Marian Wysocki

A comparative analysis of correction method for total-head probes in large velocity-gradient flows

Abstract The paper presents a comparative analysis of already published correction methods for the readings of Pitot tubes under conditions of strong velocity and pressure gradients. The results obtained suggest the superior performance of these formulae which take into account the actual value of velocity gradient in measuring point.

Hot – wire study on the axisymmetric free jet dependence on the nozzle shape

The paper presents the results of experimental research in axisymmetric free jet performed in order to verify the previous numerical calculations. During the study the influence of the initial conditions at the outlet of the nozzle on the formation of self-sustained oscillations in free jet was determined. The variables affecting the initial conditions were: the shape of nozzle tip (free – slip and no – slip), contraction ratio (C = 128 and 144) and Reynolds number (Re = 5 000 – 40 000). Measurements were taken using the CTA probes. An analysis of the distributions of mean velocity at the nozzle exit shows that a laminar boundary layer was obtained, values of integral boundary layer parameters were not significantly affected by the type of nozzle tip. Some differences were observed in the turbulence intensity distributions in the exit plane and along the jet axis, where characteristic plateau could be noted for case with the free – slip nozzle tip, which indicates the presence of coherent structures in the flow. These results suggest that for almost the same initial conditions obtained for plane and profiled nozzle tip the modification of organized structures in the far flow field was obtained. For physical explanation of these phenomena it was necessary to perform spectral and spatio – temporal correlation analysis (not discussed in the present paper).