7 Replies Latest reply on Aug 23, 2017 5:42 PM by Tim Besser

# How to give variable input(Ex- temp as a fn of time)as the inlet BC in solidworks flow simulation???

Hi how to give variable input as the inlet boundary condition in solidworks flow simulation.  Dependency is available only for external flow analysis. Is there any related thing for Internal analysis??

• ###### Re: How to give variable input(Ex- temp as a fn of time)as the inlet BC in solidworks flow simulation???

Hi,

I also have the same question. Is it possible to set a variable in the equations editor and use that in Heat Source definiton?

More generally, how can a heat source be related to a variable, and how can one heat source's power rate be related to that of another? I have tried to find goals (dummy goals for tracking values, not for convergence) which could be used to track heat source power values but didn't succeed. Jerry

• ###### Re: How to give variable input(Ex- temp as a fn of time)as the inlet BC in solidworks flow simulation???

variables in solidworks aren't used in flow

in your formula definition, you can link it to a goal, i've done it with success in the past, you'll ahve to elaborate on your workflow on what you're having trouble with. it would also help to describe your application and what you're trying to do.

• ###### Re: How to give variable input(Ex- temp as a fn of time)as the inlet BC in solidworks flow simulation???

Hi all,

I have had the same problem, and have found a workaround that functions fine for my purposes.

I basically needed an inlet boundary condition in a transient analysis with a temperature that depends on the heat flow through another surface in the model.

However, as I found, Flow Simulation only lets you define the inlet boundary condition either at a fixed temperature, or with a dependency that already can be defined a priori. It currently does not seem to be possible to directly define an inlet BC with a temperature (or other property) that reacts dynamically, depending on obtained calculation results on a given point/surface/volume during the calculation run during the transient analysis.

My workaround is as follows:

- Set up the inlet boundary condition with any given fixed temperature (e.g. 293.2 K)

- Specify a temperature goal and mass flow goal on the surface which should control the temperature of the inlet BC

- Specify an equation goal, which calculates the heat flow required to heat/cool the fluid from the fixed temperature (293.2K) to the intended end temperature. The equation goal is calculated using the mentioned temperature and mass flow goals.

- Set up a small volumetric heat source directly in front of the inlet boundary. The heat of the volumetric heat source is defined in a formula definition, depending on the equation goal (same window as shown on the bottom of Jerry's post above for a surface source)

This way, the fluid first enters the model at the given fixed temperature (293.2 K in my case), and is then heated/cooled by the volumetric heat source to achieve the intended temperature. The volumetric heat source of course needs to cover the whole inlet boundary, but does not need to extend very far in the direction of the flow (just large enough to be correctly represented by the meshing).

As I am running a calculation right now, I couldn't look into my model to double-check, so the above is out of memory. Your problem may not be 100% identical to mine, but maybe you can solve it in a similar manner. For what I needed, I have made good experiences with this workaround so far.

That said, I think it ought to be possible to set the boundary conditions within Flow Simulation directly to achieve the above, so this should definitely on the developers' to-do list for coming versions. After all, it is possible to set up such a dependency for a heat source, so why not for an inlet boundary condition?

In general, it should be possible to work with variables within Flow Simulation, and also to visualize these variables in the post-processing. I find that Flow Simulation is much too unflexible in this regard.

I hope the above was a little bit helpful to solve your problems.

Best regards,

Martin

• ###### Re: How to give variable input(Ex- temp as a fn of time)as the inlet BC in solidworks flow simulation???

Sounds reasonable. Very close to the physical case. Ie, you'd manage the temp change with a heater of some sort.

• ###### Re: How to give variable input(Ex- temp as a fn of time)as the inlet BC in solidworks flow simulation???

1. you need a time dependent solution

2. click the fx button and set the parameter as appropriate

• ###### Re: How to give variable input(Ex- temp as a fn of time)as the inlet BC in solidworks flow simulation???

Were you successful in using this technique?

• ###### Re: How to give variable input(Ex- temp as a fn of time)as the inlet BC in solidworks flow simulation???

I have a simulation that I need to run where there are multiple mass flow rate outputs points and each point consumes a variable amount over time.

EG:

Point one: Run time-1:00, consumes  30cc to Run time-1:15, then stop.

Point two: Run time-1:05, consumes 20cc to Run time-1:10, then stop.

...

Is there a way to simulate this in solidworks flow?

If you need any more information just let me know.

Any suggestions or ideas are welcome.

Thanks