scholarly journals The study of typical water header flow structure by LES and RANS

2021 ◽  
pp. 293-293
Author(s):  
Hao Qin ◽  
Bin Wang ◽  
Yun Guo ◽  
Miao Hu
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
System Analysis ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Rapid Change ◽  
Convergence Criteria ◽  
Complex Flow ◽  
Complex Flow Structure ◽  
Rans Method

Water header is the most common structure in the design of flow system for energy and power system. The complex flow structure could result in some problems when Computational Fluid Dynamic (CFD) simulation is applied in the whole system analysis. The rapid change in velocity distribution of the flow field leads to difficulties to create suitable boundary layer mesh, and the complex flow structure will also make residuals hard to reach convergence criteria. Large Eddy Simulation (LES) is promising to promote these studies, it is more accurate than RANS method and can capture many non-steady state characteristics those RANS method can?t obtain. In this study a typical water header flow structure is investigated by RANS and LES methods. By comparing the detailed flow structures in the results of two methods, the deficiency of RANS method was found. The results of LES can be used to guide the establishment of meshes and the application of time-averaged turbulence models to improve efficiency in engineering. And the asymmetric Reynolds stresses may induce asymmetric flow field in symmetric geometry.

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.

Research Analysis and Experiment Study on Flow Field of Hydrodynamic Coupling

2011 ◽  
Vol 418-420 ◽  
pp. 2006-2011
Author(s):  
Rui Zhang ◽  
Cheng Jian Sun ◽  
Yue Wang
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Internal Flow ◽  
Phase Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Operation Conditions ◽  
Hydrodynamic Coupling

CFD simulation and PIV test technology provide effective solution for revealing the complex flow of hydrodynamic coupling’s internal flow field. Some articles reported that the combination of CFD simulation and PIV test can be used for analyzing the internal flow field of coupling, and such analysis focuses on one-phase flow. However, most internal flow field of coupling are gas-fluid two-phase flow under the real operation conditions. In order to reflect the gas-fluid two-phase flow of coupling objectively, CFD three-dimensional numerical simulation is conducted under two typical operation conditions. In addition, modern two-dimensional PIV technology is used to test the two-phase flow. This method of combining experiments and simulation presents the characteristics of the flow field when charging ratios are different.

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.

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