1. http://cs.swan.ac.uk/ The Search for Swirl and Tumble Motion Robert S. Laramee Department of Computer Science Swansea University Wales, UK

2. Robert S. Laramee r.s.laramee@swansea.ac.uk 2 The Search for Swirl and Tumble Motion Outline  Problem description: swirl and tumble motion  Flow visualization classification:  direct  geometric  texture-based  feature-based  The great search  2D  2.5D (surfaces)  3D  steady and unsteady flow  Summary and conclusions

3. Robert S. Laramee r.s.laramee@swansea.ac.uk 3 The Search for Swirl and Tumble Motion Swirl and Tumble Motion  swirl motion: characterized by motion about cylinder-aligned axis  more stable (easier)  tumble motion: characterized by motion about axis orthogonal to cylinder  unstable, more difficult

4. Robert S. Laramee r.s.laramee@swansea.ac.uk 4 The Search for Swirl and Tumble Motion Swirl and Tumble Motion Achieving ideal patterns of motion leads to optimal mixing (of air and fuel) conditions  e.g., higher exhaust/gas ratio (EGR)  decrease in fuel consumption  lower emissions 1. Can visualization provide insight into or verify characteristic shape/behavior of flow? 2. What tools help to visualize swirl/tumble motion? 3. Where (in the combustion chamber) are ideal ideal flow pattern not being realized?

5. Robert S. Laramee r.s.laramee@swansea.ac.uk 5 The Search for Swirl and Tumble Motion Flow Visualization Classification 1. direct: overview of vector field, minimal computation, e.g. glyphs, color map 2. texture-based: complete coverage, more computation time, implementation time, e.g., Spot Noise, LIC 3. geometric: compute a discrete object whose geometry reflects flow characteristics, e.g. streamlines 4. feature-based: interesting subsets of the flow are first extracted

6. Robert S. Laramee r.s.laramee@swansea.ac.uk 6 The Search for Swirl and Tumble Motion The Great Search Geometric Texture- based Feature- based 2D 2.5D 3D & hybrid Both steady and unsteady flow!

7. Robert S. Laramee r.s.laramee@swansea.ac.uk 7 The Search for Swirl and Tumble Motion 2D Slices, Geometric Flow Visualization 3D streamlets for visualization of swirl motion:  Coverage is incomplete  Seeding an issue  Resampling used swirl motion good, although off-center

8. Robert S. Laramee r.s.laramee@swansea.ac.uk 8 The Search for Swirl and Tumble Motion 2D Slices, Geometric Flow Visualization Streamlines and tumble motion  Implemented via dye injection:  Coverage incomplete  Some flow features highlighted  Applicable to 3D  Downstream direction shown non-ideal tumble motion, saddle point

9. Robert S. Laramee r.s.laramee@swansea.ac.uk 9 The Search for Swirl and Tumble Motion 2D Slices, Texture-Based Flow Visualization Texture-based flow visualization and swirl motion:  Image-Based Flow Visualization (IBFV) [Van Wijk 02]  Complete coverage  Flow features shown  Hard to apply in 3D  downstream direction shown swirl behaviour evident

10. Robert S. Laramee r.s.laramee@swansea.ac.uk 10 The Search for Swirl and Tumble Motion 2D Slices, Texture-Based Flow Visualization Texture-based flow visualization and tumble motion:  Complete coverage  Flow features shown  Difficult to apply to 3D  Downstream direction shown tumble behavior non-ideal

11. Robert S. Laramee r.s.laramee@swansea.ac.uk 11 The Search for Swirl and Tumble Motion 2.5D, Geometric Flow Visualization Dye injection on surface (tumble motion):  Incomplete coverage  Flow features depend on seeding  Applies to 3D  Downstream direction shown tumble motion: separatrix highlighted

12. Robert S. Laramee r.s.laramee@swansea.ac.uk 12 The Search for Swirl and Tumble Motion 2.5D, Geometric Flow Visualization Timelines on surface:  Incomplete coverage  Flow features depend on seeding  Applicable to 3D  Downstream direction shown in animation tumble motion: divergent and convergent areas of the flow highlighted

13. Robert S. Laramee r.s.laramee@swansea.ac.uk 13 The Search for Swirl and Tumble Motion 2.5D, Texture-Based Flow Visualization Texture-based approach at surface:  Image Space Advection (ISA) [Laramee et al. 04]  Complete coverage  Flow features visible  Difficult to apply in 3D  Downstream direction shown swirl motion: generally good at surface (w/ exceptions)

14. Robert S. Laramee r.s.laramee@swansea.ac.uk 14 The Search for Swirl and Tumble Motion 2.5D, Texture-Based Flow Visualization Texture-based approach on surface:  ISA  Complete coverage  Flow features visible  Difficult to apply in 3D  Downstream direction shown tumble motion: rotation off-center? saddle point shown

15. Robert S. Laramee r.s.laramee@swansea.ac.uk 15 The Search for Swirl and Tumble Motion 3D & Hybrid, Geometric Flow Visualization 3D streamlines  Incomplete coverage  Flow features depend on seeding  Appropriate for 3D  Downstream direction sometimes shown swirl motion: (generally) prevalent inside combustion chamber

16. Robert S. Laramee r.s.laramee@swansea.ac.uk 16 The Search for Swirl and Tumble Motion 3D & Hybrid, Geometric and Texture-Based Flow Visualization Geometric and texture- based flow visualization on isosurfaces  Incomplete coverage  Flow features depend on placement  Appropriate for 3D  Downstream direction shown swirl motion: prevalent inside combustion chamber, non-ideal motion also prevalant

17. Robert S. Laramee r.s.laramee@swansea.ac.uk 17 The Search for Swirl and Tumble Motion 3D & Hybrid, Geometric and Texture-Based Flow Visualization Geometric and texture- based flow visualization on isosurfaces  Incomplete coverage  Features shown depend on placement  Applicable to 3D  Downstream direction shown tumble motion: axis of rotation is off center, cross between two ideals

18. Robert S. Laramee r.s.laramee@swansea.ac.uk 18 The Search for Swirl and Tumble Motion 2.5D Feature-Based Flow Visualization 2.5D Feature-Based Swirl Visualization  Topological skeleton of flow is extracted explicitly  Features shown automatically  Applicable to 3D  Complete coverage  Downstream direction not shown swirl motion: very complex near top of chamber red = saddle blue = sink green = source

19. Robert S. Laramee r.s.laramee@swansea.ac.uk 19 The Search for Swirl and Tumble Motion 3D, Unsteady Geometric Flow Visualization 3D, Unsteady Geometric Tumble Visualization  Pathlets seeded at inlet  Features depend on seeding  Applicable to 3D  Incomplete coverage  Downstream direction shown tumble motion: difficult to observe

20. Robert S. Laramee r.s.laramee@swansea.ac.uk 20 The Search for Swirl and Tumble Motion 3D, Feature-Based Flow Visualization 3D, Feature-Based Swirl Visualization  Boundary topology + 3D vortex core lines  Features extracted automatically  Applicable to 3D  Incomplete coverage  Downstream direction not shown Swirl motion: candidate swirl axis off- center red = saddle blue = sink green = source

21. Robert S. Laramee r.s.laramee@swansea.ac.uk 21 The Search for Swirl and Tumble Motion 3D, Unsteady Feature-Based Flow Visualization 3D, Unsteady Feature- Based Tumble Visualization  Boundary topology extracted + 3D vortex core lines  Features extracted automatically  Applicable to 3D  Incomplete coverage  Downstream direction not shown tumble motion: very transient red = saddle blue = sink green = source

22. Robert S. Laramee r.s.laramee@swansea.ac.uk 22 The Search for Swirl and Tumble Motion 3D, Feature-Based Flow Visualization 3D, Feature-Based Swirl Visualization  Boundary topology + 3D vortex core regions-lamda 2 transfer function  Features extracted automatically, resampling necessary  Applicable to 3D  Incomplete coverage  Downstream direction not shown Swirl motion: candidate swirl axis off- center red = saddle blue = sink green = source

23. Robert S. Laramee r.s.laramee@swansea.ac.uk 23 The Search for Swirl and Tumble Motion 3D, Unsteady Feature-Based Flow Visualization 3D, Unsteady Feature- Based Tumble Visualization  Boundary topology extracted + 3D vortex core regions –lambda 2 transfer function  Features extracted automatically, resampling necessary  Applicable to 3D  Incomplete coverage  Downstream direction not shown tumble motion: complex! candidate axis is revealed red = saddle blue = sink green = source

24. Robert S. Laramee r.s.laramee@swansea.ac.uk 24 The Search for Swirl and Tumble Motion 3D, Unsteady Feature-Based Flow Visualization Tumble Visualization- more difficult to visualize  Volume rendering of 3D vortex core regions –lambda 2 + helicity  Features extracted automatically, resampling necessary  Applicable to 3D  Incomplete coverage  Downstream direction not shown tumble motion: candidate axis is more clearly revealed

25. Robert S. Laramee r.s.laramee@swansea.ac.uk 25 The Search for Swirl and Tumble Motion 3D, Unsteady Feature-Based Flow Visualization Tumble Motion and Hybrid Visualizations  Volume rendering of 3D vortex core regions –lambda 2 in combination with particles  Features extracted automatically, resampling necessary  Applicable to 3D  Incomplete coverage  Downstream direction shown tumble motion: very transient, most effective up to this point

26. Robert S. Laramee r.s.laramee@swansea.ac.uk 26 The Search for Swirl and Tumble Motion 3D, Unsteady Feature-Based Flow Visualization Tumble Motion and Hybrid Visualizations  3D vortex core lines in combination with particles  Features extracted automatically  Applicable to 3D  Incomplete coverage  Downstream direction shown tumble motion: very transient, most effective up to this point

27. Robert S. Laramee r.s.laramee@swansea.ac.uk 27 The Search for Swirl and Tumble Motion 2.5D, Feature-Based Flow Visualization Tumble Motion and Periodic Orbit Extraction  Automatic periodic orbit extraction  Applicable to 3D  Incomplete coverage  Downstream direction shown (in animation) tumble motion: extracted directly, questions with interpretation

28. Robert S. Laramee r.s.laramee@swansea.ac.uk 28 The Search for Swirl and Tumble Motion Summary and Conclusions  We have presented the most comprehensive search for swirl and tumble motion ever…  The search continues!  Future feature-based flow visualization techniques need to be able to extract user-defined features directly, in 3D, and be applicable to unsteady flow

29. Robert S. Laramee r.s.laramee@swansea.ac.uk 29 The Search for Swirl and Tumble Motion Acknowledgements Thanks to the following people: Guoning Chen Christoph Garth Hans Hagen Helwig Hauser Konstantin Mischaikow Juergen Schneider Xavier Tricoche Daniel Weiskopf Eugene Zhang Thank you for your attention! Questions?