when i scale down the down the geometry i get unrealistic result.what is the problem?

rupak504 · July 30, 2018, 06:27

I am using Ubuntu -14.04, OpenFOAM-4.0, model- multiphaseInterFoam- DamBreak4phase.

I get the result when i use the tutorial as it is, problem starts when i scale down the geometry from metres to millimetres, i get unrealistic results. What could be the problem?

RobertHB · July 30, 2018, 11:02

How do you "scale down"? Did you remember to scale your dimensionless groups accordingly?

rupak504 · July 31, 2018, 06:39

I will post the videos of the two cases. Then you give me the feedback

RobertHB · July 31, 2018, 07:27

That's a beginning, but the more interesting informationen would be

What do you want to simulate?
How does your simulation setup look like?
Which parameters do you need for your simulation? Please name them and their value for both scales.
Which solver are you using?

Anything that may help us to help you. A video is only a small help, if any, i guess.

kandelabr · July 31, 2018, 07:36

Release a droplet on the table or pour a bucket of water on the floor - the result isn't the same.

You have to keep Reynolds number when scaling cases (geometry/viscosity/velocity). In any case, some results will scale linearly, other results won't...

July 30, 2018, 06:27	when i scale down the down the geometry i get unrealistic result.what is the problem?	#1
rupak504 Senior Member Lolita Join Date: Aug 2016 Posts: 115 Rep Power: 9	I am using Ubuntu -14.04, OpenFOAM-4.0, model- multiphaseInterFoam- DamBreak4phase. I get the result when i use the tutorial as it is, problem starts when i scale down the geometry from metres to millimetres, i get unrealistic results. What could be the problem?

July 30, 2018, 11:02		#2
RobertHB Senior Member Robert Join Date: May 2015 Location: Bremen, GER Posts: 292 Rep Power: 11	How do you "scale down"? Did you remember to scale your dimensionless groups accordingly? rupak504 likes this. __________________ If you liked my answer to your question, please consider leaving a "Like" in return

July 31, 2018, 07:27		#4
RobertHB Senior Member Robert Join Date: May 2015 Location: Bremen, GER Posts: 292 Rep Power: 11	That's a beginning, but the more interesting informationen would be What do you want to simulate? How does your simulation setup look like? Which parameters do you need for your simulation? Please name them and their value for both scales. Which solver are you using? Anything that may help us to help you. A video is only a small help, if any, i guess. Last edited by RobertHB; August 1, 2018 at 03:00. Reason: Edited bullet point 3 to not only ask for parameters but also for their values on both scales.

July 31, 2018, 07:36		#5
kandelabr Senior Member Nejc Join Date: Feb 2017 Location: Slovenia Posts: 196 Rep Power: 9	Release a droplet on the table or pour a bucket of water on the floor - the result isn't the same. You have to keep Reynolds number when scaling cases (geometry/viscosity/velocity). In any case, some results will scale linearly, other results won't... SRKR likes this.

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July 31, 2018, 06:39		#3
rupak504 Senior Member Lolita Join Date: Aug 2016 Posts: 115 Rep Power: 9	I will post the videos of the two cases. Then you give me the feedback