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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Vortex lattice prediction of subsonic aerodynamics of hypersonic vehicle concepts

The vortex lattice method introduced by Lamar and Gloss (1975) was applied to the prediction of subsonic aerodynamic characteristics of hypersonic body-wing configurations. The reliability of the method was assessed through comparison of the calculated and observed aerodynamic performances of two National Hypersonic Flight Research Facility craft at Mach 0.2. The investigation indicated that a vortex lattice model involving 120 or more panel elements can give good results for the lift and induced drag coefficients of the craft, as well as for the pitching moment at angles of attack below 10 to 15 deg. Automated processes for calculating the local slopes of mean-camber surfaces may also render the method suitable for use in preliminary design phases.

Pittman, J. L.↗
NASA NTRS1977

Effect of a simulated engine jet blowing above an arrow wing at Mach 2.0

The effects of a gas jet simulating a turbojet engine exhaust blowing above a cambered and twisted arrow wing were investigated. Tests were conducted in the Langley 4-foot supersonic pressure tunnel at a Mach number of 2.0. Nozzle pressure ratios from 1 to 64 were tested with both helium and air used as jet gases. The tests were conducted at angles of attack from -2 deg to 8 deg at a Reynolds number of 9,840,000 per meter. Only the forces and moments on the wing were measured. Results of the investigation indicated that the jet blowing over the wing caused reductions in maximum lift-drag ratio of about 4 percent for helium and 6 percent for air at their respective design nozzle pressure ratios, relative to jet-off data. Moderate changes in the longitudinal, vertical, or angular positions of the jet relative to the wing had little effect on the wing aerodynamic characteristics.

Shrout, B. L.↗
NASA NTRS1977

An automated data generator for NASTRAN

A modeling system based on construction-in-context of geometry and physical properties data is adapted for NASTRAN finite element data generation. This system was originally developed for generating three-dimensional finite data for composite structures in PATCHES-III using parametric cubic models. These finite line, surface and volume models constructed using simple data directives will be subdivided into NASTRAN finite elements and their supporting data in the new data generator. Any geometry can be constructed as illustrated by a compressor fan blade with camber, twist and changing airfoil section and the shape then subdivided using a uniform or non-uniform mesh. Special emphasis is given to the adaption of construction-in-context to composite material property modeling. A PMAT series of directives is described for any one, two or three-dimensionally reinforced composite that allows the phase properties, as well as composite properties, to be generated.

Stanton, E. L.↗
NASA NTRS1978

Minimum induced drag configurations with jet interaction

A theoretical method is presented for determining the optimum camber shape and twist distribution for the minimum induced drag in the wing-alone case without prescribing the span loading shape. The same method was applied to find the corresponding minimum induced drag configuration with the upper-surface-blowing jet. Lan's quasi-vortex-lattice method and his wing-jet interaction theory was used. Comparison of the predicted results with another theoretical method shows good agreement for configurations without the flowing jet. More applicable experimental data with blowing jets are needed to establish the accuracy of the theory.

Pao, J. L.↗
NASA NTRS1977

Effect of chordwise forces and deformations and deformations due to steady lift on wing flutter

This investigation explores the effects of chordwise forces and deformations and steady-state deformation due to lift on the static and dynamic aeroelastic stability of a uniform cantilever wing. Results of this analysis are believed to have practical applications for high-performance sailplanes and certain RPV's. The airfoil cross section is assumed to be symmetric and camber bending is neglected. Motions in vertical bending, fore-and-aft bending, and torsion are considered. A differential equation model is developed, which included the nonlinear elastic bending-torsion coupling that accompanies even moderate deflections. A linearized expansion in small time-dependent deflections is made about a steady flight condition. The stability determinant of the linearized system then contains coefficients that depend on steady displacements. Loads derived from two-dimensional incompressible aerodynamic theory are used to obtain the majority of the results, but cases using three-dimensional subsonic compressible theory are also studied. The stability analysis is carried out in terms of the dynamically uncoupled natural modes of vibration of the uniform cantilever.

Boyd, W. N.↗
NASA NTRS1978

Calculation of the longitudinal aerodynamic characteristics of upper-surface-blown wing-flap configurations

An engineering method for predicting the longitudinal aerodynamic characteristics of wing-flap configurations with upper surface blowing (USB) was developed. Potential flow models were incorporated into the prediction method: a wing and flap lifting surface model and a jet wake model. The wing-flap model used a vortex-lattice to represent the wing and flaps. The wing had an arbitrary planform and camber and twist, and the flap system was made up of a Coanda flap and other flap segments of arbitrary size. The jet wake model consisted of a series of closely spaced rectangular vortex rings. The wake was positioned such that it was tangent to the upper surface of the wing and flap between the exhaust nozzle and the flap trailing edge. It was specified such that the mass, momentum, and spreading rates were similar to actual USB jet wakes. Comparisons of measured and predicted pressure distributions, span load distributions, and total lift and pitching-moment coefficients on swept and unswept USB configurations are included. A wide range of thrust coefficients and flap deflection angles were considered at angles of attack up to the onset of stall.

Mendenhall, M. R.↗
NASA NTRS1978

Theoretical estimation of the transonic aerodynamic characteristics of a supercritical-wing transport model with trailing-edge controls

A method for rapidly estimating the overall forces and moments at supercritical speeds, below drag divergence, of transport configurations with supercritical wings is presented. The method was also used for estimating the rolling moments due to the deflection of wing trailing-edge controls. This analysis was based on a vortex-lattice technique modified to approximate the effects of wing thickness and boundary-layer induced camber. Comparisons between the results of this method and experiment indicate reasonably good correlation of the lift, pitching moment, and rolling moment. The method required much less storage and run time to compute solutions over an angle-of-attack range than presently available transonic nonlinear methods require for a single angle-of-attack solution.

Luckring, J. M.↗
NASA NTRS1978

Wind tunnel tests on a tail-less swept wing span-distributed cargo aircraft configuration

The configuration consisted of a 30 deg -swept, untapered, untwisted wing utilizing a low-moment cambered airfoil of 20 percent streamwise thickness designed for low wave drag at M = 0.6, C sub L = 0.4. The tests covered a range of Mach numbers 0.3 to 0.725 and chord Reynolds number 1,100,000 to 2,040,000, angles of attack up to model buffet and sideslip angles + or - 4 deg. Configuration build up, wing pod filleting, airfoil modification and trailing edge control deflection effects were briefly investigated. Three wing tip vertical tail designs were also tested. Wing body filleting and a simple airfoil modification both produced increments to maximum lift/drag ratio. Addition of pods eliminated pitch instability of the basic wing. While the magnitude of these benefits probably was Reynolds number sensitive, they underline the potential for improving the aerodynamics of the present configuration. The cruise parameter (product of Mach number and lift/drag ratio) attained a maximum close to the airfoil design point. The configuration was found to be positively stable with normal control effectiveness about all three axes in the Mach number and C sub L range of interest.

Rao, D. M.↗
NASA NTRS1978

Estimation of leading-edge thrust for supersonic wings of arbitrary planform

A numerical method for the estimation of leading edge thrust for supersonic wings of arbitrary planform was developed and was programmed as an extension to an existing high speed digital computer method for prediction of wing pressure distributions. The accuracy of the method was assessed by comparison with linearized theory results for a series of flat delta wings. Application of the method to wings of arbitrary planform, both flat and cambered, is illustrated in several examples.

Carlson, H. W.↗
NASA NTRS1978

Computational wing optimization and wind tunnel test of semi-span model

A computational transonic wing design procedure has been developed and verified by a wind tunnel test of a variable camber semi-span wing model. The Bailey-Ballhaus transonic potential flow analysis code linked to Vanderplaat's constrained minimization routine was used to optimize test configurations at 0.9 Mach number. Based on wind tunnel test results, computationally optimized designs were as efficient as the best configurations determined by previous parametric testing and performed better at off-design points. Wind tunnel wing pressures agreed well with predictions from the improved Bailey-Ballhaus code at moderate CL's. Computational optimization was shown to be an effective transonic wing design tool.

Haney, H. P.↗
NASA NTRS1978

Three-dimensional canard-wing shape optimization in aircraft cruise and maneuver environments

This paper demonstrates a numerical technique for canard-wing shape optimization at two operating conditions. For purposes of simplicity, a mean surface wing paneling code is employed for the aerodynamic calculations. The optimization procedures are based on the method of feasible directions. The shape functions for describing the thickness, camber, and twist are based on polynomial representations. The primary design requirements imposed restrictions on the canard and wing volumes and on the lift coefficients at the operating conditions. Results indicate that significant improvements in minimum drag and lift-to-drag ratio are possible with reasonable aircraft geometries. Calculations were done for supersonic speeds with Mach numbers ranging from 1 to 6. Planforms were mainly of a delta shape with aspect ratio of 1.

De Silva, B. M. E.↗
NASA NTRS1978

The exact numerical calculation of propeller noise

This paper presents a method for computing the acoustic pressure signature of a propeller due to blade thickness and steady surface pressure loading including the effect of forward motion. The tip helical speed is restricted to subsonic. The formulation is based on the Ffowcs Williams-Hawkings exact result concerning the sound generation by moving bodies. The blade surface is described in a helical coordinate system by the blade angles, positions of the leading and trailing edges along the local pitch helix, and the camber and thickness distributions along the chord. The retarded distance of the moving acoustic source on an element of surface area of the propeller blade is obtained numerically by Newton's method. The surface integration over the propeller blades is carried out in the helical coordinate system using a double Gauss-Legendre formula. Good agreement was found between analytic and experimental results, both in the time and frequency domains. Some samples showing the effects of propeller geometry and tip Mach number on the acoustic signature are included.

Woan, C. J.↗
NASA NTRS1978

Analytical studies of separated vortex flow on highly swept wings

A subsonic potential flow mathematical model of the flow past slender aerodynamic surfaces with sharp edges and separated vortex flow is reported. Comparisons with experimental data are presented for overall forces and pressure distributions for a series of thin, low aspect ratio wings, including both flat and conically cambered ones. A discussion is presented of the limitations of the current theory, and some suggestions are made as to how the theory might be improved. Details of program data input modifications for three-dimensional geometry are described in an appendix.

Kuhlman, J. M.↗
NASA NTRS1978

A new blade element method for calculating the performance of high and intermediate solidity axial flow fans

A method is presented to design and predict the performance of axial flow rotors operating in a duct. The same method is suitable for the design of ducted fans and open propellers. The unified method is based on the blade element approach and the vortex theory for determining the three dimensional effects, so that two dimensional airfoil data can be used for determining the resultant force on each blade element. Resolution of this force in the thrust and torque planes and integration allows the total performance of the rotor, fan or propeller to be predicted. Three different methods of analysis, one based on a momentum flow theory; another on the vortex theory of propellers; and a third based on the theory of ducted fans, agree and reduce cascade airfoil data to single line as a function of the loading and induced angle of attack at values of constant inflow angle. The theory applies for any solidity from .01 to over 1 and any blade section camber. The effects of the duct and blade number can be determined so that the procedure applies over the entire range from two blade open propellers, to ducted helicopter tail rotors, to axial flow compressors with or without guide vanes, and to wind tunnel drive fans.

Borst, H. V.↗
NASA NTRS1978

Interactive multi-mode blade impact analysis

The theoretical methodology used in developing an analysis for the response of turbine engine fan blades subjected to soft-body (bird) impacts is reported, and the computer program developed using this methodology as its basis is described. This computer program is an outgrowth of two programs that were previously developed for the purpose of studying problems of a similar nature (a 3-mode beam impact analysis and a multi-mode beam impact analysis). The present program utilizes an improved missile model that is interactively coupled with blade motion which is more consistent with actual observations. It takes into account local deformation at the impact area, blade camber effects, and the spreading of the impacted missile mass on the blade surface. In addition, it accommodates plate-type mode shapes. The analysis capability in this computer program represents a significant improvement in the development of the methodology for evaluating potential fan blade materials and designs with regard to foreign object impact resistance.

Alexander, A.↗
NASA NTRS1979

Aerodynamic design and analysis of the AST-200 supersonic transport configuration concept

The design and analysis of a supersonic transport configuration was conducted using linear theory methods in conjunction with appropriate constraints. Wing optimization centered on the determination of the required twist and camber and proper integration of the wing and fuselage. Also included in the design are aerodynamic refinements to the baseline wing thickness distribution and nacelle shape. Analysis to the baseline and revised configurations indicated an improvement in lift-to-drag ratio of 0.36 at the Mach 2.7 cruise condition. Validation of the design is planned through supersonic wing tunnel tests.

Walkley, K. B.↗
NASA NTRS1979

Aerodynamic characteristics at Mach numbers of 1.5, 1.8, and 2.0 of a blended wing-body configuration with and without integral canards

An exploratory, experimental, and theoretical investigation was made of a cambered, twisted, and blended wing-body concept with and without integral canard surfaces. Theoretical calculations of the static longitudinal and lateral aerodynamic characteristics of the wing-body configurations were compared with the characteristics obtained from tests of a model in the Langley Unitary Plan wind tunnel. Mach numbers of 1.5, 1.8, and 2.0 and a Reynolds number per meter of 6.56 million were used in the calculations and tests. Overall results suggest that planform selection is extremely important and that the supplemental application of new calculation techniques should provide a process for the design of supersonic wings in which spanwise distribution of upwash and leading-edge thrust might be rationally controlled and exploited.

Robins, A. W.↗
NASA NTRS1979

Comparison of three-dimensional panel methods with strip boundary-layer simulations to experiment

Several three dimensional surface panel methods coupled on a streamwise strip basis to two dimensional boundary layer methods were compared to experimental data. Several different boundary layer simulations were investigated. Comparable boundary layer effects which converge to the expected two dimensional result wind increasing aspect ratio were indicated by either a transpiration or camber line displacement simulation. The method was applied to several varied configurations. The lift predictions agreed well with an approximate method based on correcting the inviscid lift using the two dimensional section viscous characteristics. The wing pressures and the effect of the boundary layer on the wing pressures were predicted accurately.

Kjelgaard, S. O.↗