Title: Experimental Verification of CFD Modeling of Turbulent Flow over Circular Cavities using FLUENT
1University of Western Ontario Department of
Mechanical Materials Engineering
Advanced Fluid Mechanics Research Group
Experimental Verification of CFD Modeling of
Turbulent Flow over Circular Cavities using FLUENT
Presented by Thomas Hering MESc Candidate
Jesse Dybenko Research Engineer
Eric Savory Associate Professor
May 23, 2006
2Overview
- General overview of experimental parameters
- CFD grid generation
- CFD solution procedure
- Results
- Key findings
- Future work
- (Elliptical Cavities)
3Background
- Cavities may lead to increased noise and
drag on an object - Main focus on Circular cavities
-
- Resulting asymmetric flow and significant
increase in drag at - h/D 0.5
4Experimental Data Collected
- Three cases of h/D ratio 0.2, 0.47, 0.7 were
tested - Pressure transducer data was taken to plot
surface pressure contours on cavity walls and
surrounding plane - Hot Wire anemometry was used to examine the wake
flow characteristics - The free stream velocity during the experiments
was 27 0.15 m/s - The pressure coefficient was normalized using the
tunnel static pressure and free stream velocity
5Boundary Conditions and Dimensions
Velocity Inlet
The inlet velocity was set to 25 m/s, which
resulted in a free stream velocity of 26.4 m/s at
the free stream reference point
Wall
Cavity
Outflow
Wall
32D
47.3D
Y
4D
X
Z
5.5D
6Simulation Grid
Cavity
Side View
Top View
The computation domain was broken up into several
volumes which were meshed using a structured
hexagonal cooper meshing scheme
7Solution Procedure
- The solution was first iterated using the k-e
turbulence model - After initial solution convergence the Reynolds
Stress model was applied and further iterated - The tunnel length was used to develop a similar
boundary layer as measured in the experiments - A steady state solution sought
Simulated Data
Experimental Data
Boundary Layer Parameters
8Pressure Distributions
Pressure Coefficient
- Due to simulated steady state solution, only the
mean values were compared - Surface pressure distributions, wake profiles and
drag coefficients were compared
9Pressure Contours for h/D 0.7
Simulated results matched well with experimental
data
10Pressure Distributions along the Centreline for
h/D 0.7
11Pressure Contours for h/D 0.2
Similar trends along the centreline as for the
h/D 0.7 case, but the difference between
simulated and experimental data was larger
12Pressure Contours for h/D 0.47 (Asymmetric flow)
- Asymmetry is much weaker in the simulated results
- Vortex tube does not completely leave the cavity
in the simulated results
13Comparison between Turbulence Models for h/D
0.47
Asymmetry is weaker when applying the k-e
turbulence model
14Resulting Wake Comparisons
The weak asymmetry can be seen in the wake for
h/D 0.47 case
15Drag coefficient Comparison
- Experimental drag coefficient calculated using
pressure distributions along cavity wall - Weaker asymmetry the cause of the lower drag
coefficient at - h/D 0.47
Drag increment due to presence of cavity
CD Drag coefficient (normalized by the cavity
planform area) cf Skin friction coefficient
16Key Findings
- The simulated results showed the correct flow
physics involved in circular cavity flows - The asymmetric flow for a symmetric geometry, a
distinct feature of this type of flow, was
apparent in the simulations - The weaker asymmetry led to a lower drag
coefficient - The simulations constantly under predicted the
pressure values for all three configurations
tested - The Reynolds Stress Turbulence model provided
better results than the k-e Turbulence model when
comparing the strength of the asymmetry at h/D
0.47
17Elliptical Cavities h/D 0.47
18University of Western Ontario Department of
Mechanical Materials Engineering
Advanced Fluid Mechanics Research Group
http//www.eng.uwo.ca/research/afm/main.htm
Discussion and Questions are welcome
An Experimental Investigation of
Turbulent Boundary Layer Flow over
Surface-Mounted Circular Cavities J. Dybenko and
E. Savory, UWO 1220-1245 May 24, 2006 (Walker)