68,424 research outputs found
Characterization of Two-Phase Flow in Microchannels
Aluminum multi-port microchannel tubes are currently utilized in automotive air conditioners for
refrigerant condensation. Recent research activities are directed toward developing other air conditioning and
refrigeration systems with microchannel condensers and evaporators. Three parameters are necessary to analyze a
heat exchanger performance: heat transfer, pressure drop, and void fraction. The purpose of this investigation is the
experimental investigation of void fraction and frictional pressure drop in microchannels. A flow visualization
analysis is another important goal for two-phase flow behavior understanding and experimental analysis.
Experiments were performed with a 6-port and a 14-port microchannel with hydraulic diameters of 1.54 mm and
1.02 mm, respectively. Mass fluxes from 50 to 300 kg/s.m2 (range of most typical automotive applications) are
operated, with quality ranging from 0% to 100% for two-phase flow experiments. R410A, R134a, and air-water
mixtures are used as primary fluids. The results from the flow visualization studies indicate that several flow
configurations may exist in multi-port microchannel tubes at the same time while constant mass flux and quality
flow conditions are maintained. Flow mapping of the fluid regimes is accomplished by developing functions that
describe the fraction of time or the probability that the fluid exists in an observed flow configuration. Experimental
analysis and flow observations suggest that pressure drop and void fraction in microchannel is dependent on the
most probable flow regime at which the two-phase mixture is flowing. In general, correlations for void fraction and
pressure drop predictions are based in a separated flow model and do not predict the experimental results in the
range of conditions investigated. A flow regime based model is developed for pressure drop and void fraction
predictions in microchannels.Air Conditioning and Refrigeration Project 10
A Vortex Method for Bi-phasic Fluids Interacting with Rigid Bodies
We present an accurate Lagrangian method based on vortex particles,
level-sets, and immersed boundary methods, for animating the interplay between
two fluids and rigid solids. We show that a vortex method is a good choice for
simulating bi-phase flow, such as liquid and gas, with a good level of realism.
Vortex particles are localized at the interfaces between the two fluids and
within the regions of high turbulence. We gain local precision and efficiency
from the stable advection permitted by the vorticity formulation. Moreover, our
numerical method straightforwardly solves the two-way coupling problem between
the fluids and animated rigid solids. This new approach is validated through
numerical comparisons with reference experiments from the computational fluid
community. We also show that the visually appealing results obtained in the CG
community can be reproduced with increased efficiency and an easier
implementation
MFC: An open-source high-order multi-component, multi-phase, and multi-scale compressible flow solver
MFC is an open-source tool for solving multi-component, multi-phase, and bubbly compressible flows. It is capable of efficiently solving a wide range of flows, including droplet atomization, shock–bubble interaction, and bubble dynamics. We present the 5- and 6-equation thermodynamically-consistent diffuse-interface models we use to handle such flows, which are coupled to high-order interface-capturing methods, HLL-type Riemann solvers, and TVD time-integration schemes that are capable of simulating unsteady flows with strong shocks. The numerical methods are implemented in a flexible, modular framework that is amenable to future development. The methods we employ are validated via comparisons to experimental results for shock–bubble, shock–droplet, and shock–water-cylinder interaction problems and verified to be free of spurious oscillations for material-interface advection and gas–liquid Riemann problems. For smooth solutions, such as the advection of an isentropic vortex, the methods are verified to be high-order accurate. Illustrative examples involving shock–bubble-vessel-wall and acoustic–bubble-net interactions are used to demonstrate the full capabilities of MFC
Achieving Extreme Resolution in Numerical Cosmology Using Adaptive Mesh Refinement: Resolving Primordial Star Formation
As an entry for the 2001 Gordon Bell Award in the "special" category, we
describe our 3-d, hybrid, adaptive mesh refinement (AMR) code, Enzo, designed
for high-resolution, multiphysics, cosmological structure formation
simulations. Our parallel implementation places no limit on the depth or
complexity of the adaptive grid hierarchy, allowing us to achieve unprecedented
spatial and temporal dynamic range. We report on a simulation of primordial
star formation which develops over 8000 subgrids at 34 levels of refinement to
achieve a local refinement of a factor of 10^12 in space and time. This allows
us to resolve the properties of the first stars which form in the universe
assuming standard physics and a standard cosmological model. Achieving extreme
resolution requires the use of 128-bit extended precision arithmetic (EPA) to
accurately specify the subgrid positions. We describe our EPA AMR
implementation on the IBM SP2 Blue Horizon system at the San Diego
Supercomputer Center.Comment: 23 pages, 5 figures. Peer reviewed technical paper accepted to the
proceedings of Supercomputing 2001. This entry was a Gordon Bell Prize
finalist. For more information visit http://www.TomAbel.com/GB
The 1999 Center for Simulation of Dynamic Response in Materials Annual Technical Report
Introduction:
This annual report describes research accomplishments for FY 99 of the Center
for Simulation of Dynamic Response of Materials. The Center is constructing a
virtual shock physics facility in which the full three dimensional response of a
variety of target materials can be computed for a wide range of compressive, ten-
sional, and shear loadings, including those produced by detonation of energetic
materials. The goals are to facilitate computation of a variety of experiments
in which strong shock and detonation waves are made to impinge on targets
consisting of various combinations of materials, compute the subsequent dy-
namic response of the target materials, and validate these computations against
experimental data
Uncertain Flow Visualization using LIC
In this paper we look at the Line Integral Convolution method for flow visualization and ways in which this can be
applied to the visualization of two dimensional, steady flow fields in the presence of uncertainty. To achieve this,
we start by studying the method and reviewing the history of modifications other authors have made to it in order
to improve its efficiency or capabilities, and using these as a base for the visualization of uncertain flow fields.
Finally, we apply our methodology to a case study from the field of oceanography
Multi-touch 3D Exploratory Analysis of Ocean Flow Models
Modern ocean flow simulations are generating increasingly complex, multi-layer 3D ocean flow models. However, most researchers are still using traditional 2D visualizations to visualize these models one slice at a time. Properly designed 3D visualization tools can be highly effective for revealing the complex, dynamic flow patterns and structures present in these models. However, the transition from visualizing ocean flow patterns in 2D to 3D presents many challenges, including occlusion and depth ambiguity. Further complications arise from the interaction methods required to navigate, explore, and interact with these 3D datasets. We present a system that employs a combination of stereoscopic rendering, to best reveal and illustrate 3D structures and patterns, and multi-touch interaction, to allow for natural and efficient navigation and manipulation within the 3D environment. Exploratory visual analysis is facilitated through the use of a highly-interactive toolset which leverages a smart particle system. Multi-touch gestures allow users to quickly position dye emitting tools within the 3D model. Finally, we illustrate the potential applications of our system through examples of real world significance
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