Search Results

Force and moment measurements, and surface flow patterns have been obtained for a one-fifth scale model of a single-engine general aviation aircraft utilizing a 15% thick natural laminar flow wing section. The data is for typical pre- and post-stall angles of attack, aircraft yaw attitudes, surface roughness and Reynolds number conditions. Results from a separate study of the wing alone are also given for comparison. This comparison shows that the fuselage/tail assembly acts as a lifting body. The aerodynamic characteristics show marked deterioration with increasing surface roughness. In addition, the studies indicate that the transition on the wing is characterized by laminar short bubble separation. The aerodynamic characteristics are somewhat unaffected by the presence of mini-tufts. The flow visualization photographs clearly show the transition and separation regions, and document the effects of variations in angle of attack and yaw on wing body interference.

Flight test experiments were conducted to measure the extent and nature of natural laminar flow on a smoothed test region of a swept-wing business jet wing. Surface hot film aneraometry and sublimating chemicals were used for transition detection. Surface pressure distributions were measured using pressure belts. Engine noise was monitored by a microphone attached to the wing surface to study possible acoustic effects on stability of the laminar boundary layer, Side-slip conditions were flown to simulate changes in effective wing sweep. Flight instrumentation and ground data analysis techniques and a method for measuring intermittency of turbulence are described, Correlation was obtained between the hot film gage signals and chemicals for transition detection. Cross-flow vortices were observed for some flight conditions. Results of spectral and statistical analysis of the hot film signals for various flight test conditions are presented.

The results of an analytical study of aerodynamic interference effects for a light twin aircraft are presented. The data presented concentrates on the influence of a wing on a body (the fuselage). Wind tunnel comparisons of three fillets are included, with corresponding computational analysis. Results indicate that potential flow analysis is useful to guide the design of intersection fairings, but experimental tuning is still required. While the study specifically addresses a light twin aircraft, the methods are applicable to a wide variety of aircraft.

Summary findings and bibliographical information are presented for airfoil and airfoil-related research conducted at Wichita State University during the past decade. Topics include flap, aileron, and spoiler design data for new airfoils, extensive flow measurements, modifications to older airfoils, new symmetrical sections and contributions to analytical methods for cases with partial separation.

A split-film anemometer has been adapted for measurement of highly turbulent intermittently reversing flows in regions of local separation around airfoils and flaps. Analog signals from the split-film anemometer are fed directly to a mini-computer for processing and analysis. Mean velocity magnitude and direction, intermittency of reversal, turbulence intensity and histograms of the velocity are obtained as outputs of the system.

From experimental correlations of airfoil and flap pressure distributions, it is observed that flow separation is likely to occur when the canonical pressure recovery coefficient (Cpr) exceeds a critical value. A procedure is described for obtaining the Cpr parameter from modified inviscid analysis. The procedure has been applied to preliminary design studies of a new slotted flap to determine the influence of shape and location. Experiments are planned to evaluate the flap designed by this procedure.

Research has been conducted on the nature of airfoil behavior at pre- and post-separated angles of attack. Detailed wind tunnel studies have been made of boundary layer and wake fields for the GA(W)-1 airfoil, and the airfoil with a 0.3 chord Fowler flap. Experimental data are compared with theoretical predictions from a multi-element viscous flow computer program. Theoretical predictions are reasonably accurate for unseparated flows, but have serious errors when separation is present. Some recent techniques for modeling post-separated flow behavior are discussed in light of the present experiments.

Tests of a finite-span wing with an advanced technology GA(W)-1 airfoil, spoilers, and 30% full-span Fowler flap have been conducted utilizing a reflection-plane model in the WSU low speed wind tunnel. Flap settings from 0° to 40° were tested with a series of 10% chord spoilers of various cross-sectional shapes. Wing force and spoiler hinge moment measurements were made, as well as tuft studies of stalling patterns. Results show that a finite span (aspect ratio 9.5) CLmax value of 3.0 can be obtained with 40° flap at a Reynolds number of 1.0 x 106. Spoiler results correlate well with two-dimensional results, which show that satisfactory roll control can be obtained for all flap settings, with proper lower surface venting. Spoiler gap leak lift and drag penalties were found to be quite substantial, indicating a need for careful design of gaps and seals for flap and spoiler nested configurations.

As part of a general aviation airfoil development program being carried out under the direction of the NASA Langley Research Center, a 30% chord Fowler flap has been developed for the GA(W)-1 airfoil.. Wind tunnel tests at Wichita State University have demonstrated a c1max value of 3.80 for 40 deg flap deflection at a Reynolds number of 2.2 × 106. Effects of flap slot geometry have been systematically tested and optimum flap settings for any flight c1 have been obtained. Modification of the reflexed lower surface contour resulted in a reduced c1max with flap nested. Vortex generators provided an increase in c1max of 0.2 for flap nested and 40 deg flap along with a drag penalty at low c1 values. Flow visualization studies show that the stalling patterns for the new airfoil are characterized by an absence of leading edge separation for both the flap-nested and the 40 deg flap cases.

A computing routine has been developed for calculation of two-dimensional incompressible airfoil characteristics on a small (IBM 1130) digital computer. Theodorsen's method of conformal transformation is utilized to obtain potential flow pressure distributions. A selection of quadrature methods are utilized to obtain boundary layer characteristics, including laminar and turbulent layers, instability, transition, and separation. Selected results are presented which illustrate the capabilities and limitations of the program. Typical computing times and costs are presented. Several suggested improvements to the calculation routine are discussed.