Crossed beam correlation measurements and model predictions in a rocket exhaust plume

Abstract

The crossed beam correlation technique in its schlieren mode has been used to measure the rms value of the density gradient fluctuation and a weighted rms value of the density fluctuation across the exhaust plume of a static, liquid bipropellant rocket engine at four different axial stations. A transverse integral length scale, a form of time and length scales in the flow direction, and convection velocity have also been measured. Some of these experimental results are compared with predictions from a computer model. Where direct comparisons are possible, agreement is satisfactory. Where it is not, expected trends are observed. The results bring into question the validity of a key modeling assumption, that turbulent density fluctuations are negligible.