Modeling Gravity and Turbidity Currents: Computational Approaches and Challenges

2015 ◽  
Vol 67 (4) ◽  
Author(s):  
Eckart Meiburg ◽  
Senthil Radhakrishnan ◽  
Mohamad Nasr-Azadani
Keyword(s):  
Conceptual Modeling ◽  
Review Article ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Turbidity Currents ◽  
New Developments ◽  
Box Models ◽  
Large Eddy ◽  
Gravity Driven ◽  
High Reynolds

In this review article, we discuss recent progress with regard to modeling gravity-driven, high Reynolds number currents, with the emphasis on depth-resolving, high-resolution simulations. The initial sections describe new developments in the conceptual modeling of such currents for the purpose of identifying the Froude number–current height relationship, in the spirit of the pioneering work by von Kármán and Benjamin. A brief introduction to depth-averaged approaches follows, including box models and shallow water equations. Subsequently, we provide a detailed review of depth-resolving modeling strategies, including direct numerical simulations (DNS), large-eddy simulations (LES), and Reynolds-averaged Navier–Stokes (RANS) simulations. The strengths and challenges associated with these respective approaches are discussed by highlighting representative computational results obtained in recent years.

Will RANS Survive LES? A View of Perspectives

2005 ◽  
Vol 127 (5) ◽  
pp. 831-839 ◽  
Author(s):  
K. Hanjalic
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Hybrid Approaches ◽  
Large Eddy ◽  
Eddy Structures ◽  
Rans Models ◽  
High Reynolds

The paper provides a view of some developments and a perspective on the future role of the Reynolds-averaged Navier-Stokes (RANS) approach in the computation of turbulent flows and heat transfer in competition with large-eddy simulations (LES). It is argued that RANS will further play an important role, especially in industrial and environmental computations, and that the further increase in the computing power will be used more to utilize advanced RANS models to shorten the design and marketing cycle rather than to yield the way to LES. We also discuss some current and future developments in RANS aimed at improving their performance and range of applicability, as well as their potential in hybrid approaches in combination with the LES strategy. Limitations in LES at high Reynolds (Re) and Rayleigh (Ra) number flows and heat transfer are revisited and some hybrid RANS/LES routes are discussed. The potential of very large eddy simulations (VLES) of flows dominated by (pseudo)-deterministic eddy structures, based on transient RANS (T-RANS) and similar approaches, is discussed and illustrated in an example of “ultra-hard” (very high Ra) thermal convection.

Will RANS Survive LES? A View of Perspectives

2004 ◽  
Author(s):  
K. Hanjalic´
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Hybrid Approaches ◽  
Large Eddy ◽  
The Future ◽  
Eddy Structures ◽  
Rans Models ◽  
High Reynolds

The paper provides a view of some developments and a perspective on the future role of the Reynolds-averaged Navier-Stokes (RANS) approach in the computation of turbulent flows and heat transfer in competition with Large-eddy simulations (LES). It is argued that RANS will further play an important role, especially in industrial and environmental computations, and that the future increase in the computing power will be used more to utilize advanced RANS models to shorten the design and marketing cycle rather than to yield the way to LES. We also discuss some current and future developments in RANS aimed at improving their performance and range of applicability, as well as their potential in hybrid approaches in combination with the LES strategy. Limitations in LES at high Reynolds (Re) and Rayleigh (Ra) number flows and heat transfer are revisited and some hybrid RANS/LES routes are discussed. The potential of very large eddy simulations (VLES) of flows dominated by (pseudo)-deterministic eddy structures, based on transient RANS (T-RANS) and similar approaches is discussed and illustrated in an example of “ultra-hard” (very high Ra) thermal convection.

Simulating flow separation from continuous surfaces: routes to overcoming the Reynolds number barrier

2009 ◽  
Vol 367 (1899) ◽  
pp. 2885-2903 ◽  
Author(s):  
Michael Leschziner ◽  
Ning Li ◽  
Fabrizio Tessicini
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Major Elements ◽  
Wall Layer ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Models ◽  
High Reynolds ◽  
Near Wall

This paper provides a discussion of several aspects of the construction of approaches that combine statistical (Reynolds-averaged Navier–Stokes, RANS) models with large eddy simulation (LES), with the objective of making LES an economically viable method for predicting complex, high Reynolds number turbulent flows. The first part provides a review of alternative approaches, highlighting their rationale and major elements. Next, two particular methods are introduced in greater detail: one based on coupling near-wall RANS models to the outer LES domain on a single contiguous mesh, and the other involving the application of the RANS and LES procedures on separate zones, the former confined to a thin near-wall layer. Examples for their performance are included for channel flow and, in the case of the zonal strategy, for three separated flows. Finally, a discussion of prospects is given, as viewed from the writer's perspective.

Disruption of the bottom log layer in large-eddy simulations of full-depth Langmuir circulation

2012 ◽  
Vol 699 ◽  
pp. 79-93 ◽  
Author(s):  
A. E. Tejada-Martínez ◽  
C. E. Grosch ◽  
N. Sinha ◽  
C. Akan ◽  
G. Martinat
Keyword(s):  
Gravity Waves ◽  
Large Eddy Simulations ◽  
Stokes Drift ◽  
Navier Stokes ◽  
Wake Region ◽  
Langmuir Circulation ◽  
Mean Velocity ◽  
Wave Forcing ◽  
Large Eddy ◽  
Shear Current

AbstractWe report on disruption of the log layer in the resolved bottom boundary layer in large-eddy simulations (LES) of full-depth Langmuir circulation (LC) in a wind-driven shear current in neutrally-stratified shallow water. LC consists of parallel counter-rotating vortices that are aligned roughly in the direction of the wind and are generated by the interaction of the wind-driven shear with the Stokes drift velocity induced by surface gravity waves. The disruption is analysed in terms of mean velocity, budgets of turbulent kinetic energy (TKE) and budgets of TKE components. For example, in terms of mean velocity, the mixing due to LC induces a large wake region eroding the classical log-law profile within the range $90\lt { x}_{3}^{+ } \lt 200$. The dependence of this disruption on wind and wave forcing conditions is investigated. Results indicate that the amount of disruption is primarily determined by the wavelength of the surface waves generating LC. These results have important implications for turbulence parameterizations for Reynolds-averaged Navier–Stokes simulations of the coastal ocean.

scholarly journals Quasi-periodic forces and conditionally averaged characteristics of unsteady cavitation flow around a hydrofoil

2021 ◽  
Vol 2119 (1) ◽  
pp. 012030
Author(s):  
E I Ivashchenko ◽  
M Yu Hrebtov ◽  
R I Mullyadzhanov
Keyword(s):  
Reynolds Number ◽  
Liquid Phase ◽  
High Reynolds Number ◽  
Velocity Fields ◽  
Large Eddy Simulations ◽  
Two Dimensional ◽  
Cavitation Flow ◽  
Large Eddy ◽  
High Reynolds ◽  
Conditional Averaging

Abstract Large-eddy simulations are performed to investigate the cavitating flow around two dimensional hydrofoil section with angle of attack of 9° and high Reynolds number of 1.3×106. We use the Schnerr-Sauer model for accurate phase transitions modelling. Instantaneous velocity fields are compared successfully with PIV data using the methodology of conditional averaging to take into account only the liquid phase characteristics as in PIV. The presence of two frequencies in a spectrum corresponding to the full and partial cavity detachments is analysed.

scholarly journals Three-Dimensional Turbulent Vortex Shedding From a Surface-Mounted Square Cylinder: Predictions With Large-Eddy Simulations and URANS

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
B. A. Younis ◽  
A. Abrishamchi
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Navier Stokes Equations ◽  
Large Eddy

The paper reports on the prediction of the turbulent flow field around a three-dimensional, surface mounted, square-sectioned cylinder at Reynolds numbers in the range 104–105. The effects of turbulence are accounted for in two different ways: by performing large-eddy simulations (LES) with a Smagorinsky model for the subgrid-scale motions and by solving the unsteady form of the Reynolds-averaged Navier–Stokes equations (URANS) together with a turbulence model to determine the resulting Reynolds stresses. The turbulence model used is a two-equation, eddy-viscosity closure that incorporates a term designed to account for the interactions between the organized mean-flow periodicity and the random turbulent motions. Comparisons with experimental data show that the two approaches yield results that are generally comparable and in good accord with the experimental data. The main conclusion of this work is that the URANS approach, which is considerably less demanding in terms of computer resources than LES, can reliably be used for the prediction of unsteady separated flows provided that the effects of organized mean-flow unsteadiness on the turbulence are properly accounted for in the turbulence model.

Hybrid RANS/ILES for Aero Engine Intake

2014 ◽  
Author(s):  
Ugochukwu R. Oriji ◽  
Xiaoyu Yang ◽  
Paul G. Tucker
Keyword(s):  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Model Simulations ◽  
Rans Model ◽  
Acceleration Parameter ◽  
Separated Shear Layer ◽  
Turbulent Statistics ◽  
Large Eddy ◽  
Aero Engine ◽  
Aero Engines

Hybrid, Implicit Large Eddy Simulations (ILES) for an idealized aero engine intake in a crosswind is performed. The ILES zone is smoothly blended to a near wall Reynolds Averaged Navier-Stokes (RANS) zone. The flow has a region of high favourable pressure gradient (FPG) where the streamwise acceleration parameter (KS) is found to be greater than 3×10−6. This is sufficient to laminarize the boundary layer (BL). As a consequence, the turbulence in the boundary is severely suppressed and this interacts with a shock causing separation and distortion at the engine fan face. This is known to be undesirable for aero engines. The separated shear layer reenergizes turbulence and this promotes reattachment. The calculation in the RANS zone has been enhanced with a novel three-component RANS model and this is used in the hybrid RANS/ILES framework. Simulations also consider the modelling of roughness. The turbulent statistics and the engineering relevance of these are also discussed in this work. Broadly, encouraging agreement is found with measurements. Substantial accuracy improvements are found relative to standard RANS model simulations. The accuracy of the hybrid simulations is also contrasted with pure ILES and the critical need for the RANS layer shown for modest grids.

Approximation of attractors, large eddy simulations and multiscale methods

1991 ◽  
Vol 434 (1890) ◽  
pp. 23-39 ◽  
Keyword(s):  
Turbulent Flows ◽  
Mathematical Theory ◽  
Stokes Equations ◽  
Multiscale Methods ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Theory Approach ◽  
Navier Stokes Equations ◽  
Approximate Inertial Manifolds ◽  
Large Eddy

Recent advances in the mathematical theory of the Navier-Stokes equations have produced new insight in the mathematical theory of turbulence. In particular, the study of the attractor for the Navier-Stokes equations produced the first connection between two approaches to turbulence that seemed far apart, namely the conventional approach of Kolmogorov and the dynamical systems theory approach. Similarly the study of the approximation of the attractor in connection with the newly introduced concept of approximate inertial manifolds has produced a new approach to large eddy simulations and the study of the interaction of small and large eddies in turbulent flows. Our aim in this article is to survey and describe some of the new results concerning the functional properties of the Navier-Stokes equations and to discuss their relevance to turbulence.

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