Experimental study on velocity-pressure correlation in turbulent mixing layer out of equilibrium state

A novel experimental technique to measure static pressure fluctuation was applied to evaluate velocity-pressure correlation in a turbulent mixing layer. The developing region of the mixing layer was found to be out of equilibrium state, indicating the oscillatory velocity fluctuation due to vortex shedding and remarkable production of turbulence. A simple model for pressure diffusion by Lumley gave satisfactory approximation when the flow approached to the self-similar state. The contribution of pressure-related terms in the transport equation of Reynolds stress is found to be well captured by the present method. The analogy between pressure diffusion and turbulent diffusion becomes weaker when the flow exhibits characteristics which are not found in equilibrium state.