visualization of dns isot code results - research...

Visualization of DNS isoT Code ResultsResearch Summary

Mishaal Aleem

Computational Fluid Mechanics LabAeronautics & AstronauticsUniversity of Washington

June 17, 2015

Mishaal Aleem (UW) Visualization of DNS isoT Code Results June 17, 2015 1 / 22

Outline

1 Objective

2 Background

3 Methodology

4 Results

5 Summary & Future Work

6 Acknowledgments


Outline

1 Objective

2 Background

3 Methodology

4 Results


6 Acknowledgments


Objective

Research Topic

Research visualization methods for the results of a direct numericalsimulation (DNS) code of droplet-laden isotropic turbulence. Create3-dimensional plots and animations given varying input parameters.

The importance of CFD visualization:

Humans are highly visual creatures and process information based onwhat they see

65% of humans are visual learners [1]The brain processes visual information 60,000 times faster than text [2]40% of all nerve fibers connected to a brain are linked to the retina [2]

Visualization of data is an important part of the validation of thecomputer methods and the physics/math used in the modeling

Visuals can provide insight that may be hard to deduce from theenormous data sets created from a CFD computer code


Outline

1 Objective

2 Background

3 Methodology

4 Results


6 Acknowledgments


Background

Non-evaporating droplet-laden isotropic turbulence

At the initial time, droplets are at rest

Once the simulation begins, droplets interact with turbulence andwith other droplets

Applicable to combustion engine theory

Developed by Michael Dodd (University of Washington)


Outline

1 Objective

2 Background

3 Methodology

4 Results


6 Acknowledgments


Methodology: Set-up I

Compare single phase (droplet-free) case to multiphase(droplet-laden) cases

Compare multiphase cases of various Weber numbers

Weber NumberDimensionless number used where there is an interface between two different fluids,especially for multiphase flows with strongly curved surfaces [3]

We =ρv 2l

σ(1)

ρ = density of fluidv = velocityl = characteristic length (droplet diameter)

σ = surface tension


Methodology: Set-up II

The visualizations look at the following droplet characteristics:

Droplet Surface (Volume of Fluid = 0.5)

Droplet Velocity (Calculated in post-processing)

The visualizations also consider the following qualities in the domain:

Turbulence Kinetic Energy

Turbulence Dissipation (∼SijSij)

Λ2

Enstrophy

Pressure Transport


Methodology: Post-Processing

Velocity vectors of the droplets were calculated in Python using ascript from Michael Dodd, created for the 2015 JFM paper, modifiedfor the 3D case

Stored the velocity vector data as simple text files and opened themin the visualization tool


Methodology: About VisIt

VisIt

Open Source,interactive, scalable,visualization, animationand analysis tool

Can be used to visualizescalar and vector fieldsdefined on 2D and 3Dmeshes

Designed to handle verylarge data sets

HDF5 Reader

Plug-in for to handle the.h5dns code output files

Developed by Darren Adams(University of Illinois)


Methodology: VisIt Process

Creating Plots

Use the GUI to set upplots, including recordingcommands and savingthe corresponding outputPython script(“Command” option)

Using the recorded codesand referring to the VisItPython manual, createcomplete Python scriptsthat will make all plotsdesired (both Webernumber cases at varioustime steps)


Outline

1 Objective

2 Background

3 Methodology

4 Results


6 Acknowledgments


Initial Plots

Figure 1 : We=0.1, t=1, greendroplets and red Λ2 = -50iso-surfaces, full domain

Figure 2 : We=5, t=1.5, opaquewhite droplets and red Λ2 = -50iso-surfaces, background enstrophycontours, 1

64 domain


Final Plots - Examples I

Figure 3 : We=0.1, t=2.25, whitetransparent droplets and redΛ2 = −50 iso-surfaces, full domain

Figure 4 : We=5, t=2.25, whitetransparent droplets, red Λ2 = −50iso-surfaces


Final Plots - Examples II

Figure 5 : We=0.1, t=1.5, whitetransparent droplets, red TKE =0.01 iso-surfaces, grey dropletvelocity vectors, 1

64 domain

Figure 6 : We=5, t=1.5, whitetransparent droplets, red TKE =0.01 iso-surfaces, grey dropletvelocity vectors, 1

64 domain


Final Plots - Examples III

Figure 7 : We=0.1, t=1.5, whitetransparent droplets, red Enstrophy= 150 iso-surfaces, grey dropletvelocity vectors, 27

8000 domain

Figure 8 : We=5, t=1.5, whitetransparent droplets, red Enstrophy= 150 iso-surfaces, grey dropletvelocity vectors, 27

8000 domain


Final Plots - Examples III

Figure 9 : We=0.1, t=1.5, whitetransparent droplets, red ptr =0.015 iso-surfaces, blue ptr = -0.015iso-surfaces, grey droplet velocityvectors, 1

64 domain

We = 5 case is still beingcomputed on Hyak ...


Outline

1 Objective

2 Background

3 Methodology

4 Results


6 Acknowledgments


Summary & Future Work

Summary of completed work:

Introduced to the research topic, CFD, the importance of visualization

Explored the fundamentals of CFD: Linux operating system, supercomputing

Understood the particular scenario being simulated in the code:droplet-laden isotropic turbulence

Updated a post-processing method to calculate droplet velocity vectors

After various iterations, created snapshots of the DNS code results givenvarying Weber numbers at 4 time steps using VisIt visualization software

Future work to be completed:

Create a 3-minute long animation that explores the quantities described

Include side-by-side videos of single-phase and multi-phase casesInclude side-by-side videos of various Weber numbers

Submit the animation to the American Physical Society - Gallery of FluidMotion 2015


Outline

1 Objective

2 Background

3 Methodology

4 Results


6 Acknowledgments


Acknowledgements

Advisors− Prof. Antonino Ferrante

− Michael Dodd

Computing− University of Washington Hyak

− NSF XSEDE Maverick

References

[1] Why Infographics RuleForbeshttp://www.forbes.com/sites/tjmccue/2013/01/08/what-is-an-infographic-and-ways-to-make-it-go-viral/

[2] Statistics on Visual LearnersStudyMode - KdyiamShttp://www.studymode.com/essays/Statistics-On-Visual-Learners-1211593.html

[3] Weber NumberThe Engineering Toolboxhttp://www.engineeringtoolbox.com/weber-number-d 583.html


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