Mass transfer cooling in high-speed couette flow of an absorbing-emitting gas.
Temperature profiles and heat transfer in high speed Couette flow with mass transfer where gas is absorbing and emitting radiative energy
COUETTE FLOW↗
SEARCH · Engineering Papers
Results for “dynamic mass 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.
Oceanographic mapping of structure and dynamics of the northern Gulf of California by the use of spectral modeling and ERTS-1
Distribution and flow of water masses at four depth intervals were determined by analyzing ERTS imagery through the use of optical models of classes of vertical oceanographic profiles. Data used for these models was obtained from shipboard measurements including surface spectral radiance, and optical and more conventional oceanographic depth profiles. The spectral models obtained were applied to radiance-contoured ERTS imagery in band 4, 5, 6, and 7. Features mapped by direct photointerpretation of ERTS imagery include submerged shoals, current streamlines, and location of possible upwellings, downwellings and submarine springs.
Lepley, L. K.↗
Minimum Energy Test Direction Design in the Control of Cryogenic Wind Tunnels
The advent of the cryogenic wind tunnel concept is attributable to the need for high Reynolds number flow in wind tunnels. The cryogenic wind tunnel concept consists of operating the test medium of a conventional tunnel at cryogenic temperatures down to 80 K. Nitrogen gas, cooled by injected liquid nitrogen, proves to be ideal for the cryogenic tunnel test medium because of its near perfect behavior in insentropic flow. Cryogenic operation of a wind tunnel results in reduced fan power consumption and no penalty in flow dynamic pressure. In a cryogenic tunnel, the flow parameters (Reynolds number, Mach number and flow dynamic pressure) can be independently controlled by separately controlling the tunnel flow variables: total temperature, test section mass flow, and the tunnel total pressure. The problem of closed-loop control of the tunnel total temperature, flow Mach number, and total pressure is addressed and reported.
Balakrishna, S.↗
Thrust and ignition transients of the Space Shuttle solid rocket motor
Techniques developed for predicting and analyzing ignition, pressurization, and thrust transients in large segmented motors were applied to the four developmental Space Shuttle solid rocket motors. Following the first test, attention was focused on understanding dynamic thrust and the rate of thrust increase during pressurization and predicting effects of reduced igniter mass flow rate and gas temperature. The close coupling between the igniter and the head-end segment and the high length-to-diameter ratio make understanding of the longitudinal pressure waves essential. The igniter performance along with igniter to head-end segment geometry govern the induction interval and head-end segment ignition. Following ignition of the head-end segment, subsequent flame spreading and pressurization tend to be motor properties which are not appreciably altered by changes in the head-end igniter mass flow rate.
Caveny, L. H.↗
Predicting Flow-Induced Vibrations In A Convoluted Hose
Composite model constructed from two less accurate models. Predicts approximately frequencies and modes of vibrations induced by flows of various fluids in convoluted hose. Based partly on spring-and-lumped-mass representation of dynamics involving springiness and mass of convolution of hose and density of fluid in hose.
Harvey, Stuart A.↗
Hinode: A Decade of Success in Capturing Solar Activity
As the present solar cycle passes into its minimum phase, the Hinode mission marks its tenth year of investigating solar activity. Hinode's decade of successful observations have provided us with immeasurable insight into the solar processes that invoke space weather and thereby affect the interplanetary environment in which we reside. The mission's complementary suite of instruments allows us to probe transient, high energy events alongside long-term, cycle-dependent phenomena from magnetic fields at the Sun's surface out to highly thermalized coronal plasma enveloping active regions (ARs). These rich data sets have already changed the face of solar physics and will continue to provoke exciting research as new observational paradigms are pursued. Hinode was launched as part of the Science Mission Directorate's (SMD) Solar Terrestrial Probes Program in 2006. It is a sophisticated spacecraft equipped with a Solar Optical Telescope (SOT), an Extreme-ultraviolet Imaging Spectrometer (EIS), and an X-Ray Telescope (XRT) (see x 4). With high resolution and sensitivity, Hinode serves as a microscope for the Sun, providing us with unique capabilities for observing magnetic fields near the smallest scales achievable, while also rendering full-Sun coronal context in the highest thermal regimes. The 2014 NASA SMD strategic goals objective to "Understand the Sun and its interactions with the Earth and the solar system, including space weather" forms the basis of three underlying Heliophysics Science Goals. While Hinode relates to all three, the observatory primarily addresses: Explore the physical processes in the space environment from the Sun to the Earth and through the solar system. Within the NASA National Research Council (NRC) Decadal Survey Priorities, Hinode targets: (a) Determine the origins of the Sun's activity and predict the variations of the space environment and (d) Discover and characterize fundamental processes that occur both within the heliosphere and throughout the universe. In response to the 2012 NRC Decadal Survey Science Challenges and 2014 Heliophysics Roadmap Research Focus Areas, the Hinode mission has set forth four Prioritized Science Goals (PSGs): (a) Study the sources and evolution of highly energetic dynamic events; (b) Characterize cross-scale magnetic field topology and stability; (c) Trace mass and energy flow from the photosphere to the corona; and (d) Continue long term synoptic support to quantify cycle variability.
review↗
Dynamical relations for left ventricular ejection - Flow rate, momentum, force and impulse
An investigation was carried out to quantitatively evaluate left ventricular volume flow rate, momentum, force and impulse derived from application of conservation principles for mass and momentum of blood within the ventricle during the ejection phase. An automated digital image processing system was developed and applied to left ventricular angiograms which are computer processed and analyzed frame by frame to determine the dynamical relations by numerical methods. The initial experience with force and impulse has indicated that neither quantity seemed to be a sensitive indicator of coronary artery disease as evaluated by qualitative angiography for the particular patient group studied. Utilization of the dynamical relations in evaluating human left ventricular performance requires improved means of measurement and interpretation of clinical studies.
Back, L. H.↗
Investigation of countercurrent flow profile and liquid holdup in random packed column with local CFD data
Liquid holdup and mass transfer area are critical parameters used in packed column design and CO 2 capture efficiency prediction. Compared to experimental methods, 3D computational fluid dynamics (CFD) can provide high-resolution data for studying countercurrent flow hydrodynamics in a packed column. In this paper, a framework was established for modeling the liquid–gas countercurrent flow in a random packed column with pall rings. Besides the column-averaged information, the radial pall ring distribution, velocity, and liquid holdup profiles are obtained in the simulations. The radial two-phase velocity and liquid holdup profiles show significant fluctuations caused by the non-uniform pall ring distribution. The entrance effect and wall influence are also observed in the packed column. By using local countercurrent flow information, the packing specific area $a_p$ and liquid velocity $u_L$ range are significantly expanded for liquid holdup hL prediction. This enables us to develop the liquid holdup correlation with one packing size and six CFD runs only. The proposed power law of the liquid holdup correlation $h_L~u_L^{0.44}$ indicates the random packed column falls in a viscous to turbulent transition regime with a Reynolds Number range of [6.7–40.2]. The derived liquid holdup correlation is in good agreement with existing correlations that are developed using the column-averaged experimental data.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Experiments on the dynamic behavior of cavitating pumps
This paper describes experiments performed to measure the dynamic transfer matrices for cavitating (and noncavitating) pumps. These transfer matrices describe the relationship between small linear oscillatory perturbations in the pressures and mass flow rates at inlet and discharge from the hydraulic machine. The matrices were deduced from direct measurements of these fluctuating quantities for different modes of excitation of the machine. Results for a cavitating inducer are presented as functions of frequency and mean operating state. Though some of the trends in the data are consistent with existing theoretical models of inducer dynamics, others are not, indicating a need for further theoretical investigation of the dynamic characteristics of such flows. The results exhibit increasingly complex dynamics with increasing cavitation; it appears that the hydraulic machine deviates from an essentially passive response without cavitation to an increasingly active response as the cavitation number is reduced.
Ng, S. L.↗
A three-dimensional model of corotating streams in the solar wind. I - Theoretical foundations
The paper is concerned with the development of the theoretical and mathematical background pertinent to the study of steady, corotating solar wind structure in all three spatial dimensions. The dynamical evolution of the plasma in interplanetary space (defined as the region beyond roughly 35 Rs where the flow is supersonic) is approximately described by the nonlinear, single-fluid, polytropic magnetohydrodynamic or hydrodynamic equations. Efficient numerical techniques are outlined for solving this complex system of coupled, hyperbolic partial differential equations. The present formulation is inviscid and nonmagnetic, but the methods used allow for the potential inclusion of both features with only modest modifications. A simple, highly idealized hydrodynamic model stream is examined to illustrate the fundamental processes involved in the three-dimensional dynamics of stream evolution. It is found that spatial variations in the rotational stream interaction mechanism produce small nonradial flows on a global scale that lead to the transport of mass, energy, and momentum away from regions of relative compression and into regions of relative rarefaction. Comparison with simpler models demonstrates the essential nonlinear, multidimensional nature of the interplanetary dynamics.
Pizzo, V.↗
Understanding flow dynamics in membrane distillation: Effects of reactor design on polarization
Optimization and design of full-scale membrane distillation (MD) systems usually require Sherwood and Nusselt correlations that are developed from lab-scale systems. However, entrance effects in lab-scale systems can significantly impact heat, mass and momentum transfer in the reactor, therefore affect the accuracy of the developed experimental Sherwood and Nusselt correlations. Here, Computational Fluid Dynamics (CFD) simulations using OpenFOAM are performed to understand the effects of right-angled bends and inlet design on flow dynamics, temperature and concentration polarization in MD systems. Simulation results show that the presence of right-angled bends and inlets with sudden expansions lead to the formation of Dean vortices. Dean vortices enhance perpendicular mixing in MD systems and reduce both temperature and concentration polarization. Temperature and concentration polarization coefficients in MD systems with right-angled bends and inlets with sudden expansions vary significantly for the same volumetric flow rate. Our studies show that lab-scale systems with the same volumetric flow rate but different designs lead to significantly different Nusselt and Sherwood correlations. Here, this study demonstrates the importance of CFD-informed design of lab-scale systems to minimize entrance effects and suppress Dean vortices for consistent model development and calibration across multiple scales.
42 ENGINEERING↗
Monitoring Preferential Flow of Water in Sand Using Thermoacoustics Wave Imaging
Abstract Accurate predictions of fluid flow, mass transport, and reaction rates critically impact the efficiency and reliability of subsurface exploration and sustainable use of subsurface resources. Quantitative dynamical sensing and imaging can play a pivotal role in the ability to make such predictions. Geophysical thermoacoustic technology has the potential to provide the aforementioned capabilities, since it builds upon the principle that electromagnetic and mechanical wave fields can be coupled through a thermodynamic process. In this letter, we present laboratory experiments featuring the efficacy of thermoacoustic imaging in the monitoring of preferential flow of water in porous media. Our laboratory experimental equipment can be readily packaged in a form factor that fits in a borehole, and the use of multiple acoustic transducers—which can be combined with volumetric coding techniques—has the potential to provide quasi‐real‐time imaging (0.5 Hz video rate) of regions in close proximity (a few meters) of an open field well.
Geology↗
On the Fidelity of Computational Models for the Flow of Milled Loblolly Pine: A Benchmark Study on Continuum-Mechanics Models and Discrete-Particle Models
The upstream of bioenergy industry has suffered from unreliable operations of granular biomass feedstocks in handling equipment. Computational modeling, including continuum-mechanics models and discrete-particle models, offers insightful understandings and predictive capabilities on the flow of milled biomass and can assist equipment design and optimization. This paper presents a benchmark study on the fidelity of the continuum and discrete modeling approaches for predicting granular biomass flow. We first introduce the constitutive law of the continuum-mechanics model and the contact law of the coarse-grained discrete-particle model, with model parameters calibrated against laboratory characterization tests of the milled loblolly pine. Three classical granular material flow systems (i.e., a lab-scale rotating drum, a pilot-scale hopper, and a full-scale inclined plane) are then simulated using the two models with the same initial and boundary conditions as the physical experiments. The close agreement of the numerical predictions with the experimental measurements on the hopper mass flow rate, the hopper critical outlet width, the material stopping thickness on the inclined plane, and the dynamic angle of repose, clearly indicates that the two methods can capture the critical flow behavior of granular biomass. The qualitative comparison shows that the continuum-mechanics model outperforms in parameterization of materials and wall friction, and large-scale systems, while the discrete-particle model is more preferred for discontinuous flow systems at smaller scales. Industry stakeholders can use these findings as guidance for choosing appropriate numerical tools to model biomass material flow in part of the optimization of material handling equipment in biorefineries.
Jin, Wencheng↗
Finite element modeling of biomass hopper flow
Hoppers are widely used biomass handling devices that channel bulk biomass from storage to subsequent handling equipment. Jenike’s longstanding approach, based on the Mohr-Coulomb model, has been successfully used to design hoppers handling cohesionless granular materials such as grains and other agricultural produces. However, designing a hopper to ensure reliable biomass flow is found to be challenging due to cohesion, irregular particle shape, and bulk material elastoplasticity. This study aims to address the biomass handling engineering challenge with alternative constitutive material models concerning the flow behavior of bulk solids. Finite element modeling is an approach that allows for implementation of different material models, whose underlying constitutive theories assist in investigating the origin and manifestation of bulk mechanical behavior of granular materials. This study focuses on the incipient gravity hopper flow of two types of biomass feedstocks, i.e., ground corn stover and Douglas fir wood. Three widely used constitutive material models, i.e., Mohr-Coulomb model, modified Cam-Clay model, and Drucker-Prager/Cap model, are implemented. Using the flow pattern represented by the volume of biomass exhibiting more than 7% of axial strain (Kamath and Puri, 1999), the finite element model predicts that the bulk corn stover particulate material forms an arch, which represents a hampered transition from the static state to the dynamic flow-state out of the hopper, whereas bulk Douglas fir wood particulate material develops a reliable mass flow pattern. A laboratory scale hopper was used to experimentally determine the biomass flow conditions, which were subsequently compared with the predicted onset of flow by a finite element model (FEM). The developed FEM was found to correctly predict the initiation of mass flow for the milled Douglas fir wood, whereas corn stover was predicted to establish a strong core flow suggesting an unreliable handling characteristic. This observation aligns with the reported poor handling of milled corn stover.
09 BIOMASS FUELS↗
What is the Relationship between the Solar Wind and Storms/Substorms?
The interplanetary magnetic field (IMF) carried past the Earth by the solar wind has long been known to be the principal quantity that controls geomagnetic storms and substorms. Intervals of strong southward IMF with durations of at least a significant fraction of a day produce storms, while more typical, shorter intervals of less-intense southward fields produce substorms. The strong, long-duration southward fields are generally associated with coronal mass ejections and magnetic clouds or else they are produced by interplanetary dynamics initiated by fast solar wind flows that compress preexisting southward fields. Smaller, short-duration southward fields that occur on most days are related to long period waves, turbulence, or random variations in the IMF. Southward IMF enhances dayside reconnection between the IMF and the Earth's dipole with the reconnected field lines supplementing open field lines of the geomagnetic tail and producing an expanded polar cap and increased tail energy. Although the frequent storage of solar wind energy and its release during substorms is the most common mode of solar wind/magnetosphere interaction, under certain circumstances, steady southward IMF seems to produce intervals of relatively steady magnetosphere convection without substorms. During these latter times, the inner magnetosphere remains in a stressed tail-like state while the more distant magnetotail has larger northward field and more dipolar-like field lines. Recent evidence suggests that enhanced magnetosphere particle densities associated with enhanced solar wind densities allow more particles to be accelerated for the ring current, thus creating larger storms.
Fairfield, D. H.↗
Comparisons of CFD Simulations of Icing Wind Tunnel Clouds with Experiments Conducted at the NASA Propulsions Systems Laboratory
This paper evaluates simulation predictions against experimental test data of icing clouds that were produced during 2018 ice crystal icing physics tests conducted at the NASA Propulsion Systems Laboratory icing wind tunnel. Aero-thermal and cloud parameters are set and known upstream at the tunnel inlet and spray system, but change as the cloud and air thermodynamically interact as the flowing masses reach the tunnel test section. Utilizing the ANSYS Fluent Discrete Phase Model function, 3D computational fluid dynamics (CFD) simulations were performed, capturing the thermodynamic interactions between the test parameters, and providing predictions of the aero thermal and cloud conditions at the tunnel test section. Simulation predictions were compared with test data that were measured at the tunnel exit plane. Evaluations focused on the cloud concentration (total water content), humidity content, and air temperature. CFD simulation predictions showed areas of agreement and disagreement. Simulations showed that cloud concentration profiles at the test section are strongly related to the initial spray nozzle pattern used at the tunnel inlet. Experimental data suggest that greater dispersion of the cloud occurred as the simulated cloud predicted areas of high and low cloud concentration compared to test data profiles. Simulations, however, captured the magnitude and location of the change in humidity content and the change in air temperature due to the presence of the cloud reasonably well, when compared to test data. This result would suggest that while the ANSYS simulation did not fully predict the spreading of the cloud as measured during experiment, it did capture evaporation and the molecular movements of air and vapor relatively well.
CFD↗
Comparisons of CFD Simulations of Icing Wind Tunnel Clouds with Experiments Conducted at the NASA Propulsions Systems Laboratory
This paper evaluates simulation predictions against experimental test data of icing clouds that were produced during 2018 ice crystal icing physics tests conducted at the NASA Propulsion Systems Laboratory icing wind tunnel. Aero-thermal and cloud parameters are set and known upstream at the tunnel inlet and spray system, but change as the cloud and air thermodynamically interact as the flowing masses reach the tunnel test section. Utilizing the ANSYS Fluent Discrete Phase Model function, 3D computational fluid dynamics (CFD) simulations were performed, capturing the thermodynamic interactions between the test parameters, and providing predictions of the aero thermal and cloud conditions at the tunnel test section. Simulation predictions were compared with test data that were measured at the tunnel exit plane. Evaluations focused on the cloud concentration (total water content), humidity content, and air temperature. CFD simulation predictions showed areas of agreement and disagreement. Simulations showed that cloud concentration profiles at the test section are strongly related to the initial spray nozzle pattern used at the tunnel inlet. Experimental data suggest that greater dispersion of the cloud occurred as the simulated cloud predicted areas of high and low cloud concentration compared to test data profiles. Simulations, however, captured the magnitude and location of the change in humidity content and the change in air temperature due to the presence of the cloud reasonably well, when compared to test data. This result would suggest that while the ANSYS simulation did not fully predict the spreading of the cloud as measured during experiment, it did capture evaporation and the molecular movements of air and vapor relatively well.
CFD↗
Properties of Longitudinal Flux Tube Waves: Wave Propagation in Solar and Stellar Wind Flows - III
We discuss the analytic properties of longitudinal tube waves taking into account ambient wind flows. This is an extension of the studies of Papers I and II, which assumed a mean flow speed of zero and also dealt with a simplified horizontal pressure balance. Applications include the study of longitudinal flux tube waves in stars with significant mass loss and heating and dynamics of plumes in the solar wind. Slow magnetosonic waves, also called longitudinal waves, have been observed in solar plumes and are likely an important source of heating. We show that the inclusion of ambient wind flows considerably alters the limiting shock strength as well as the energy damping length of waves.
Cuntz, M.↗