Engineering topics

Kleiser, Leonhard

Publications and source records attributed to Kleiser, Leonhard.

3 records

NASA NTRS1991

Numerical simulation of transition in wall-bounded shear flows

The current status of numerical simulation techniques for the transition to turbulence in incompressible channel and boundary-layer flows is surveyed, and typical results are presented graphically. The focus is on direct numerical simulations based on the full nonlinear time-dependent Navier-Stokes equations without empirical closure assumptions for prescribed initial and boundary conditions. Topics addressed include the vibrating ribbon problem, space and time discretization, initial and boundary conditions, alternative methods based on the triple-deck approximation, two-dimensional channel and boundary-layer flows, three-dimensional boundary layers, wave packets and turbulent spots, compressible flows, transition control, and transition modeling.

Kleiser, Leonhard↗

NASA NTRS1990

Direct numerical simulation of the transitional zone

Properties of the transitional zone in channel and boundary-layer flow are determined from the results of direct numerical simulations of forced transition. Three channel flow cases produce similar behavior, particularly in the 'transition function' relevant for some algebraic eddy viscosity models of the transitional zone. Moreover, the transitional zone from the computed forced boundary-layer transition is qualitatively similar to experimental data for natural transition and to the computed channel flow transition.

Zang, Thomas A.↗

NASA NTRS1990

Nonlinear development of crossflow vortices

Nonlinear crossflow vortices in an incompressible three-dimensional boundary layer are computed by weakly nonlinear theory and direct numerical simulations. The parallel basic flow is defined by Falkner-Skan-Cooke similarity profiles. The temporal evolution of spanwise periodic, quasi-two-dimensional disturbances without variations along the vortex axis is considered. The nonlinear theory is based on the approach of Herbert (1980, 1983). The theory predicts the existence of the finite amplitude equilibrium states seen in earlier simulations. When the disturbance amplitudes are small, there is very good quantitative agreement in the fundamental disturbance velocity components between the theory and the simulations.

Singer, Bart A.↗