An experimental study was carried out into a single circular jet impinging onto a flat ground board. The jet was running at a fixed nozzle pressure ratio (NPR) of 1.05 (Reynolds number of 90,000 based on nozzle exit conditions), the nozzle to ground board separation (Hn) varying between 2 and 10 diameters (Dn). Measurements were performed in the free and wall-jets using cross-wire hot-wire anemometry, mean velocity, normal and shear stress results being presented. Nozzle height was found to affect the initial thickness of the wall-jet leaving the impingement region, increasing Hn/Dn increasing the wall-jet thickness. Nozzle height was also found to have a large effect on the peak level of turbulence found in the wall-jet up to a radial distance of r/Dn≈4.5, after which the profiles became self-similar, the peak value occurring around r/Dn=2.0. Lower Hn/Dn caused an increase in the peak level measured in all the turbulent stresses within the impingement region. This was attributed to greater shearing of the flow at the lower nozzle height due to a thinner wall-jet leaving the impingement region.
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