Engineering topics

Schreiner, John A.

Publications and source records attributed to Schreiner, John A..

4 records

NASA NTRS1990

Canard-wing vortex interactions at subsonic through supersonic speeds

The NASA-Ames 6 x 6-foot Transonic/Supersonic Wind Tunnel has been used to conduct a study of canard-wing flowfield interactions at sub-, trans-, and supersonic speeds, giving attention to vortex interactions, vortex breakdown, shock-wave development, and vortex-shock interactions. The results obtained show that the canard-wing flowfield interaction delays vortex breakdown to a higher angle-of-attack at sub- and transonic speeds; while the flowfield interference eliminates shock-induced secondary boundary layer separation on the wing, it does not alter the location and development of a rear shock wave extending laterally across the wing. A canard-induced upwash field accelerates the upward migration of the wing vortex at sub-through-supersonic speeds, but is most pronounced at transonic speeds due to the interaction of the vortical flow with the rear shock wave.

Erickson, Gary E.↗

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.↗