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Kopriva, David A.

Publications and source records attributed to Kopriva, David A..

12 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

A conservative staggered-grid Chebyshev multidomain method for compressible flows

We present a new multidomain spectral collocation method that uses staggered grids for the solution of compressible flow problems. The solution unknowns are defined at the nodes of a Gauss quadrature rule. The fluxes are evaluated at the nodes of a Gauss-Lobatto rule. The method is conservative, free-stream preserving, and exponentially accurate. A significant advantage of the method is that subdomain corners are not included in the approximation, making solutions in complex geometries easier to compute.

Kopriva, David A.↗
NASA NTRS1994

Spectral solution of the viscous blunt body problem. 2: Multidomain approximation

We present steady solutions of high speed viscous flows over blunt bodies using a multidomain Chebyshev spectral collocation method. The region with the shock layer is divided into subdomains so that internal layers can be well-resolved. In the interiors of the subdomains, the solution is approximated by Chebyshev collocation. At interfaces between subdomains, the advective terms are upwinded and the viscous terms are treated by a penalty method. The method is applied to five flows, the Mach number range 5-25 and Reynolds number range 2,000 - 83,000, based on nose radius. Results are compared to experimental data and to a finite difference result.

Kopriva, David A.↗
NASA NTRS1993

Spectral solution of the viscous blunt-body problem

The viscous blunt-body problem is solved with a shock-fitted Chebyshev spectral method. No explicit artificial viscosity or filtering is needed to obtain smooth, converged solutions. The method is applied to two problems. First, results for the flow over a right circular cylinder in the Mach number range of 5.5-6.0 are compared with experimental data. Second, a solution for a Mach 25 flow over a hyperbolic cone is compared with a viscous shock-layer calculation.

Kopriva, David A.↗
NASA NTRS1993

A multidomain spectral method for viscous compressible flows

We present a new multidomain spectral method for the solution of the compressible Navier-Stokes equations. In the subdomain interiors, Chebyshev spectral collocation is used. At interfaces, the advective terms are upwinded and the viscous terms are treated by a penalty method. The method is applied to the solution of a viscous hypersonic flow over a blunt body.

Kopriva, David A.↗
NASA NTRS1992

Spectral solution of inviscid supersonic flows over wedges and axisymmetric cones

A shock-fitted multidomain spectral collocation method is used to solve both steady and unsteady inviscid supersonic flows over bodies. New aspects of the method include two subdomain interface types and a zonal solution procedure to get efficient convergence to steady-state in supersonic regions. Steady-state examples include flow over a sharp cone, a hyperbolic cone and a hyperbolic wedge. For the cone, the exact flow solution is used to show that the method is spectrally accurate. As an example of an unsteady flow, a calculation of the interaction of a free-stream hot ring with the flow over a sharp cone is presented.

Kopriva, David A.↗
NASA NTRS1991

Multidomain spectral solution of the Euler gas-dynamics equations

The present interfacial treatments for Euler gasdynamic equation computations via the multidomain Chebyshev spectral collocation method are applicable both at subdomain corners and in overlapping or patched subdomains, for interfaces located in the sub-, super-, or transonic regions of a flow. The results thus obtained are found to be (1) spectrally accurate, (2) both more accurate and more efficient than a single-domain calculation, and (3) potentially more accurate and efficient than a single-domain calculation. Interfacial wave reflection is insignificant.

Kopriva, David A.↗
NASA NTRS1991

Spectral methods for the Euler equations - The blunt body problem revisited

The present use of the Chebyshev spectral collocation method, in conjunction with shock-fitting, to solve the blunt-body problem gives attention to the boundary and the shock-acceleration equations. The crux of these procedures is the use of the characteristic compatibility relations to compute the body pressure and shock velocity. It is shown that converged solutions are obtainable without artificial smoothing, and that spectral accuracy is achieved.

Kopriva, David A.↗
NASA NTRS1990

Spectral solution of acoustic wave-propagation problems

The Chebyshev spectral collocation solution of acoustic wave propagation problems is considered. It is shown that the phase errors decay exponentially fast and that the number of points per wavelength is not sufficient to estimate the phase accuracy. Applications include linear propagation of a sinusoidal acoustic wavetrain in two space dimensions, and the interaction of a sound wave with the bow shock formed by placing a cylinder in a uniform Mach 4 supersonic free stream.

Kopriva, David A.↗
NASA NTRS1989

Multidomain spectral solution of shock-turbulence interactions

The use of a fitted-shock multidomain spectral method for solving the time-dependent Euler equations of gasdynamics is described. The multidomain method allows short spatial scale features near the shock to be resolved throughout the calculation. Examples presented are of a shock-plane wave, shock-hot spot and shock-vortex street interaction.

Kopriva, David A.↗
NASA NTRS1987

A practical assessment of spectral accuracy for hyperbolic problems with discontinuities

Physical and transform space filtering has been applied to the Fourier spectral collocation solution of the constant coefficient scalar wave equation with a discontinuous initial condition. High order accuracy can be extracted from the unfiltered solution. Smooth, high order Fourier space filtering gives expected polynomial order solutions away from the discontinuity. Spectral accuracy is observed with the physical space filter of Gottlieb and Tadmor.

Kopriva, David A.↗
NASA NTRS1986

A practical assessment of spectral accuracy for hyperbolic problems with discontinuities

Physical and transform space filtering has been applied to the Fourier spectral collocation solution of the constant coefficient scalar wave equation with a discontinuous initial condition. High order accuracy can be extracted from the unfiltered solution. Smooth, high order Fourier space filtering gives expected polynomial order solutions away from the discontinuity. Spectral accuracy is observed with the physical space filter of Gottlieb and Tadmor.

Kopriva, David A.↗