Scaling law for supersonic core length in circular and elliptic free jets

We present here the experiments demonstrating the scaling law for supersonic core length in circular and elliptic free jets. A proper scale for the supersonic core length of free jets is found as L c *</mml:msubsup> <mml:msqrt> A R</mml:msqrt> e - 0.11 gamma M j 2</mml:msubsup>, where L c * is the core length normalized by nozzle throat diameter D-th, AR is the aspect ratio of the elliptic nozzle, gamma is the specific heats ratio, and M-j is the ideally expanded jet Mach number. The scaling law developed for supersonic core length shows a close dependence with nozzle expansion ratio <mml:msub> p e / <mml:msub> p a and agrees well with the results reported in open literature, including the data reported for gamma =1.28-1.67. In spite of their uniqueness, the present results refer to circular and elliptic jets only. Thus, other similar studies on rectangular and square jets for a wide range of parameters are needed for a full comprehension of the universality of the scaling law for non-circular jets.