Velocity measurements of a square jet

The paper presents the velocity measurements of an unheated jet issuing from a square nozzle into stagnant ambient air. Measurements were accomplished by means of single hot-wire and X-wire probes. Experimental results showed that the jet initial boundary layer was laminar. Based on the local maximum velocity and half-width, the interaction region was determined to be 8De. Decaying and spreading rates of the jet were also studied and compared with those of other researchers. It was found that the root mean square axial (also lateral) velocity and Reynolds shear stress achieved self-preservation state at 20De and 30 De respectively. Lastly, comparison of velocity half-width along the y- and w-axes as well as the mean velocity profiles indicated that there were axis-switching in the present square jet although more measurement evidence is required.