Hydrodynamic sound generated by collapse of vapor bubbles in subcooled liquid flow

Sound generated by collapse of vapor bubbles injected into a subcooled water pipe flow was measured to investigate the effects of temperature gradient forming at the pipe wall on the sound level. The degree, ∆T, of subcooling was 20 K, the water velocity was 1.2 m/s, and the vapor was injected from a circular hole of 1 mm in diameter placed on the pipe wall. Water was heated just upstream of the test section to make ∆T non-uniform. The smaller ∆T due to heating made the noise level smaller. The noise level cannot be correlated in terms of the local ∆T at the bubble collapse event in spite of the rapid condensation, whereas the noise level with temperature gradient agrees with that of uniform ∆T by taking into account the temperature variation in the region from the vapor inlet to the position of collapse event. © 2019 by Begell House, Inc.