Robert S. Laramee Department of Computer Science University of Wales, Swansea, UK Effective Visualization of Heat Transfer

2 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

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

4Effective Visualization of Heat Transfer The Ideal Cooling Jacket Flow Two major components to the ideal pattern of flow: Longitudinal: lengthwise along geometry 1.Transversal: ”up-and-over” direction of the geometry i.e. shortest path(s) from inlet to outlet

5Effective Visualization of Heat Transfer Cooling Jacket Design Goals major design goals: transfer heat away from engine block 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

6Effective Visualization of Heat Transfer Flow Visualization Classification 1.direct: overview of vector field, minimal computation, e.g. glyphs, color mapping 2.texture-based: complete coverage, more computation time, implementation time, e.g., Spot Noise, LIC, ISA 3.geometric: a discrete object(s) whose geometry reflects flow characteristics, e.g. streamlines 4.feature-based: both automatic and interactive feature-based techniques, e.g. flow topology

7Effective Visualization of Heat Transfer Applying Visualization Techniques Across Multiple Classifications and Comparing directtexture-basedgeometric feature-based: automaticfeature-based: interactive approaches from all five categories are systematically applied to same application.

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

9Effective Visualization of Heat Transfer 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

10Effective Visualization of Heat Transfer 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)

11Effective Visualization of Heat Transfer 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)

12Effective Visualization of Heat Transfer 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)

13Effective Visualization of Heat Transfer 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

14Effective Visualization of Heat Transfer 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

15Effective Visualization of Heat Transfer 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 Visual complexity: still a problem Cutting plane topology appropriate given a priori knowledge

16Effective Visualization of Heat Transfer 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

17Effective Visualization of Heat Transfer 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.

18Effective Visualization of Heat Transfer 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)

19Effective Visualization of Heat Transfer 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)

20Effective Visualization of Heat Transfer 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

21Effective Visualization of Heat Transfer 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 Gasket holes are high- pressure gradient regions Design is sub-optimal from this perspective

22Effective Visualization of Heat Transfer 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

23Effective Visualization of Heat Transfer Thank you for your attention! Questions? Thanks To: 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 CFD simulation data courtesy of AVL. For more information please visit:

24Effective Visualization of Heat Transfer 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

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