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November 3, 2008, 07:46 |
Hello World.
I made a stran
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#1 |
Senior Member
Sebastian Gatzka
Join Date: Mar 2009
Location: Frankfurt, Germany
Posts: 729
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Hello World.
I made a strange experience some days ago. I started a two-phase-flow simulation not knowing how long it will take so reach its final equilibrium state. My first, second and third guesses of the simulation time were too short. In all cases I restarted the calculation by putting the latest time into the startTime entry. Due to insufficient disc space I had to recalculate the simulation on another system. As a matter of fact I knew the correct simulation time and simulated straight from 0 to the final timestep. I compared a characteristic value of the two simulations (magU in this case) and found that they differ over time! Interrupted simulation: Continuous simulation: Strange to me are the tree peaks at the interrupted simulation plot. They are not exactly at but following a short time after the three interruption-times. What went wrong? Did I made something wrong?
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Schrödingers wife: "What did you do to the cat? It's half dead!" |
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November 3, 2008, 09:18 |
did you write your data as asc
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#2 |
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Niklas Nordin
Join Date: Mar 2009
Location: Stockholm, Sweden
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did you write your data as ascii or binary?
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November 3, 2008, 11:49 |
Ascii in both cases.
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#3 |
Senior Member
Sebastian Gatzka
Join Date: Mar 2009
Location: Frankfurt, Germany
Posts: 729
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Ascii in both cases.
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Schrödingers wife: "What did you do to the cat? It's half dead!" |
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November 3, 2008, 13:27 |
Use binary, and run in double
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#4 |
Senior Member
Francesco Del Citto
Join Date: Mar 2009
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Use binary, and run in double precision.
Your restart will behave much better! I guess this is what Niklas was thinking of... Francesco |
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November 3, 2008, 14:29 |
It is http://www.cfd-online.co
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#5 |
Super Moderator
Niklas Nordin
Join Date: Mar 2009
Location: Stockholm, Sweden
Posts: 693
Rep Power: 29 |
It is
restarting in ascii files is nasty business. You lose alot of the accuracy, which you just have witnessed I guess. I still remember the trouble I faced when I was implementing the spray and saved the data in ascii... If a drop is close to a face it might actually end up in another cell when you do a restart, because of the round-off errors. would be nice to see what you got when you use binary. |
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