The Effect of a Spanwise Blowing Jet on the Separation Bubble Length Behind a Rearward Facing Step

Author: Miyata, Gavien Nobuyuki

Year: 1972

Degree: Engineer's thesis

Advisor: Harris, Gordon L.

Committee Member: Unknown, Unknown

Option: Aeronautics

DOI: 10.7907/EFBF-0016

Abstract

The problem of the effect of a spanwise blowing jet on the flow past a rearward facing step is considered both theoretically and experimentally. The primary flow is considered to be a finite two dimensional jet blowing past a step and the spanwise jet is assumed to blow perpendicular to this primary flow. The equations predicting the separation bubble length are de rived by assuming that the two dimensional jet is thin enough so that its radius of curvature can be determined by the pressure difference across the primary jet and the jet momentum. Then by doing a momentum balance at the reattachment point, the angle of reattachment is determined and the bubble geometry is fixed. The effect of the spanwise blowing jet is modeled by a two-dimensional sink with the sink strength given by the mass entrainment per unit length of a round jet in a semi-confined space.

The experimental work, which measured the bubble length as a function of the two-dimensional jet thickness and the strength of the spanwise blowing jet, is matched with the theoretical predictions giving the spreading parameters of the shear layers on both sides of the primary jet.

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