A Study of Flow-Induced Noise in Sudden Expansion Pipes
Details
The flow-induced noise was experimentally studied for sudden expansion pipes with low Mach number flow (0.1<M<0.2). The results showed that the sound pressure level of the flow induced noise for a sudden expansion pipe was larger than that for a straight pipe and was almost independent of the expansion angle within the range from 15 to 90 degrees. The sound power was proportional to the sixth power of the inlet flow velocity for sudden expansion pipes. This fact shows that the noise source was acoustic dipoles generated by the pressure fluctuation acting on the inner wall downstream of the sudden expansion. The sound power of the flow-induced noise decreased with the expansion pipe length. The reduction effect of the flow-induced noise was attained by the reduction of the fluid collision on the wall. The turbulence was generated by the jet flow in the expansion pipe and the turbulence intensity was smaller with shorter expansion length.
