Search NASA⌕ Search

SEARCH · Search NASA

Results for “FREE FLOW”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Calculation of supersonic three-dimensional free-mixing flows using the parabolic-elliptic Navier-Stokes equations

A numerical method is presented which is valid for integration of the parabolic-elliptic Navier-Stokes equations. The solution procedure is applied to the three-dimensional supersonic flow of a jet issuing into a supersonic free stream. Difficulties associated with the imposition of free-stream boundary conditions are noted, and a coordinate transformation, which maps the point at infinity onto a finite value, is introduced to alleviate these difficulties. Results are presented for calculations of a square jet and varying-aspect-ratio rectangular jets. The solution behavior varies from axisymmetry for the square jet to nearly two-dimensional for the high-aspect-ratio rectangle, although the computation always calculates the flow as though it were truly three-dimensional.

Hirsh, R. S.↗
NASA NTRS1976

Turbulence measurements in a transonic boundary layer and free-shear flow using laser velocimetry and hot-wire anemometry techniques

Quantitative measurements of the turbulence fluctuations in velocity and mass flux have been obtained in Mach 0.6 and 0.8 turbulent boundary layer and free-shear layer flows by laser velocimetry and hot-wire anemometry techniques. To evaluate the effects of compressibility, these transonic data are compared to available incompressible and supersonic results. Based on some simplifying assumptions, estimates of the rms density fluctuations are made for which error bounds are given. In addition to these fluctuation data, the compressible mean velocity data obtained with the laser velocimeter are presented and compared to pitot tube results. The investigation was conducted in the Ames 6- by 6-Foot Supersonic Wind Tunnel at free-stream Mach numbers of 0.6 and 0.8 for a unit Reynolds number of about 10,000,000 per meter.

Johnson, D. A.↗
NASA NTRS1998

Internal Flows in Free Drops (IFFD)

Within the framework of an Earth-based research task investigating the internal flows within freely levitated drops, a low-gravity technology development experiment has been designed and carried out within the NASA Glovebox facility during the STS-83 and STS-94 Shuttle flights (MSL-1 mission). The goal was narrowly defined as the assessment of the capabilities of a resonant single-axis ultrasonic levitator to stably position free drops in the Shuttle environment with a precision required for the detailed measurement of internal flows. The results of this entirely crew-operated investigation indicate that the approach is fundamentally sound, but also that the ultimate stability of the positioning is highly dependent on the residual acceleration characteristic of the Spacecraft, and to a certain extent, on the initial drop deployment of the drop. The principal results are: the measured dependence of the residual drop rotation and equilibrium drop shape on the ultrasonic power level, the experimental evaluation of the typical drop translational stability in a realistic low-gravity environment, and the semi-quantitative evaluation of background internal flows within quasi-isothermal drops. Based on these results, we conclude that the successful design of a full-scale Microgravity experiment is possible, and would allow accurate the measurement of thermocapillary flows within transparent drops. The need has been demonstrated, however, for the capability for accurately deploying the drop, for a quiescent environment, and for precise mechanical adjustments of the levitator.

Trinh, E. H.↗
NASA NTRS1984

Classical free-streamline flow over a polygonal obstacle

In classical Kirchhoff flow, an ideal incompressible fluid flows past an obstacle and around a motionless wake bounded by free streamlines. Since 1869 it has been known that in principle, the two-dimensional Kirchhoff flow over a polygonal obstacle can be determined by constructing a conformal map onto a polygon in the log-hodograph plane. In practice, however, this idea has rarely been put to use except for very simple obstacles, because the conformal mapping problem has been too difficult. This paper presents a practical method for computing flows over arbitrary polygonal obstacles to high accuracy in a few seconds of computer time. We achieve this high speed and flexibility by working with a modified Schwarz-Christoffel integral that maps onto the flow region directly rather than onto the log-hodograph polygon. This integral and its associated parameter problem are treated numerically by methods developed earlier by Trefethen for standard Schwarz-Christoffel maps.

Elcrat, A. R.↗
NASA NTRS1986

Classical free-streamline flow over a polygonal obstacle

In classical Kirchhoff flow, an ideal incompressible fluid flows past an obstacle and around a motionless wake bounded by free streamlines. Since 1869 it has been known that in principle, the two-dimensional Kirchhoff flow over a polygonal obstacle can be determined by constructing a conformal map onto a polygon in the log-hodograph plane. In practice, however, this idea has rarely been put to use except for very simple obstacles, because the conformal mapping problem has been too difficult. This paper presents a practical method for computing flows over arbitrary polygonal obstacles to high accuracy in a few seconds of computer time. We achieve this high speed and flexibility by working with a modified Schwarz-Christoffel integral that maps onto the flow region directly rather than onto the log-hodograph polygon. This integral and its associated parameter problem are treated numerically by methods developed earlier by Trefethen for standard Schwarz-Christoffel maps.

Elcrat, A. R.↗
NASA NTRS1977

Finite element solutions of free surface flows

A procedure is presented for using NASTRAN to determine the flow field about arbitrarily shaped bodies in the presence of a free surface. The fundamental unknown of the problem is the velocity potential which must satisfy Laplace's equation in the fluid region. Boundary conditions on the free surface may involve second order derivatives in space and time. In cases involving infinite domains either a tractable radiation condition is applied at a truncated boundary or a series expansion is used and matched to the local finite elements. Solutions are presented for harmonic, transient, and steady state problems and compared to either exact solutions or other numerical solutions.

Zarda, P. R.↗
NASA NTRSDate not supplied

Three-Dimensional, Multi-Phase Unsteady Flow of Water Undergoing Multiple Flow Regimes (Free Surface, Droplet, and Fluid Film)

Upgrades to the Mobile Launcher Rainbird nozzles were implemented for the Artemis II launch to increase water flow rates and improve the mobile launcher deck water coverage while minimizing the water throw distance to avoid impacting the Space Launch System (SLS) rocket nozzles. This analysis describes the use of a three-dimensional, multi-phase, free surface transient computational fluid dynamics (CFD) model to simulate the water flowing out through the Rainbird nozzle and ensure compliance with current Artemis requirements. Flow rates, pressures, velocities, nozzle throw distances and coverage areas were analyzed to ensure that system requirements are met. The completed results were used to make necessary modifications to the Ignition Overpressure Protection and Sound Suppression (IOP/SS) system Rainbird design by reshaping the nozzle used in the system.

CFD↗
NASA NTRS1977

Experimental and analytical dynamic flow characteristics of an axial-flow fan from an air cushion landing system model

An investigation was conducted to compare the steady-state and dynamic flow characteristics of an axial-flow fan which had been used previously as the air supply fan for some model air cushion landing system studies. Steady-state flow characteristics were determined in the standard manner by using differential orifice pressures for the flow regime from free flow to zero flow. In this same regime, a correlative technique was established so that fan inlet and outlet pressures could be used to measure dynamic flow as created by a rotating damper. Dynamic tests at damper frequencies up to 5 Hz showed very different flow characteristics when compared with steady-state flow, particularly with respect to peak pressures and the pressure-flow relationship at fan stall and unstall. A generalized, rational mathematical fan model was developed based on physical fan parameters and a steady-state flow characteristic. The model showed good correlation with experimental tests at damper frequencies up to 5 Hz.

Thompson, W. C.↗
NASA NTRS1991

A fully coupled flow simulation around spacecraft in low earth orbit

The primary objective of this investigation is to provide a full flow simulation of a spacecraft in low earth orbit (LEO). Due to the nature of the environment, the simulation includes the highly coupled effects of neutral particle flow, free stream plasma flow, nonequilibrium gas dynamics effects, spacecraft charging and electromagnetic field effects. Emphasis is placed on the near wake phenomenon and will be verified in space by the Wake Shield Facility (WSF) and developed for application to Space Station conditions as well as for other spacecraft. The WSF is a metallic disk-type structure that will provide a controlled space platform for highly accurate measurements. Preliminary results are presented for a full flow around a metallic disk.

Justiz, C. R.↗
DOE OSTI2022

High-energy and low-cost membrane-free chlorine flow battery

Abstract Grid-scale energy storage is essential for reliable electricity transmission and renewable energy integration. Redox flow batteries (RFB) provide affordable and scalable solutions for stationary energy storage. However, most of the current RFB chemistries are based on expensive transition metal ions or synthetic organics. Here, we report a reversible chlorine redox flow battery starting from the electrolysis of aqueous NaCl electrolyte and the as-produced Cl 2 is extracted and stored in the carbon tetrachloride (CCl 4 ) or mineral spirit flow. The immiscibility between the CCl 4 or mineral spirit and NaCl electrolyte enables a membrane-free design with an energy efficiency of >91% at 10 mA/cm 2 and an energy density of 125.7 Wh/L. The chlorine flow battery can meet the stringent price and reliability target for stationary energy storage with the inherently low-cost active materials (~$5/kWh) and the highly reversible Cl 2 /Cl − redox reaction.

25 ENERGY STORAGE↗
NASA NTRS1982

The NASA Langley laminar flow control airfoil experiment

A large chord swept supercritical LFC airfoil has been constructed for NASA-Langley's research program to determine the compatibility of supercritical airfoils with suction laminarization and to establish a technology base for future transport designs. Features include a high design Mach number and shock-free flow, as well as the minimization of the laminarization suction through a choice of airfoil geometry and pressure distribution. Two suction surface concepts and a variety of hybrid suction concepts involving combinations of natural and forced laminar flow are to be investigated. The test facility has been modified to insure achievement of required flow quality and transonic interference-free flow over the yawed LFC airfoil.

Harvey, W. D.↗
NASA NTRS1992

Modified k-epsilon model for compressible free shear flows

The k-epsilon model has heretofore been unable to predict experimentally observed decreases in the spreading rate of turbulent supersonic free-shear layers encountered with increasing Mach number. The present modification of the two-equation k-epsilon-1 model is able to effectively reduce the model to a 1-equation k model in highly compressible flows; as a result, a significant improvement in accuracy is obtained for predictions concerning supersonic shear layers.

Brescianini, C. P.↗
NASA NTRS1982

NASA Langley laminar flow control airfoil experiment

The design and construction of an advanced swept supercritical airfoil for commercial aircraft to be tested in a transonic wind tunnel is described. The swept LFC airfoil was designed for a given thickness ratio and lift coefficient, with emphasis placed on high critical Mach number with shock-free flow. It is compatible with satisfactory low speed and buffeting characteristics and minimizing the suction laminarization. Further emphasis was placed on achieving shock-free flow over a wide range of off-design conditions including trailing edge flap control. The requirements and design of the suction system and modifications to the Langley 8 foot transonic pressure tunnel is briefly described. Contouring of nonporous test section walls for free air simulation and flow quality improvements is included.

Harvey, W. D.↗
NASA NTRS1992

Planar laser-induced fluorescence measurements of high-enthalpy free jet flow with nitric oxide

Planar laser-induced fluorescence (PLIF) measurements of property fields in a high-enthalpy, supersonic, underexpanded free jet generated in a reflection-type shock tunnel are reported. PLIF images showing velocity and temperature sensitivity are presented. The inferred radial velocity and relative rotational temperature fields are found to be in agreement with those predicted by a numerical simulation of the flowfield using the method of characteristics.

Palmer, Jennifer L.↗
NASA NTRS1929

The Effect of Fuel Consumption on Cylinder Temperatures and Performance of a Cowled Wright J-5 Engine

Given here are the results of tests made to determine the effect of fuel consumption on the cylinder temperatures and the performance of a cowled Wright J-5 engine. The results of these tests indicate that enriching the mixture by increasing the carburetor size results in a reduction in cylinder head and barrel temperatures. The cylinders shielded by the magnetos or the points on the cylinder that do not receive a free flow of cooling air increase most rapidly in temperature as the mixture is leaned. A free flow of air past the cylinders is essential for satisfactory operation on a lean mixture. The results of these tests show that the Wright J-5 engine can withstand severe temperatures for short periods of operation. The test results also show to what extent destructive temperatures may be avoided by enriching the mixture.

Schey, Oscar W↗
DOE OSTI2022

Metal-free polypeptide redox flow batteries

Metal-free redox flow batteries with TEMPO-based polypeptide catholytes and viologen-based polypeptide anolytes were demonstrated. Post-cycling analysis indicated the main source of capacity fade was degradation of the redox-active pendant groups.

Liang, Zhiming↗
NASA NTRS1979

Test technique development in interference free testing, flow visualization, and remote control model technology at Langley's Unitary Plan wind tunnel

A metric half-span model is considered as a means of mechanical support for a wind-tunnel model which allows measurement of aerodynamic forces and moments without support interference or model distortion. This technique can be applied to interference-free propulsion models. The vapor screen method of flow visualization at supersonic Mach numbers is discussed. The use of smoke instead of water vapor as a medium to produce the screen is outlined. Vapor screen data are being used in the development of analytical vortex tracking programs. Test results for a remote control model system are evaluated. Detailed control effectiveness and cross-coupling data were obtained with a single run. For the afterbody tail configuration, tested control boundaries at several roll orientations were established utilizing the facility's on-line capability to 'fly' the model in the wind tunnel.

Corlett, W. A.↗
NASA NTRS1961

Loads Induced on a Flat-Plate Wing by an Air Jet Exhausting Perpendicularly through the Wing and Normal to a Free-Stream Flow of Mach Number 2.0

Measurements were made of loads induced on a flat-plate wing by an air jet exhausting perpendicularly through the wing and normal to the free-stream flow.The investigation was conducted at a free-stream Mach number of 2.0 and a Reynolds number per foot of 14.4 x 10(exp 6). An axially symmetric sonic nozzle and two supersonic nozzles were employed for the jets. The supersonic nozzles consisted of an axially symmetric nozzle with exit Mach number of 3.44 and a two-dimensional nozzle with exit Mach number of 1.76. The ratio of nozzle total pressure to free-stream static pressure was varied from 20 to 110. Negative loads were induced on the flat-plate wing by all the jets. As the nozzle pressure ratio was increased the magnitude of interference loads due to jet thrust decreased. The chordwise center-of-pressure location generally moved toward the nozzle center line as the pressure ratio was increased.

Janos, Joseph J.↗