Http://cs.swan.ac.uk/ The Search for Swirl and Tumble Motion Robert S. Laramee Department of...

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The Search for Swirl and Tumble Motion

Robert S. LarameeDepartment of Computer Science

Swansea University

Wales, UK

2 The Search for Swirl and Tumble Motion

Robert S. [email protected]

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



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



Swirl and Tumble MotionAchieving 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?



Flow Visualization Classification1. 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



The Great SearchGeometric Texture-

basedFeature-based

2D

2.5D

3D & hybrid

Both steady and unsteady flow!



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



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



2D Slices, Texture-Based Flow VisualizationTexture-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



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



2.5D, Geometric Flow VisualizationDye injection on

surface (tumble motion):

Incomplete coverage Flow features depend

on seeding Applies to 3D Downstream direction

shown

tumble motion: separatrix

highlighted



2.5D, Geometric Flow VisualizationTimelines 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



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)



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



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



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



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



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



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



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



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



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




3D, Unsteady Feature-Based Tumble Visualization

Boundary topology extracted + 3D vortex core regions –lambda 2 transfer function



tumble motion: complex!

candidate axis is revealed

red = saddle

blue = sink

green = source




Tumble Visualization-more difficult to visualize

Volume rendering of 3D vortex core regions –lambda 2 + helicity



tumble motion: candidate axis is

more clearly revealed




Tumble Motion and Hybrid Visualizations

Volume rendering of 3D vortex core regions –lambda 2 in combination with particles


Applicable to 3D Incomplete coverage Downstream direction shown

tumble motion: very transient, most effective up to

this point




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



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



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



AcknowledgementsThanks to the following people:

Guoning ChenChristoph GarthHans HagenHelwig HauserKonstantin MischaikowJuergen SchneiderXavier TricocheDaniel WeiskopfEugene Zhang

Thank you for your attention!Questions?

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