Abstract

Experimental evidence of scattering of an ultrasound wave interacting with a thermal plume is reported, to validate a new non-intrusive measurement technique for the detection of structures in non-isothermal turbulent flows. The results allow the verification of some theoretical predictions, such as the existence of a non-dispersive scattering angle and the linear behavior of the phase. Also, the Doppler shift of the signal with respect to time and to the incoming wave frequency can be verified. The Doppler shift, corresponding to the velocity of flow structures, was shown to be sensitive to the direction of the vector of the resulting wave, i.e. to the scattering angle, which could be defined as either negative or positive. The values of the advection velocity are in agreement with variations of temperature and with those obtained using traditional measurement techniques. By its characteristics, ultrasound scattering constitutes a complementary and appropriate technique for turbulence studies.