Optimal Control of Nonstationary Processes of Heat and Mass Exchange with a Complex Flow Structure

1999 ◽  
Vol 31 (4-5) ◽  
pp. 106-115
Author(s):  
R. Ts. Oganesyan
Keyword(s):  
Optimal Control ◽  
Flow Structure ◽  
Mass Exchange ◽  
Nonstationary Processes ◽  
Complex Flow ◽  
Heat And Mass Exchange ◽  
Complex Flow Structure

Fluid Flow Structure in Arterial Bypass Anastomosis

2005 ◽  
Vol 127 (4) ◽  
pp. 611-618 ◽  
Author(s):  
C. M. Su ◽  
D. Lee ◽  
R. Tran-Son-Tay ◽  
W. Shyy
Keyword(s):  
Fluid Flow ◽  
Flow Structure ◽  
Bypass Graft ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Arterial Bypass ◽  
Flow Recirculation ◽  
Area Reduction ◽  
Complex Flow Structure

The fluid flow through a stenosed artery and its bypass graft in an anastomosis can substantially influence the outcome of bypass surgery. To help improve our understanding of this and related issues, the steady Navier-Stokes flows are computed in an idealized arterial bypass system with partially occluded host artery. Both the residual flow issued from the stenosis—which is potentially important at an earlier stage after grafting—and the complex flow structure induced by the bypass graft are investigated. Seven geometric models, including symmetric and asymmetric stenoses in the host artery, and two major aspects of the bypass system, namely, the effects of area reduction and stenosis asymmetry, are considered. By analyzing the flow characteristics in these configurations, it is found that (1) substantial area reduction leads to flow recirculation in both upstream and downstream of the stenosis and in the host artery near the toe, while diminishes the recirculation zone in the bypass graft near the bifurcation junction, (2) the asymmetry and position of the stenosis can affect the location and size of these recirculation zones, and (3) the curvature of the bypass graft can modify the fluid flow structure in the entire bypass system.

Natural Convection in a Horizontal Cavity Partially Occupied by a Porous Media Saturated by a Coolant Liquid

2006 ◽  
Author(s):  
Fakhreddine S. Oueslati ◽  
Rachid Bennacer ◽  
Habib Sammouda ◽  
Ali Belghith
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Natural Convection ◽  
Flow Structure ◽  
Boussinesq Approximation ◽  
Density Variation ◽  
Heat Fluxes ◽  
Complex Flow ◽  
Coupled Equations ◽  
Complex Flow Structure

The natural convection is studied in a cavity witch the lower half is filled with a porous media that is saturated with a first fluid (liquid), and the upper is filled with a second fluid (gas). The horizontal borders are heated and cooled by uniform heat fluxes and vertical ones are adiabatic. The formulation of the problem is based on the Darcy-Brinkman model. The density variation is taken into account by the Boussinesq approximation. The system of the coupled equations is resolved by the classic finite volume method. The numerical results show that the variation of the conductivity of the porous media influences strongly the flow structure and the heat transfer as well as in upper that in the lower zones. The effect of conductivity is conditioned by the porosity which plays a very significant roll on the heat transfer. The structures of this flow show that this kind of problem with specific boundary conditions generates a complex flow structure of several contra-rotating two to two cells, in the upper half of the cavity.

Flow Field Analysis of Under-Expanded Supersonic Jets Impinging on an Inclined Flat Plate: Analysis With PSP/Schlieren Images and CFD Simulations

2005 ◽  
Author(s):  
Kozo Fujii ◽  
Akira Oyama ◽  
Nobuyuki Tsuboi ◽  
Moto Tsukada ◽  
Hirofumi Ouchi ◽  
...  
Keyword(s):  
Flat Plate ◽  
Flow Structure ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Flow Fields ◽  
Field Analysis ◽  
Geometrical Parameters ◽  
Complex Flow ◽  
Plate Analysis ◽  
Complex Flow Structure

Flow fields of Mach number 2.2 jet impinging on an inclined flat plate are experimentally investigated using the Pressure Sensitive Paints (PSP) and Schlieren flow visualization. The flow filed structure is mainly determined by two geometrical parameters (nozzle-plate distance and plate angle against the jet) and one flow parameter (pressure ratio). The results suggest that all the observed flow fields can actually be classified into three types of flow structure based on the three parameters above. As an extension of the authors’ earlier work, experiments are carried out for higher plate angles. The new results show the effectiveness and limitation of the classification that we proposed. To find out the flow structure, some of the flow fields are computationally simulated. Good agreement of the pressure distributions with the experiment validates the simulation. Although analysis so far is limited, the result reveals three dimensional complex flow structure that created pressure peaks over the plate surface.

Volumetric Three-Componential Velocity Measurements (V3V) of Flow Structure Behind Mangrove-Root Type Models

2020 ◽  
Author(s):  
Amirkhosro Kazemi ◽  
Eduardo E. Castillo ◽  
Oscar Curet ◽  
Ruben Hortensius ◽  
Pothos Stamatios
Keyword(s):  
Flow Structure ◽  
Vortex Structure ◽  
Streamwise Velocity ◽  
Circular Cylinders ◽  
Complex Flow ◽  
Time Resolved ◽  
Mangrove Root ◽  
Mangrove Roots ◽  
A Chain ◽  
Complex Flow Structure

Abstract Mangrove roots produce complex flow structure interactions with their environment, which affect the nutrient, habitat and aquatic animals. Analysis of the flow structure behind the roots extends to a broad range of mangrove-inspired applications that provides understanding into complex flows encountered in unidirectional riverine flows. In this work, we modeled the mangrove roots with a cluster of rigid circular cylinders to investigate the vortex structure downstream of the models. The vortex organization of the patch of cylinder wakes was studied experimentally by time-resolved volumetric three-componential volumetric velocimetry (V3V) at Reynolds numbers 1014 and 3549. The results show that the vortex structure in the 3-D flow field reveals a regular shedding at Re = 1014, forming von Kármán vortices dominating the 3D motion. The flow structure behind rigid patches is coherent and the streamwise velocity remains unchanged. The regime for a flexible patch at Re = 3549 produces an intricate pattern where the multiple counter-rotating vortexes distorted substantially and forming a chain of rhombus-like vortex cells in the near wake. The information for the 3D flow feature provides useful information to a robust structure for Seawall erosion.

Measurements of Flow Modification by Particle Deposition Inside a Packed Bed Using Time-Resolved PIV

2008 ◽  
Author(s):  
Elvis E. Dominguez-Ontiveros ◽  
Carlos Estrada-Perez ◽  
Yassin A. Hassan
Keyword(s):  
Heat Transfer ◽  
Velocity Field ◽  
Flow Structure ◽  
Particle Deposition ◽  
Packed Bed ◽  
Packed Bed Reactor ◽  
Temperature Fields ◽  
Complex Flow ◽  
Flow Modification ◽  
Complex Flow Structure

In the Advanced Gas Cooled Pebble Bed Reactors for nuclear power generation, the fuel is spherical coated particles. The energy transfer phenomenon requires detailed understanding of the flow and temperature fields around the spherical fuel pebbles. Detailed information of the complex flow structure within the bed is needed. Generally, for computing the flow through a packed bed reactor or column, the porous media approach is usually used with lumped parameters for hydrodynamic calculations and heat transfer. While this approach can be reasonable for calculating integral flow quantities, it may not provide all the detailed information of the heat transfer and complex flow structure within the bed. The present experimental study presents the full velocity field using particle image velocity technique (PTV) in a conjunction with matched refractive index fluid with the pebbles to achieve optical access. Velocity field measurements are presented delineating the complex flow structure.

Matched refractive-index PIV visualization of complex flow structure in a three-dimentionally connected dual elbow

2011 ◽  
Vol 241 (11) ◽  
pp. 4544-4550 ◽  
Author(s):  
Kazuhisa Yuki ◽  
Shunsuke Hasegawa ◽  
Tsukasa Sato ◽  
Hidetoshi Hashizume ◽  
Kosuke Aizawa ◽  
...  
Keyword(s):  
Refractive Index ◽  
Flow Structure ◽  
Complex Flow ◽  
Complex Flow Structure

Computation of the Flow Around a Simplified Car Using the Rescaled v2–f Model

2003 ◽  
Author(s):  
Re´mi Manceau
Keyword(s):  
Flow Structure ◽  
Automotive Industry ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
The Body ◽  
Complex Flow ◽  
Eddy Viscosity Model ◽  
Body Experiences ◽  
Complex Flow Structure ◽  
Better Than

The Ahmed body is a simplified car used in automotive industry to investigate the influence of the flow structure on the drag. When the angle of the hatchback approaches 30°, the wake of the body experiences a transition from a quasi-2-D to a fully 3-D structure, which is at the origin of a drag crisis. Many turbulence models have been tested for the case at 25° and none of them was able to reproduce correctly the complex flow structure. The paper aims at investigating the performances of a recently developed near-wall eddy-viscosity model, the rescaled v2–f model, which is derived from the well known v2–f model. It is shown that the model does not perform better than models of the same class. Indeed, the predicted wake is nearly 2-D, massively separated, which is characteristic of the low-drag configuration: the transition of the wake to a fully 3-D, highly dissipative structure is not reproduced.

scholarly journals Mangrove vegetation inspires a new approach to protect shorelines

2018 ◽  
Author(s):  
Robert Segmaier ◽  
Stephanie Staggs ◽  
Sarah Palmer
Keyword(s):  
Flow Structure ◽  
Mangrove Forest ◽  
Storm Surges ◽  
Complex Flow ◽  
New Approach ◽  
Tropical Regions ◽  
Water Currents ◽  
Long Time ◽  
Mangrove Roots ◽  
Complex Flow Structure

I. AbstractMangroves are found worldwide across the rivers and coastlines in tropical regions. They are robust against storm surges and tsunamic for a long time. The roots have the most contributions for their resiliency and therefore can be inspired for future manmade structures. The motion of water in riverine mangrove forest is expected to be impacted by mangrove roots, which in turn disturb the transport of nutrients, contaminants, and residues in these systems. In this paper, a facile method for protecting shoreline is described and review and the significant impact of this method were reviewed. Bioinspired simplified models as and obstruction to water currents in shorelines, and coastal areas are presented. It was found that Mangrove roots produce complex flow structure interactions with their environment, which affect the nutrient, habitat and aquatic animals. Analysis of the flow structure behind the roots extend to a broad range of mangrove-inspired applications and provide understandings into flows that are more complex and more indicative of the flows encountered in the unidirectional riverine flow.

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