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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Design of a bleed system for a Mach 3.5 inlet

An analytical bleed system design procedure is applied to a Mach 3.5, axisymmetric, translating centerbody inlet. The design features a traveling centerbody bleed system with a ducting arrangement separating low-, medium-, and high-pressure bleed. Three forward plenums and nine throat plenums are installed on the centerbody to meet the bleed requirements in the started Mach range between 1.6 and 3.5. The cowl contains four stationary plenums, three for forward and one for throat bleed. To achieve maximum bleed plenum pressure and thereby minimize bleed drag all bleed holes are inclined 20 deg to the surface except in the cowl throat region. Here the requirement of high stability margin with minimum total pressure recovery penalty resulted in 90 deg bleed holes. The bleed hole diameter varies from bleed plenum to bleed plenum to achieve the most efficient boundary layer control, while the bleed exits are sized to operate at the highest possible plenum pressure without unchoking the bleed holes. Bleed flow rates, bleed plenum pressures, and boundary layer development along the cowl and centerbody are predicted over the entire started Mach range.

Syberg, J.↗
NASA NTRS2002

Active Control of Turbulent Boundary Layer Induced Sound Radiation from Multiple Aircraft Panels

The objective of this work is to experimentally investigate active structural acoustic control of turbulent boundary layer (TBL) induced sound radiation from multiple panels on an aircraft sidewall. One possible approach for controlling sound radiation from multiple panels is a multi-input/multi-output scheme which considers dynamic coupling between the panels. Unfortunately, this is difficult for more than a few panels, and is impractical for a typical aircraft which contains several hundred such panels. An alternative is to implement a large number of independent control systems. Results from the current work demonstrate the feasibility of reducing broadband radiation from multiple panels utilizing a single-input/single-output (SISO) controller per bay, and is the first known demonstration of active control of TBL induced sound radiation on more than two bays simultaneously. The paper compares sound reduction for fully coupled control of six panels versus independent control on each panel. An online adaptive control scheme for independent control is also demonstrated. This scheme will adjust for slow time varying dynamic systems such as fuselage response changes due to aircraft pressurization, etc.

Gibbs, Gary P.↗
NASA NTRS1996

Experimental Investigation of Crossing Shock Wave-Turbulent Boundary Layer-Bleed Interaction

Results of an experimental investigation of a symmetric crossing shock wave/turbulent boundary layer/bleed interaction are presented for a freestream unit Reynolds number of 1.68 x 10(exp 7)/m, a Mach number of 2.81, and deflection angles of 8 degrees. The data obtained in this study are bleed mass flow rate using a trace gas technique, qualitative information in the form of oil flow visualization, flow field Pitot pressures, and static pressure measurements using pressure sensitive paint. The main objective of this test is two-fold. First, this study is conducted to explore boundary layer control through mass flow removal near a large region of separated flow caused by the interaction of a double fin-induced shock wave and an incoming turbulent boundary layer. Also, a comprehensive data set is needed for computational fluid dynamics code validation.

Kim, Hyun↗
NASA NTRS1986

Aircraft drag prediction and reduction. Addendum 1: Computational drag analyses and minimization; mission impossible?

The Special Course on Aircraft Drag Prediction was sponsored by the AGARD Fluid Dynamics Panel and the von Karman Institute and presented at the von Karman Institute, Rhode-Saint-Genese, Belgium, on 20 to 23 May 1985 and at the NASA Langley Research Center, Hampton, Virginia, USA, 5 to 6 August 1985. The course began with a general review of drag reduction technology. Then the possibility of reduction of skin friction through control of laminar flow and through modification of the structure of the turbulence in the boundary layer were discussed. Methods for predicting and reducing the drag of external stores, of nacelles, of fuselage protuberances, and of fuselage afterbodies were then presented followed by discussion of transonic drag rise. The prediction of viscous and wave drag by a method matching inviscid flow calculations and boundary layer integral calculations, and the reduction of transonic drag through boundary layer control are also discussed. This volume comprises Paper No. 9 Computational Drag Analyses and Minimization: Mission Impossible, which was not included in AGARD Report 723 (main volume).

Slooff, J. W.↗
NASA NTRS1994

Wind Tunnel Testing for the Stratospheric Observatory for Infrared Astronomy

NASA Ames Research Center is pursuing the development of SOFIA, the Stratospheric Observatory For Infrared Astronomy. SOFIA will consist of a 2.5 meter telescope mounted aft of the wing of a Boeing 747 aircraft. Since a large portion of the infrared spectrum is not visible at ground level due to absorption by water vapor in the atmosphere below 40,000 feet, it is highly desirable to make observations above this altitude. SOFIA will provide the opportunity for astronomers to conduct high-altitude research for extended periods of time. Current study is focused on wind tunnel testing for the open cavity. If not controlled, air would create resonance and damage the telescope. For this reason, SOFIA will design a boundary layer control device to achieve laminar flow over the cavity. This also provides a clearer flow for seeing, thus improving resolution on infrared sources. Other effects being tested in the wind tunnel are aerodynamic torque loads on the telescope, and flutter loads on the tail.

Schenberger, Deborah↗
NASA NTRS1995

Experimental testing using a remotely operated flap with a 2D high lift model

The problem of efficient wind tunnel testing for multi-element airfoils was first addressed by the author during a previous ASEE fellowship. A modern three element model with internal actuators to position a flap in two degrees of freedom was designed and later built. Some preliminary testing proved that the approach was viable. The purpose of this summer's work was to fully develop experimental methods including efficient data acquisition. The final goal is to develop dense data sets for both lift and drag measurements as a function of flap position for both take-off and landing configurations. The model has a span of 36 in. and chord of 18 in. and is currently being fitted for a 3 ft. x 4 ft. low speed wind tunnel. The flap was reworked to allow all pressure taps to function after initial tests showed two blocked ports. The serial method of obtaining pressures from the surface taps was found to be exceedingly slow so a new method using 12 pressure transducers and a 12 port parallel scanning valve were developed. A new automated data acquisition and control algorithm was developed using LabView software and a PC platform. Flow two-dimensionality is currently under investigation with boundary layer control by blowing; this was previously omitted for initial testing. By the end of the summer a detailed data set (uncorrected) consisting of lift coefficient versus flap position for the landing configuration should be available.

Landman, Drew↗
NASA NTRS1984

Recent modifications and calibration of the Langley low-turbulence pressure tunnel

Modifications to the Langley Low-Turbulence Pressure Tunnel are presented and a calibration of the mean flow parameters in the test section is provided. Also included are the operational capability of the tunnel and typical test results for both single-element and multi-element airfoils. Modifications to the facility consisted of the following: replacement of the original cooling coils and antiturbulence screens and addition of a tunnel-shell heating system, a two dimensional model-support and force-balance system, a sidewall boundary layer control system, a remote-controlled survey apparatus, and a new data acquisition system. A calibration of the mean flow parameters in the test section was conducted over the complete operational range of the tunnel. The calibration included dynamic-pressure measurements, Mach number distributions, flow-angularity measurements, boundary-layer characteristics, and total-pressure profiles. In addition, test-section turbulence measurements made after the tunnel modifications have been included with these calibration data to show a comparison of existing turbulence levels with data obtained for the facility in 1941 with the original screen installation.

Mcghee, R. J.↗
NASA NTRS2001

Development of Advanced Casing Treatments for Flow Control

Under the Base R&T and Ultra Efficient Engine Technology programs, the NASA-Goddard Space Flight Center Compressor Branch is investigating flow control strategies required to increase the loading and efficiency of core compressors while maintaining current levels of operability. Flow-control strategies being studied include advanced casing treatments, wall jet injection, and blade-tip injection for compressor stability enhancement, directed jets for surface boundary layer control, and vortex-generating devices. The use of computational fluid dynamics (CFD) simulations to assess the effectiveness of flow-control devices and to guide their design is a key element in this research. CFD simulations serve to screen potential flow-control concepts at a lower cost than executing physical experiments in turbomachinery facilities. CFD simulations also provide guidance in designing physical experiments for those flow control concepts, which appear promising.

Keith, Theo G., Jr.↗
NASA NTRS1990

Radiative control on tropical convective boundary layer equilibrium

How the near-balance between the radiative cooling and the surface fluxes in the tropics controls boundary layer, the height of cloud-base and the top of the convective boundary layer over the tropical oceans is discussed. The impact of boundary layer cloudiness and upper level moisture on the equilibrium solutions is explored.

Betts, Alan K.↗
NASA NTRS1978

A flight investigation of the stability, control, and handling qualities of an augmented jet flap STOL airplane

The stability, control, and handling qualities of an augmented jet flap STOL airplane are presented. The airplane is an extensively modified de Havilland Buffalo military transport. The modified airplane has two fan-jet engines which provide vectorable thrust and compressed air for the augmentor jet flap and Boundary-Layer Control (BLC). The augmentor and BLC air is cross ducted to minimize asymmetric moments produced when one engine is inoperative. The modifications incorporated in the airplane include a Stability Augmentation System (SAS), a powered elevator, and a powered lateral control system. The test gross weight of the airplane was between 165,000 and 209,000 N (37,000 and 47,000 lb). Stability, control, and handling qualities are presented for the airspeed range of 40 to 180 knots. The lateral-directional handling qualities are considered satisfactory for the normal operating range of 65 to 160 knots airspeed when the SAS is functioning. With the SAS inoperative, poor turn coordination and spiral instability are primary deficiencies contributing to marginal handling qualities in the landing approach. The powered elevator control system enhanced the controllability in pitch, particularly in the landing flare and stall recovery.

Vomaske, R. F.↗
NASA NTRS2011

Large-Scale Low-Boom Inlet Test Overview

This presentation provides a high level overview of the Large-Scale Low-Boom Inlet Test and was presented at the Fundamental Aeronautics 2011 Technical Conference. In October 2010 a low-boom supersonic inlet concept with flow control was tested in the 8'x6' supersonic wind tunnel at NASA Glenn Research Center (GRC). The primary objectives of the test were to evaluate the inlet stability and operability of a large-scale low-boom supersonic inlet concept by acquiring performance and flowfield validation data, as well as evaluate simple, passive, bleedless inlet boundary layer control options. During this effort two models were tested: a dual stream inlet intended to model potential flight hardware and a single stream design to study a zero-degree external cowl angle and to permit surface flow visualization of the vortex generator flow control on the internal centerbody surface. The tests were conducted by a team of researchers from NASA GRC, Gulfstream Aerospace Corporation, University of Illinois at Urbana-Champaign, and the University of Virginia

Hirt, Stefanie↗
NASA NTRS1977

Feasibility of modern airships - Preliminary assessment

Attention is given to the NASA program, Feasibility Study of Modern Airships, initiated to investigate potential research and technology programs associated with airship development. A historical survey of the program is presented, including the development of past airship concepts, aerodynamical and design improvements, structure and material concepts, and research in controls, avionics, instrumentation, flight operations, and ground handling. A mission analysis was carried out which considered passenger and cargo transportation, heavy-lift, short-haul applications, surveillance missions, and the transportation of natural gas. A vehicle parametric analysis examined the entire range of airship concepts, discussing both conventional airships and hybrids. Various design options were evaluated, such as choice of structural materials, use of boundary-layer control, and choice of lifting gas.

Ardema, M. D.↗
NASA NTRS1985

Parametric study of supersonic STOVL flight characteristics

A number of different control devices and techniques are evaluated to determine their suitability for increasing the short takeoff performance of a supersonic short-takeoff/vertical landing (STOVL) aircraft. Analysis was based on a rigid-body mathematical model of the General Dynamics E-7, a single engine configuration that utilizes ejectors and thrust deflection for propulsive lift. Alternatives investigated include increased static pitch, the addition of a close-coupled canard, use of boundary layer control to increase the takeoff lift coefficient, and the addition of a vectorable aft fan air nozzle. Other performance studies included the impact of individual E-7 features, the sensitivity to ejector performance, the effect of removing the afterburners, and a determination of optional takeoff and landing transition methods. The results pertain to both the E-7 and other configurations. Several alternatives were not as well suited to the E-7 characteristics as they would be to an alternative configuration, and vice versa. A large amount of supporting data for each analysis is included.

Rapp, David C.↗
NASA NTRS1992

Supersonic HLFC: Potential benefits and technology development requirements

The viewgraphs and discussion of the potential benefits and technology development requirements of supersonic Hybrid Laminar Flow Control (HLFC) are reviewed. For the last three years, Boeing has performed studies on the application of laminar flow control to High Speed Civil Transport (HSCT) configurations. Large potential net benefits were identified for laminar flow control, even after accounting for the significant implementation penalties. However, the technical risks are high at this time, and an early, aggressive technology development program is required if laminar flow control (LFC) is to be incorporated in a year 2005 HSCT program. The benefits and required development effort are addressed. Of all the aerodynamic advances that are being considered for the HSCT, LFC has the largest potential for improving the supersonic lift drag ratio of a given configuration. The work accomplished to date, sponsored by NASA Langley, is summarized. This work includes studies on HLFC application to HSCT, cruise HLFC/low speed boundary layer control (BLC) compatibility, and impact of M 0.9 HLFC and high lift BLC. Requirements for production committments are listed. The need for a HSCT-HLFC Risk Reduction Program is addressed. Supersonic HLFC development planning and future applications are addressed. Laminar flow/high-lift integration is addressed.

Neumann, Frank↗
NASA NTRS1981

A Jet-diffuser ejector for a V/STOL fighter

A single ejector equipped with only one vector control jet and a diffuser flap was installed close to the leading edge of the strake of a one-fifth scale, semi-span model of the aircraft, without wing, canard, or tail surface. Tests of the system at a nozzle pressure ratio of 1.24 indicated a thrust augmentation of 1.92 and a thrust in the flight direction of about 12% of the total thrust under static conditions. An ejector stall occured at a ratio of tunnel dynamic pressure to nozzle gage pressure of about 0.008. Ejector stall speed can be delayed by using a boundary layer control jet at the front inlet lip of the ejector.

Alperin, M.↗
NASA NTRS1988

Control of the boundary layer separation about an airfoil by active surface heating

Application of active control to separated flow on the RC(6)-08 airfoil at high angle of attack by localized surface heating is numerically simulated by integrating the compressible two-dimensional nonlinear Navier-Stokes equations solver. Active control is simulated by local modification of the temperature boundary condition over a narrow strip on the upper surface of the airfoil. Both mean and perturbed profiles are favorably altered when excited with the same natural frequency of the shear layer by moderate surface heating for both laminar and turbulent separation. The shear layer is found to be very sensitive to localized surface heating in the vicinity of the separation point. The excitation field at the surface sufficiently altered both the local as well as the global circulation to cause a significant increase in lift and reduction in drag.

Maestrello, Lucio↗
NASA NTRS1967

Experimental scaling study of fluid amplifier elements

Study examines scaling parameters of three fluid amplifier elements - a bistable device, a boundary layer control device, and a vortex device. Variations in performance due to size, fluid, and other conditions are studied. Even with restricted examples the large number of variables impedes the establishment of these scaling laws.

Abler, J.↗