Two-dimensional estimation of Reynolds-fluxes and -stresses in a Jet-in-Crossflow arrangement by simultaneous 2D-LIF and PIV

Two-dimensional maps of Reynolds-fluxes and -stresses are obtained in a Jet-in-Crossflow arrangement by measuring velocity- as well as scalar concentration-fields simultaneously. The data obtained are of special concern with respect to the development and validation of turbulence- and mixing-models. The experimental results are in good agreement with a Large Eddy Simulation of the flow configuration under investigation. A combination of 2D-LIF- and PIV-measuring technique is applied. For PIV-measurements, droplets are added to the airflow of the crossflow and the jet, respectively. Additionally, a molecular tracer is added to the jet. The concentration distribution of this tracer is detected in the interaction zone of the jet with the crossflow by 2D-LIF. NO2 is chosen as the tracer, because it absorbs the wavelength of the frequency doubled Nd:YAG-laser used for the PIV-measurements. Therefore, in contrast to the few simultaneous LIF-PIV-measurements known from the literature for gaseous flows, only one single double pulse laser is used for the detection of the two-dimensional concentration- and the velocity-maps. The broadband Stokes-shifted NO2-fluorescence signal induced by one of both Nd:YAG-double laser pulses is detected perpendicular to the propagation direction of the laser beam through an additional window in the measuring section which is also used for the detection of the Mie-scattered light. Both signals are separated from each other by a 45 degrees dichroic mirror which transmits the fluorescence-signal whereas the Mie-scattered light is reflected perpendicular with respect to the first. The Mie-scattered light from both laser-pulses is detected by the CCD-camera of the PIV-system.