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Technical Paper

Aerodynamic Investigation of Wing Tip Sails

Wing tip sails were investigated to determine potential aerodynamic improvements for a wing having an aspect ratio of 10 and a taper ratio of 0.43. The airfoil section used for the wing was an NLF- 0215 and the wing tip was rounded. Three tip sails were utilized for all investigations with each tip sail having a root chord that was 20 percent tip chord of the wing. The wing sails were mounted at the tip of the wing along the chord line. Looking along the span towards the wing root the orientation of each sail tip was the same as the wing tip. Initial studies used sails constructed from two Wortman airfoils. A generic cambered tip-sail was also investigated. Individual sail angle of attack as well as sail dihedral and anhedral were investigated. PMARC, an aerodynamic paneling code was used to predict lift, induced drag, and viscous drag with the use of a momentum integral analysis. All viscous predictions were calculated for a Re/foot = 2.19 × 106.
Technical Paper

An Inviscid Aerodynamic Investigation of Wing/Winglet Geometries for RPV Applications

Wings constructed using the Wortmann FX 63-137 low speed airfoil, which operates in a Reynold's number range from 0.28 * 106 to 0.7 * 106, with the addition of winglets are studied to determine the winglet geometry that produces the best increase in wing efficiency. The analysis was done using VSAERO, an inviscid panel code program. All configurations are compared to a wing without winglets to determine the percent increase in efficiency. It is demonstrated that with proper selection of winglet taper ratio, tip setback, height, cant angle, geometric twist angle, and airfoil section induced drag can be significantly reduced. Wings with winglets are shown to be more efficient than wings without winglets for all cases.
Technical Paper

Non Linear Induced Drag Study of Generically Cambered Closely Coupled Dual Wings

A non-linear thin vortex lattice method, BSAERO, with wake rollup has been used to analyze closely coupled generic dual wings. These induced drag studies involved using generic mean camber line wings created using two parabolas. Using this parabola method the location of maximum camber and the magnitude of the maximum camber were varied independently of one another. CL/CDi was used as the success parameter for a particular wing system configuration. The best dual wing geometry configuration had a CL/CDi 18% greater than the comparable dual baseline with symmetric wings. The worst dual wing configuration had a CL/CDi which was 63% below the dual wing baseline. Systematic result are presented which will demonstrate trends as well as magnitudes for the best types of dual wing configurations for minimum induced drag.
Technical Paper

CFD Calculations of Closely Coupled Scissor Wings-Inviscid, Viscous, and Vortex Lattice with Rollup Results

The Scissor Wing Configuration was investigated in the takeoff, landing, and low speed maneuverability area. In this area of operation the scissor lifting surfaces are close to each other and are strongly coupled aerodynamically. Two dimensional viscous and three dimensional vortex lattice results are presented for the scissor wings both of which used a NASA 64A-006 wing section. A multi-element vortex panel code was utilized for the inviscid predictions along with a momentum integral boundary layer code for the viscous predictions. A non-linear vortex-lattice code with wake roll-up was used for the induced drag predictions. Studies were conducted with gap variations between the two wings, longitudinal variation between the two wings, variations in the relative angle between the two wings, leading edge flap variations, and trailing edge flap variations.
Technical Paper

Some Additional Stability and Performance Characteristics of the Scissor/Pivot Wing Configurations

The scissor wing configuration is analyzed for unequal forward/rearward wing area ratios and for different wing sweep schedules of the forward and rearward wings. Clα, CMα, static margin, and sweep schedule results are presented as a function of flight Mach number for various sweep schedules and two wing area ratios. Complete aircraft, lift to drag ratio, and power required results are presented for the configuration that was able to maintain static margin over the largest range of Mach numbers. The potential benefits of the scissor wing configuration are presented and discussed in terms of potential increased performance potential or smaller engine.
Technical Paper

Analysis of the Effect of Heat Strips on Boundary Layer Development Over a Flat Plate

Two dimensional fourth order boundary layer calculations were made for flows over a flat plate with and without flush mounted surface heating. Constant wall temperature, increasing wall temperature and decreasing wall temperature heating cases were studied for different surface heating lengths. The boundary layer properties; temperature, tangential velocity, normal velocity, vorticity and transition location were studied for these temperature distributions. The boundary layer results indicate that with the proper selection of surface temperature variation and length the transition location can be either increased or decreased. Modified boundary layer properties, due to heating are shown to persist well after heating is stopped, even when the flow is turbulent. The results indicate that this technique may be useful in modifying transition and separation locations over airfoils.
Technical Paper

Some Aerodynamic Characteristiscs of the Scissor Wing Configuration

A scissor wing configuration, consisting of four adjustable wing surfaces, is compared with a comparable fixed wing baseline configuration. Wave drag, induced drag, viscous drag, thrust required, and gust loading are calculated for both configurations. The scissor wing is shown to have lower zero lift wave drag and higher total lift to drag ratios than the baseline. It is demonstrated that the scissor configurations' sweep can be programmed to keep the static margin fixed. Thrust required for both the fixed static margin case and a constant sweep angle case are presented with the scissor configuration requiring lower thrust levels. The gust loading ratio of the scissor wing to the baseline is also shown to be significantly less than 1.0 for sweep angles greater than 20 degrees.
Technical Paper

Analytical Study of Three-Surface Lifting Systems

Conventional, canard, and three surface aircraft configurations are investigated analytically to determine each configuration's induced drag, as well as the pressure and viscous drag. A vortex panel method in conjunction with momentum integral boundary layer method is used to predict inviscid and viscous characteristics. Vortex lattice methods are used to trim the aircraft as well as to predict the induced drag of each configuration. Viscous and induced drag results are presented for two different payloads, a six-place and a twelve-place configuration. For both payloads the conventional configuration had the highest lift over drag. However, the canard and the three surface were close enough to warrant consideration based on other criteria.