Engineering topics

Visser, K. D.

Publications and source records attributed to Visser, K. D..

4 records

NASA NTRS1993

Measurements of circulation and vorticity in the leading-edge vortex of a delta wing

The present cross-wire measurements of the flowfield above a 75-deg flat-plate delta wing have yielded distributions of velocity, axial vorticity, and circulation which exhibit strongly conical behavior upstream of the breakdown region and away from the apex and trailing edge regions. The conical character of these properties is most pronounced over the central portion of the planform, away from the apex and trailing-edge regions. This behavior is further documented by the roughly linear increase in vortex strength with distance from the apex over the forward area of the wing.

Visser, K. D.↗

NASA NTRS1989

A flow visualization and aerodynamic force data evaluation of spanwise blowing on full and half span delta wings

A wind-tunnel investigation has been performed to quantify the effects of a jet on the leading-edge vortices generated by a 70-deg-sweep sharp-edged delta wing at low Reynolds numbers. Efforts were made ot optimize the jet nozzle position with respect to maximum lift increments. Both half-span force-balance testing and half- and full-span flow visualization tests were conducted. Two angles of attack were investigated, 30 and 35 deg, at Reynolds numbers of 150,000 and 200,000. Aerodynamic enhancement, including lift and drag gains of about 20 and 17 percent respectively, were measured. Results indicate an optimum jet nozzle location to be close to the leading edge, tangent to the upper wing surface, and in a direction aligned parallel to the leading edge. Nozzle interference effects, especially near the apex, were not negligible.

Visser, K. D.↗

NASA NTRS1988

Method of cold smoke generation for vortex core tagging

Attention is given to the flow-visualization problem posed by the 'dark-core' region of the vortices formed on the upper side of a delta wing; the low particle density in the core region minimizes the density of tracing particles whose presence is essential in LDV measurements. An effort is presently undertaken using TiCl4 smoke in subsonic wind tunnel tests of a 70-deg sweep delta wing model.

Nelson, R. C.↗

NASA NTRS1988

Control of leading edge vortex breakdown by blowing

An investigation into the effects of using a jet of air to control the vortex breakdown position on a 70 degree delta wing is presented. The specific objectives focused on optimizing the blowing positions in terms of maximum lift increments obtained for minimum blowing rates. The tests were conducted at chord Reynolds numbers of 150,000, 200,000, and 250,000 at angles of incidence of 30 and 35 degrees. Visualization and force data is presented to show the effect of the jet on the wing aerodynamic characteristics. The results indicate a jet position located at and aligned parallel to the leading edge to be the optimum. Nearness to the apex and tangency to the upper surface were also crucial factors. The influence of the jet on the leading edge vortex structure was examined using laser Doppler anemometry. Velocity surveys through the vortex showed that at high blowing rates the parallel velocity in the outer swirling region of the vortex increased and the normal velocity decreased. This resulted in a decrease in the swirling angle in the outer region. The peak core velocity was reduced and the vortex breakdown was delayed.

Visser, K. D.↗