Experimental study of inclined jets cross flow interaction in compressibleregime. I. Effect of compressibility in subsonic regime on velocity and temperature fields.

The results of the investigation of the interaction of a row of jets with a compressible cross flow are compared with their counterpart obtained in in compressible regime. The comparison reported here focuses on the flow field resulting from the interaction above and at the wall. The velocity and tem perature fields are measured respectively by laser Doppler velocimetry and thermocouple probes. The wall temperature distributions are measured using an infrared camera. The experiments are performed for cross flow Mach numbe rs of 0.72 and 0.1 for respectively the compressible and incompressible reg imes with almost the same injection rate (R = 0.50 and 0.6). Significant di fferences are noticed between the two flow fields in particular on the vert ical development of the jets in the cross flow and on the turbulent diffusi on. The jet penetration is found to be higher in the compressible regime wi th less interaction between the jets. The comparison also shows that the wa ll heat transfer modifications induced by the jets are less pronounced in t he compressible case as a result of the higher penetration of the jets. The se results show that neither the mass flux ratio nor the momentum ratio are good candidates for extrapolation of the cooling efficiency from the incom pressible case to the real compressible case as encountered in the practica l applications. (C) 2000 Editions scientifiques et medicales Elsevier SAS.