Structure of Turbulent Wakes of Hypersonic Spheres as Inferred with Ion Probes
DEFENCE RESEARCH ESTABLISHMENT VALCARTIER (QUEBEC)
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Survey arrays of ion probes have been used to study the structure of the ionized turbulent wakes of 2.7 inch diameter spheres flown at 14,500 feet second in atmospheres of nitrogen at pressures of 7.6 and 20 torr. For various radial distances measured from wake axis, matrices of data points have been obtained giving random values of the axial distance behind the projectile at which ionization begins, the first ionized eddy occurs, and continuous turbulence begins. A wake radius separating the significantly ionized wake from the unionized wake has been obtained, and found to lie intermediate between the inviscid wake radius defined by Wilson from schlieren measurements and an electron density radius corresponding to the 1e points of the electron density distribution defined by microwave interferometric measurements. A radius defining the extent of the ionized portion of the turbulent core has been determined This radius is of the order of 80 of the schlieren radius of the turbulence core.
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