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).




Nonequilibrium Hypersonic Stagnation Flow at Low Reynolds Numbers


Book Description

An analysis of nonequilibrium-dissociated stagnation point flow on highly cooled blunt bodies in a hypersonic stream of air or diatomic gas at low Reynolds numbers is presented. An arbitrary atom recombination rate on the surface is allowed. With the use of a continuum, thin shock layer model, it is shown that for flight speeds on the order of 25,000 ft/sec or less, the problem can be broken down into two regimes, both of which can be treated analytically with good approximation. The first is a generalized nonequilibrium vorticity-interaction flow regime where most of the significant gas phase reaction effects occur, including the transition from recombination rate to dissociation rate-controlled behavior. The closed form solutions given for this regime predict atom concentrations and nonequilibrium heat transfer within 10 percent of exact numerical solutions down to shock layer Reynolds numbers of roughly 100. The second and lower Reynolds number regime embraces fully viscous shock layer flow with appreciable nonadiabatic shock slip effects; here an analytical solution is given by treating the flow as nearly chemically frozen throughout. (Author).