Engineering topics

Chipman, R. R.

Publications and source records attributed to Chipman, R. R..

6 records

NASA NTRS1980

An alternating-direction-implicit algorithm for the unsteady potential equation in conservation form

An implicit finite difference scheme for an efficient computation of unsteady potential flow about airfoils is presented. The formulation uses density and velocity potential as dependent variables, and is cast in conservation form to assure the theoretically correct determination of shockwave location and speed. To enable boundary conditions to be imposed directly on the airfoil surface, a time varying sheared rectilinear coordinate transformation is employed. Calculated time history solutions on a pulsating airfoil are compared with the results of another unsteady transonic code. It is concluded that the method has excellent numerical stability and gives accurate solutions with sharply resolved shocks.

Chipman, R. R.↗

NASA NTRS1975

Analytical and experimental study of the effects of wing-body aerodynamic interaction on space shuttle subsonic flutter

The effects on flutter of the aerodynamic interaction between the space shuttle bodies and wing, 1/80th-scale semispan models of the orbiter wing, the complete shuttle and intermediate component combinations were tested in the NASA Langley Research Center 26-inch Transonic Blowdown Wind Tunnel. Using the double lattice method combined with slender body theory to calculate unsteady aerodynamic forces, subsonic flutter speeds were computed for comparison. Using calculated complete vehicle modes, flutter speed trends were computed for the full scale vehicle at an altitude of 15,200 meters and a Mach number of 0.6. Consistent with findings of the model studies, analysis shows the shuttle to have the same flutter speed as an isolated cantilevered wing.

Chipman, R. R.↗

NASA NTRS1974

Analysis of wing-body interaction flutter for a preliminary space shuttle design

Subsonic flutter analyses for a preliminary space shuttle design were performed to determine the effect of wing-body aerodynamic interaction on the vehicle flutter speed. It was found that the proximity of the large bodies of the shuttle to the wing reduces critical flutter speed by 11%. Aerodynamic reflection off the bodies is the dominant interaction effect while aerodynamic forces caused by body motion are of secondary importance in most cases. The analyses employed a doublet-lattice representation of the space shuttle, where in the wing and body surfaces were modeled by a lattice of nonplanar lifting surface elements. Axial singularities were introduced to account for body incidence, volume, and camber (slender body) effects. A series of studies on the placement and number of these elements was performed to ensure convergence of the results.

Chipman, R. R.↗

NASA NTRS1974

Space Shuttle flutter as affected by wing-body aerodynamic interaction

In the NASA Langley Research Center 26-inch transonic blowdown wind-tunnel, flutter speeds were measured on 1/80-th scale semispan models of the orbiter wing, the complete Space Shuttle, and intermediate component combinations. Using the doublet lattice method combined with slender body theory to calculate unsteady aerodynamic forces, subsonic flutter speeds were computed for comparison. Aerodynamic interaction was found by test and analysis to raise the flutter speed in some configurations while lowering it in others. Although at Mach number less than 0.7, predicted speeds correlated to within 6% of those measured, rapid deterioration of the agreement occurred at higher subsonic Mach numbers, especially on the more complicated configurations. Additional analysis showed that aerodynamic forces arising from body flexibility potentially can have a large effect on flutter speed, but that the current shuttle design is not so affected.

Chipman, R. R.↗

NASA NTRS1973

Flutter analysis and testing of pairs of aerodynamically interfering delta wings

To examine the effect on flutter of the aerodynamic interference between pairs of closely spaced delta wings, several structurally uncoupled 1/80th-scale models were studied by experiment and analysis. Flutter test boundaries run in a 26-in transonic blowdown wind tunnel were compared with subsonic analytical results generated using the doublet lattice method. Trends for several combinations of vertical and longitudinal wing separation showed that flutter speeds can be significantly lowered in closely spaced configurations. For some configurations, a new flutter mechanism, characterized by coupling of the flexible modes from both surfaces at a distinctive flutter frequency, was predicted and observed.

Chipman, R. R.↗

NASA NTRS1973

Flutter of pairs of aerodynamically interfering delta wings.

To examine the effect on flutter of the aerodynamic interference between pairs of closely spaced delta wings, several structurally uncoupled 1/80th-scale models were studied by experiment and analysis. Flutter test boundaries obtained in NASA Langley's 26-in. transonic blowdown wind tunnel were compared with subsonic analytical results generated using the doublet lattice method. Trends for several combinations of vertical and longitudinal wing separation were determined, showing flutter speed significantly affected in the closely spaced configurations. A new flutter mechanism coupling one wing's first bending mode with the other wing's first torsion mode was predicted and observed.

Chipman, R. R.↗