NITROGEN INJECTION INTO THE BASE REGION OF A HYPERSONIC WAKE,

An experimental investigation was made of the changes occurring in the near wake of a cylinder at M 6.0 when nitrogen was injected into the base region. The free stream Reynolds number based on cylinder diameter was 30,000 and the rate of injection was varied from zero to 3 percent of the frontal area free stream mass flow. Pitot pressure profiles across the wake, Schlhlieren photographs annd measurement of the boundary layer separation point on the cylinder were used to define the changes in wake geometry. Static pressure and temperature surveys were made along the wake centerline starting at the base of the cylinder and continuing downstream to XD 6.0. The injection reduced the recompression in the neck region and left only a slight insentropic compression in place of the strong wake shock. The recirculation of mass in the base-region was eliminated with approximately 1.5 percent injection. An automated hot wire recordrding sysystem which produced datadata suitable for computer reduction was developed and used to measure temperature. Author