Visualization Techniques for Fluid Flow in Cooling Jacket Design

1. Robert S Laramee 1 Christoph Garth 2 Helmut Doleisch 1 Jürgen Schneider 3 Helwig Hauser 1 Hans Hagen 2 1 The VRVis Reseach Center, Austria 2 University of Kaiserslautern, Germany 3 AVL-AST, Austria Visual Analysis and Exploration of Fluid Flow in a Cooling Jacket

2. Outline • Cooling jacket design: ideal flow and design goals • Visualization classification: direct, geometric, texture-based, and feature-based flow visualization: both automatic and interactive • Applying visualization techniques across five categories • (1) direct, (2) geometric, (3) texture-based • (4) automatic and semi-automatic feature extraction • (5) interactive feature extraction • Summary and conclusions

3. Cooling Jacket Design • Three Major Components of the Geometry: • cylinder head (top) • gasket (middle) • cylinder block (bottom) • Pulled apart for illustration only

4. The Ideal Cooling Jacket Flow Two major components to the ideal pattern of flow: • Longitudinal: lengthwise along geometry • Transversal: ”up-and-over” direction of the geometry i.e. shortest path(s) from inlet to outlet

5. Cooling Jacket Design Goals Four major design goals: • an even distribution of flow to each engine cylinder • avoid regions of stagnant flow • avoid very high velocity flow • minimize fluid pressure loss between inlet and outlet

6. Flow Visualization Classification • direct: overview of vector field, minimal computation, e.g. glyphs, color mapping • texture-based: complete coverage, more computation time, implementation time, e.g., Spot Noise, LIC, ISA • geometric: a discrete object(s) whose geometry reflects flow characteristics, e.g. streamlines • feature-based: both automatic and interactive feature-based techniques, e.g. flow topology

7. Applying Visualization Techniques Across Multiple Classifications and Comparing texture-based geometric direct feature-based: automatic feature-based:interactive • First time approaches from all five categories are systematically applied to same application.

8. High Temperature and Direct Flow Visualization Remarks about cooling jacket application: • Can help to visualize areas of high temperature • Can give initial overview Observations about visualization: • Tedious and error prone searching • Limited to surface (or slices)

9. Identifying Recirculation with Texture-Based Flow Visualization • Recirculation zones are less effective in transferring heat away • one goal is to minimize recirculation zones • Useful because of fast overview and coverage • perceptual challenges due to complexity

10. Identifying Recirculation with Texture-Based Flow Visualization • Cylinder heads receive extra attention • Bridge between exhaust side ports is critical • Appears not to be a problem here • But, manual inspection and must still look within volume • (color is mapped to velocity magnitude)

11. Visualizing Flow Distribution with Geometric Approaches (Streamlines) • Engineers try to maintain an even distribution of flow to each cylinder • Realized through placement, number, and size of gasket holes • Interactive seeding is tedious • not actually easy to see distribution, but pressure drop is evident • (streamline color mapped to pressure)

12. Visualizing Flow Distribution with Geometric Approaches (Particles) • Too many streamlines create perceptual problems (too much complexity) • Automatic Seeding is applied at inlet • Avoid perceptual problems, leaving no trails behind • slow/stagnant flow is easy to see • may miss recirculation zones • (particles color-mapped according to velocity magnitude)

13. Visualizing Flow Distribution with Geometric Approaches (Streamsurfaces) • Laminar flow characteristics in cylinder block are evident • laminar flow is broken up at gasket, resulting in very complex structure

14. Visualizing Flow Distribution with Geometric Approaches (Streamsurfaces) • Laminar flow characteristics in cylinder block are evident • laminar flow is broken up at gasket, resulting in very complex structure • Seeding: still a problem • Visual complexity: still a problem

15. Cutting plane topology appropriate given a priori knowledge • Visual complexity: still a problem Extracting Singularities with (Semi-)Automatic Feature-Extraction (Cutting Plane Topology) • Vortices have both beneficial (mixing of cool + hot fluid) and non-beneficial properties (increased resistance in ideal flow directions) • Many vortices present

16. Automatic Vortex Core Line Extraction (Sujudi-Haimes) • Cutting plane technique does not detect all vortices • Sujudi-Haimes vortex core line extraction method was also applied • Visual complexity: less but still a problem • Not necessarily what the engineer is interested in

17. Interactive Feature Extraction • A relatively new flow visualization classification • User specifies a region of interest in an information visualization view, e.g., a scatter plot • corresponding geometry is then shown in Focus+Context style visualization. • Smooth brushing is appropriate for CFD simulation data • Engineers may extract a more semantically oriented result.

18. Interactive Feature Extraction: Extracting Regions of Stagnant Flow • Regions of stagnant flow are the least effective for heat transfer • Can even lead to boiling conditions: ultimately a shorter product life span • Regions of stagnant flow are shown in magenta • Context is grey-shaded • color is mapped to temperature (blue- highest)

19. Interactive Feature Extraction: Extracting Regions of Stagnant Flow + High Temperature • Stagnant flow + high temperature is a bad combination • Multi-attribute brushing can extract these regions • Very little of the volume corresponds to this selection • Design is rather good from this perspective (v<0.1 m/s) AND (365K < t)

20. Interactive Feature Extraction: Extracting Reverse-Longitudinal Flow • Ideal pattern of flow has both longitudinal and transversal directions • Regions of backward flow are to be avoided • Very little of the volume corresponds to this selection • Design is rather good from this perspective

21. Gasket holes are high-pressure gradient regions • Design is sub-optimal from this perspective Interactive Feature Extraction: Extracting High Pressure Gradient • Ideal cooling jacket design minimizes pressure drop between inlet and outlet • Regions of high pressure drop are sub-optimal

22. Summary and Conclusions • We applied a feature-rich spectrum of visualization techniques to analyze flow through a cooling jacket: direct, texture-based, geometric, automatic feature-extraction, interactive feature-extraction • 2D slices were generally absent • Complex geometry makes parameterization unattractive • Texture-based visualization useful because it’s fast and provides overview • Simple particle visualization appealing for perceptual reasons • Automatic feature extraction useful, but still limited • Interactive feature extraction advantageous in this application due to arbitrary levels of abstraction

23. Acknowledgements Thank you for your attention! Questions? This work was supported by the Austrian program Kplus (kplus.at) and AVL (avl.com). CFD simulation data courtesy of AVL. For more information please visit: http://www.VRVis.at/scivis/laramee/jacket/ http://www.SImVis.at/

24. What about Unsteady Flow? Thank you for the excellent question! • Engineers are mostly interested in steady state simulation results, for the case of a cooling jacket • The ideal cooling jacket should quickly reach the conditions under which it stabilizes

25. What about Perceptual Problems with Texture-Based Flow Visualization? This is a super good question! • Image overlay opacity is arbitrary and thus user-controlled!