Analytical nodel of supersonic, turbulent, near-wake flows /

An analytical model for planar and axisymmetric, supersonic, turbulent, near-wake flows is presented. The viscous region behind the blunt base is described by the integral form of the boundary-layer equations, and the inviscid outer-flow region, including the remnant of the initial turbulent boundary layer, is computed with the rotational method of characteristics. The solution of the two regions is fully coupled. The saddle-point singularity, similar to the Crocco-Lees critical point, occurs downstream of the rear stagnation point. The base pressure is obtained by iteration of the initial conditions until the flow-field solution will pass through the singularity. Base bleed of a gas different from the outer-stream gas is included in the formulation, and provision is made to treat equilibrium chemical reactions in the viscous wake. However, an unresolved problem has been encountered in the solution of the species conservation equations. Therefore, results for only single gas flows are presented. The analytical model is shown to adequately predict the effect of free-stream Mach number and initial boundary layer on the planar base pressure. In addition, the planar flow-field structure is well predicted. Axisymmetric base pressure and flow-field structure are reasonably well predicted for free-stream Mach numbers greater than 2.0, but the turbulent transport model used yields only fair results for Mach numbers less than 1.7. The effect of base bleed on the axisymmetric base pressure is well predicted. (Author)."September 1976.""Final Report: July 1973 -- December 1975."Includes bibliographical references (pages 60-64).An analytical model for planar and axisymmetric, supersonic, turbulent, near-wake flows is presented. The viscous region behind the blunt base is described by the integral form of the boundary-layer equations, and the inviscid outer-flow region, including the remnant of the initial turbulent boundary layer, is computed with the rotational method of characteristics. The solution of the two regions is fully coupled. The saddle-point singularity, similar to the Crocco-Lees critical point, occurs downstream of the rear stagnation point. The base pressure is obtained by iteration of the initial conditions until the flow-field solution will pass through the singularity. Base bleed of a gas different from the outer-stream gas is included in the formulation, and provision is made to treat equilibrium chemical reactions in the viscous wake. However, an unresolved problem has been encountered in the solution of the species conservation equations. Therefore, results for only single gas flows are presented. The analytical model is shown to adequately predict the effect of free-stream Mach number and initial boundary layer on the planar base pressure. In addition, the planar flow-field structure is well predicted. Axisymmetric base pressure and flow-field structure are reasonably well predicted for free-stream Mach numbers greater than 2.0, but the turbulent transport model used yields only fair results for Mach numbers less than 1.7. The effect of base bleed on the axisymmetric base pressure is well predicted. (Author).Report supported by the Air Force Systems Command and prepared by ARO, Inc, under Program Element,Mode of access: Internet