A Row of Streamwise-Inclined Jets in Crossflow: Measurements and Calculations

Abstract

The velocity profiles and turbulence characteristics are measured for a row of square jets inclined at 30° to the streamwise direction. The jet spacing-to-width ratio is 3.0 and no temperature (density) difference between the jets and the crossflow is introduced. Measurements are made using a three-component LDV system operating in coincidence mode which provides three components of velocity and all six turbulent Reynolds stresses at each location. Jet-to-crossflow velocity ratios (blowing ratios) of 1.5. 1.0, and 0.5 are used and the jet Reynolds number is fixed at about 5000 for all velocity ratios. The results are compared with previous data from normal jets at the same blowing ratios so that the influence of inclination on vortex formation can be shown. Calculations are carried out for all cases using a non-orthogonal finite volume computer code with the k-ε turbulence model. It is shown that the flow field at the jet exit is strongly influenced by the crossflow as well as by the inlet conditions at the entrance to the jet orifice. Therefore it is very useful to extend the computational domain into the plenum. Computational results compared with experimental results for a velocity ratio of 0.5 agree reasonably well. Some under-prediction of the streamwise flow velocity is observed. The computed turbulence kinetic energy values also drop below the experimental values downstream and near the wall. Agreement is not as good for the higher velocity ratios, particularly for the turbulence kinetic energy. Strong non-isotropy of the turbulence field can be observed from the experimental data.