Engineering topics

Doggett, Glen P.

Publications and source records attributed to Doggett, Glen P..

3 records

NASA NTRS2007

Spanwise Wing Loads on the Space Shuttle Orbiter during Roll Maneuver

Spanwise aerodynamic loads for the low-Mach, high-attitude portion of ascent for the Space Shuttle Orbiter are presented. In this Mach 0.3 flight regime, also called the roll maneuver, pre-stall and post-stall distributions of aerodynamic wing shear force, bending moment, and torsion moment were obtained from wind tunnel test data and computational fluid dynamics simulations of the Space Shuttle Launch Vehicle. The spanwise loads were computed by integration of surface pressure data. The existing historical operational database of spanwise wing loads for the Orbiter does not cover this low-Mach, high-attitude condition, however for Mach 0.6 low-attitude conditions the experimental and computational results compare well with the operational data which has been validated by past flight measurements. Spanwise load distributions exhibit typical delta-wing characteristics. The computational results capture well the peak loading condition in the pre-stall case, but show more load relief for the post-stall case than was observed in the wind tunnel test data.

Doggett, Glen P.↗

NASA NTRS1996

Hypersonic Boundary-Layer Stability Experiments on a Flared-Cone Model at Angle of Attack in a Quiet Wind Tunnel

An experimental investigation of the effects of angle of attack on hypersonic boundary-layer stability on a flared-cone model was conducted in the low-disturbance Mach-6 Nozzle-Test Chamber Facility at NASA Langley Research Center. This unique facility provided a 'quiet' flow test environment which is well suited for stability experiments because the low levels of freestream 'noise' minimize artificial stimulation of flow-disturbance growth. Surface pressure and temperature measurements documented the adverse-pressure gradient and transition-onset location. Hot-wire anemometry diagnostics were applied to identify the instability mechanisms which lead to transition. In addition, the mean flow over the flared-cone geometry was modeled by laminar Navier-Stokes computations. Results show that the boundary layer becomes more stable on the windward ray and less stable on the leeward ray relative to the zero-degree angle-of-attack case. The second-mode instability dominates the transition process at a zero-degree angle of attack, however, on the windward ray at an angle of attack this mode was completely stabilized. The less-dominant first-mode instability was slightly destabilized on the windward ray. Non-linear mechanisms such as saturation and harmonic generation are identified from the flow-disturbance bispectra.

Doggett, Glen P.↗

NASA NTRS1992

A large-field laser holographic focusing schilieren system

A large-field laser holographic focusing schlieren system for high-speed flow visualization has been built and evaluated. This system is based on a recently improved large-field focusing schlieren technique and is combined with laser holography methods to record three-dimensional flows. A coordinated experimental and computational study of supersonic flows over wedge, cone, and sphere geometries was conducted to evaluate the capabilities and limitations of the system. The ability of the system to focus on planes normal to its optical axis is demonstrated. The sharpness of focus of the present system was found to be limited. Issues regarding obtaining quantitative measurements of the density gradient are discussed.

Doggett, Glen P.↗