How to make immersed solid not cross wall(boundary)?

NCKU5566 · May 12, 2018, 04:40

Greetings everyone!
I am still a beginer in CFX and there is nobody to ask around me, so please forgive me for asking stupid question.

I was simulating a ball free fall in a tank with full water(2.5D,with bouyancy.). The initial condition in the fluid domain and the ball(immersed solid with rigid body motion) is stationary. The top, bottom, left and the right boundary is no-slip wall, the front and the behind wall is symmertry.
Here is the issure i have encountered：when the ball(cylinder) touched the bottom, the ball should be stopped, but it was not! It just cross the no-slip wall and keep going out of the fluid domain(even though there is no mesh out side the fluid domain). Let me show you some picture

figure. 1

figure. 2

figure. 3

figure. 4

The figure. 1 is the initial state; the figure. 2 is the situation i have mentioned; the figure. 3 is that i added a solid retangular at the bottom(not work). And~~~the figure. 4 is that i removed the gravity, left the bouyancy only(final state). You can see that the top wall was woking!!!! But why the bottom wall was alway not working?
All the wall's mesh motion is shown in the figure.5

and the "wall. vel. ref. to" , i have tried "mesh motion" and " boundary fram", but both of them wasn't working.

Is any one had this problem before? if so, how do you solved this problem?

NCKU5566 · May 14, 2018, 00:02

sorry, i dont know why the image didn't show up.
https://imgur.com/a/lsCV2vr
https://imgur.com/a/SV7ZC4P
https://imgur.com/a/R779NzR
https://imgur.com/a/uzqyapJ

urosgrivc · May 14, 2018, 02:04

this should work with imersed solid yes,

Where is your water surface0 => (watervolumefreaction plot)? this might be the problem.
How do you initialize your domain? you should initialize the water location
othervise the water will be dispersed throughout the domain and it will take some time to setle dovn due to gravity till then the ball will drop through the botom of the tank.

The simualtion will work, you just need to sort some things out.

It could be also the timestep problem or mesh resolution.

May 12, 2018, 04:40	How to make immersed solid not cross wall(boundary)?	#1
NCKU5566 New Member MarkTang Join Date: Feb 2018 Posts: 5 Rep Power: 8	Greetings everyone! I am still a beginer in CFX and there is nobody to ask around me, so please forgive me for asking stupid question. I was simulating a ball free fall in a tank with full water(2.5D,with bouyancy.). The initial condition in the fluid domain and the ball(immersed solid with rigid body motion) is stationary. The top, bottom, left and the right boundary is no-slip wall, the front and the behind wall is symmertry. Here is the issure i have encountered：when the ball(cylinder) touched the bottom, the ball should be stopped, but it was not! It just cross the no-slip wall and keep going out of the fluid domain(even though there is no mesh out side the fluid domain). Let me show you some picture figure. 1 figure. 2 figure. 3 figure. 4 The figure. 1 is the initial state; the figure. 2 is the situation i have mentioned; the figure. 3 is that i added a solid retangular at the bottom(not work). And~~~the figure. 4 is that i removed the gravity, left the bouyancy only(final state). You can see that the top wall was woking!!!! But why the bottom wall was alway not working? All the wall's mesh motion is shown in the figure.5 and the "wall. vel. ref. to" , i have tried "mesh motion" and " boundary fram", but both of them wasn't working. Is any one had this problem before? if so, how do you solved this problem? Last edited by NCKU5566; May 12, 2018 at 08:49.

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May 14, 2018, 00:02		#2
NCKU5566 New Member MarkTang Join Date: Feb 2018 Posts: 5 Rep Power: 8	sorry, i dont know why the image didn't show up. https://imgur.com/a/lsCV2vr https://imgur.com/a/SV7ZC4P https://imgur.com/a/R779NzR https://imgur.com/a/uzqyapJ

May 14, 2018, 02:04		#3
urosgrivc Senior Member urosgrivc Join Date: Dec 2015 Location: Slovenija Posts: 365 Rep Power: 12	this should work with imersed solid yes, Where is your water surface0 => (watervolumefreaction plot)? this might be the problem. How do you initialize your domain? you should initialize the water location othervise the water will be dispersed throughout the domain and it will take some time to setle dovn due to gravity till then the ball will drop through the botom of the tank. The simualtion will work, you just need to sort some things out. It could be also the timestep problem or mesh resolution.