Air turbulence-induced vibration of SCUBA breathing apparatus

Abstract

The first study of the underlying mechanism of noise generation in SCUBA was reported at the previous 153rd ASA meeting (D. Donskoy, Acoustic Emission Mechanism from Scuba Diving Equipment). It was shown that the primary originating source of SCUBA vibration and subsequent acoustic emission is a combination of non‐stationary shocks and separated turbulent flow that occurs within the first stage air pressure regulator during the inhale phase of breathing. The separation mechanism is due to a combination of two factors: Shock‐induced separation and geometrical discontinuities in the regulator’s internal surface topology. The separated flow manifests itself through the presence of three‐dimensional vortices and turbulent pressure fluctuations that excite structural resonances of the regulator and connected air tank, resulting in a complicated resonance dynamic behavior of the system. For the air flow dynamic analysis, we utilized a scale‐adaptive detached eddy simulation model, which is based on the solution of unsteady, three‐dimensional compressible Navier‐Stokes equation solved on a hybrid unstructured computational mesh. The CFD simulations were applied to different topologies representing major types of regulators (piston and diaphragm types) to reveal the complex mechanics of the flow and their dependence on the regulator design. [Work supported by ONR.]