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The effect of injection Mach number on jet penetration was determined from concentration measurements. Helium was injected transversely to the free stream from a flat plate at injection Mach numbers of 1, 2.4, 2.7, 3.5, and 4.0 and various total pressures. Jet penetration was found to increase with injection Mach number, the penetration dependence on Mach number increasing with downstream distance. For equal mass flows, supersonic injection resulted in as much as a 25% increase in penetration over that obtained with sonic injection. Existing correlations were found to be inadequate to fully describe the data. Penetration varied with jet to free-stream momentum ratio to the one-half power but only for a given Mach number and downstream position. Dividing the penetration by mass flow correlated the data for all Mach numbers for a given downstream position only. An expression based on momentum, Mach number, and downstream distance was developed which correlated both the present data and a set of data found in the literature. NomenclatureA,d = nozzle area and diameter, respectively M = Mach number m = mass flow Po = total pressure q = dynamic pressure, pv*/2 v = velocity x = downstream distance from nozzle centerline y = penetration (1% He concentration point) measured normal to plate surface a = angle of injection with horizontal 7 = specific heat ratio p = density Subscripts a,e,j -free stream, exit, and jet, respectively s = supersonic Superscripts * = throat ' -sonic

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