Scalar dispersion in the near wake of a simplified model car

Abstract : Experimental results on tracer gas diffusion within the near wake of a simplflied model car (Ahmed model with a rear slant angle of 25 degrees) are presented. Pollutant emission is simulated using heated air injected through a small pipe at one side of the model base. Fine cold wire thermometry is used to measure instantaneous temperature excess in the near wake. Characteristics of the temperature field over the Reynolds number range (1.3 x 10(4) < Re-L< 7 x 10(4)) show strong differences as a result of transition in the wake at a critical Reynolds number Re-Lc = 2.7 x 10(4).