On Fiber Optic Probe Hydrophone Measurements in a Cavitating Liquid (L)

The measurement of high-pressure signals is often hampered by cavitation activity. The usage of a fiber optic probe hydrophone possesses advantages over other hydrophones, yet when measuring in a cavitating liquid large variations in the signal amplitude are found; in particular when the pressure signal recovers back to positive values. With shadowgraphy the wave propagation and cavity dynamics are imaged and the important contributions of secondary shock-waves emitted from collapsing cavitation bubbles are revealed. Interestingly, just adding a small amount of acidic acid reduces the cavitation activity to a large extend. With this treatment we find an altered primary pressure profile which does not force the cavitation bubbles close to fiber tip into collapse. Thereby, the shot-to-shot variations are greatly reduced.