Adaptive Grid Algorithm Research Articles

The Influence of Surface Chemistry on the Development of Minor Species Profiles in the Premixed Boundary Layer Combustion of an H2/Air Mixture

Abstract The combustion of premixed hydrogen/air mixtures flowing over a hot catalytic and non-catalytic surface has been modelled using a modified Newton's method and an adaptive gridding algorithm for the solution of the governing boundary layer equations. Detailed transport, including thermophoretic effects, and gas phase chemical kinetics were included in the model. The surface boundary conditions in the catalytic case include a mass transport limited surface reaction of H2 and O2 to form H2Oand OH. The relative amounts of H,0 and OH were taken from available experimental data and were varied to test the effect of the amount of desorbed OH on radical profile shapes. Heat release and O-atom profiles exhibit a double peak as a result of OH desorption. The heat release in the catalytic case is significantly lower near the leading edge of the plate resulting in slower flame propagation into the boundary layer. Recombination reactions of the unstable species (O, OH, H, HO2, H2O2) on the wall were included in the non-catalytic case. The sticking coefficients of the recombination reactions were varied to test the effect of the recombination rate on radical profile shapes.

Solution of the Fourth-moment Equation by an Adaptive Grid Method

Abstract The parabolic fourth moment equation for a plane wave is integrated numerically using an adaptive grid algorithm. Results are compared with those from an accurate, but far less efficient, operator splitting method, and agree very closely. The adaptive approach has several advantages over current fixed grid methods. The primary one is that significant reductions in computer memory usage can be obtained without a concomitant increase in run time. It is also ideally suited for accurate integration of the fourth-moment equation for an extremely large range of values of both the scattering parameter, Γ, and the wave propagation distance.

Adaptive triangular mesh generation

A general adaptive grid algorithm is developed on triangular grids. The adaptivity is provided by a combination of node addition, dynamic node connectivity and a simple node movement strategy. While the local restructuring process and the node addition mechanism take place in the physical plane, the nodes are displaced on a monitor surface, constructed from the salient features of the physical problem. An approximation to mean curvature detects changes in the direction of the monitor surface, and provides the pulling force on the nodes. Solutions to the axisymmetric Grad-Shafranov equation demonstrate the capturing, by triangles, of the plasma-vacuum interface in a free-boundary equilibrium configuration.

A finite-volume, adaptive grid algorithm applied to planetary entry flowfields

An adaptive grid, finite volume method has been applied to problems of planetary entry in computing complete flowfields. The adaptation algorithm is implicit in nature and is keyed to resolve user-specified gradients. The finite-volume algorithm is explicit, utilizing a maximum time step advancement at each grid point to accelerate convergence to the steady state. The present version of the code is for the laminar flow of a perfect gas. The role of the adaptation algorithm in resolving various features of blunt body/wake flow for planetary entry conditions is emphasized. The algorithm is demonstrated on problems involving massive blowing from the surface of the Galileo probe and moderate blowing from the surface of a sphere.