Learning Forum

[adarsh thakur]

Hi, I want to simulate fluid flow transfer from one tank to another tank in zero gravity environment ( creating a space environment) , i have done some simulation of fluid flow transfer by just switching off the gravity but its not creating this environment. my aim is to transfer the fluid by using moving piston in zerogravity condition. Can you please help me out, what should i do to simulate this model. Thank You

[Rob]

Do you need to include the gas part? If not then layering should do it but you'll need to be careful to link the two pistons. 

Turning gravity off (or rather leaving it off) removes the gravity term from all equations. 

[adarsh thakur]

Yeah I need to include gas also, and by turning off the gravity does it make space environment into the system, or something extra requirement is there. And is moving meshing is also required here?

[Rob]

You need to decide if gravity is off, or a small value. What does the gas do in your model? Ie sketch out the full system and add all boundary information: that's your plan for the modelling work. 

Re the moving mesh, yes, if you want both gas volumes you still need moving mesh but also then need to account for gas expansion. Set up is not too disimilar but the physics will be harder to converge. 

[adarsh thakur]

Yes one side tank has compressed gas which gives pushing action at the expanse of its expansion to piston due to which fluid starts to transfer into another and other tank gas gets compressed. I  just want to know how this phenomenon will effect in antigravity space.How to model this please help me out.

[Rob]

OK, so what drives the liquid after the higher pressure tank equalises with the other side? 

The only difference between gravity on/off is you won't see any natural convection in the system. 

[adarsh thakur]

we only have fill other tank once, but total fluid of left tank should transfer to another so right one is kept smaller in size compare to left tank. Means piston should at the lower most position in left tank.  

[Rob]

Is the piston driven by the gas, or by some external force? Just trying to figure out exactly what you need to include. Otherwise, you can add layering to all three fluid regions but need to ensure the liquid volume remains constant: that then suggests you may need at least 1DOF motion UDF. 

[adarsh thakur]

yes piston is driven by gas.

[Rob]

OK, and why does it move? Ie why would the gas force the piston to move at that specific time?

[adarsh thakur]

Because to fill the other tank, our main aim is to fill the other tank. So some external force is required to transfer the fluid that's why pressurized gas will be use.

[Rob]

But why do you then need the gas side? The force can be assigned as a fixed motion. We can model all of it, but without a clear picture of what, why and how the real system works all I can say is use 1DOF and UDFs: they're covered in the documentation. 

[adarsh thakur]

Sir in actual working refueling system compressed gas is used to give a motion to piston, we need to see how gas and fluid both behave in zero gravity that's why I need to add gas also.

[Rob]

So you'll need two instances of 1DOF to control the piston motion based on pressure, and three fluid zones. 

[adarsh thakur]

how to do this sir can you provide me more insights

[Rob]

Have a look here,  https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v232/en/flu_ug/flu_ug_sec_dynamic_using.html   You'll need to control the motion using 6DOF (1DOF) and remesh using layering. There are some examples in the wider Help, and if you look for the incylinder models (car engines) you'll get more tips.