Engineering Papers⌕ Search

Engineering topics

Lamar, J. E.

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

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Description of the F-16XL Geometry and Computational Grids Used in CAWAPI

The objective of the Cranked-Arrow Wing Aerodynamics Project International (CAWAPI) was to allow a comprehensive validation of Computational Fluid Dynamics methods against the CAWAP flight database. A major part of this work involved the generation of high-quality computational grids. Prior to the grid generation an IGES file containing the air-tight geometry of the F-16XL aircraft was generated by a cooperation of the CAWAPI partners. Based on this geometry description both structured and unstructured grids have been generated. The baseline structured (multi-block) grid (and a family of derived grids) has been generated by the National Aerospace Laboratory NLR. Although the algorithms used by NLR had become available just before CAWAPI and thus only a limited experience with their application to such a complex configuration had been gained, a grid of good quality was generated well within four weeks. This time compared favourably with that required to produce the unstructured grids in CAWAPI. The baseline all-tetrahedral and hybrid unstructured grids has been generated at NASA Langley Research Center and the USAFA, respectively. To provide more geometrical resolution, trimmed unstructured grids have been generated at EADS-MAS, the UTSimCenter, Boeing Phantom Works and KTH/FOI. All grids generated within the framework of CAWAPI will be discussed in the article. Both results obtained on the structured grids and the unstructured grids showed a significant improvement in agreement with flight test data in comparison with those obtained on the structured multi-block grid used during CAWAP.

Boelens, O. J.↗
NASA NTRS2003

Recommended Experimental Procedures for Evaluation of Abrupt Wing Stall Characteristics

This paper presents a review of the experimental program under the Abrupt Wing Stall (AWS) Program. Candidate figures of merit from conventional static tunnel tests are summarized and correlated with data obtained in unique free-to-roll tests. Where possible, free-to-roll results are also correlated with flight data. Based on extensive studies of static experimental figures of merit in the Abrupt Wing Stall Program for four different aircraft configurations, no one specific figure of merit consistently flagged a warning of potential lateral activity when actual activity was seen to occur in the free-to-roll experiments. However, these studies pointed out the importance of measuring and recording the root mean square signals of the force balance.

Capone, F. J.↗
NASA NTRS2003

AWS Figure of Merit (FOM) Developed Parameters from Static, Transonic Model Tests

This paper provides an approach to answer the question of whether one can rely solely on static data taken during a transonic model test to provide the certainty needed that a new aircraft will or will not have Abrupt Wing Stall (AWS) events during its flight operations. By comparing traditional- and alternate-static-Figures of Merit (FOMs) with the Free-To-Roll (FTR) response data, a rational basis for assessing the merits of using standard testing techniques for the prediction of AWS events has been established. Using the FTR response data as a standard, since these results compare well with flight, the conclusion from this study is that neither traditional nor alternate FOMs can be trusted to provide an indication as to whether a configuration will or will not have AWS tendencies. Even though these FOMs may flag features which have a high degree of correlation with the FTR response data, there are as many or more of these FOM flagged features which do not correlate. Thus, one needs to use the FTR rig to assess AWS tendencies on new configurations.

Lamar, J. E.↗
NASA NTRS1987

Review of vortex flow flight projects on the F-106B

NASA-Langley's F-106B research aircraft is being used in vortex flow-research flight experiments in order to determine the effects of Re number and Mach number on the lee-side vortex system generated at angles-of-attack up to maneuver condition, as well as to evaluate the aerodynamic characteristics of a sharp leading-edge vortex flap system. The wing vortex system is visualized at a fixed position by means of the vapor-screen technique. Comparisons are made between a measured value and two theoretical estimates of a pertinent vortex system property, core location.

Lamar, J. E.↗
NASA NTRS1986

In-flight and wind tunnel leading-edge vortex study on the F-106B airplane

The vapor screen technique was successfully applied to an F-106B fighter aircraft during subsonic and transonic maneuvers. This system has allowed the viewing of multiple vortex systems on the wing upper surface at angles of attack less than 19 deg. In addition, similarities as well as differences were determined to exist between the vortex systems for a full scale semispan model and the flight vehicle at 20 deg incidence. Furthermore, variations in Reynolds number and Mach number were identified as to how they affect vortex system details at flight conditions.

Lamar, J. E.↗
NASA NTRS1986

In-flight flow visualization of F-106B leading-edge vortex using the vapor-screen technique

A flight program was conducted with the objective to study the vortex flow systems existing around the F-106B aircraft. Level 1-G decelerating flight with varying angle of attack was considered along with conditions involving G levels in the range from 4.5 to 5.5 and angles of attack in the range from 16 to 19 degrees. It was demonstrated that the vapor screen technique can be applied successfully to flight vehicles under a variety of test conditions, taking into consideration the transonic maneuver performed by fighter aircraft. Details regarding the employed in-flight flow visualization technique are discussed, taking into account the seeding system, the light sheet system, the video system, the control system, and the recording of the data. Attention is also given to the flight program, the data development, and the scientific observations.

Lamar, J. E.↗
NASA NTRS1986

Nonlinear lift control at high speed and high angle of attack using vortex flow technology

Nonlinear lift control at subsonic, transonic and low supersonic speeds owes its origin to the separated but organized vortical flows interacting with the wing upper surface. Since most of this flow originates near the wing or control-surface leading-edge, a variety of devices have been studied experimentally which interact with and/or control this flow in order to gain a beneficial effect. The benefits (effects) originally studied were only associated with lift enhancement. Whereas, now the studied benefits encompass performance increase, attention to changes in trimmed conditions and longitudinal stability, improvements in lateral stability, and the attendant variation with changing Mach number. For those devices that can be theoretically modeled, state-of-the-art computer codes have been used for device design and/or analysis. Comparisons at design and off-design conditions are presented for validation purposes.

Lamar, J. E.↗
NASA NTRS1986

Summary of a high subsonic force/pressure experiment for 58 deg cambered/twisted thick delta wings

This paper summarizes the results of a force, moment, and pressure experiment involving six thick, cambered and twisted, delta wings with 58 deg leading-edge sweep. This experiment was conducted in the NASA Langley 7- by 10-foot High-Speed Tunnel at Mach numbers of 0.75, 0.80, and 0.83. The design goal was a configuration which was self-trimming at a lift coefficient of 0.25 and Mach number of 0.80. Although the design goal was not met, the configuration which came closest and which had the best overall performance was selected for further study. Wing surface pressure data and limited surface oil flow data for this configuration are presented to show the extent of attached flow at the design point. For selected cases, inviscid solutions from vortex lattice method/suction analogy, PAN AIR, FLO-28, and FLO-57 are compared with the experimental force, moment, and pressure data.

Chu, J.↗
NASA NTRS1985

An attached flow design of a noninterfering leading edge extension to a thick delta wing

The analytical procedure presented for leading edge extension (LEE) determination, in keeping with such design criteria as noninterference at the wing design point, is applied to thick delta wings. The LEE device thus defined is to be mounted on a wing along a dividing stream surface that is associated with an attached flow design lift coefficient greater than zero. The delta wing in question is of twisted and cambered type. It is demonstrated that span reductions for the candidate LEEs has the most detrimental effect on overall aerodynamic efficiency, irrespective of area or shape.

Ghaffari, F.↗
NASA NTRS1984

Vortex flaps - Advanced control devices for supercruise fighters

Prompted by the extensive experience obtained with vortex lift-generating leading edges in the SR-71, Concorde and F-16 supersonic aircraft, development efforts have recently been made toward the use of variable incidence angle delta wing leading edge 'vortex flaps' for supersonic cruise and maneuvering performance improvements in fighter aircraft. Vortex lift flaps have been wind tunnel tested on scale models, and it has been noted that a variety of effects can be obtained through the use of folding, hinged, and tabbed flap designs. Flap planforms can, moreover, be varied in length and in total area, as well as segmented, to yield unique combinations of drag reduction, vortex generation, longitudinal stability, and vortex flow reattachment. It is speculated that the vortex flap may be applicable to multimission fighters, and promote STOL performance.

Lamar, J. E.↗
NASA NTRS1983

Extended Vortex Lattice Method

Extended NASA Langley Vortex Lattice Method computer program VLM, estimates subsonic aerodynamic characteristics of up to four complex planforms. Planforms include wings with variable-sweep outer panels, wings with several changes in dihedral angle across span, wings with winglets, and wing (or wings) in conjunctions with tail and/or canard. VLM written in FORTRAN IV.

Lamar, J. E.↗
NASA NTRS1983

Recent studies at NASA-Langley of vortical flows interacting with neighboring surfaces

The importance of leading edge vortical flows, which occur near and interact with neighboring surfaces, is stressed. Research in this area conducted or sponsored by the NASA Langley Research Center since 1978 is surveyed. Particular attention is given to the cumulative results of a number of theoretical and experimental studies. It is noted that these studies have been carried out in order to understand and use this kind of flow. Much of the work has been devoted to improving the lift-to-drag ratio and pitch characteristics for wings in this flow, although work has also been done on examining the unsteady and lateral characteristics.

Lamar, J. E.↗
NASA NTRS1983

Recent studies at NASA-Langley of vortical flows interacting with neighboring surfaces

The importance of leadingedge vortical flows, which occur near and interact with neighboring surfaces, is stressed. Research in this area conducted or sponsored by the NASA Langley Research Center since 1978 is surveyed. Particular attention is given to the cumulative results of a number of theoretical and experimental studies. It is noted that these studies have been carried out in order to understand and use this kind of flow. Much of the work has been devoted to improving the lift-to-drag ratio and pitch characteristics for wings in this flow, although work has also been done on examining the unsteady and lateral characteristics.

Lamar, J. E.↗
NASA NTRS1982

The use of linearized-aerodynamics and vortex-flow methods in aircraft design /invited paper/

This paper deals with selected linearized-aerodynamic and vortex-flow methods as applied to aircraft design problems at high subsonic speeds. In particular, the NASA Vortex Lattice and Modified Multhopp methods are the linearized techniques employed, and the suction analogy is used to provide estimates associated with vortex-flow aerodynamics. Many examples are given as to how researchers at Langley have used these methods to design the high subsonic, wing-mean-camber shapes for various configurations such as a supersonic transport, high-aspect-ratio transport, trapezoidal fighter wing, strake wing, tandem wing, joined wing, delta wing, and slender cranked wing. Many of these have been built, tested, and have had their data compared with theory. In addition, a technique for defining efficiently performing strake planforms for use in strake-wing combinations is discussed, and further improvements in wing design are outlined. The latter may be obtained by using higher-ordered linear panel methods as well as nonlinear-transonic methods.

Lamar, J. E.↗
NASA NTRS1982

Production version of the extended NASA-Langley Vortex Lattice FORTRAN computer program. Volume 1: User's guide

The latest production version, MARK IV, of the NASA-Langley vortex lattice computer program is summarized. All viable subcritical aerodynamic features of previous versions were retained. This version extends the previously documented program capabilities to four planforms, 400 panels, and enables the user to obtain vortex-flow aerodynamics on cambered planforms, flowfield properties off the configuration in attached flow, and planform longitudinal load distributions.

Lamar, J. E.↗
NASA NTRS1982

Production version of the extended NASA-Langley vortex lattice FORTRAN computer program. Volume 2: Source code

The source code for the latest production version, MARK IV, of the NASA-Langley Vortex Lattice Computer Program is presented. All viable subcritical aerodynamic features of previous versions were retained. This version extends the previously documented program capabilities to four planforms, 400 panels, and enables the user to obtain vortex-flow aerodynamics on cambered planforms, flowfield properties off the configuration in attached flow, and planform longitudinal load distributions.

Herbert, H. E.↗