I have a tube ( smaller dia) in a system through which vacuum pump is pulling the air . Also air is being blown from outer nozzle (bigger dia). I have specified the side to which vacuum pump is attched as static pressure BC. My model ends at the pipe. Is that BC right as immediately after the boundary you have air which is at atmospheric pressure ?
Do you think I can have use a external fan boundary condition with pressure increase from vacuum setpoint to atm pressure? Regarding the flow, i can have a constant flow which is equal to that of vacuum pump.
Modeling the pump will do but it will take time.
fan or outlet volume flow rate should work
Jared, I have used fan B.C . This fan switches on at certain time and stays for some milliseconds. I have defined a new fan with a fan curve and assigned to the B.C. I have also given pressure values with time which in this case is the value of the vacuum at the boundary. But, I dont see flow happening at the boundary. Am i defining fan right ?
you have 2 boundary conditions applied on the same face? i'm not really following what your setup is
also how are you measuring flow rate
regardless, i don't think you can do what you want to do. it may have allowed you to do it but i don't think you can have a zero flow at an outlet
what is your goal on this analysis?
Thank you Jared. Outflow boundary condition with varying flow with time solved the problem (though its an approximation). I was not using it earlier as generally solvers are not stable having inflow and outflow boundary conditions together.
I have some general queries.:
1. By default (ie. if i dont specify wall BCs) does solidworks assume the wall as slip wall and adiabatic?
2. If i assign a wall as real wall (without specifying the h or T ), what does it do ?
3. if i specify a real wall with roughness, does it calculate h based on roughness ? I am trying to understand how roughness influences the thermal boundary layer. One for sure, the flow might become turbulent based on roughness. Am i missing something here?
inflow/outflow > i'm not sure what you mean here, as long as you can conserve mass, the solver doesn't really care.
1. all walls are real by default unless you make them ideal/adiabatic
2. i don't think it would do anything, have you tried it?
3. i do believe that h is affected by roughness, i'd suggest checking the kb, help and tech reference or running a test to confirm
"all walls are real by default unless you make them ideal/adiabatic" by that do you mean it assings certain roughness or default h to wall ?
The reason I am asking this question is that there are so many surfaces in my model. It is difficult to assign h for each surface.
What do you sugest ? tweaking with roughness inorder to improve the results?
why do you want to apply h?
I have to use convective boundary condition at outer walls as it is external flow .
i'm not sure i'm following
is this an internal or external analysis?
are you using heat condition in the solids only or not?
if it is an internal analysis, you can set the default wall condition on the outside to be what the majority is and then just override the ones that are different. note, roughness is not used here.
if you have an external analysis, you generally would not apply any h values, they are calculated as part of the CFD
Thanks man. Looking back, I think my head was not clear while posting the query.
I am using external analysis and I havent applied it.
why not make your vaccuum pump and outlet volume flow rate? it is not ideal as outlet volume flow rates are not recommended by the developers but should make your BCs more straight forward.
if you want to go with a pressure, you need to use the BC condition that you know. if you have static, apply static. if you have total, put in total. and remember to generate a flow rate, there needs to be a difference between atm and the outlet. and also that solidworks works in absolute pressure, not gauge.