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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

User-defined feature comparison for vector field ensembles

Most of the existing approaches to visualize vector field ensembles are to reveal the uncertainty of individual variables, for example, statistics, variability, etc. However, a user-defined derived feature like vortex or air mass is also quite significant, since they make more sense to domain scientists. In this paper, we present a new framework to extract user-defined derived features from different simulation runs. Specially, we use a detail-to-overview searching scheme to help extract vortex with a user-defined shape. We further compute the geometry information including the size, the geo-spatial location of the extracted vortexes. We also design some linked views to compare them between different runs. At last, the temporal information such as the occurrence time of the feature is further estimated and compared. Results show that our method is capable of extracting the features across different runs and comparing them spatially and temporally.

Comparative visualization↗
NASA NTRS2016

Tracking Blade Tip Vortices for Numerical Flow Simulations of Hovering Rotorcraft

Blade tip vortices generated by a helicopter rotor blade are a major source of rotor noise and airframe vibration. This occurs when a vortex passes closely by, and interacts with, a rotor blade. The accurate prediction of Blade Vortex Interaction (BVI) continues to be a challenge for Computational Fluid Dynamics (CFD). Though considerable research has been devoted to BVI noise reduction and experimental techniques for measuring the blade tip vortices in a wind tunnel, there are only a handful of post-processing tools available for extracting vortex core lines from CFD simulation data. In order to calculate the vortex core radius, most of these tools require the user to manually select a vortex core to perform the calculation. Furthermore, none of them provide the capability to track the growth of a vortex core, which is a measure of how quickly the vortex diffuses over time. This paper introduces an automated approach for tracking the core growth of a blade tip vortex from CFD simulations of rotorcraft in hover. The proposed approach offers an effective method for the quantification and visualization of blade tip vortices in helicopter rotor wakes. Keywords: vortex core, feature extraction, CFD, numerical flow visualization

Numerical↗
NASA NTRS2002

Vortex Wake Geometry of a Model Tilt Rotor in Forward Flight

The vortex wake trajectory from one rotor of a 0.25-scale V-22 tiltrotor model was measured for four test conditions in the NASA Ames 40- by 80-Foot Wind Tunnel. Vortex wake images were acquired using a laser light sheet and video camera. Wake trajectories were constructed by extracting vortex positions from the video images. Wake trajectories were also calculated using the comprehensive analysis CAMRAD II. Measured and calculated wake geometries exhibit similar trends when advance ratio is varied at fixed thrust or when thrust is varied at fixed advance ratio.

Yamauchi, G. K.↗
NASA NTRS1984

Large-scale turbulence in the Jovian atmosphere

Voyager 1 and 2 image pairs taken one rotation period (10 hr) apart are analyzed in order to compute average cloud velocities in the Jovian atmosphere, as well as to study the global energetics of the processes, in particular the sign and the magnitude of the energy transfer from the fluctuating to the mean flow. Particular attention is paid to the Great Red Spot phenomenon; it is suggested to have originated as a small vortex extracting energy from the surrounding flow. Since the eddy, presently in its near-equilibrium state, has reached a considerable size, while the mean shear lies close to that of a neutrally stable profile, it can be concluded that the presence of one large eddy precludes the growth of any others in the depleted mean shear.

Mitchell, J. L.↗
NASA NTRS1995

Euler technology assessment for preliminary aircraft design employing OVERFLOW code with multiblock structured-grid method

The viability of applying a state-of-the-art Euler code to calculate the aerodynamic forces and moments through maximum lift coefficient for a generic sharp-edge configuration is assessed. The OVERFLOW code, a method employing overset (Chimera) grids, was used to conduct mesh refinement studies, a wind-tunnel wall sensitivity study, and a 22-run computational matrix of flow conditions, including sideslip runs and geometry variations. The subject configuration was a generic wing-body-tail geometry with chined forebody, swept wing leading-edge, and deflected part-span leading-edge flap. The analysis showed that the Euler method is adequate for capturing some of the non-linear aerodynamic effects resulting from leading-edge and forebody vortices produced at high angle-of-attack through C(sub Lmax). Computed forces and moments, as well as surface pressures, match well enough useful preliminary design information to be extracted. Vortex burst effects and vortex interactions with the configuration are also investigated.

Treiber, David A.↗
NASA NTRS1999

Summary of Work for Joint Research Interchanges with DARWIN Integrated Product Team 1998

The intent of Stanford University's SciVis group is to develop technologies that enabled comparative analysis and visualization techniques for simulated and experimental flow fields. These techniques would then be made available under the Joint Research Interchange for potential injection into the DARWIN Workspace Environment (DWE). In the past, we have focused on techniques that exploited feature based comparisons such as shock and vortex extractions. Our current research effort focuses on finding a quantitative comparison of general vector fields based on topological features. Since the method relies on topological information, grid matching and vector alignment is not needed in the comparison. This is often a problem with many data comparison techniques. In addition, since only topology based information is stored and compared for each field, there is a significant compression of information that enables large databases to be quickly searched. This report will briefly (1) describe current technologies in the area of comparison techniques, (2) will describe the theory of our new method and finally (3) summarize a few of the results.

Hesselink, Lambertus↗
NASA NTRS1999

Summary of Work for Joint Research Interchanges with DARWIN Integrated Product Team

The intent of Stanford University's SciVis group is to develop technologies that enabled comparative analysis and visualization techniques for simulated and experimental flow fields. These techniques would then be made available un- der the Joint Research Interchange for potential injection into the DARWIN Workspace Environment (DWE). In the past, we have focused on techniques that exploited feature based comparisons such as shock and vortex extractions. Our current research effort focuses on finding a quantitative comparison of general vector fields based on topological features. Since the method relies on topological information, grid matching an@ vector alignment is not needed in the comparison. This is often a problem with many data comparison techniques. In addition, since only topology based information is stored and compared for each field, there is a significant compression of information that enables large databases to be quickly searched. This report will briefly (1) describe current technologies in the area of comparison techniques, (2) will describe the theory of our new method and finally (3) summarize a few of the results.

Hesselink, Lambertus↗
NASA NTRS2000

Evaluation of the Use of Second Generation Wavelets in the Coherent Vortex Simulation Approach

The objective of this study is to investigate the use of the second generation bi-orthogonal wavelet transform for the field decomposition in the Coherent Vortex Simulation of turbulent flows. The performances of the bi-orthogonal second generation wavelet transform and the orthogonal wavelet transform using Daubechies wavelets with the same number of vanishing moments are compared in a priori tests using a spectral direct numerical simulation (DNS) database of isotropic turbulence fields: 256(exp 3) and 512(exp 3) DNS of forced homogeneous turbulence (Re(sub lambda) = 168) and 256(exp 3) and 512(exp 3) DNS of decaying homogeneous turbulence (Re(sub lambda) = 55). It is found that bi-orthogonal second generation wavelets can be used for coherent vortex extraction. The results of a priori tests indicate that second generation wavelets have better compression and the residual field is closer to Gaussian. However, it was found that the use of second generation wavelets results in an integral length scale for the incoherent part that is larger than that derived from orthogonal wavelets. A way of dealing with this difficulty is suggested.

Goldstein, D. E.↗
NASA NTRS2002

Rotor Wake Vortex Definition: Initial Evaluation of 3-C PIV Results of the Hart-II Study

An initial evaluation is made of extensive three-component (3C) particle image velocimetry (PIV) measurements within the wake across a rotor disk plane. The model is a 40 percent scale BO-105 helicopter main rotor in forward flight simulation. This study is part of the HART II test program conducted in the German-Dutch Wind Tunnel (DNW). Included are wake vortex field measurements over the advancing and retreating sides of the rotor operating at a typical descent landing condition important for impulsive blade-vortex interaction (BVI) noise. Also included are advancing side results for rotor angle variations from climb to steep descent. Using detailed PIV vector maps of the vortex fields, methods of extracting key vortex parameters are examined and a new method was developed and evaluated. An objective processing method, involving a center-of-vorticity criterion and a vorticity 'disk' integration, was used to determine vortex core size, strength, core velocity distribution characteristics, and unsteadiness. These parameters are mapped over the rotor disk and offer unique physical insight for these parameters of importance for rotor noise and vibration prediction.

Burley, Casey L.↗
DOE OSTI2024

An Accurate and Automated Convective Vortex Detection Method for Long-Duration Infrasound Microbarometer Data

Heating of the surficial layer of the atmosphere often generates convective vortices, known as “dust devils” when they entrain visible debris. Convective vortices are common on both Earth and Mars, where they affect the climate via dust loading, contribute to wind erosion, impact the efficiency of photovoltaic systems, and potentially result in injury and property damage. However, long-duration terrestrial convective vortex activity records are rare. We have developed a high-precision and high-recall method to extract convective vortex signatures from infrasound microbarometer data streams. The techniques utilizes a wavelet-based detector to capture potential events and then a template matching system to extract the duration of the vortex. Since permanent and temporary infrasound sensors networks are present throughout the globe (many with open data), our method unlocks a vast new convective vortex dataset without requiring the deployment of specialized instrumentation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Using geochemical indicators to distinguish high biogeochemical activity in floodplain soils and sediments, Science of the Total Environment: Dataset

Data associated with analysis of sediment samples collected in the East River watershed and Rifle floodplain sites, CO. Samples were collected and analyzed as part of two student MS theses at Colorado School of Mines (Kenwell and Prugue) over a time period ranging from 2012 to 2015. Analyses include total organic carbon, leachable Fe and Mn, and total microbial DNA; all analyses performed at Colorado School of Mines. Methods: Samples were collected from core during a drilling campaign at the Rifle Site. Samples were collected every 1.5 m. At the East River site soil and sediment samples were collected using hand-augered bulk density sampler. Collected samples were stored at -20C until analysis. Samples were thawed in an anaerobic chamber and subsampled for extractions and DNA analysis. Samples for DNA analysis were freeze-dried, the remaining sample was oven dried and ground to 0.991 cm for TOC and leaching analysis. TOC analysis was performed on duplicate samples using a CM 5014 Coulometer (UIC, Joliet, IL, USA). Two chemical extractions were performed: hydroxylamine (HA) extraction of Fe and Mn adapted from Lovley et al., 1987 and synthetic precipitation (ppt) leaching adapted from EPA method 1312 (EPA, 1994) . For theHA extraction 3g of wet sediment was mixed with 150 mL of 0.5 N HCl in one bottle and another 3 g of sediment was mixed with 150 mL of 0.25 N hydroxylamine hydrochloride in 0.5 N HCl. Extraction were performed for 24 hours at room temperature after which samples of the liquid were removed and filtered to 0.45 micron and analyzed by ICP-AES. HA-reducible iron and manganese concentrations were determined by difference between the two extractions. For ppt leaches, a 60:40 sulfuric:nitric acid mixture was added to Milliq water to a pH of 4.2 and combined with sediment in a 20:1 mass ratio of acid to sediment. The extraction was performed for 18 hours at room temperature after which the samples of the liquid were removed and filtered to 0.45 micron and analyzed by ICP-AES. DNA was sampled from sediment using a PowerSoil DNA Isolation Kit and extractions were performed according to manufactured instuctions with one adjustment, a 1 minute bead beating replaced the 10 minute vortexing step. Extracted DNA was stored at -20C. Quantitative PCR was performed in triplicate on a Roche LightCycler 480 system and working curves were created by amplifying environmental samples with primers and bead purifying them with Agencourt AMPure XP. Analysis was performed with a Qubit 2.0 Fluorometer and Qubit dsDNA High Sensitivity Assay Kit with results converted to copies using the URI Genomics and Sequencing Center converter (Staroscik, 2004). Additional method details can be found in Kenwell et al., 2016. Lovley, D.R., Phillips, E.J.P. (1987). Rapid assay for microbially reducible ferric iron in aquatic sediments. Applied and Environmental Microbiology, 53(7), 1536-1540. Staroscik, A. (2004). Calculator for determining the number of copies of a template. URI Genomics & Sequencing Center. <http://cels.uri.edu/gsc/cndna.html>. EPA. (1994). Method 1312: Synthetic precipitation leaching procedure.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1993

Vortex-Shedding Meters For Liquid And Liquid/Gas Flows

Flowmeters without moving parts developed as replacements for conventional turbine flowmeters. No maintenance required so meters installed permanently. In vortex-shedding flowmeter, piezoelectric or other suitable transducer probe senses changes of pressure caused by passage of vortices. Electronic circuitry processes pressure-change signals to extract vortex-passage frequency representing rate of flow.

Howard, Robert H.↗
NASA NTRS2002

Flow-Field Measurement of Device-Induced Embedded Streamwise Vortex on a Flat Plate

Detailed flow-field measurements were performed downstream of a single vortex generator (VG) using an advanced Stereo Digital Particle Image Velocimetry system. Thc passive flow-control devices examined consisted of a low-profile VG with a device height, h, approximately equal to 20 percent of the boundary-layer thickness, sigma, and a conventional VG with h is approximately sigma. Flow-field data were taken at twelve cross-flow planes downstream of the VG to document and quantify the evolution of embedded streamwise vortex. The effects of device angle of attack on vortex development downstream were compared between the low-profile VG and the conventional VG. Key parameters including vorticity, circulation, trajectory, and half-life radius - describing concentration, strength, path, and size, respectively--of the device-induced streamwise vortex were extracted from the flow-field data. The magnitude of maximum vorticity increases as angle of attack increases for the low-profile VG, but the trend is reversed for the conventional VG, probably due to flow stalling around the larger device at higher angles of attack. Peak vorticity and circulation for the low-profile VG decays exponentially and inversely proportional to the distance downstream from the device. The device-height normalized vortex trajectories for the low-profile VG, especially in the lateral direction, follow the general trends of the conventional VG. The experimental database was used to validate the predictive capability of computational fluid dynamics (CFD). CFD accurately predicts the vortex circulation and path; however, improvements are needed for predicting the vorticity strength and vortex size.

Yao, Chung-Sheng↗
DOE OSTI2022

Surface Impedance of Nb$_3$Sn and YBa$_2$Cu$_3$O$_{7-\sigma}$ in High Magnetic Fields

New potential rf applications of superconductors emerged with the need to operate in high dc magnetic fields (up to 16 T) where vortex motion dictates the response: the beam screen coating of the Future Circular Collider (FCC) [1] and haloscopes, i.e. rf cavities for the axions detection [2]. However, very few data are available in the required regimes. We present in this work measurements of the surface impedance Z up to 12 T on bulk Nb₃Sn and YBCO thin films grown by different techniques. The measurements are performed with a dielectric loaded resonator operating at 15 GHz. We obtained the vortex motion resistivity and extracted the high frequency vortex motion parameters [3]: the depinning frequency, the flux-flow resistivity and the pinning constant, as well as their temperature and field dependences. Substantial differences are highlighted in the high frequency pinning properties of the studied materials, providing useful information on possible improvements in view of applications. A comparison with the results obtained in the microwave frequency range at lower fields (up to 1 T) is given.

43 PARTICLE ACCELERATORS↗
NASA NTRS1995

Tracking a turbulent spot in an immersive environment

We describe an interactive, immersive 3D system called Tracktur, which allows a viewer to track the development of a turbulent flow. Tracktur displays time-varying vortex structures extracted from a numerical flow simulation. The user navigates the space and probes the data within a windy 3D landscape. In order to sustain a constant frame rate, we enforce a fixed polygon budget on the geometry. We supplement the interactive system with interactive, hypertext documentation available on the World Wide Web. In actual use by a fluid dynamicist, the system has yielded new insights into the transition to turbulence in a laminar flow.

Banks, David C.↗
NASA NTRS2003

Software Aids Visualization of Computed Unsteady Flow

Unsteady Flow Analysis Toolkit (UFAT) is a computer program that synthesizes motions of time-dependent flows represented by very large sets of data generated in computational fluid dynamics simulations. Prior to the development of UFAT, it was necessary to rely on static, single-snapshot depictions of time-dependent flows generated by flow-visualization software designed for steady flows. Whereas it typically takes weeks to analyze the results of a largescale unsteady-flow simulation by use of steady-flow visualization software, the analysis time is reduced to hours when UFAT is used. UFAT can be used to generate graphical objects of flow visualization results using multi-block curvilinear grids in the format of a previously developed NASA data-visualization program, PLOT3D. These graphical objects can be rendered using FAST, another popular flow visualization software developed at NASA. Flow-visualization techniques that can be exploited by use of UFAT include time-dependent tracking of particles, detection of vortex cores, extractions of stream ribbons and surfaces, and tetrahedral decomposition for optimal particle tracking. Unique computational features of UFAT include capabilities for automatic (batch) processing, restart, memory mapping, and parallel processing. These capabilities significantly reduce analysis time and storage requirements, relative to those of prior flow-visualization software. UFAT can be executed on a variety of supercomputers.

Kao, David↗