update on cast cfd simulations ideas for coherence length parameterization and tuning windows...
DESCRIPTION
Problem1: Short length for tilted sims Tilted Simulations can have very short length due to hydrostatic pressure differenceTRANSCRIPT
![Page 1: Update on CAST CFD Simulations Ideas for coherence length parameterization and Tuning Windows Temperatures 06.08.2013 Cenk Yildiz](https://reader033.vdocument.in/reader033/viewer/2022051202/5a4d1b767f8b9ab0599b75ff/html5/thumbnails/1.jpg)
Update on CAST CFD Simulations
Ideas for coherence length parameterizationand
Tuning Windows Temperatures
06.08.2013 – Cenk Yildiz
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Part 1:Coherence Length
Parametrization
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Problem1: Short length for tilted sims• Tilted Simulations can have very short length
due to hydrostatic pressure difference
![Page 4: Update on CAST CFD Simulations Ideas for coherence length parameterization and Tuning Windows Temperatures 06.08.2013 Cenk Yildiz](https://reader033.vdocument.in/reader033/viewer/2022051202/5a4d1b767f8b9ab0599b75ff/html5/thumbnails/4.jpg)
Problem1: Short length for tilted sims• One should be able to use the rest of the profile
(with different photon mass)
![Page 5: Update on CAST CFD Simulations Ideas for coherence length parameterization and Tuning Windows Temperatures 06.08.2013 Cenk Yildiz](https://reader033.vdocument.in/reader033/viewer/2022051202/5a4d1b767f8b9ab0599b75ff/html5/thumbnails/5.jpg)
Solution• Remove effect of hydrostatic pressure from the profile(remove the tilt)• Calculate coherence
length for DST=1E-3• Use the coherence
length, P_CB and Peng-Robinson equation(or Refprop) to calculate the density at any point inside this length.
• Calculate conversion probability integrating through the whole length. (effective photon mass will be a function of length)
• The cost will be computing time.
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Problem 2: How to find length for any angle• How can we parametrize the length for
(pressure, angle)?• How can we chose model for intermediate
angles:– The horizontal simulations use laminar model on
both MFB,MRB– Tilted simulations use half Laminar model
(MFB:laminar, MRB:turbulent)
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• Comparing different models:Problem 2: How to find length for any angle
Big difference in laminar side
Tiny difference in turbulent side
Very big difference from tilted to horizontal simulation
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• Comparing different models:Problem 2: How to find length for any angle
Note that for angles < 1deg, half Laminar simulations
doesn’t converge! (under investigation)
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Solution
• Simulating -6,-3,-1,0 degree for all pressures, and do a 2 dimensional fit for pressure – angle?
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Part 2:Tuning Windows
Temperatures
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Reminder…
• Laminar horizontal, and Half Laminar tilted simulations gives the closest pressure difference when tilting, thus is the model we chose for cold windows.
• Windows Temperature values and change in windows temperature while tilting is worse.
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Reminder: Comparison of Pressure Change
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Reminder: Comparison of Change in TMFB
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Reminder: Comparison of Change in TMRB
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Update: Changing CW Boundary Condition
Set to 130K
instead of 90K With this change, simulated temperatures are closer to experimental temperatures
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Comparison of Temperatures(only laminar/half Laminar models)
T-MFB
T-MRB
Horizontal(Laminar) Tilted(Half Laminar)
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Comparison of Change in TMFB
BC=130K
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Comparison of Change in TMRB
BC=130K
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Pressures and Coherence Length
• Pressure change is within 0.03mbar of old boundary condition(Only for 98 mbar change in pressure is 0.13mbar higher)
• Gas is pushed more to inside, the coherence length is smaller– Around 0.5m for horizontal cases(laminar)– Around 0.2m for tilted cases(half laminar)
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Conclusion
• Coherence length:– We need to use a new method to be able to use
the whole length in the tilted cases.• With new Temperature boundary condition:– Temperatures are closer to experimental values.– Temperature change during tilting is worse.– Coherence length differs in order of 0.1-0.5m– We can always fine tune temperatures to reach
the experimental data, but is there a point?