Large eddy simulation of droplet dispersion for inhomogeneous turbulent wall flow

2006 ◽  
Vol 32 (3) ◽  
pp. 344-364 ◽  
Author(s):  
I. Vinkovic ◽  
C. Aguirre ◽  
S. Simoëns ◽  
M. Gorokhovski
Keyword(s):  
Large Eddy Simulation ◽  
Droplet Dispersion ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wall Flow ◽  
Turbulent Wall

Quantifying Turbulent Wall Shear Stress in an Arteriovenous Graft Using Large Eddy Simulation

2012 ◽  
Author(s):  
L. D. Browne ◽  
P. Griffin ◽  
M. T. Walsh
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Large Eddy Simulation ◽  
Secondary Patency ◽  
Arteriovenous Graft ◽  
Venous Anastomosis ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wall Shear ◽  
Turbulent Wall

Hemodialysis patients require a vascular access capable of accommodating the high blood flow rates required for effective dialysis treatment. The arteriovenous graft is one such access. However, this access type suffers from reduced one year primary & secondary patency rates of 59–90% and 50–82% respectively [1]. The main contributor to the failure of this access is stenosis via the development of intimal hyperplasia (IH) that predominately occurs at the venous anastomosis. It is hypothesized that the resulting transitional to turbulent flow regime within the venous anastomosis contributes to the development of IH. The aim of this study is to investigate the influence of this transitional to turbulent behavior on wall shear stress within the venous anastomosis via the use of large eddy simulation.

Quantifying Turbulent Wall Shear Stress in a Stenosed Pipe Using Large Eddy Simulation

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Roland Gårdhagen ◽  
Jonas Lantz ◽  
Fredrik Carlsson ◽  
Matts Karlsson
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Large Eddy Simulation ◽  
Recirculation Zone ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Large Fluctuations ◽  
Time Average ◽  
Wall Shear ◽  
Turbulent Wall

Large eddy simulation was applied for flow of Re=2000 in a stenosed pipe in order to undertake a thorough investigation of the wall shear stress (WSS) in turbulent flow. A decomposition of the WSS into time averaged and fluctuating components is proposed. It was concluded that a scale resolving technique is required to completely describe the WSS pattern in a subject specific vessel model, since the poststenotic region was dominated by large axial and circumferential fluctuations. Three poststenotic regions of different WSS characteristics were identified. The recirculation zone was subject to a time averaged WSS in the retrograde direction and large fluctuations. After reattachment there was an antegrade shear and smaller fluctuations than in the recirculation zone. At the reattachment the fluctuations were the largest, but no direction dominated over time. Due to symmetry the circumferential time average was always zero. Thus, in a blood vessel, the axial fluctuations would affect endothelial cells in a stretched state, whereas the circumferential fluctuations would act in a relaxed direction.

scholarly journals Large Eddy Simulation and RANS Analysis of the End-Wall Flow in a Linear Low-Pressure-Turbine Cascade—Part II: Loss Generation

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Michele Marconcini ◽  
Roberto Pacciani ◽  
Andrea Arnone ◽  
Vittorio Michelassi ◽  
Richard Pichler ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Low Pressure ◽  
Companion Paper ◽  
Turbine Cascade ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wall Flow ◽  
End Wall

In low-pressure turbines (LPT) at design point, around 60–70% of losses are generated in the blade boundary layers far from end walls, while the remaining 30–40% is controlled by the interaction of the blade profile with the end-wall boundary layer. Increasing attention is devoted to these flow regions in industrial design processes. This paper discusses the end-wall flow characteristics of the T106 profile with parallel end walls at realistic LPT conditions, as described in the experimental setup of Duden, A., and Fottner, L., 1997, “Influence of Taper, Reynolds Number and Mach Number on the Secondary Flow Field of a Highly Loaded Turbine Cascade,” Proc. Inst. Mech. Eng., Part A, 211(4), pp.309–320. Calculations are carried out by both Reynolds-averaged Navier–Stokes (RANS), due to its continuing role as the design verification workhorse, and highly resolved large eddy simulation (LES). Part II of this paper focuses on the loss generation associated with the secondary end-wall vortices. Entropy generation and the consequent stagnation pressure losses are analyzed following the aerodynamic investigation carried out in the companion paper (GT2018-76233). The ability of classical turbulence models generally used in RANS to discern the loss contributions of the different vortical structures is discussed in detail and the attainable degree of accuracy is scrutinized with the help of LES and the available test data. The purpose is to identify the flow features that require further modeling efforts in order to improve RANS/unsteady RANS (URANS) approaches and make them able to support the design of the next generation of LPTs.

scholarly journals Wall-resolved large eddy simulation for aeroengine aeroacoustic investigation

2017 ◽  
Vol 121 (1242) ◽  
pp. 1032-1050 ◽  
Author(s):  
Y. Lin ◽  
R. Vadlamani ◽  
M. Savill ◽  
P. Tucker
Keyword(s):  
Large Eddy Simulation ◽  
Research Group ◽  
Near Field ◽  
Wake Flow ◽  
Computational Simulations ◽  
Trailing Edge Noise ◽  
Eddy Simulation ◽  
Flow Development ◽  
Large Eddy ◽  
Wall Flow

ABSTRACTThe work presented here forms part of a larger project on Large-Eddy Simulation (LES) of aeroengine aeroacoustic interactions. In this paper, we concentrate on LES of near-field flow over an isolated NACA0012 aerofoil at zero angle-of-attack and a chord based Reynolds number ofRec= 2 × 105. A wall-resolved compressible Numerical Large Eddy Simulation (NLES) approach is employed to resolve streak-like structures in the near-wall flow regions. The calculated unsteady pressure/velocity field will be imported into an analyticallybased scheme for far-field trailing-edge noise prediction later. The boundary-layer mean and root-mean-square (rms) velocity profiles, the surface pressure fluctuation over the aerofoil, and the wake flow development are compared with experimental data and previous computational simulations in our research group. It is found that the results from the wall-resolved compressible NLES are very encouraging as they correlate well with test data. The main features of the wall-resolved compressible NLES, as well as the advantages of such compressible NLES over previous incompressible LES performed in our research group, are also discussed.

scholarly journals Large-Eddy Simulation and RANS Analysis of the End-Wall Flow in a Linear Low-Pressure Turbine Cascade, Part I: Flow and Secondary Vorticity Fields Under Varying Inlet Condition

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Richard Pichler ◽  
Yaomin Zhao ◽  
Richard Sandberg ◽  
Vittorio Michelassi ◽  
Roberto Pacciani ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Secondary Flow ◽  
Low Pressure ◽  
Eddy Simulation ◽  
Wall Boundary Layer ◽  
Wall Boundary ◽  
Large Eddy ◽  
Wall Flow ◽  
End Wall

Abstract In low-pressure turbines (LPTs), around 60–70% of losses are generated away from end-walls, while the remaining 30–40% is controlled by the interaction of the blade profile with the end-wall boundary layer. Experimental and numerical studies have shown how the strength and penetration of the secondary flow depends on the characteristics of the incoming end-wall boundary layer. Experimental techniques did shed light on the mechanism that controls the growth of the secondary vortices, and scale-resolving computational fluid dynamics (CFD) allowed to dive deep into the details of the vorticity generation. Along these lines, this paper discusses the end-wall flow characteristics of the T106 LPT profile at Re = 120 K and M = 0.59 by benchmarking with experiments and investigating the impact of the incoming boundary layer state. The simulations are carried out with proven Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulation (LES) solvers to determine if Reynolds-averaged models can capture the relevant flow details with enough accuracy to drive the design of this flow region. Part I of the paper focuses on the critical grid needs to ensure accurate LES and on the analysis of the overall time-averaged flow field and comparison between RANS, LES, and measurements when available. In particular, the growth of secondary flow features, the trace and strength of the secondary vortex system, and its impact on the blade load variation along the span and end-wall flow visualizations are analyzed. The ability of LES and RANS to accurately predict the secondary flows is discussed together with the implications this has on design.

Large eddy simulation of a plane turbulent wall jet

2005 ◽  
Vol 17 (2) ◽  
pp. 025102 ◽  
Author(s):  
A. Dejoan ◽  
M. A. Leschziner
Keyword(s):  
Large Eddy Simulation ◽  
Wall Jet ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbulent Wall
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