1. Explicit Filtering for Large Eddy
Simulation (LES)
MI-491
TRAINING AND SEMINAR
By
ANKUR AGRAWAL
ENROLMENT NUMBER-12117014
UNDER THE SUPERVISION OF
Prof. Andreas Kempf and Fabian Proch
DUISBURG ESSEN UNIVERSITY

2. INDEX
INTRODUCTION TO LES
EXPLICIT FILTERING
CODE SNIPPETS
PROJECT APPROACH
RESULTS (GNUPLOTS AND MTV PLOTS)
RESULT INFERENCES

3. 1. INTRODUCTION TO LES
• A mathematical model for turbulence used in computational fluid
dynamics.
• A substitute for Direct Numerical Simulation.
REQUIREMENTS :-
A filter width needs to be defined.
Filter Width >= Grid Spacing

4. 2. EXPLICIT FILTERING
Reduction of computational cost achieved.
Navier-Stokes equation is filtered.
Definition required unlike implicit filtering.
TYPES :-
a) Filtering the velocity term.
b) Filtering the convection term.

5. Filtering the velocity term

6. Filtering the convection term
 The errors due to the 3-step procedure for filtering
velocities are avoided.

7. A COMPARISON

8. 3. CODE SNIPPETS
Before filter
implementation

9. After filter
implementation

10. 4. PROJECT APPROACH
 Simulations were run on the in-house code which implemented combustion in a
Cambridge-stratified burner.
 After every change, simulations were run and results obtained which were in turn
compared with the experimental values.
 Different combinations of values of turbulence and filter width were checked for.
 The graphs for non-reactive case were plotted and the most accurate combinations
were applied for the reactive case as well.

11. CAMBRIDGE STRATIFIED BURNER

12. Graphs were plotted for the filtered values of radial and axial velocities
and a comparison was obtained at different axial distances.
5. RESULTS
-30 -20 -10 0 10 20 30
0
2
4
6
8
10
12
14
16
18
20
Z=50
reactive (unfil) delta M
Filt.75delta
values reactive
Filt.75delta_and_turb
U (mean) V (mean)

13. -30 -20 -10 0 10 20 30
0
5
10
15
20
25
Z=50
unfiltered
Filt.75delta_and_turb
Filt.75delta
values
U (rms) V (rms)
-30 -20 -10 0 10 20 30
0
1
2
3
4
5
6
7
8
9
Z=50
Filt.75delta_and_turb
values

14. 6. RESULT INFERENCES
Considerably accurate results which are open for further
improvements.
A better approach than the lengthy DNS procedure.
Successful application of an explicit filter.

15. AN ENRICHING
EXPERIENCE

16. THANK YOU