Engineering topics

Erickson, Gary E.

Publications and source records attributed to Erickson, Gary E..

43 records · Page 3

NASA NTRS1990

Multiple vortex and shock interactions at subsonic, transonic, and supersonic speeds

A wind tunnel experiment was conducted at subsonic, transonic, and supersonic speeds of the vortex-vortex and vortex-shock interactions about a tailless, general research fighter model having chine-like forebody strakes faired into a 55 deg cropped delta wing. The present paper isolates the results obtained at angle of attack 20 deg and free-stream Mach = 0.6 to 1.6, which include off-surface and on-surface flow visualizations, two-component laser velocimeter measurements, and wing upper surface static pressure distributions. Increasing the Mach number decreased the direct interaction (intertwining) of the forebody strake and wing vortex cores. An early bursting of the wing vortex occurred at free-stream Mach = 0.8, where the flow field was in transition from the intertwining vortices characteristic of the lower subsonic speeds to the decoupled vortices at the transonic and supersonic speeds. The vortex interaction and breakdown were sensitive to the character of the secondary boundary layer separation on the wing, which may be shock-induced at free-stream Mach = 0.8 to 0.95.

Erickson, Gary E.↗

NASA NTRS1989

On the structure, interaction, and breakdown characteristics of slender wing vortices at subsonic, transonic, and supersonic speeds

Slender wing vortex flows at subsonic, transonic, and supersonic speeds were investigated in a 6 x 6 ft wind tunnel. Test data obtained include off-body and surface flow visualizations, wing upper surface static pressure distributions, and six-component forces and moments. The results reveal the transition from the low-speed classical vortex regime to the transonic regime, beginning at a freestream Mach number of 0.60, where vortices coexist with shock waves. It is shown that the onset of core breakdown and the progression of core breakdown with the angle of attack were sensitive to the Mach number, and that the shock effects at transonic speeds were reduced by the interaction of the wing and the lead-edge extension (LEX) vortices. The vortex strengths and direct interaction of the wing and LEX cores (cores wrapping around each other) were found to diminish at transonic and supersonic speeds.

Erickson, Gary E.↗

NASA NTRS1989

Experimental investigation of the F/A-18 vortex flows at subsonic through transonic speeds

A subsonic-to-transonic speed wind tunnel study has been conducted to deepen understanding of the nature and possibilities for control of vortical flows associated with wing leading edge extensions (LEXs) on the F/A-18 aircraft; these vortical phenomena encompass vortex breakdown and vortex interactions with vertical stabilizers. Wind tunnel results were correlated with in-flight flow visualizations as well as handling-qualities trend data from a USN F-18 with LEX fences to improve the vertical tail buffet environment. Attention is given to the sensitivity of the vortex flows to Re and Mach numbers, reduced vertical tail excitation due to the presence of a LEX fence, and the interpretation of off-body flow visualizations.

Erickson, Gary E.↗

NASA NTRS1987

On the nonlinear aerodynamic and stability characteristics of a generic chine-forebody slender-wing fighter configuration

An exploratory investigation was conducted of the nonlinear aerodynamic and stability characteristics of a tailless generic fighter configuration featuring a chine-shaped forebody coupled to a slender cropped delta wing in the NASA Langley Research Center's 12-Foot Low-Speed Wind Tunnel. Forebody and wing vortex flow mechanisms were identified through off-body flow visualizations to explain the trends in the longitudinal and lateral-directional characteristics at extreme attitudes (angles of attack and sideslip). The interactions of the vortical motions with centerline and wing-mounted vertical tail surfaces were studied and the flow phenomena were correlated with the configuration forces and moments. Single degree of freedom, free-to-roll tests were used to study the wing rock susceptibility of the generic fighter model. Modifications to the nose region of the chine forebody were examined and fluid mechanisms were established to account for their ineffectiveness in modulating the highly interactive forebody and wing vortex systems.

Erickson, Gary E.↗

NASA NTRS1987

Experimental study of the vortex flow behavior on a generic fighter wing at subsonic and transonic speeds

A subsonic and transonic investigation of the vortex flow behavior of a generic fighter configuration with 55-deg cropped delta wing has been conducted in order to improve current understanding of vortical motions on a wing with deflected leading edge flap at moderate and high angles-of-attack. The leading edge vortex strength was reduced, and the vortex was flatter and closer to the wing surface, as the Mach number increased. Transonically, at high angles-of-attack, the test data suggested the development of a cross-flow shock wave above the vortex sheet which coexisted with a rear shock wave. Subsonically, a deflected leading edge flap was able to sustain a concentrated vortex on the forward-facing surface.

Erickson, Gary E.↗

NASA NTRS1987

Water facilities in retrospect and prospect: An illuminating tool for vehicle design

Water facilities play a fundamental role in the design of air, ground, and marine vehicles by providing a qualitative, and sometimes quantitative, description of complex flow phenomena. Water tunnels, channels, and tow tanks used as flow-diagnostic tools have experienced a renaissance in recent years in response to the increased complexity of designs suitable for advanced technology vehicles. These vehicles are frequently characterized by large regions of steady and unsteady 3-D flow separation and ensuing vortical flows. The visualization and interpretation of the complicated fluid motions about isolated vehicle components and complete configurations in a time and cost effective manner in hydrodynamic test facilities is a key element in the development of flow control concepts, and, hence, improved vehicle designs. A historical perspective of the role of water facilities in the vehicle design process is presented. The application of water facilities to specific aerodynamic and hydrodynamic flow problems is discussed, and the strengths and limitations of these important experimental tools are emphasized.

Erickson, Gary E.↗

NASA NTRS1987

On the nonlinear aerodynamic and stability characteristics of a generic chine-forebody slender-wing fighter configuration

An exploratory investigation was conducted of the nonlinear aerodynamic and stability characteristics of a tailless generic fighter configuration featuring a chine-shaped forebody coupled to a slender cropped delta wing in the NASA Langley Research Center's 12-Foot Low-Speed Wind Tunnel. Forebody and wing vortex flow mechanisms were identified through off-body flow visualizations to explain the trends in the longitudinal and lateral-directional characteristics at extreme attitudes (angles of attack and sideslip). The interactins of the vortical motions with centerline and wing-mounted vertical tail surfaces were studied and the flow phenomena were correlated with the configuration forces and moments. Single degree-of-freedom, free-to-roll tests were used to study the wing rock susceptibility of the generic fighter model. Modifications to the nose region of the chine forebody were examined and fluid mechanisms were established to account for their ineffectiveness in modulating the highly interactive forebody and wing vortex systems.

Erickson, Gary E.↗