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: 1) to extend one method—the suction analogy—to more general configurations and evaluate it 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 postmaximum lift characteristics.

Analysis and Design of Strake-Wing Configurations

Flow studies of slender wing vortices

1Therefore, in keeping with the spirit of the Wright brothers research and design accomplishments, as well as the scope of this meeting, I have elected to review some of the aerodynamic research performed at the Langley Research Center related to the application of slender wing benefits in the design of high-speed military aircraft In the context of this paper, slender wing benefits refer primarily to the supersonic performance and leading edge vortex flow associated with very highly sweptback wings Following a review of some early slender wing research, the paper presents several case histories of Langley contributions to the development of aircraft incorporating slender wing benefits and then summarizes some vortex flow technology that may contribute to future aircraft

Applying slender wing benefits to military aircraft

This paper presents a survey of the effects of Reynolds number on the low- speed lift characteristics of wings encountering separated flows at their leading and side edges, with emphasis on the region near the stall. The influence of leading-edge profile and Reynolds number on the stall characteristics of two- dimensional airfoils are reviewed first to provide a basis for evaluating three- dimensional effects associated with various wing planforms. This is followed by examples of the effects of Reynolds number and geometry on the lift characteristics near the stall for a series of three-dimensional wings typical of those suitable for high-speed aircraft and missiles. Included are examples of the effects of wing geometry on the onset and spanwise progression of turbulent reseparation near the leading edge and illustrations of the degree to which simplified theoretical approaches can be useful in defining the influence of the various geometric parameters. Also illustrated is the manner in which the Reynolds number and wing geometry parameters influence whether the turbulent reseparation near the leading edge results in a sudden loss of lift, as in the two-dimensional case, or the formation of a leading-edge vortex with Rs increase in lift followed by a gentle stall as in the highly swept wing case. Particular emphasis is placed on the strong influence of 'induced camber' on the development of turbulent reseparation. R is believed that the examples selected for this report may be useful in evaluating viscous flow solutions by the new computational methods based on the Navier-Stokes equations as well as defining fruitful research areas for the high-Reynolds-number wind tunnels.

A Survey of Reynolds Number and Wing Geometry Effects on Lift Characteristics in the Low Speed Stall Region

An unsteady vortex lattice method is presented for the calculation of the aerodynamic forces acting on lifting surfaces undergoing complex three dimensional motion. For the present case the nonsymmetric motion of a slender delta wing was considered and the resulting lateral characteristics were calculated. The flow separation line was specified along the wing leading edge and the emanating vortex sheet shape and rollup was then calculated. Numerical results are presented for the combined high angle of attack and side slip condition and for the wing constant roll and coning motions.

Lateral aerodynamics of delta wings with leading-edge separation

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.

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.

J. E. Lamar

Papers

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

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