1. 1 GMUWCollaborative Research Lab Advanced Turbulence Modeling for engine applications Chan Hee Son University of Wisconsin, Engine Research Center Advisor: Professor Christopher J. Rutland Sponsor: General Motors

2. 2 GMUWCollaborative Research Lab Motivation  Linear k-  model  widely used, but compromise between expense and accuracy  Inherently unable to account for secondary flows  Poor predictions for separated or curved streamline flows  Non-linear models  Able to predict secondary flow of the second kind  Numerical instability leads to excessive computational expense  Wallin-Johansson's explicit Algebraic Reynolds Stress Model as a representative case  v 2 -f model  Two turbulence scales are used  More accurate representation of the physics (eddy viscosity) close to the wall  Very good performance in flow separation regions

3. 3 GMUWCollaborative Research Lab Model formulation  Turbulence governing equations of v 2 - f

4. 4 GMUWCollaborative Research Lab Sandia National Lab Optical engine  Specifications  Bore – 79.5mm, Stroke – 85.0 mm  C R = 18.7  1500 RPM  R S = 1.5 ~ 3.5  Cold flow (no spray or combustion)  Measurement locations  3 clusters of 5 points located in a vertical plane bisecting the exhaust valves  The 3 center points are at r= 13.6 mm with all neighboring measurement points being 1mm away.

5. 5 GMUWCollaborative Research Lab Radial and tangential velocities @ 5 ATDC with swirl ratio 3.5 v 2 -fW-J

6. 6 GMUWCollaborative Research Lab TKE history for case with swirl ratio = 3.5

7. 7 GMUWCollaborative Research Lab Conclusion For the Sandia National lab optical engine simulation, W-J eARSM does not show any improvement for the mean flow. Even the k-  model is better. For the Sandia National lab optical engine simulation, W-J eARSM does not show any improvement for the mean flow. Even the k-  model is better. Potential reason: the W-J ARSM is originally derived for 2D flow. 3D version is quartic order. Thus, too complex for practical use. l Increased levels of turbulence is predicted by the WJ model. At swirl ratio 2.5 and 3.5, TKE prediction over time is very similar to k-  model in trend, but about 50% higher in turbulence level. This is not due to the ability of this model to capture turbulence anisotropy, as the trend is almost exactly the same as k-  t high swirl anisotropy increases. l The v 2 -f model consistently shows improved results. Still it fails to catch the trends of the experimental turbulent kinetic energy results.