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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Overview of initial research into the effects of strong vortex flow on hybrid rocket combustion and performance

An examination of the effect of vortex flow on hybrid rocket combustion and performance is underway. Emphasis is on response of the fuel regression rate when subjected to vortex flow. Initial results show that there is a definite effect of the vortex on fuel regression rate. Future work will focus on quantitatively measuring this regression rate. This work is part of an overall program to develop an ultra low cost fuel system for hybrid rocket engines.

Gloyer, P.↗
NASA NTRS1979

Water tunnel visualization of the vortex flows of the F-15

Flow visualization studies were conducted in a diagnostic water tunnel to provide details of the wing, glove, and forebody vortex flow fields of the F-15 aircraft over a range of angles of attack and sideslip. Both the formation and breakdown of the vortex flow as a function of angle of attack and sideslip are detailed for the basic aircraft configuration. Additional tests showed that the wing upper surface vortex flows were sensitive to variations in an inlet mass flow ratio and an inlet cowl deflection angle. Two lengthened forebodies, one with a modified cross-sectional shape, were tested in addition to the basic forebody. Asymmetric forebody vortices were observed at zero sideslip and high angles of attack on each forebody. A large nose boom was added to each of the three forebodies, and it was observed that the turbulent wake shed from the boom disrupted the forebody vortices.

Lorincz, D. J.↗
NASA NTRS1986

Vortex flow hysteresis

An experimental study was conducted to quantify the hysteresis associated with various vortex flow transition points and to determine the effect of planform geometry. The transition points observed consisted of the appearance (or disappearance) of trailing edge vortex burst and the transition to (or from) flat plate or totally separated flows. Flow visualization with smoke injected into the vortices was used to identify the transitions on a series of semi-span models tested in a low speed tunnel. The planforms tested included simple deltas (55 deg to 80 deg sweep), cranked wings with varying tip panel sweep and dihedral, and a straked wing. High speed movies at 1000 frames per second were made of the vortex flow visualization in order to better understand the dynamics of vortex flow, burst and transition.

Cunningham, A. M., Jr.↗
NASA NTRS1984

Applications of CONMIN to wing design optimization with vortex flow effect

Slender wings on supersonic cruise configurations are expected to be thin and highly swept. As a result, edge-separated vortex flow is inevitable and must be accounted for in aerodynamic analysis and design. The present method is based on the method of suction analogy to calculate the total aerodynamic characteristics. The method requires the solution of the attached flow problem, the latter being solved by a low-order panel method in subsonic and supersonic flow. In essence, the lifting pressure is calculated by using a pressure-doublet distribution satisfying the Prandtl-Glauert equation. From the pressure distribution, the leading-edge suction is calculated. The latter is assumed to be the vortex lift through the method of suction analogy. For a cambered wing, the location of vortex-lift action point is important in predicting the aerodynamic characteristics. It is also seen that the effect of camber shape appears nonlinearly in all aerodynamic expressions. To design the camber shape, the camber slope is represented by a cosine Fourier series at each of several spanwise stations. The Fourier coefficients are the design variables. To design a leading-edge flap in the vortex flow (i.e., a vortex flap), the coordinates of corner points and the deflection angle are the design variables. The process of wing design is to determine the camber shape and twist distribution such that an objective function, typically the drag, is minimized, subject to various constraints.

Lan, C. E.↗
NASA NTRS1988

Ground vortex flow field investigation

Flow field investigations were conducted at the NASA Ames-Dryden Flow Visualization Facility (water tunnel) to investigate the ground effect produced by the impingement of jets from aircraft nozzles on a ground board in a STOL operation. Effects on the overall flow field with both a stationary and a moving ground board were photographed and compared with similar data found in other references. Nozzle jet impingement angles, nozzle and inlet interaction, side-by-side nozzles, nozzles in tandem, and nozzles and inlets mounted on a flat plate model were investigated. Results show that the wall jet that generates the ground effect is unsteady and the boundary between the ground vortex flow field and the free-stream flow is unsteady. Additionally, the forward projection of the ground vortex flow field with a moving ground board is one-third less than that measured over a fixed ground board. Results also showed that inlets did not alter the ground vortex flow field.

Kuhn, Richard E.↗
DOE OSTI2017

Expanding and Contracting Coronal Loops as Evidence of Vortex Flows Induced by Solar Eruptions

Eruptive solar flares were predicted to generate large-scale vortex flows at both sides of the erupting magnetic flux rope. This process is analogous to a well-known hydrodynamic process creating vortex rings. The vortices lead to advection of closed coronal loops located at the peripheries of the flaring active region. Outward flows are expected in the upper part and returning flows in the lower part of the vortex. Here, we examine two eruptive solar flares, the X1.1-class flare SOL2012-03-05T03:20 and the C3.5-class SOL2013-06-19T07:29. In both flares, we find that the coronal loops observed by the Atmospheric Imaging Assembly in its 171 Å, 193 Å, or 211 Å passbands show coexistence of expanding and contracting motions, in accordance with the model prediction. In the X-class flare, multiple expanding and contracting loops coexist for more than 35 minutes, while in the C-class flare, an expanding loop in 193 Å appears to be close by and cotemporal with an apparently imploding loop arcade seen in 171 Å. Later, the 193 Å loop also switches to contraction. These observations are naturally explained by vortex flows present in a model of eruptive solar flares.

79 ASTRONOMY AND ASTROPHYSICS↗
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.↗
DOE OSTI2019

Simulation of Wingtip Vortex Flows with Reynolds-Averaged Navier–Stokes and Scale-Resolving Simulation Methods

The simulation of wingtip vortex flows is reported on with Reynolds-averaged Navier–Stokes (RANS) equations and scale-resolving simulation (SRS) models. These range from turbulent viscosity and Reynolds-stress model (RSM) RANS closures, to hybrid and bridging SRS methods. The aim of the study was threefold: assess the relevance of replicating the experimental flow conditions, evaluate the numerical requisites of each mathematical model, and determine their modeling accuracy in prediction of a representative wingtip vortex flow. The selected problem is the flow around a NACA 0012 wing at 10 deg of angle of attack and Reynolds number of 4.60×10 6 . The results confirm the relevance of reproducing the experimental flow conditions, in particular at the inlet boundary where the flow is not uniform. For this reason, the evaluation of modeling errors using the available measurements requires the specification of the experimental inlet conditions. On the other hand, the quantification of the modeling error indicates that solely RANS–RSM can achieve an accurate representation of the flow dynamics. Whereas the well-recognized limitations of turbulent viscosity RANS closures to deal with solid-body rotation lead to the overprediction of turbulence and consequent rapid diffusion of the wingtip vortex, the predictive use of SRS methods may reveal excessively complex and demanding.

42 ENGINEERING↗
DOE OSTI2018

Formation of Vortex Flows in Liquid Crystal Phases Encapsulated in Microliter Volumes under the Action of Focused Laser Radiation

A theoretical description of the process of formation of vortex flows v(t, r) and the evolution of the director field n̂ in microliter liquid crystal (LC) volumes with a free surface under the influence of a temperature gradient ∇T(t, r), which is initiated by focused laser radiation, has been proposed. Thermomechanical contributions to both the stress tensor and viscous moment which are acting per unit volume of the LC phase were taken into account in the framework of the nonlinear generalization of the classical Ericksen−Leslie theory, which allowed describing the origin and formation of vortex flows in nematics formed by 4-n-pentyl- 4'-cyanobiphenyl molecules. Various hydrodynamic modes of vortex formation in microsized LC volumes under the action of focused laser radiation have been investigated by numerical methods.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2008

Initial Experiments and Analysis of Blunt-Edge Vortex Flows

A review is presented of the initial experimental results and analysis that formed the basis the Vortex Flow Experiment 2 (VFE-2). The focus of this work was to distinguish the basic effects of Reynolds number, Mach number, angle of attack, and leading edge bluntness on separation-induced leading-edge vortex flows that are common to slender wings. Primary analysis is focused on detailed static surface pressure distributions, and the results demonstrate significant effects regarding the onset and progression of leading-edge vortex separation.

Luckring, James M.↗
NASA NTRS2009

Initial Experiments and Analysis of Blunt-Edge Vortex Flows

A review is presented of the initial experimental results and analysis that formed the basis the Vortex Flow Experiment 2 (VFE-2). The focus of this work was to distinguish the basic effects of Reynolds number, Mach number, angle of attack, and leading edge bluntness on separation-induced leading-edge vortex flows that are common to slender wings. Primary analysis is focused on detailed static surface pressure distributions, and the results demonstrate significant effects regarding the onset and progression of leading-edge vortex separation.

Luckring, James M.↗
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 NTRS1995

Incompressible Navier-Stokes Simulation Procedure for a Wingtip Vortex Flow Analysis

The pacing items to reach the highly desirable goal of obtaining computationally accurate flow simulation of a wingtip vortex include; super-computer development, solver accuracy, grid generation and turbulence modeling. In these four areas, many advances have been made but the fact remains that most wing computations are, at best, five percent accurate (in drag coefficient, for example). This level of accuracy has been sufficient for many purposes such as airfoil design, rudimentary wing design, and some forms of optimization. However, this accuracy level will not allow commercial aircraft designers to extract the remaining few percent of efficiency theoretically possible for conventional aircraft configurations. Thus further research is needed, particularly in the areas of solver development and turbulence modeling, to advance the state of the art of viscous computational techniques as applied to problems in aerodynamics. During the course of this study, a substantial amount of measured and computed results have been acquired. In this paper, only a small selection of experimental and computational results will be presented. This paper will outline and discuss a simulation procedure for a wingtip vortex flow analysis using the method of artificial compressibility to solve the three-dimensional, incompressible, Navier-Stokes equations (INS3D-UP).

Jennifer Dacles-Mariani↗
NASA NTRS2005

Turbulent Vortex-Flow Simulation Over a 65 deg Sharp and Blunt Leading-Edge Delta Wing at Subsonic Speeds

Turbulent thin-layer, Reynolds-Averaged Navier-Stokes solutions, based on a multi-block structured grid, are presented for a 65 deg delta wing having either a sharp leading edge (SLE) or blunt leading edge (BLE) geometry. The primary objective of the study is to assess the prediction capability of the method for simulating the leading-edge flow separation and the ensuing vortex flow characteristics. Computational results are obtained for two angles of attack of approximately 13 and 20 deg, at free-stream Mach number of 0.40 and Reynolds number of 6 million based on the wing mean aerodynamic chord. The effects of two turbulence models of Baldwin-Lomax with Degani-Schiff (BL/DS) and the Spalart-Allmaras (SA) on the numerical results are also discussed. The computations also explore the effects of two numerical flux-splitting schemes, i.e., flux difference splitting (fds) and flux vector splitting (fvs), on the solution development and convergence characteristics. The resulting trends in solution sensitivity to grid resolution for the selected leading-edge geometries, angles of attack, turbulence models and flux splitting schemes are also presented. The validity of the numerical results is evaluated against a unique set of experimental wind-tunnel data that was obtained in the National Transonic Facility at the NASA Langley Research Center.

Ghaffari, Farhad↗
NASA NTRS2002

An Overview of the RTO Symposium on Vortex Flow and High Angle of Attack Aerodynamics

In May of 2001 the Research and Technology Organization (RTO) sponsored a symposium on Vortex Flow and High Angle of Attack aerodynamics. Forty-six papers, organized into nine sessions, addressed computational and experimental studies of vortex flows pertinent to both aircraft and maritime applications. The studies also ranged from fundamental fluids investigations to flight test results. Selected highlights are included in this paper to provide a perspective toward the scope of the full symposium.

Luckring, James M.↗
NASA NTRS1992

Vortex flow aerodynamics

The principal emphasis of the meeting was to be on the understanding and prediction of separation-induced vortex flows and their effects on vehicle performance, stability, control, and structural design loads. This report shows that a substantial amount of the papers covering this area were received from a wide range of countries, together with an attendance that was even more diverse. In itself, this testifies to the current interest in the subject and to the appropriateness of the Panel's choice of topic and approach. An attempt is made to summarize each paper delivered, and to relate the contributions made in the papers and in the discussions to some of the important aspects of vortex flow aerodynamics. This reveals significant progress and important clarifications, but also brings out remaining weaknesses in predictive capability and gaps in understanding. Where possible, conclusions are drawn and areas of continuing concern are identified.

Smith, J. H. B.↗