Hypersonic Viscous Shock Layer of Nonequilibrium Dissociating Gas [with List of References]


Book Description

The nonequilibrium chemical reaction of dissociation and recombination is studied theoretically for air in the viscous shock layer at the stagnation region of axisymmetric bodies. The flight regime considered is for speeds near satellite speed and for altitudes between 200,000 and 300,000 feet. The convective heat transfer to noncatalytic wall is obtained. The effects of nose radius, wall temperature, and flight attitude on the chemical state of the shock layer are studied. An analysis is also made on the simultaneous effect of nonequilibrium chemical reaction and air rarefaction on the shock layer thickness.










A Thin-shock-layer Solution for Nonequilibrium, Inviscid Hypersonic Flows in Earth, Martian, and Venusian Atmospheres


Book Description

An approximate inverse solution is presented for the nonequilibrium flow in the inviscid shock layer about a vehicle in hypersonic flight. The method is based upon a thin-shock-layer approximation and has the advantage of being applicable to both subsonic and supersonic regions of the shock layer. The relative simplicity of the method makes it ideally suited for programming on a digital computer with a significant reduction in storage capacity and computing time required by other more exact methods. Comparison of nonequilibrium solutions for an air mixture obtained by the present method is made with solutions obtained by two other methods. Additional cases are presented for entry of spherical nose cones into representative Venusian and Martian atmospheres. A digital computer program written in FORTRAN language is presented that permits an arbitrary gas mixture to be employed in the solution. The effects of vibration, dissociation, recombination, electronic excitation, and ionization are included in the program.







Merged Stagnation Shock Layer of Nonequilibrium Dissociating Gas


Book Description

The paper presents the formulation of the problem, the numerical method leading to solution, and the physical significance of the results obtained for the fluid flow of a viscous merged layer with nonequilibrium chemical reactions. The solution is limited to the stagnation region of a blunt body. The chemical reactions considered are the dissociation and the recombination of air. It is first shown that the reduced Navier-Stokes equation and the corresponding energy and species conservation equations, wherein certain curvature effects have been neglected, are sufficiently accurate for the flow regime in which Re> or approx. 20, where Re is the Reynolds number behind the bow shock. It is also shown that only in this regime are the nonequilibrium chemical reactions important. From the solutions it was found, as was expected, that a strong coupling exists between the chemical reactions and the rarefaction of the shock layer. One of the unexpected results is that, for a given flight condition, increase of the surface catalycity causes the shock layer to become thinner. Since the increase in surface catalycity reduces the degree of dissociation within the merged shock layer, it had been expected that it would increase the shock layer thickness instead of decreasing it. The physical interpretation of the phenomenon and its possible implications are discussed. (Author).







Similarity Studies for Dissociating Gases in Hypersonic, Low Density Flow


Book Description

Contents: Viscous and inviscid hypersonic similitude for an equilibrium dissociating gas Inviscid hypersonic similitude Viscous hypersonic similitude Experimental and numerical verification of viscous and inviscid hypersonic similitude Simulation requirements in the flight spectrum associated with hypersonic velocity vehicles Spark-heated and shock tunnel simulation capability Hypersonic nonequilibrium gas flows The presence and influence of dissociation Nonequilibrium in hypersonic nozzle flow Hypersonic nonequilibrium gas flows about arbitrary shapes The approach to equilibrium behind a normal shock wave Rarefied gas flows Hypersonic gas flows at low Reynolds number Free molecular flows.




Viscous Shock-layer Analysis on Hypersonic Flow Over Reentry Capsule with Nonequilibrium Chemistry


Book Description

The aerothermodynamic environment around a "EXPRESS" reentry capsule at hypersonic speed is studied in the flight regime of the severe wall heating rate with emphasis on the effects of the wall catalycity and temperature by using the axisymmetric viscous shock-layer equations with the seven-air-species non equilibrium chemistry. The wall heating rate and the electron number density in the shock-layer over the capsule are predicted at various altitudes on its night trajectory. In order to evaluate the wall catalycity, the finite catalytic wall model is introduced. The sensitivity of the wall heating rate to the uncertainties in the chemical reaction model and the wall condition model is investigated parametrically. The extent of the influences of the wall conditions on the shock-layer flow properties strongly depends on the extent of flow non equilibrium.