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Published online by Cambridge University Press: 04 July 2016
Flow transition in the developing region of a planewall jet is studied experimentally by means ofhot-wire measurements. The Reynolds number, based onthe jet exit velocity and nozzle exit height, variesfrom 3 x 102 to 3 x 104 in theinvestigations. The results indicate that the mostimportant factor causing wall jet flow to changefrom the initial exit state to the final turbulentstate is the rapid increase of turbulent intensityfrom the formation of vortical structures and theirinteractions with the wall. Data also shows that thetransition process of the wall jet depends on theReynolds number in the operating range. When theReynolds number is greater than 2000, the meanvelocity distribution of the wall jet changesdirectly from a top-hat profile at the nozzle exitto a turbulent profile in the turbulent developedregion. When the Reynolds number is smaller than2000, Glauert's laminar velocity profile is foundbetween the nozzle exit and the turbulent region. Itis also found that the transition will be delayedand the transition region prolonged with thedecrease of the Reynolds number.