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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Structural Dynamic/CFD Interaction for Computation of Vertical Tail Buffet

The multi-disciplinary problem of tail buffeting is solved using three sets of equations. The first set is the unsteady, compressible, full Navier Stokes equations which are used for obtaining the flow-field vector and the aerodynamic loads. The second set is the coupled aeroelastic equations which are used for obtaining the bending and torsional deflections of the tail. The third set is the grid-displacement equations which are used for updating the grid coordinates due to the tail deflections. For the computational applications a sharp-edged delta wing of aspect ratio one and a rectangular vertical tail of aspect ratio one placed in the plane of geometric symmetry behind the wing are considered. The configuration is pitched at a critical angle of attack (alpha = 38 deg.) which produces asymmetric, vortex-breakdown flow of the delta wing primary vortices. The results show the effects of coupled and uncoupled bending-torsional responses and the effects of the Reynolds number.

Kandil, Osama A.↗
DOE OSTI2017

A non-linear k-{epsilon} turbulent model sensitivity analysis for flow across a PWR spacer grid with mixing vanes

In this work we studied the sensitivity of different computational fluid dynamics (CFD) numerical solutions on turbulence model, domain discretization mesh type, and inlet boundary conditions. The case under examination is a turbulent one-phase flow (water) through a scaled nuclear pressurized water reactor (PWR) fuel assembly. The main feature of this geometrical configuration is the presence of a spacer grid with mixing vanes. The design of a spacer grid with mixing vanes plays a key role for the core heat transfer efficiency, increasing the coolant heat transfer coefficient. The main reason for this is the introduction of the top mixing vanes, which consist of an ordered repetitive succession of wings that generate secondary swirling flows. The increase of heat transfer efficiency also increases the critical heat flux (CHF), making it possible to increase the design and operational limits, far from boiling crises (departure of nucleate boiling in case of a PWR). The main focus of this work was to analyze the simulation capabilities of Reynolds-averaged Navier-Stokes (RANS) models (a cubic non-linear k-epsilon model formulation) for this complex flow geometry. The CFD code used was CD-Adapco STAR-CCM+.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Experimental Study of the Mold Flow Induced by a Swirling Flow Nozzle and Electromagnetic Stirring for Continuous Casting of Round Blooms

This study focuses on an experimental investigation of the fluid flow in round bloom continuous casting using a 1:3 model of the industrial casting process. A swirling flow nozzle, represented by the specific design of the RHI Magnesita GYRONOZZLE, is used to produce a swirling motion in the cylindrical mold. The test section is integrated into the Mini-LIMMCAST facility at HZDR, which is operated at room temperature using the ternary alloy GaInSn. Systematic measurements of horizontal and vertical velocity profiles are performed by means of the Ultrasound Doppler Velocimetry. The second part of the study focuses on the interaction between the flow driven by the GYRONOZZLE and concurrent electromagnetic stirring in the mold (M-EMS) by applying rotating magnetic fields (RMFs) at different magnetic flux densities. The effect of the GYRONOZZLE on the flow pattern inside the mold is examined with and without superimposed RMFs and compared to those of a standard single-port nozzle. The measurements reveal that the GYRONOZZLE induces a swirling flow in the whole mold. It is further shown that the influence of a simultaneously applied RMF is mainly restricted to the lower part of the mold since the transport of angular momentum to the top is suppressed by the jets pouring out from the GYRONOZZLE.

36 MATERIALS SCIENCE↗
NASA NTRS1999

A Parametric Study of Accelerations of an Airplane Due to a Wake Vortex System

A study was conducted using strip theory to systematically investigate the effects of progressively more complete descriptions of the interaction of an airplane with a wake vortex system. The emphasis was in roll-dominant, parallel, vortex encounters. That is, the simulated airplane's longitudinal axis was nearly parallel to the rotation axis of the vortex system for most of the results presented. The study began with a drag-less rectangular wing in the flow field of a single vortex and progressed to a complete airplane with aerodynamic surfaces possessing taper, sweep, dihedral, and stalling and immersed in the flow field of a vortex pair in ground effect. The effects of the pitch, roll, and yaw attitudes of the airplane on the calculated accelerations were also investigated. The airplane had the nominal characteristics of a Boeing 757, and the vortex flow field had the nominal characteristics of the wake of a Boeing 767. The Bumham-Hallock model of a vortex flow field was used throughout the study. The data are presented mainly in terms of contours of equal acceleration in a two-dimensional area centered on the vortex pair and having dimensions of 300 feet by 300 feet.

Stewart, Eric C.↗
NASA NTRS1983

Topology of vortices in conical flow

The possibility of the existence of a viscous vortex in a conical flow is discussed. Existence of a viscous vortex is shown to be consistent with a flow-field model where only the velocity components and the total enthalpy behave conically. Existence of a viscous vortex is not consistent with the fully conical, flow-field model; however, far from the nose tip, the physical flow quantities tend to behave asymptotically as a full conical flow. Such a viscous vortex, when it exists, must spiral inwards to the focal point. It can be used as a reasonable model to start numerical solutions of various kinds.

Almosnino, D.↗
NASA NTRS2004

Wind Tunnel Application of a Pressure-Sensitive Paint Technique to a Faceted Missile Model at Subsonic and Transonic Speeds

A pressure-sensitive paint (PSP) technique was applied in a wind tunnel experiment in the NASA Langley Research Center 8-Foot Transonic Pressure Tunnel to quantify the vortex-induced surface static pressures on a slender, faceted missile model at subsonic and transonic speeds. Global PSP calibrations were obtained using an in-situ method featuring the simultaneous electronically-scanned pressures (ESP) measurements. Both techniques revealed the significant influence leading-edge vortices on the surface pressure distributions. The mean error in the PSP measurements relative to the ESP data was approximately 0.6 percent at M(sub infinity)=0.70 and 2.6 percent at M(sub infinity)=0.90 and 1.20. The vortex surface pressure signatures obtained from the PSP and ESP techniques were correlated with the off-surface vortex cross-flow structures obtained using a laser vapor screen (LVS) flow visualization technique. The on-surface and off-surface techniques were complementary, since each provided details of the vortex-dominated flow that were not clear or apparent in the other.

Erickson, Gary E.↗
NASA NTRS2004

Wind Tunnel Application of a Pressure-Sensitive Paint Technique to a Faceted Missile Model at Subsonic and Transonic Speeds

A pressure-sensitive paint (PSP) technique was applied in a wind tunnel experiment in the NASA Langley Research Center 8-Foot Transonic Pressure Tunnel to quantify the vortex-induced surface static pressures on a slender, faceted missile model at subsonic and transonic speeds. Satisfactory global calibrations of the PSP were obtained at =0.70, 0.90, and 1.20, angles of attack from 10 degrees to 20 degrees, and angles of sideslip of 0 and 2.5 degrees using an in-situ method featuring the simultaneous acquisition of electronically-scanned pressures (ESP) at 57 discrete locations on the model. Both techniques clearly revealed the significant influence on the surface pressure distributions of the vortices shed from the sharp, chine-like leading edges. The mean error in the PSP measurements relative to the ESP data was approximately 0.6 percent at M infinity =0.70 and 2.6 percent at M infinity =0.90 and 1.20. The vortex surface pressure signatures obtained from the PSP and ESP techniques were correlated with the off-surface vortex cross-flow structures obtained using a laser vapor screen (LVS) flow visualization technique. The on-surface and off-surface techniques were complementary, since each provided details of the vortex-dominated flow that were not clear or apparent in the other.

Erickson, Gary E.↗
DOE OSTI2021

Reversible ratchet effects in a narrow superconducting ring

We study the ratchet effect in a narrow pinning-free superconductive ring based on time-dependent GinzburgLandau (TDGL) equations. Voltage responses to external dc and ac currents at various magnetic fields are studied. Due to asymmetric barriers for flux penetration and flux exit in the ring-shaped superconductor, the critical current above which the flux-flow state is reached, as well as the critical current for the transition to the normal state, are different for the two directions of applied current. Furthermore, these effects cooperatively cause ratchet signal reversal at high magnetic fields, which has not been reported to date in a pinning-free system. The ratchet signal found here is larger than those induced by asymmetric pinning potentials. Our results also demonstrate the feasibility of using mesoscopic superconductors to employ a superconducting diode effect in versatile superconducting devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1992

Two-fence concept for efficient trapping of vortices on airfoils

Previous work on the use of a vortex trapped above a wing in order to produce high lift at low angles of attack is extended here. It is first postulated that the optimum way to trap a vortex is to design the airfoil section and wing so that the flow along the vortex core is minimized. It is then shown that a vertical fence both in front of and behind the separation bubble generated by the trapped vortex is an effective way to reduce the mass flow removal and its associated drag to a negligible amount. In order to show that vertical surfaces upstream and downstream of the vortex separation bubble have an opposite effect on the source requirements for vortex trapping, conformal mapping methods are used to obtain the solutions for a variety of simple two-dimensional, inviscid, incompressible flow configurations. Trapped-vortex flowfield solutions for the flow over flat plate and Clark-Y airfoils are then used to demonstrate that the heights of the fences can be tailored to make the required mass withdrawal (and therefore, the drag due to trapping) to be vanishingly small.

Rossow, Vernon J.↗
DOE OSTI2019

Problems of Developing Solid Mineral Deposits on the Sea and Ocean Floor

Brief characteristics of the mineral raw material potential of the deep-sea deposits of ferromanganese nodules in the area of the Clarion-Clipperton Zone leased by Russia in the Pacific Ocean are presented. The creation at the Moscow Mining Institute (MGI) of the USSR’s first Scientific and Technical Problems Laboratory and the results of its work on extraction of minerals from the sea and ocean floor are reviewed. The research works carried out by MGI on underwater mining of ilmenite-rutile-zirconium sands on the Baltic Sea shelf and Iturup Island and tin under conditions of northern seas and the development of the technogenic placer of the East Siberian Sea are analyzed. The concept of using the kinetic energy of coaxially swirled fluid jets in hydrotransport-hoisting devices of vortex slurry preparation, which was tested in the Black Sea and an air-lift mud intake by mechanical and hydraulic loosening for extracting diamond-containing gravel-pebble rocks on the Namibia shelf is given.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Driving large magnetic Reynolds number flow in highly ionized, unmagnetized plasmas

Electrically driven, unmagnetized plasma flows have been generated in the Madison plasma dynamo experiment with magnetic Reynolds numbers exceeding the predicted Rm crit = 200 threshold for flow-driven MHD instability excitation. The plasma flow is driven using ten thermally emissive lanthanum hexaboride cathodes which generate a J × B torque in helium and argon plasmas. Detailed Mach probe measurements of plasma velocity for two flow topologies are presented: edge-localized drive using the multi-cusp boundary field and volumetric drive using an axial Helmholtz field. Here radial velocity profiles show that the edge-driven flow is established via ion viscosity but is limited by a volumetric neutral drag force, and measurements of velocity shear compare favorably to the Braginskii transport theory. Volumetric flow drive is shown to produce larger velocity shear and has the correct flow profile for studying the magnetorotational instability.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Implementation of a generalized actuator line model for wind turbine parameterization in the Weather Research and Forecasting model

A generalized actuator line (GAL) wind turbine parameterization is implemented within the Weather Research and Forecasting model to enable high-fidelity large-eddy simulations of wind turbine interactions with boundary layer flows under realistic atmospheric forcing conditions. Numerical simulations using the GAL parameterization are evaluated against both an already implemented generalized actuator disk (GAD) wind turbine parameterization and two field campaigns that measured the inflow and near-wake regions of a single turbine. The representation of wake wind speed, variance, and vorticity distributions is examined by comparing fine-resolution GAL and GAD simulations and GAD simulations at both fine and coarse-resolutions. The higher-resolution simulations show slightly larger and more persistent velocity deficits in the wake and substantially increased variance and vorticity when compared to the coarse-resolution GAD. The GAL generates distinct tip and root vortices that maintain coherence as helical tubes for approximately one rotor diameter downstream. Coarse-resolution simulations using the GAD produce similar aggregated wake characteristics to both fine-scale GAD and GAL simulations at a fraction of the computational cost. Furthermore, the GAL parameterization provides the capability to resolve near wake physics, including vorticity shedding and wake expansion.

17 WIND ENERGY↗
DOE OSTI2021

An LES study of secondary motion and wall shear stresses in a pipe bend

In this study, large-eddy simulations (LES) of a single-phase, turbulent flow in a 90 ° pipe bend are performed at three Reynolds numbers (5300, 27 000, and 45 000) to investigate the correlation between secondary flow motion and wall shear stresses, which is suspected to be a potential mechanism responsible for material erosion. The isothermal flows are validated against available experimental and numerical data first. The snapshot proper orthogonal decomposition (POD) is applied for the medium and high Reynolds number flows to identify the secondary flow motions and the oscillation of the Dean vortices that are found to cause swirl-switching. Distinguished frequencies of the POD time coefficients at Strouhal numbers of 0.25 and 0.28 are identified for Reynolds numbers at 27 000 and 45 000, respectively. Moreover, shear stress on the pipe wall and the associated power spectral density are obtained and shown to have the same oscillating frequency as the swirl-switching.

42 ENGINEERING↗
DOE OSTI2021

Vortex rings from high energy central 𝑝 + 𝐴 collisions

Relativistic p + A collisions may produce droplets of quark gluon plasma (QGP) that quickly develop a toroidal vortex structure similar to that of an expanding smoke ring. We present viscous relativistic hydrodynamic calculations of ultra-central p + A collisions and develop an experimental observable to probe the structure, correlating the polarization and momentum of hyperons emitted from the collision. This effect is robust against changes in the definition of vorticity used to calculate the polarization. Experiments at RHIC and LHC may test the existence and strength of the vortex toroids, bringing new evidence to bear on the question of collectivity in the smallest QGP droplets.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Universal Anomalous Diffusion of Quantized Vortices in Ultraquantum Turbulence

In classical viscous fluids, turbulent eddies are known to be responsible for the rapid spreading of embedded particles. However, in inviscid quantum fluids where the turbulence is induced by a chaotic tangle of quantized vortices, dispersion of the particles can be achieved via a nonclassical mechanism, i.e., their binding to the evolving vortices. However, knowledge on how the vortices diffuse and spread in quantum-fluid turbulence is very limited, especially for the so-called ultraquantum turbulence (UQT) generated by a random tangle of vortices. Here we report a systematic numerical study of the apparent diffusion of vortices in UQT in superfluid helium-4 using the full Biot-Savart simulation. We reveal that the vortices in the superfluid exhibit a universal anomalous diffusion (superdiffusion) at small times, which transits to normal diffusion at large times. This behavior is found to be the result of a generic scaling property of the vortex velocity. Our simulation at finite temperatures also nicely reproduces recent experimental observations. Lastly, the knowledge obtained from this study may form the base for understanding turbulent transport and universal vortex dynamics in various quantum fluids.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗