50 m/s using an optical fiber-linked LDV (Laser Doppler Velocimeter) probe of 160 mm focal length. Accurate measurements of turbulence spectra due to Karman vortices were obtained by data sampling at 20-45 KHz for 10,000 samples at a measuring point. A smoke generator (Rosco Co.) was very useful for producing the seeding particles. Sound pressure spectra were measured and compared with the discrete frequency of the turbulent velocity.
LDVによる乱流音場のスペクトル測定法に関する研究
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