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Results for “MINIMUM DRAG”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1957

Bodies of Revolution Having Minimum Drag at High Supersonic Airspeeds

Approximate shapes of nonlifting bodies having minimum pressure foredrag at high supersonic airspeeds are calculated. With the aid of Newton's law of resistance, the investigation is carried out for various combinations of the conditions of given body length, base diameter, surface area, and volume. In general, it is found that when body length is fixed, the body has a blunt nose; whereas, when the length is not fixed, the body has a sharp nose. The additional effect of curvature of the flow over the surface is investigated to determine its influence on the shapes for minimum drag. The effect is to increase the bluntness of the shapes in the region of the nose and the curvature in the region downstream of the nose. These shape modifications have, according to calculation, only a slight tendency to reduce drag. Several bodies of revolution of fineness ratios 3 and 5, including the calculated shapes of minimum drag for given length and base diameter and for given base diameter and surface area, were tested at Mach numbers from 2.73 to 6.28. A comparison of theoretical and experimental foredrag coefficients indicates that the calculated minimum-drag bodies are reasonable approximations to the correct shape.

Eggers, A J , Jr↗
NASA NTRS1976

The minimum drag of thin wings in frictionless flow

The assumptions of the thin airfoil theory are found to provide certain necessary conditions for the minimum drag of airfoils having a given total lift, a given maximum thickness, or a given volume. The conditions are applicable to steady or unsteady motions and to subsonic or supersonic speeds without restriction on the planform. The computation of drag and the statement of the conditions for minimum drag depend on the consideration of a combined flow field, which is obtained by superimposing the disturbance velocities in forward and reversed motions. If the planform of the airfoil and its total lift are given, it is found that, for minimum drag, the lift must be distributed in such a way that the downwash in the combined field is constant over the entire planform. If the planform is given and the thickness of the airfoil is required to contain a specified volume, then the thickness must be distributed over the planform in such a way that the pressure gradient of the combined field in the direction of flight is constant at all points of the wing.

Robert T. Jones↗
NASA NTRS1991

Super/hypersonic aerodynamic characteristics for a transatmospheric vehicle concept having a minimum drag forebody

Experimental longitudinal and lateral-directional aerodynamic characteristics were obtained for a generic transatmospheric vehicle concept having a replaceable minimum drag forebody shape. The alternate forebody tested was a 1/4-power series body. Tests were made over a range of Mach numbers from 2 to 10 at a nominal Reynolds number, based on a length of 2.3 x 10 to the 8th and angles of attack from -4 to 20 deg. The minimum drag forebody provided significant improvements in minimum drag and L/D for the configuration as well as a longitudinally stabilizing increment. Although the baseline configuration is longitudinally unstable, the L/D improvements at low to moderate angles of attack would enhance cruise performance. Varying wing incidence angles was demonstrated as an effective horizontal trim device without significant trim drag penalties.

Phillips, W. P.↗
NASA NTRS1976

Theoretical determination of the minimum drag of airfoils at supersonic speeds

A method is reported for determining mathematically the combined disturbance field, and in certain cases the minimum drag, of wings at supersonic speeds. The simplest analytic example is provided by the wing of elliptic planform, which achieves its minimum drag when the lift is distributed uniformly over the surface. With a symmetrical distribution of thickness, the requirement of minimum drag for a given total volume is found to lead to profiles of constant curvature.

Jones, R. T.↗
NASA NTRS1989

The minimum drag of thin wings at supersonic speed according to Kogan's theory

In the theory of thin lifting surfaces the minimum drag consistent with a given total lift occurs when the downwash, averaged between forward and reversed motion of the wing, has the same value at all points of the wing planform. In Kogan's theory the conditions for minimum drag are determined on the forward sloping characteristic surface touching the trailing edge of the wing and it is shown that such a surface plays the role of the Trefftz plane familiar in subsonic wing theory. This paper shows how Kogan's theory may be applied to determine the drag of elliptic wings at supersonic speed. It appears that such wings have lower drag than the conventional 'delta' wing.

Jones, Robert T.↗
NASA NTRS1982

Automated design of minimum drag light aircraft fuselages and nacelles

The constrained minimization algorithm of Vanderplaats is applied to the problem of designing minimum drag faired bodies such as fuselages and nacelles. Body drag is computed by a variation of the Hess-Smith code. This variation includes a boundary layer computation. The encased payload provides arbitrary geometric constraints, specified a priori by the designer, below which the fairing cannot shrink. The optimization may include engine cooling air flows entering and exhausting through specific port locations on the body.

Smetana, F. O.↗
NASA NTRS1972

Numerical method for design of minimum-drag supersonic wing camber with constraints on pitching moment and surface deformation

A numerical method, based on linearized theory, for designing minimum-drag supersonic wing camber surfaces of arbitrary planform for a given lift, with options for constraining the pitching moment and/or the surface deformation at the trailing edge of the root chord and for selecting any desired combination of eight specified wing-loading distributions to be employed in the optimization procedure is presented. Two examples are given to illustrate applications of the method. The results indicate that relatively small drag penalties are incurred in designing wings to be self-trimming and to have a reasonable camber surface.

Sorrells, R. B.↗
NASA NTRS1944

Intercooler cooling-air weight flow and pressure drop for minimum drag loss

An analysis has been made of the drag losses in airplane flight of cross-flow plate and tubular intercoolers to determine the cooling-air weight flow and pressure drop that give a minimum drag loss for any given cooling effectiveness and, thus, a maximum power-plant net gain due to charge-air cooling. The drag losses considered in this analysis are those due to (1) the extra drag imposed on the airplane by the weight of the intercooler, its duct, and its supports and (2) the drag sustained by the cooling air in flowing through the intercooler and its duct. The investigation covers a range of conditions of altitude, airspeed, lift-drag ratio, supercharger-pressure ratio, and supercharger adiabatic efficiency. The optimum values of cooling air pressure drop and weight flow ratio are tabulated. Curves are presented to illustrate the results of the analysis.

Reuter, J George↗
NASA NTRS1995

Computing Trimmed, Mean-Camber Surfaces At Minimum Drag

VLMD computer program determines subsonic mean-camber surfaces of trimmed noncoplanar planforms with minimum vortex drag at specified lift coefficient. Up to two planforms designed together. Method used that of subsonic vortex lattice method of chord loading specification, ranging from rectangular to triangular, left specified by user. Program versatile and applied to isolated wings, wing/canard configurations, tandem wing, and wing/-winglet configuration. Written in FORTRAN.

Lamar, John E.↗
NASA NTRS1955

Minimum-drag ducted and pointed bodies of revolution based on linearized supersonic theory

The linearized drag integral for bodies of revolution at supersonic speeds is presented in a double-integral form which is not based on slender-body approximations but which reduces to the equal slender-body expression in the proper limit. With the aid of a suitably chosen auxiliary condition, the minimum-external-wave-drag problem is solved for a transition section connecting two semi-infinite cylinders. The projectile tip is a special case and is compared with the Von Karman projectile tip. Calculations are presented which indicate that the method of analysis gives good first-order results in the moderate supersonic range.

Parker, Hermon M↗