Computation of Locally Mass-Conservative Flow Flux in Multidimensions

2010 ◽  
Author(s):  
J.R.C. Cheng ◽  
H.P. Cheng ◽  
M.W. Farthing
Keyword(s):  
Flow Flux ◽  
Conservative Flow

Abstract 249: Stationary Signal and Flow Velocity Assessment by MRI of a New Nitinol Nanocomposite Polymer Stent-Graft

2012 ◽  
Vol 32 (suppl_1) ◽  
Author(s):  
Mital Desai ◽  
Rachel E Clough ◽  
Nicholas R Gaddum ◽  
Kawal Rhode ◽  
Xiang Zhou ◽  
...  
Keyword(s):  
Steady Flow ◽  
Stent Graft ◽  
Signal Attenuation ◽  
Stent Grafts ◽  
Mean Velocity ◽  
Nanocomposite Polymer ◽  
Significant Difference ◽  
Flow Phantom ◽  
Flow Flux ◽  
Commercial Device

Objective: To assess MRI compatibility and suitability of a new sutureless stent-graft made from Nitinol bonded to nanocomposite polymer (NP). Methods: 1. Using MRI and Magnevist contrast, isotropic 3D T1-weighted FFE images of NP stent-graft were acquired to observe artefacts and stationary signal attenuation. Average signal magnitude was calculated. Medtronic ValiantTM was used as control. 2. In second stage, steady flow phantom was setup for flow-encoded MRI signal assessment of both stent-grafts. Baseline values were obtained by velocity measurements without stent-graft using identical settings. 2D through-plane phase contrast images were acquired and average velocity and amount of flow (flux) were calculated. Results: On static assessment of NP and ValiantTM stent-grafts no significant image artefacts were seen. The signal inside and outside the ValiantTM stent-graft was 644.2(SD 36.2) and 659.6(SD 85.8) respectively. The signal attenuation for this device was 2.39%. The signal inside and outside the NP stent graft was 1561.7(SD 31.2) and 1595.5(SD 40.8) respectively with comparable signal attenuation of 2.16%. In MRI velocity attenuation study, steady flow phantom was set at mean volume of 105.3 ml and mean velocity of 79.5 cm/sec. Flux measured in ValiantTM stent-graft was 102±2.27 ml/sec with no significant difference to baseline (104±1.98 ml/sec; P=0.892). Similarly flux for NP stent-graft at mean stroke volume 104.4 ml and mean velocity of 92.3 cm/sec showed no difference to baseline (99.8±2.4 vs. 104±0.96 ml/sec; P=0.176). There was no significant difference in flux between Medtronic and NP stent-grafts (102±2.27 vs. 99.8±2.4 ml/sec; P=0.328). Conclusion: NP stent-graft does not display any material-induced artefacts on MRI. On flow assessment, signal attenuation is comparable with the commercial device. These properties are important in developing this stent-graft, compliant, durable, visco-elastic, biocompatible and anti-thrombogenic, for future clinical use.

Compressor Maps and Coupling: Symmetry, Paradox, and Clarity

2021 ◽  
Author(s):  
Benjamin Iwrey
Keyword(s):  
Temperature Ratio ◽  
Independent Variables ◽  
Dependent Variables ◽  
In Series ◽  
Compressor Performance ◽  
Multistage Compressor ◽  
Compressor Map ◽  
Flow Flux ◽  
Operating Points ◽  
Corrected Flow

Abstract The most common compressor map framework, referred to here as the β-framework, will be shown to suffer from limitations that grow more troublesome in the multiple-map environment. When maps are coupled in series in the β-framework, it is very common to find operating points that are physically unrealizable, but these cannot generally be avoided without first generating them. A feasible situation is described in which the β-framework leads to an apparent physical paradox. In the proposed S-framework, the map itself is recast in terms of independent variables (corrected speed and exit corrected flow) and dependent variables (inlet corrected flow and temperature ratio). The propagation of information in map coupling is split into an upstream-marching corrected flow ‘flux’ and a downstream-marching temperature ‘flux’. Finding the equilibrium operating point requires only finding a simple intersection between curves. The S-framework is then developed further into a more compact S’-framework that exhibits a natural set of qualitative symmetries. The S- and S’-frameworks are shown to simplify compressor map expression, resolve the problems shown with the β-framework, and aid intuition with regard to off-design phenomena. The resolution of the paradox using the S’-framework is a new description of multistage compressor performance hysteresis.

Flow, Flux, and Feeding in Freshwater Mussels

2018 ◽  
Vol 54 (10) ◽  
pp. 7619-7630 ◽  
Author(s):  
Rakesh Mistry ◽  
Josef D. Ackerman
Keyword(s):  
Freshwater Mussels ◽  
Flow Flux

scholarly journals Exceedance of power barriers for integrated continuous-time stationary ergodic stable processes

2009 ◽  
Vol 41 (03) ◽  
pp. 874-892
Author(s):  
Uğur Tuncay Alparslan
Keyword(s):  
Continuous Time ◽  
Stable Process ◽  
Tail Probability ◽  
Exceedance Probability ◽  
Dependence Structure ◽  
Stable Processes ◽  
Limiting Behavior ◽  
Order Of Magnitude ◽  
The Difference ◽  
Conservative Flow

We study the asymptotic behavior of the tail probability of integrated stable processes exceeding power barriers. In the first part of the paper the limiting behavior of the integrals of stable processes generated by ergodic dissipative flows is established. In the second part an example with the integral of a stable process generated by a conservative flow is analyzed. Finally, the difference in the order of magnitude of the exceedance probability in the two cases is related to the dependence structure of the underlying stable process.

Design of Flow Stability System Based on Information Fusion

2010 ◽  
Vol 426-427 ◽  
pp. 170-175 ◽  
Author(s):  
Yu Hong Du ◽  
Xiu Ming Jiang ◽  
Gong Yuan Yang ◽  
Zhen Hong Zhao
Keyword(s):  
Neural Network ◽  
Flow Velocity ◽  
Detection System ◽  
Control Strategies ◽  
Fusion Center ◽  
Factors Affecting ◽  
Network Method ◽  
Flow Flux ◽  
Textile Sector ◽  
Global Data

Stability of cotton flow velocity determines the accuracy of foreign fiber detection system. There are many factors affecting fiber flow flux. In the process of operational control, recent research has been directed towards synthetically and effectively adjusting the relative parameters, and thus achieving a stable and economic foreign fiber detection system in textile sector. In the foreign fiber detection system, the parameters of flow velocity are affected by the temperature, pressure, density, which are also interrelated and redundant information. Based on Clustering Fusion, the design of the flow velocity used in the detection device is provided in this paper. Using captured parameter characteristic information, clustering fusion control, conducts the second fusion for ART-2 and BP neural network, and sends to fusion center, then fusion center process the data using neural network method. Linking with synthesis repository and global data base, different control strategies can be utilized to adjust velocity of flow parameter. The cluster control strategy that keeps output velocity of flow stable are proposed to improve the fiber measure precision in foreign fiber detection system. This system can be used in indigenous foreign fiber detection system, and significantly improve the performance of the entire system.

Spray Cooling of Small-Pitched, Straight-Finned, Copper Heat Sinks

2005 ◽  
Author(s):  
Johnathan S. Coursey ◽  
Jungho Kim ◽  
Kenneth T. Kiger
Keyword(s):  
Single Phase ◽  
Flat Surface ◽  
Heated Surface ◽  
Spray Cooling ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Lower Wall ◽  
Projected Area ◽  
Two Phase ◽  
Flow Flux

Spraying a dielectric liquid such as PF-5060 (95% pure FC-72) has been shown to be an effective method of cooling high power electronics. Recent studies have illustrated the potential enhancement of spray cooling by the addition of extended structures, particularly straight fins, to the heated surface. In the current work, these studies are extended to finer fin widths and pitches and longer fin lengths. Four such heat sinks were EDM wire machined. These 1.41 × 1.41 cm2 heat sinks featured a fin pitch of 0.86 mm; a fin width of 0.5 mm; and fin lengths of 0.5 mm, 1 mm, 3 mm, and 5 mm, which substantially increase the total area, allowing more residence time for the incoming liquid to be heated by the wall. The four enhanced surfaces and a flat surface with the same projected area were sprayed with a full cone nozzle using PF-5060 at 96 mL/min, 24°C, and 3.65 atm (38.5 psig). In all cases, the enhanced surfaces improved thermal performance. Longer fins were found to outperform shorter ones in the single-phase regime. Adding fins also resulted in two-phase effects and higher heat transfer at lower wall temperatures than the flat surface. Finally, the two-phase regime appeared to be marked by a balance between added area, changing flow flux, channeling, and added conduction resistance. Although critical heat flux (CHF) was not reached for the finned surfaces, fin lengths between 1–3 mm appeared to be optimum for heat fluxes as high as 131 W/cm2 and the range of conditions studied.

CFD Application on Ventilation System of Hydro-Generator

2011 ◽  
Vol 383-390 ◽  
pp. 3561-3565
Author(s):  
Qun Feng Zhang ◽  
Jin Li Yan ◽  
Min Wang ◽  
Zhi Xiang Chen
Keyword(s):  
Pressure Loss ◽  
Rational Design ◽  
Ventilation System ◽  
Local Pressure ◽  
Porous Media Model ◽  
Air Cooler ◽  
Frame Method ◽  
Flow Flux ◽  
Icem Cfd ◽  
Different Parts

Averaged 3D N-S equations and RNG k-ε equations were solved with parallel computing CFD code on the flow field of dual radial ventilation system without fan for a hydro-generator. The MRF(multiple implicit rotating frame) method was used to simulated the rotating motion of the generator and porous media model were used to simulate the pressure loss of air cooler. Rational tactics were selected to generate calculation grids to compromise with calculation CPU time and result accuracy and the grids of different parts were generated with ICEM-CFD. The flow characteristic of different parts was analyzed and flow flux of different section was obtained. The research indicated that the flow from leakage gap between poles and stators formed "air wall", which generated a recirculation zone and made the bar cooling bad. The local pressure loss of stator entrance is dominant. There are leeward and windward areas for the air flowing with circumferential velocity component. Rational design of stator ducts entrance with some diversion effect, can reduce the pressure loss of the stator ventilation and improve the cooling of leeward area in stator ducts.

1215 Numerical Calculation of Curved Pipe Flow with Constant Flow Flux Condition

2015 ◽  
Vol 2015.53 (0) ◽  
pp. _1215-1_-_1215-2_
Author(s):  
Takuya MASUDA ◽  
Yasunori NAGATA ◽  
Toshinori KOUCHI ◽  
Yasutaka HAYAMIZU ◽  
Shinichiro YANASE
Keyword(s):  
Numerical Calculation ◽  
Pipe Flow ◽  
Constant Flow ◽  
Curved Pipe ◽  
Flux Condition ◽  
Flow Flux
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