Turbulence characteristics of the three-dimensional boundary layer on a rotating disk with jet impingement

Abstract.

An experimental study was carried out using hot-wire anemometry to investigate the turbulence characteristics of the three-dimensional boundary layer on a rotating disk with jet impingement at its center. A spanwise flow (radial outflow) generated from the impinging jet is added to the spanwise flow induced by the rotating disk, so that the mean flow direction is considerably changed and the structural parameter in the near-wall region significantly decreases. The strong asymmetry in the velocity cross-correlation coefficient in the local spanwise direction and that in the conditionally averaged velocity signals in the vicinity of a strong ejection or sweep, which existed in the free rotating disk flow, disappear as the ratio of the jet Reynolds number to the rotational Reynolds number increases. A quadrant analysis shows that the Reynolds-shear-stress-producing eddies become nearly symmetric in the local spanwise direction and the Reynolds-shear-stress-producing vortical structures are destroyed as the ratio of the jet Reynolds number to the rotational Reynolds number increases.