Showing papers on "Vortex lift published in 1979"
01 Nov 1979
TL;DR: In this paper, the suction effect of coiled vortices generated through controlled separation over leading edge flap surfaces to produce a thrust component was discussed, and a series of vortex-flap configurations were investigated to explore the effect of some primary geometric variables.
Abstract: Exploratory wind tunnel tests are reported on a 74 deg. delta wing model. The potential of a vortex flap concept in reducing the subsonic lift dependent drag of highly swept, slender wings is examined. The suction effect of coiled vortices generated through controlled separation over leading edge flap surfaces to produce a thrust component is discussed. A series of vortex-flap configurations were investigated to explore the effect of some primary geometric variables.
23 citations
01 May 1979
TL;DR: In this article, the aerodynamic characteristics of a circulation control elliptic airfoil section with a 15-percent thickness-to-chord ratio were evaluated subsonically, and critical Mach numbers in excess of 0.7 were predicted analytically for several typical operating conditions.
Abstract: : The aerodynamic characteristics of a circulation control elliptic airfoil section with a 15-percent thickness-to-chord ratio were evaluated subsonically. The airfoil, designated NCCR1513-7559E, incorporates a high degree of nose camber and an increased leading edge radius in a profile designed for high subsonic speeds. Critical Mach numbers in excess of 0.7 were predicted analytically for several typical operating conditions. Lift coefficients up to 4.63 were produced at momentum coefficients of 0.22. Equivalent lift-to-drag ratios of approximately 40 were also produced at C(l)= 0.8. (Author)
12 citations
TL;DR: In this article, a new technique to improve Woodward's (1968) unified subsonic and supersonic panel method is described based on a new two-dimensional theory, which can be used not only to predict the vortex lift of complex planforms through the method of suction analogy, but also to calculate some lateral directional stability derivatives.
Abstract: A new technique to improve Woodward's (1968) unified subsonic and supersonic panel method is described. The pressure prediction is improved based on a new two-dimensional theory. The method used by Lan (1977) is then used to calculate the leading-edge and side-edge suction forces by direct use of the predicted pressure distribution. The method is applicable to both subsonic and supersonic flow. It is shown that the improved Woodward panel method is capable of accurately predicting leading-edge and side-edge suction forces in subsonic and supersonic flow. Therefore, the method can be used not only to predict the vortex lift of complex planforms through the method of suction analogy, but also to calculate some lateral-directional stability derivatives.
6 citations
15 Jan 1979
TL;DR: In this article, general integral expressions are derived for the nonlinear lift and pitching moment of arbitrary wing planforms in subsonic flow. The analysis uses the suction analogy and an assumed pressure distribution based on classical linear theory results.
Abstract: General integral expressions are derived for the nonlinear lift and pitching moment of arbitrary wing planforms in subsonic flow. The analysis uses the suction analogy and an assumed pressure distribution based on classical linear theory results. The potential flow lift constant and certain wing geometric parameters are the only unknowns in the integral expressions. Results of the analysis are compared with experimental data and other numerical methods for several representative wings, including ogee and double-delta planforms. The present method is shown to be as accurate as other numerical schemes for predicting total lift, induced drag, and pitching moment. b c c CL CD Cm CT Cs cc, ccd E2 Nomenclature = aspect ratio = wing span =chord = reference length = lift coefficient = drag coefficient = pitching moment coefficient = thrust coefficient = suction coefficient = section lift coefficient = section induced drag coefficient = section suction coefficient = pressure loading coefficient = drag = proportionality constant, Eq. (32) = proportionality constant, Eq. (53) = chordwise function, Eq. (44) ff(rj) = span wise f unction, Eq. (28) K = potential constant L =lift loading constant, Eq. (5) S = suction force SR = reference area s = suction force per unit length T = leading edge thrust, Eq. (7) T' = leading edge thrust per unit length V = freestream speed Wj = downwash velocity component, Eq. (11) a. = angle of attack F = vorticity p = freestream density £ = nondimensional chordwise coordinate 77 = nondimensional spanwise coordinate A = leading edge sweep angle Subscripts P = potential flow E =edge / = induced VLE = leading edge vortex VSE = side edge vortex
5 citations
Patent•
12 Jul 1979
TL;DR: In this article, an annular lift surface-cum-flywheel rotating about a cylindrical control and cargo compartment as its axis, supported on hydrodynamic, aerodynamic or magnetic bearings is designed to obtain lift by dynamics of rotation.
Abstract: The flying machine is designed to obtain lift by dynamics of rotation. It comprises an annular lift surface-cum-flywheel rotating about a cylindrical control and cargo compartment as its axis, supported on hydrodynamic, aerodynamic or magnetic bearings. The lift surface has a concave undeside. Rotational energy is provided from tangential thrust orifices symmetrically disposed around the lift surface underside near the rim, on limited movement universal mountings. Orifices may be integral with thrust generating units, or the latter may be inboard with ducting to the former. Orifices may be used selectively to give a propulsive effect.
4 citations
01 Feb 1979
TL;DR: The effects of spanwise blowing on the surface pressures of a 44 deg swept trapezoidal wing-strake configuration were measured in this paper, where wind tunnel data were obtained at a free stream Mach number of 026 for a range of model angle of attack, jet thrust coefficient, and nozzle chordwise location.
Abstract: The effects of spanwise blowing on the surface pressures of a 44 deg swept trapezoidal wing-strake configuration were measured Wind tunnel data were obtained at a free stream Mach number of 026 for a range of model angle of attack, jet thrust coefficient, and nozzle chordwise location Results showed that spanwise blowing delayed the leading edge vortex breakdown to larger span distances and increased the lifting pressures Vortex lift was achieved at span stations immediately outboard of the strake-wing junction with no blowing, but spanwise blowing was necessary to achieve vortex lift at increased span distances Blowing on the wing in the presence of the strake was not as effective as blowing on the wing alone Spanwise blowing increased lift throughout the angle-of-attack range, improved the drag polars, and extended the linear pitching moment to higher values of lift The leading edge suction analogy can be used to estimate the effects of spanwise blowing on the aerodynamic characteristics
4 citations
01 Jul 1979
TL;DR: In this article, a numerical procedure for determining the position (horizontal location, vertical location, and deflection) of a leading edge slat that maximizes the lift of multielement airfoils is presented.
Abstract: A numerical procedure for determining the position (horizontal location, vertical location, and deflection) of a leading edge slat that maximizes the lift of multielement airfoils is presented. The structure of the flow field is calculated by iteratively coupling potential flow and boundary layer analysis. This aerodynamic calculation is combined with a constrained function minimization analysis to determine the position of a leading edge slat so that the suction peak on the nose of the main airfoil is minized. The slat position is constrained by the numerical procedure to ensure an attached boundary layer on the upper surface of the slat and to ensure negligible interaction between the slat wake and the boundary layer on the upper surface of the main airfoil. The highest angle attack at which this optimized slat position can maintain attached flow on the main airfoil defines the optimum slat position for maximum lift. The design method is demonstrated for an airfoil equipped with a leading-edge slat and a trailing edge, single-slotted flap. The theoretical results are compared with experimental data, obtained in the Ames 40 by 80 Foot Wind Tunnel, to verify experimentally the predicted slat position for maximum lift. The experimentally optimized slat position is in good agreement with the theoretical prediction, indicating that the theoretical procedure is a feasible design method.
3 citations
01 Jul 1979
TL;DR: In this article, the effect of the walls of a wind tunnel on the subsonic, two-dimensional flow past airfoils at high angles of attack is studied theoretically and experimentally.
Abstract: The effect of the walls of a wind tunnel on the subsonic, two-dimensional flow past airfoils at high angles of attack is studied theoretically and experimentally. The computerized analysis, which is based on iteratively coupled potential-flow, boundary-layer, and separated-flow analyses, includes determining the effect of viscosity and flow separation on the airfoil/wall interaction. Predictions of the effects of wind-tunnel wall on the lift of airfoils are compared with wall corrections based on inviscid image analyses, and with experimental data. These comparisons are made for airfoils that are large relative to the size of the test section of the wind tunnel. It is shown that the inviscid image modeling of the wind-tunnel interaction becomes inaccurate at lift coefficients near maximum lift or when the airfoil/wall interaction is particularly strong. It is also shown that the present method of analysis (which includes boundary-layer and flow-separation effects) will provide accurate wind-tunnel wall corrections for lift coefficients up to maximum lift.