Simulation and Modeling of Turbulent Flows

1996 ◽  
Keyword(s):  
Numerical Simulation ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Simulation And Modeling ◽  
Simulation Techniques ◽  
Rational Development ◽  
Group Methods ◽  
Turbulent Closure ◽  
The Subject ◽  
Renormalization Group Methods

This book provides students and researchers in fluid engineering with an up-to-date overview of turbulent flow research in the areas of simulation and modeling. A key element of the book is the systematic, rational development of turbulence closure models and related aspects of modern turbulent flow theory and prediction. Starting with a review of the spectral dynamics of homogenous and inhomogeneous turbulent flows, succeeding chapters deal with numerical simulation techniques, renormalization group methods and turbulent closure modeling. Each chapter is authored by recognized leaders in their respective fields, and each provides a thorough and cohesive treatment of the subject.

Large Eddy Simulation

1996 ◽  
Author(s):  
Joel H. Ferziger
Keyword(s):  
Numerical Simulation ◽  
Large Eddy Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Flow Simulation ◽  
Simulation Methods ◽  
Eddy Simulation ◽  
Simulation Techniques ◽  
Large Eddy

Over a decade ago, the author (Ferziger, 1983) wrote a review of the then state-of-the-art in direct numerical simulation (DNS) and large eddy simulation (LES). Shortly thereafter, a second review was written by Rogallo and Moin (1984). In those relatively early days of turbulent flow simulation, it was possible to write comprehensive reviews of what had been accomplished. Since then, the widespread availability of supercomputers has led to an explosion in this field so, although the subject is undoubtedly overdue for another review, it is not clear that the task can be accomplished in anything less than a monograph. The author therefore apologizes in advance for omissions (there must be many) and for any bias toward the accomplishments of people on the west coast of North America. In the earlier review, the author listed six approaches to the prediction of turbulent flow behavior. The list included: correlations, integral methods, single-point Reynolds-averaged closures, two-point closures, large eddy simulation and direct numerical simulation. Even then the distinction between these methods was not always clear; if anything, it is less clear today. It was possible in the earlier review to give a relatively complete overview of what had been accomplished with simulation methods. Since then, simulation techniques have been applied to an ever expanding range of flows so a thorough review of simulation results is no longer possible in the space available here. Simulation techniques have become well established as a means of studying turbulent flows and the results of simulations are best presented in combination with experimental data for the same flow. There is also a danger that the success of simulation methods will lead to attempts to apply them too soon to flows which the models and techniques are not ready to handle. To some extent, this is already happening. Direct numerical simulation (DNS) is a method in which all of the scales of motion of a turbulent flow are computed. A DNS must include everything from the large energy-containing or integral scales to the dissipative scales; the latter is usually taken to be the viscous or Kolmogoroff scales.

scholarly journals The CAD-Compatible VHP-Male Computational Phantom

2020 ◽  
pp. 309-323
Author(s):  
Gregory M. Noetscher
Keyword(s):  
Numerical Simulation ◽  
Diagnostic Techniques ◽  
Anatomical Features ◽  
Simulation Techniques ◽  
Medical Diagnostic ◽  
The Subject ◽  
External Stimuli ◽  
Computational Phantoms ◽  
Computational Phantom ◽  
Visible Human

AbstractAnatomically accurate and numerically efficient computational phantoms of humans are essential to characterizing the response of a body to a variety of electromagnetic, acoustic and other types of external stimuli. In conjunction with advances in numerical simulation techniques and computational hardware, these computational phantoms enable exploration of innovative and exciting applications, from medical diagnostic techniques and therapeutic treatments to new ways of on- and in-body communications. However, in order to provide realistic estimates through simulation, the model must represent the subject as closely as possible, necessitating that all relevant anatomical features are captured. If this is not accomplished, the model will misrepresent the true physical environment, and critical information will not be captured during the simulation. This work presents a model of a male subject based on the Visible Human Project dataset. Each component of the model is constructed of triangular surface elements, making it compatible with CAD packages and facilitating its use in simulations based on major numerical methodologies. A description of the model, the procedure used for its construction and a baseline simulation are presented together with future integration and augmentation ideas.

Distortion of line and surface elements in model turbulent flows

1991 ◽  
Vol 225 ◽  
pp. 529-543 ◽  
Author(s):  
I. T. Drummond ◽  
W. Münch
Keyword(s):  
Numerical Simulation ◽  
Simple Model ◽  
Velocity Field ◽  
Turbulent Flow ◽  
Time Evolution ◽  
Turbulent Flows ◽  
Principal Curvature ◽  
Line Element ◽  
Surface Patch ◽  
Exponential Rate

Material lines and surfaces transported in a random velocity field undergo bending and stretching. In this paper we investigate the time evolution of curvature in line and surface elements both analytically and by numerical simulation for a simple model turbulence. Our analysis is close to that of Pope (1988) for the evolution of curvature in surface elements. We show that the equation governing the evolution of curvature in a line element is very similar to that governing the evolution of the principal curvature in a surface patch. We investigate the circumstances in which the effect of straining fluctuations is to cause the exponential rate of growth of curvature discovered by Pope et al. (1989). Our simulation confirms that the presence of helicity in the turbulent flow results in the development of a non-vanishing mean torsion in a line element. The results of the simulation also suggest that the generation of curvature tends to occur in regions different from those associated with rapid stretching. The generation of torsion, however, is found not to be correlated with either bending or stretching.

Introduction

1996 ◽  
Keyword(s):  
Energy Transfer ◽  
Turbulent Flows ◽  
Turbulence Models ◽  
Spectral Energy ◽  
Wavelet Representations ◽  
Turbulent Closure ◽  
Scaling Parameters ◽  
The Subject ◽  
Compressible Turbulent Flow ◽  
Insightful Analysis

The aim of this book is to provide the engineer and scientist with the necessary understanding of the underlying physics of turbulent flows, and to provide the user of turbulence models with the necessary background on the subject of turbulence to allow them to knowledgeably assess the basis for many of the state-of-the-art turbulence models. While a comprehensive review of the entire field could only be thoroughly done in several volumes of this size, it is necessary to focus on the key relevant issues which now face the engineer and scientist in their utilization of the turbulent closure model technology. The organization of this book is intended to guide the reader through the subject starting from key observations of spectral energy transfer and the physics of turbulence through to the development and application of turbulence models. Chapter 1 focuses on the fundamental aspects of turbulence physics. An insightful analysis of spectral energy transfer and scaling parameters is presented which underlies the development of phenomenological models. Distinctions between equilibrium and nonequilibrium turbulent flows are discussed in the context of modifications to the spectral energy transfer. The non-equilibrium effects of compressibility are presented with particular focus on the alteration to the turbulent energy dissipation rate. The important topical issue of coherent structures and their representation is presented in the latter half of the chapter. Both Proper Orthogonal Decomposition and wavelet representations are discussed. With an understanding of the broad dynamic With an understanding of the broad dynamic range covered by both the turbulent temporal and spatial scales, as well as their modal interactions, it is apparent that direct numerical simulation (DNS) of turbulent flows would be highly desirable and necessary in order to capture all the relevant dynamics of the flow. Such DNS methods, in which all the important length scales in the energy-containing range and in the dissipation range are accounted for explicitly is presented in Chapter 2. Emphasis is on spectral methods for incompressible flows, including the divergence-free expansion technique. Vortex methods for incompressible bluff body flows are described and some techniques for compressible turbulent flow simulations are also discussed briefly.

Study of turbulent flow past a square cylinder using partially-averaged Navier–Stokes method in OpenFOAM

2020 ◽  
Vol 234 (14) ◽  
pp. 2821-2832 ◽  
Author(s):  
Arnab Chakraborty ◽  
HV Warrior
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
Normal Direction ◽  
Navier Stokes ◽  
Square Cylinder ◽  
Mean Velocity ◽  
Wide Range ◽  
Reynolds Averaged Navier Stokes

The present paper reports numerical simulation of turbulent flow over a square cylinder using a novel scale resolving computational fluid dynamics technique named Partially-Averaged Navier–Stokes (PANS), which bridges Reynolds-Averaged Navier–Stokes (RANS) with Direct Numerical Simulation (DNS) in a seamless manner. All stream-wise and wall normal mean velocity components, turbulent stresses behavior have been computed along the flow (streamwise) as well as in transverse (wall normal) direction. The measurement locations are chosen based on the previous studies so that results could be compared. However, the Reynolds number ( Re) of the flow is maintained at 21,400 and K– ω turbulence model is considered for the present case. All the computations are performed in OpenFOAM framework using a finite volume solver. Additionally, turbulent kinetic energy variations are presented over a wide range of measurement planes in order to explain the energy transfer process in highly unsteady turbulent flow field. The fluctuating root mean square velocities in the streamwise as well as in the wall normal direction have been discussed in the present work. It has been found that Partially-Averaged Navier–Stokes (PANS) model is capable of capturing the properties of highly unsteady turbulent flows and gives better results than Reynolds-Averaged Navier–Stokes (RANS). The results obtained using Partially-Averaged Navier–Stokes (PANS) are quite comparable with Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) data available in literature. The partially-averaged Navier–Stokes results are compared with our simulated Reynolds-Averaged Navier–Stokes (RANS) results, available experimental as well as numerical results in literature and it is found to be good in agreement.

Comparison of Characteristics of Flow Around a Sphere With Trip Wire Using Different Turbulence Modeling Approaches

2017 ◽  
Author(s):  
Madhu Vellakal ◽  
Muris Torlak ◽  
Seid Koric ◽  
Ahmed Taha
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
High Performance ◽  
Turbulence Modeling ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Bluff Bodies ◽  
Eddy Simulation ◽  
Simulation Techniques ◽  
Turbulent Models

The flow characteristics of spherical bodies, arising in a variety of important engineering and environmental problems, range from laminar to turbulent flow. Turbulent flows are predominantly studied using the models based on Reynolds-averaged Navier-Stokes (RANS) equations. Especially, in case of flows around bluff bodies RANS models have limitations in capturing flow separation and other characteristic flow properties. Hence, the use of high-fidelity turbulent models is required to investigate the physics of these types of flow in detail. This study aims to compare and analyze the results of an incompressible turbulent flow around a sphere with additional geometric detail, like a trip wire, using different simulation techniques: Large Eddy Simulation (LES) and RANS. Modeling bodies with different characteristic geometric scales may require high-performance computing (HPC) resources due to the need to include accurate spatial and temporal resolution using unstructured mesh generation. This may be under circumstances additional criterion for decision which simulation approach is to be adopted.

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