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

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.

Sedimentation Control before the Weir of Dayuandu Navigation and Hydropower Project

2014 ◽  
Vol 1030-1032 ◽  
pp. 598-602
Author(s):  
Xiao Ping Liu ◽  
Qiong Huang ◽  
Da Bin Xu
Keyword(s):  
Mathematical Models ◽  
Ternary Complex ◽  
Flow Patterns ◽  
Surface Wear ◽  
Hydropower Project ◽  
Complex Flow ◽  
Scheduling Method ◽  
Flow Intensity ◽  
Underwater Camera ◽  
Desirable Effect

Through an underwater camera at the WES Weir of the Dayuandu Project, the heavy sedimentation on the Weir’s floor can be observed. The sediment changes the water flow patterns before the Weir, resulting in Weir surface wear and sluice leakage. Mathematical models and physical had been builded to analyze the effect of the erosion. The results of these observations provide a reasonable and effective scheduling method to solve the siltation problems in front ofthe WES Weir. Once there are sufficient flow intensity, the ternary complex flow patterns will contribute to the incipient motions of sediment, acquireing desirable effect of sedimentation Control.

Targeted Particle Tracking in Computational Models of Human Carotid Bifurcations

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Ian Marshall
Keyword(s):  
Healthy Volunteer ◽  
Carotid Artery ◽  
Flow Region ◽  
Carotid Bifurcation ◽  
Flow Patterns ◽  
External Carotid ◽  
Complex Flow ◽  
Imaging Science ◽  
Carotid Bulb ◽  
Human Carotid

A significant and largely unsolved problem of computational fluid dynamics (CFD) simulation of flow in anatomically relevant geometries is that very few calculated pathlines pass through regions of complex flow. This in turn limits the ability of CFD-based simulations of imaging techniques (such as MRI) to correctly predict in vivo performance. In this work, I present two methods designed to overcome this filling problem, firstly, by releasing additional particles from areas of the flow inlet that lead directly to the complex flow region (“preferential seeding”) and, secondly, by tracking particles both “downstream” and “upstream” from seed points within the complex flow region itself. I use the human carotid bifurcation as an example of complex blood flow that is of great clinical interest. Both idealized and healthy volunteer geometries are investigated. With uniform seeding in the inlet plane (in the common carotid artery (CCA)) of an idealized bifurcation geometry, approximately half the particles passed through the internal carotid artery (ICA) and half through the external carotid artery. However, of those particles entering the ICA, only 16% passed directly through the carotid bulb region. Preferential seeding from selected regions of the CCA was able to increase this figure to 47%. In the second method, seeding of particles within the carotid bulb region itself led to a very high proportion (97%) of pathlines running from CCA to ICA. Seeding of particles in the bulb plane of three healthy volunteer carotid bifurcation geometries led to much better filling of the bulb regions than by particles seeded at the inlet alone. In all cases, visualization of the origin and behavior of recirculating particles led to useful insights into the complex flow patterns. Both seeding methods produced significant improvements in filling the carotid bulb region with particle tracks compared with uniform seeding at the inlet and led to an improved understanding of the complex flow patterns. The methods described may be combined and are generally applicable to CFD studies of fluid and gas flow and are, therefore, of relevance in hemodynamics, respiratory mechanics, and medical imaging science.

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