An Inclined Jet through a Forward Expanded Hole Ejected into Mainstream over a Concave Surface

Abstract

This study employs a digital Particle Image Velocimetry (PIV) to obtain detailed velocity distributions and flow visualization for an inclined jet through a forward expanded hole into mainstream over a concave surface at three different blowing ratios (M) of 0.5, 1.0, and 1.5. In this study, measurements are made in three different cases to identify the interaction between the ejected flow and the mainstream. These three cases are particles seeded in the ejected flow only, particles seeded in the mainstream only, and particles seeded in both the ejected flow and the mainstream. Measured results show that the blowing ratio can significantly affect the flow field of an ejected flow into the mainstream. From the 2D velocity measurement on the central plane of the injection hole at M=1.0, measured results show that a strong interaction occurs between the ejected flow and the mainstream at the leeward side of the ejected jet. In this region, the mainstream is entrained into the center plane that produces an outward radial velocity to lift the ejected flow away from the concave wall. In this study, there is no obvious radial velocity of the jet flow to up-lift itself on the central plane. The decay of the lift-off velocity from the mainstream along the streamwise direction is a cause for reattachment of a jet flow on the concave surface.

Keywords

• ejected flow
• mainstream
• particle image velocimetry
• particle concentration
• velocity defect
• lift-off velocity