DISTURBANCE GROWTH TRIGGERED BY STEADY HEATING OF A JETS NOZZLE EXIT BOUNDARY-LAYER

Experiments were conducted to investigate how heating only the nozzle exit boundary layer of an axisymmetric jet, with an unheated potential core, affects disturbance growth in the initial shear layer. The exit boundary layer had a minimum density ratio of 0.74, was laminar, and had a constant momentum thickness (theta) for all levels of nozzle heating used in this study. The fluctuating velocity (u') and temperature (t') in the exit boundary layer increased monotonically with increasing nozzle temperature. Low-amplitude acoustic excitation produced a more rapid growth of coherent velocity fluctuations for the heated case than for the unheated. (C) 1995 American Institute of Physics.