Yade

sign of flow.bndCondValue

Asked by azim

Dear all,

my question is about the sign of flow.bndCondValue in:

bndCondValue=[-x,+x,-y,+y,-z,+z]

What is the difference between [0,1000,0,0,0,0] and [0,-1000,0,0,0,0]????

what is the rule?
for example like the rule for stress: compression stress= - tension stress= +

thanks,

Azim

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Robert Caulk
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Best Robert Caulk (rcaulk) said : 		#1

Hello,

bndCondValue [1] will prescribe pressure if the boundary condition is indicated as pressure [2]. Otherwise, the flux will be zero.

>What is the difference between [0,1000,0,0,0,0] and [0,-1000,0,0,0,0]????

Since these values are the imposed pressure, 1000 would be imposed as a positive pressure value, and -1000 would be imposed as a negative pressure value.

Cheers,

Robert

[1]https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.FlowEngine.bndCondValue
[2]https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.FlowEngine.bndCondIsPressure

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azim (mirzavand) said : 		#2

Hi Robert,

thank you for your reply. it really solved my problem but, I want to be more sure, so:

1)what if I set the bndCondValue like below????
flow.bndCondIsPressure=[1,1,0,0,0,0]
flow.bndCondValue=[1000,-1000,0,0,0,0]
what would be the cumulative effect of imposed pressure in x direction???

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Robert Caulk (rcaulk) said : 		#3

Hello Azim,

>what would be the cumulative effect of imposed pressure in x direction???

I suppose your block would have pressure delta of 2000 along the x direction.

I should say that I have not used negative pressures in Yade, so I am unsure if Yade handles them correctly or not (I see no reason why it would not handle them well). Let me know what you find out!

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azim (mirzavand) said : 		#4

Hi Robert,

thank you.
I have a problem in using FlowEngine as explained here:

https://answers.launchpad.net/yade/+question/662276

after solving the problem I will check it, and let you know.

thanks again

Azim

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azim (mirzavand) said : 		#5

Thanks Robert Caulk, that solved my question.