Mojtaba Mehrjooei, Nader Montazerin* and Abraham Damangir
The Journal of Mechanical Science and Technology, vol. 26, no. 4, pp.1049-1057, 2012

Abstract : Mixing layers are sensitive to the mixing angle and turbulence in the primary streams. Although there is extensive available research on this rather basic flow, there are still no suggestions for a clearly best configuration. For example, the combination of a laminar initial boundary layer and a large mixing angle has received little attention. In this work we test a new experimental configuration with large mixing angle and laminar/turbulent initial boundary layer that was not examined experimentally by LDA and PIV. This setup is expected to be a representation of the initial conditions that must result in better mixing. A plane mixing layer with a velocity ratio of 0.6 is produced by rebuilding an open circuit wind tunnel. Extensive calibration tests on velocity profiles and Reynolds stresses established the position of the self similar region. Velocity field measurements with laser Doppler anemometer (LDA) and particle image velocimeter (PIV) showed enhanced mixing layer growth. PIV plots showed the presence of stream-wise and cross stream vortices in the self-similar region without any considerable change in turbulence characteristics to that of reported in the literature. The article presents a combination of different experimental results that give a deeper understanding of this very configuration.

Keyword : Laser Doppler anemometry; Mixing angle; Particle image velocimetry; Plane mixing layer