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Lamar, J. E.

Publications and source records attributed to Lamar, J. E..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Experimental and analytical study of the longitudinal aerodynamic characteristics of analytically and empirically designed Strake-wing configurations at subcritical speeds

Sixteen analytically and empirically designed strakes have been tested experimentally on a wing-body at three subcritical speeds in such a way as to isolate the strake-forebody loads from the wing-afterbody loads. Analytical estimates for these longitudinal results are made using the suction analogy and the augmented vortex lift concepts. The synergistic data are reasonably well estimated or bracketed by the high- and low-angle-of-attack vortex lift theories over the Mach number range and up to maximum lift or strake-vortex breakdown over the wing. Also, the strake geometry is very important in the maximum lift value generated and the lift efficiency of a given additional area. Increasing size and slenderness ratios are important is generating lift efficiently, but similar efficiency can also be achieved by designing a strake with approximately half the area of the largest gothic strake tested. These results correlate well with strake-vortex-breakdown observations in the water tunnel.

Lamar, J. E.↗
NASA NTRS1981

Aerodynamic features of designed strake-wing configurations

Sixteen analytically and empirically designed strakes have been aerodynamically tested on a common wing-body to determine the longitudinal characteristics of the configurations. These strakes were selected, in general, due to their superior performance in a water-tunnel test. There they exhibited a good correlation between the hypothesized high value of angle of attack for strake vortex breakdown and the high value of leading-edge suction at the strake tip. The lift and pitch data were reasonably well predicted by an extended suction analogy method, and the lift agreement improved with increasing strake area. The strake-vortex-breakdown angle and configuration maximum lift generally increase with increasing strake area and, to some extent, strake tip leading-edge suction value. The best strake configurations all developed about the same maximum area efficiency value despite their differences in size.

Lamar, J. E.↗
NASA NTRS1980

Water-tunnel and analytical investigation of the effect of strake design variables on strake vortex breakdown characteristics

A systematic water-tunnel study was made to determine the vortex breakdown characteristics of 43 strakes. The strakes were mounted on a 1/2-scale model of a Langley Research Center general research fighter fuselage model with a 44deg leading-edge-sweep trapezoidal wing. The analytically designed strake shapes provided examples of the effects of the primary design parameters (size, span, and slenderness) on vortex breakdown characteristics. These effects were analyzed in relation to the respective strake leading-edge suction distributions. Included were examples of the effects of detailed strake planform shaping. It was concluded that, consistent with the design criterion, those strakes with leading-edge suction distributions which increase more rapidly near, and have a higher value at, the spanwise tip of the strake produce a more stable vortex.

Frink, N. T.↗
NASA NTRS1980

Development of a vortex-lift-design method and application to a slender maneuver-wing configuration

A method has been developed to optimize the mean camber surface of a cranked slender wing having leading-edge vortex flow at transonic-maneuver conditions using the suction analogy. This type of flow was assumed because it was anticipated that the slenderness of the wing would preclude attached flow at the required lift coefficient. A constraint was imposed in that the camber deflections were to be restricted by a realistic structural-box requirement. The resulting application yielded mean-camber shapes which produced effective suction levels equivalent to 77 percent of the full-planar leading-edge value at the design lift coefficient.

Lamar, J. E.↗
NASA NTRS1980

An analysis of strake vortex breakdown characteristics in relation to design features

This paper describes a water tunnel study of the vortex breakdown characteristics of a large number of analytically designed vortex strakes tested in combination with a moderate aspect ratio trapezoidal wing. A wide range of strake sizes and slenderness ratios are covered, and examples of the effects of the primary design parameters of size, span, and slenderness on the vortex breakdown characteristics are presented and analyzed in relation to the leading-edge suction distributions. Several examples of detailed planform shaping on strakes of the same general size and slenderness are shown from which it can be concluded that, consistent with the design criterion, those with leading-edge suction distributions which increase more rapidly near, and have a higher value at, the spanwise tip of the strake produce a more stable vortex.

Frink, N. T.↗
NASA NTRS1979

Vortex-lift roll-control device

A wing is described for aircraft of cropped, arrow-type planform with thin leading and side edges. The wing has a pivotable tip to alter the crop angle of the wing during flight. Increasing the crop angle causes the wing side edge to become a trailing edge which reduces the strength of the side edge vortex flow. Decreasing the crop angle causes opposite results, in particular the side edge is now a leading edge and can generate a leading edge vortex flow. The wing constitutes a roll control device for aircraft of the stated design particularly effective at higher angles of attack.

Lamar, J. E.↗
NASA NTRS1979

Recent theoretical developments and experimental studies pertinent to vortex flow aerodynamics, with a view towards design

Recent progress in a research program directed toward an improved vortex flow technology base was reviewed. Analysis methods for conical flow and analysis and design methods for nonconical flows are presented. Applications are made for a variety of planar, nonplanar, and interferring lifting surfaces. Several methods are shown to provide reasonable estimates of over-all forces and moments for simple wing planforms with the suction analogy method currently offering the most versatility for arbitrary configuration applications. For the prediction of surface loadings the free vortex sheet method being developed by Boeing is shown to have considerable promise and further development of this type of method is encouraged. A data base for ogee strake-wing configurations is summarized with an emphasis on the requirements for maximizing the interference lift. A strake planform design procedure is discussed and a first solution (gothic in planview) is integrated with a wing body. The data show the strake to exhibit expected stable vortex characteristics. It was found that, apart from increasing sweep, conically cambered delta wings developed drag levels approaching that of attached flow with increasing either the lift or the wing camber height, lastly, an approximate vortex flow design method, based on the suction analogy, is outlined and an example is given.

Lamar, J. E.↗
NASA NTRS1978

Recent theoretical developments and experimental studies pertinent to vortex flow aerodynamics - With a view towards design

A review is presented of recent progress in a research program directed towards the development of an improved vortex-flow technology base. It is pointed out that separation induced vortex-flows from the leading and side edges play an important role in the high angle-of-attack aerodynamic characteristics of a wide range of modern aircraft. In the analysis and design of high-speed aircraft, a detailed knowledge of this type of separation is required, particularly with regard to critical wind loads and the stability and performance at various off-design conditions. A description of analytical methods is presented. The theoretical methods employed are divided into two classes which are dependent upon the underlying aerodynamic assumptions. One conical flow method is considered along with three different nonconical flow methods. Comparisons are conducted between the described methods and available aerodynamic data. Attention is also given to a vortex flow drag study and a vortex flow wing design using suction analogy.

Lamar, J. E.↗
NASA NTRS1978

Strake-wing analysis and design

The technology is still evolving for improving the transonic maneuver capability of strake-wing configurations. Much of the work to date has been of an experimental nature; whereas, the theories that are available to handle vortex-flow aerodynamics have mostly treated wings of constant sweep. Hence, two efforts were undertaken. They are: (1) to extend the suction analogy to more general configurations and evaluate the method by using selected critical planforms; and (2) to develop a procedure for strake planform shaping and test the resulting shape in conjunction with a wing-body. The conclusions from this study are that (1) some improvement has been made in estimating high-angle-of-attack longitudinal aerodynamics, and (2) the gothic strake designed with the developed procedure does produce a stable vortex system in the presence of a wing body and flat post-maximum-lift characteristics.

Lamar, J. E.↗
NASA NTRS1978

Subsonic vortex-flow design study for slender wings

A theoretical study describing the effects of spanwise camber on the lift dependent drag of slender delta wings having leading-edge-vortex-flow is presented. The earlier work by Barsby, using conical flow, indicated that drag levels similar to those in attached flow could be obtained. This is reexamined and then extended to the more practical case of nonconical flow by application of the vortex-lattice method coupled with the suction-analogy and the recently developed Boeing free-vortex-sheet method. Lastly, a design code is introduced which employs the suction analogy in an attempt to define 'optimum' camber surfaces for minimum lift dependent drag for vortex flow conditions

Lamar, J. E.↗
NASA NTRS1977

On the logarithmic-singularity correction in the kernel function method of subsonic lifting-surface theory

A logarithmic-singularity correction factor is derived for use in kernel function methods associated with Multhopp's subsonic lifting-surface theory. Because of the form of the factor, a relation was formulated between the numbers of chordwise and spanwise control points needed for good accuracy. This formulation is developed and discussed. Numerical results are given to show the improvement of the computation with the new correction factor.

Lan, C. E.↗
NASA NTRS1977

Trimmed noncoplanar planforms with minimum vortex drag

Vortex-lattice subsonic method determines mean camber surface for trimmed noncoplanar planforms with minimum vortex drag. Multiple surfaces can be designed together to yield trimmed configuration with minimum induced drag at some specified lift coefficient. Program is applicable to isolated wings, wing-canard configuration, tandem wing, and wing-winglet configuration.

Lamar, J. E.↗
NASA NTRS1976

Longitudinal aerodynamic characteristics of 45 deg swept wings at Mach approximately 0

Wind tunnel tests were conducted in the Langley 7 x 10 foot wind tunnel at Mach numbers less than 0.20 and at Reynolds numbers less than 3.74 million. The effect of the aft area on the 45 deg swept wing longitudinal aerodynamic characteristics at low subsonic speeds and at an angle of attack range from approximately -2 deg to 28 deg was studied. The data are presented without analysis.

Lamar, J. E.↗
NASA NTRS1976

Summary of some recent studies of subsonic vortex lift and parameters affecting the leading-edge vortex stability

Various subsonic configurations which develop vortex lift are examined herein. Comparisons are made with data and the combination of direct and indirect edge forces through use of the suction analogy. For most configurations, the use of the indirect or augmented vortex lift leads to improved agreement with data. The studies conducted showed that it is possible for the leading-edge vortex to exhibit bursting on a cropped wing and the wing aerodynamic characteristics not show the effect. It was further found that the distributions of leading-edge suction correlate well with the maintenance of vortex flow aerodynamic characteristics. Lastly, a method is presented for relating the initial value of circulation and axial velocity of the leading-edge shed vortex to the wing geometry.

Lamar, J. E.↗
NASA NTRS1976

A vortex-lattice method for the mean camber shapes of trimmed noncoplanar planforms with minimum vortex drag

A new subsonic method has been developed by which the mean camber surface can be determined for trimmed noncoplanar planforms with minimum vortex drag. This method uses a vortex lattice and overcomes previous difficulties with chord loading specification. A Trefftz plane analysis is utilized to determine the optimum span loading for minimum drag, then solved for the mean camber surface of the wing, which provides the required loading. Sensitivity studies, comparisons with other theories, and applications to configurations which include a tandem wing and a wing winglet combination have been made and are presented.

Lamar, J. E.↗
NASA NTRS1976

Some recent applications of the suction analogy to vortex-lift estimates

An extension of the suction analogy for the estimation of vortex lift along the side edge of wings is reviewed along with the concept of an augmented vortex lift to account for the effect of the leading-edge vortex passing downstream over an aft part of the model. Applications of these extensions have resulted in an improved estimating capability for a wide range of isolated sharp-edge planforms and also for multiple lifting surfaces. Hence, the suction analogy concept can now have wider applicability at both subsonic and supersonic speeds, especially in the preliminary design cycle.

Lamar, J. E.↗
NASA NTRS1976

Vortex maneuver lift for super-cruise configurations

Some of the theoretical and experimental research conducted at the NASA Langley Research Center is presented to investigate the subsonic vortex-lift producing capabilities for two classes of Super-Cruise designs: a close-coupled wing-canard arrangement and a slender wing configuration. In addition, several analytical methods are discussed for estimating critical structural design loads for thin, highly swept wings having separated leading-edge vortex flows.

Campbell, J. F.↗