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Hessenius, K. A.

Publications and source records attributed to Hessenius, K. A..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Three-dimensional, conservative, Euler computations using patched grid systems and explicit methods

The method of 'zonal approach' (in which the flow field is partitioned into regions with independent grids) for computation of flow over complex geometries, such as aircraft configuration, requires application of a grid-interfacing procedure. A three-dimensional conservative, boundary scheme for patched grids, applicable in generalized coordinates for arbitrary point distributions on a planar zonal surface is presented. The computation technique is derived within the framework of the Osher (1983) upwind scheme, using Euler equations. The three-dimensional interfacing method is applied to the computation of flow about a wing-canard combination using a two-zone, patched grid.

Hessenius, K. A.↗
NASA NTRS1984

Applications of a conservative zonal scheme to transient and geometrically complex problems

A conservative zoning technique, wherein the flow field for a finite-difference calculation is divided into several regions to simplify grid generation, is discussed and is applied in the solution of a two-dimensional problem of complex topology. Calculations are performed on two zonal, or patched, grid systems for the supersonic flow over a double-airfoil configuration. The solution is smooth and continuous across the zonal interfaces, and shock waves pass through the boundaries without distortion. In addition, the time-accuracy of the zonal-boundary method is verified by a two-zone cyclinder calculation with a stationary inner and a rotating outer mesh.The feasibility of the zonal approach for use in the solution of geometrically complex and unsteady problems is thus demonstrated.

Hessenius, K. A.↗
NASA NTRS1984

Metric-discontinuous zonal grid calculations using the Osher scheme

Computations on zonal grids - in particular, grids with metric discontinuities resulting from the interspersion of highly clustered regions with coarse regions - are possible using a fully conservative form of the Osher upwind scheme. These zonal grids can result from an abrupt clustering of points near solution discontinuities or near other flow features that require improved resolution. The zonal approach is shown to capture shocks with almost 'shock-fitting' quality but with minimal effort. Results for inviscid flow, including quasi-one-dimensional nozzle flow, supersonic flow over a cylinder, and blast-wave diffraction by a ramp, are presented. These calculations demonstrate the powerful capabilities of the Osher scheme used in conjunction with zonal grids in simulating flow fields with complex shock patterns.

Rai, M. M.↗
NASA NTRS1982

A zonal approach to solution of the Euler equations

A technique for the solution of the one- and two-dimensional Euler equations in a partitioned flow field is presented. The field is divided into distinct 'zones', each of which is computed separately. An implicit boundary procedure based on the characteristic propagaion of information and flux splitting methods is applied at the zonal interfaces. Numerical results are presented for both quasi-one-dimensional nozzle flows with shock waves and the unsteady shock-tube problem. These calculations demonstrate the capability of shock propagation through arbitrarily located zonal boundaries in a stable, conservative, and accurate manner. Two-dimensional results include the zonal computation of flows over blunt bodies and airfoils.

Hessenius, K. A.↗
NASA NTRS1981

A validation of LTRAN2 with high frequency extensions by comparisons with experimental measurements of unsteady transonic flows

A high frequency extension of the unsteady, transonic code LTRAN2 was created and is evaluated by comparisons with experimental results. The experimental test case is a NACA 64A010 airfoil in pitching motion at a Mach number of 0.8 over a range of reduced frequencies. Comparisons indicate that the modified code is an improvement of the original LTRAN2 and provides closer agreement with experimental lift and moment coefficients. A discussion of the code modifications, which involve the addition of high frequency terms of the boundary conditions of the numerical algorithm, is included.

Hessenius, K. A.↗