On the Impact of the Addition of Steady Flow to Oscillatory Flow in a Diffuser

Separating oscillating and pulsating flows in an internal adverse pressure gradient geometry are studied experimentally. Simultaneous velocity-pressure measurements demonstrate that the minor losses associated with oscillating flow in an adverse pressure gradient geometry can be smaller or larger than for steady flow. The minor losses grow with increasing displacement amplitude in the range 10 < L0/h < 37. Losses decrease with Reδ in the range of 380 < Re < 740. The extent and duration of boundary separation increase with L0/h. It is found that the losses increase with increasing diffuser angle for 12° < θ < 30°. The addition of steady flow can cause the in decrease if the flow becomes more turbulent as a result, or increase when the flow was already turbulent.