Large-Eddy
Simulation of Turbulent Flows
(ME EN 7960-003)
Fall 2014
Instructor: |
Rob Stoll, Ph.D
Department of Mechanical Engineering
581-3405
rstoll@eng.utah.edu |
Credit
Hours: |
3 credit |
Lecture: |
T, Th 3:40-5:00 |
Room: |
WEB 2470 |
Office Hours: |
KENN 1012 by appointment (check my
calendar & email or just stop in) |
Web Site: |
http://www.eng.utah.edu/~rstoll/LES/ |
Recommended
Texts: |
B. Geurts (Edwards, 2004)
P. Sagaut and C. Meneveau
(Springer-Verlag, 2005)
S. Pope (Cambridge University
Press, 2000)
|
Required
Prerequisites: |
ME EN 6700 or Instructor consent |
Good to have
Prerequisites: |
ME EN 7710, ME EN 7720 |
Course
Description:
This
course
covers topics related to Large-Eddy
Simulation (LES).
An advanced Computational Fluid
Dynamics (CFD)
technique. LES
is quickly replacing traditional Reynolds
Averaged Navier-Stokes
(RANS) modeling as the method of
choice for researchers and practitioners studying turbulent fluid flow
phenomena in engineering and environmental problems. LES
explicitly solves for the larger scale turbulent motions that are highly
dependent on boundary conditions (e.g., geometry, large scale forcing)
while using a turbulence model only for the smaller (and presumably more
universal) motions. This is a distinct advantage over traditional
RANS models where the effects of turbulence on the flow field are
entirely dependent on the turbulence parameterizations.
This course will provide students with an introduction to the concepts
and principles of the LES technique
for
numerical simulation of turbulent flows. The course will start by
discussing filtering and the turbulence closure problem in the context
of LES. It will then move on to derive and examine the filtered
forms of the governing equations. Modeling the effect of
unresolved turbulence, with SubGrid-Scale
(SGS) models, will constitute a
significant portion of the course content. Students will learn how
to formulate SGS models, how to test SGS models off-line with
experimental data and evaluate the performance of SGS models from the
results of turbulent flow simulations. The last part of the class
will examine issues pertaining to LES of specific flow cases of interest
to the class. For example, this might include wall-boundary
conditions for wall bounded flows , turbulent inlet and exit conditions,
SGS models for high-Reynolds number flows, Lagrangian particle methods
for LES, and SGS modeling for turbulent reacting flows. Time
permitting, other topics specific to student interests will be covered.
Course
Objectives:
- Become familiar with the filtering
concept in a turbulent flow and how the idea of scale
separation forms the basis for LES.
- Gain familiarity with the filtered
forms of the conservation equations (e.g., mass, momentum, turbulent
kinetic energy), how they are derived and how the different terms in
the equations can be interpreted.
- Obtain a basic working knowledge of
common subgrid-scale (SGS) parameterizations used in LES of turbulent
flows.
- Understand how to carry out a
priori analysis of SGS models from experimental and Direct
Numerical Simulation
(DNS) data sets.
- Understand common techniques for a
posteriori evaluation of SGS models and what conditions are
necessary and sufficient for a 'good' SGS model.
- Become familiar with LES SGS models and
techniques used in specific flow cases of interest (e.g., isotropic
turbulence, high-Reynolds number boundary layers, turbulent
reacting flows, etc.)
Course
Outline:
- Intro and motivation
- Analysis tools
- Turbulence and scale separation
- Equations of motion
- Filtering
- Filtered equations of motion
- Approaches to turbulence modeling
- Numerics and LES
- Basic SGS models
- eddy viscosity
- similarity
- nonlinear
- mixed
- dynamic models
- Using Fourier methods to simulate isotropic turbulence (Project #1)
- Evaluating LES (a postiori)
- Evaluating SGS models (a priori,
Project #2)
- Special Topics in LES (cover some set of the following examples)
- Boundary and initial conditions
- Anisotropic models
- Probability based methods
- Lagrangian particle models
- LES of compressible and/or reacting flows
- LES case studies of interest
Grading:
Grades will be based on a series of
homework assignments and two course projects. The grades in each
of these categories will be broken down as follows:
Homework |
40% |
Project #1 |
25% |
Project #2 |
35% |
Homework:
Approximately 3-4 homework assignments will be given during the
semester. These assignments will focus on basic topics and ideas that
will be needed in the projects (statistics of turbulence, filtering,
power spectra estimation, model formulations, etc.). The
assignments will be given throughout the semester when material is
covered with an emphasis on the time period before the 1
st
project.
Project
#1
(tentative):
Project #1 will focus on the application of LES SGS models in 3D
turbulence simulations. Students will be provided a basic 3D
numerical code which they will add their own SGS models to and will then
examine the effect of base model type, model coefficient specification
and grid resolution on the resolved simulated velocity fields. The
project will be submitted in the form of a short report (~4 pages)
outlining the basics of the simulation code used, the chosen SGS models
and the results of parameter studies.
Project
#2:
Project #2 will consist of gaining experience on doing
a
priori analysis of LES SGS models from experimental or
numerical data. Data sets from various experimental setups (high
speed turbulence sensors, PIV) or high resolution DNS will be provided
for students to use in the projects based on the students research
interests. Alternatively, if students have appropriate data sets
(experimental or numerical) that they wish to use for their project they
will be free to do so. The project will be submitted in the form of a
short report (~4-6 pages) including: basics and background of the
SGS models to be tested, a short description of the data set used in the
analysis and a short summary of key results/incites gained from the
tests. In addition to the project report, all students will be
required to give a short presentation (~15 minutes) during the last
weeks of class.
Useful
Information: