Numerical simulation of electroosmotic complex flow patterns in a microchannel

2011 ◽  
Vol 52 ◽  
pp. 104-115 ◽  
Author(s):  
Yasser Aboelkassem
Keyword(s):  
Numerical Simulation ◽  
Flow Patterns ◽  
Complex Flow

Stability Analysis of Hydropower Stations With Complex Flow Patterns in the Tailrace Tunnel

2013 ◽  
Author(s):  
Jianxu Zhou ◽  
Fulin Cai ◽  
Ming Hu
Keyword(s):  
Free Surface ◽  
Stability Analysis ◽  
Flow Patterns ◽  
Normal Operation ◽  
Complex Flow ◽  
Diversion Tunnel ◽  
Implicit Model ◽  
Special Cases ◽  
Tailrace Tunnel ◽  
Hydropower Stations

For some special tailrace tunnels in the hydropower stations, including the changing top-altitude tailrace tunnel and the tailrace tunnel with downstream reused flat-ceiling diversion tunnel, during normal operation and hydraulic transients, the flow patterns inside are relatively complex mainly including the free-surface pressurized flow and partial free flow if the tail water level is lower than the top elevation of tunnel’s outlet. These complex flow patterns have obvious effect on system’s stability, and can not be simulated accurately by the traditional models. Therefore, a characteristic implicit model is introduced to simulate these complex flow patterns for further stability analysis. In some special cases, the characteristic implicit model also fails to completely simulate the mixed free-surface pressurized flow in the flat-ceiling tailrace tunnel. A new method is presented based on both experimental research and numerical simulation, and then, system’s stability is analyzed by compared with traditional ordinary boundary condition. The results indicate that, with different simulation models for the complex water flow in the tailrace tunnel, system’s dynamic characteristic can be actually revealed with the consideration of the effect of complex flow patterns in the tailrace tunnel on system’s stability and regulation performance.

scholarly journals Characterization of complex flow patterns in the ascending aorta in patients with aortic regurgitation using conventional phase-contrast velocity MRI

2017 ◽  
Vol 34 (3) ◽  
pp. 419-429 ◽  
Author(s):  
Odd Bech-Hanssen ◽  
Frida Svensson ◽  
Christian L. Polte ◽  
Åse A. Johnsson ◽  
Sinsia A. Gao ◽  
...  
Keyword(s):  
Aortic Regurgitation ◽  
Phase Contrast ◽  
Flow Patterns ◽  
Ascending Aorta ◽  
Complex Flow

Computational Study of Gas Turbine Blade Cooling Channel

2010 ◽  
Author(s):  
R. S. Amano ◽  
Krishna Guntur ◽  
Jose Martinez Lucci
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Gas Turbine ◽  
Turbulence Models ◽  
Flow Patterns ◽  
Higher Order ◽  
Secondary Flows ◽  
Complex Flow ◽  
Cooling Performance ◽  
Cooling Channels

It has been a common practice to use cooling passages in gas turbine blade in order to keep the blade temperatures within the operating range. Insufficiently cooled blades are subject to oxidation, to cause creep rupture, and even to cause melting of the material. To design better cooling passages, better understanding of the flow patterns within the complicated flow channels is essential. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, both refined turbulence models and higher-order numerical schemes are indispensable for turbine designers to improve the cooling performance. Power output and the efficiency of turbine are completely related to gas firing temperature from chamber. The increment of gas firing temperature is limited by the blade material properties. Advancements in the cooling technology resulted in high firing temperatures with acceptable material temperatures. To better design the cooling channels and to improve the heat transfer, many researchers are studying the flow patterns inside the cooling channels both experimentally and computationally. In this paper, the authors present the performance of three turbulence models using TEACH software code in comparison with the experimental values. To test the performance, a square duct with rectangular ribs oriented at 90° and 45° degree and placed at regular intervals. The channel also has bleed holes. The normalized Nusselt number obtained from simulation are validated with that of experiment. The Reynolds number is set at 10,000 for both the simulation and experiment. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, both refined turbulence models and higher-order numerical schemes are indispensable for turbine designers to improve the cooling performance. The three-dimensional turbulent flows and heat transfer are numerically studied by using several different turbulence models, such as non-linear low-Reynolds number k-omega and Reynolds Stress (RSM) models. In k-omega model the cubic terms are included to represent the effects of extra strain-rates such as streamline curvature and three-dimensionality on both turbulence normal and shear stresses. The finite volume difference method incorporated with the higher-order bounded interpolation scheme has been employed in the present study. The outcome of this study will help determine the best suitable turbulence model for future studies.

scholarly journals Numerical Simulation of Solids Conveying in Grooved Feed Sections of Single Screw Extruders

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 256
Author(s):  
Florian Brüning ◽  
Volker Schöppner
Keyword(s):  
Numerical Simulation ◽  
Analytical Modeling ◽  
Flow Behavior ◽  
Analytical Calculation ◽  
Statistical Design ◽  
Simulation Software ◽  
Special Focus ◽  
Statistical Design Of Experiments ◽  
Complex Flow ◽  
Single Screw Extruders

For plastic processing extruders with grooved feed sections, the design of the feed section by means of analytical calculation models can be useful to reduce experimental costs. However, these models include assumptions and simplifications that can significantly decrease the prediction accuracy of the throughput due to complex flow behavior. In this paper, the accuracy of analytical modeling for calculating the throughput in a grooved barrel extruder is verified based on a statistical design of experiments. A special focus is placed on the assumptions made in the analytics of a backpressure-independent throughput, the assumption of a block flow and the differentiation of the solids conveying into different conveying cases. Simulative throughput tests with numerical simulation software using the discrete element method, as well as experimental throughput tests, serve as a benchmark. Overall, the analytical modeling already shows a very good calculation accuracy. Nevertheless, there are some outliers that lead to larger deviations in the throughput. The model predominantly overestimates the throughputs, whereby the origin of these deviations is often in the conveying angle calculation. Therefore, a regression-based correction factor for calculating the conveying angle is developed and implemented.

scholarly journals Complex flow patterns through Hydrate Ridge and their impact on seep biota

2001 ◽  
Vol 28 (14) ◽  
pp. 2863-2866 ◽  
Author(s):  
Michael D. Tryon ◽  
Kevin M. Brown
Keyword(s):  
Flow Patterns ◽  
Complex Flow ◽  
Hydrate Ridge
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