SimScale CAE Forum

Cannot find the solution to error message - basic CFD analysis


#1

The project I’m working on can be found here:
https://www.simscale.com/projects/raulab22/firstcfdflow_containmenttank/
"FirstCFDflow_ContainmentTank "

I am a senior studying Mechanical Engineering at the U of Colorado. I am new to the SimScale program.

I have successfully been able to complete the tutorial that walks you through a CFD analysis of a pipe. However when I try to apply what I learned on my actual part file I am testing I get an ERROR when trying to simulate it. It tells me to check my solver log or my event log. My event log only says the project was prepared successfully and then it tells me that “An error occurred”. I have tried changing settings within timestep menu and I keep getting the same error.

What could I be doing wrong? Perhaps someone can open my part file and see if you are able to make it run? I have tried running by tweaking the time step settings over 10x and am not sure what else to try.

Very simple boundary constraints:
-Fully developed, incompressible Water flowing through device through those 4 inlet tubes.
-Inlet Flow rate at 500 000 in^3/sec
-Outlet Pressure at 0 kPa

Any suggestions or advice would be helpful,

Thank you


#2

Hi @raulab22!

The geometry you have is not watertight in the first place for the mesh to be properly done. I assume you have the inlets as described and the outlet is not very clear to me because how would your flow be lead to the outlet? This is not quite clear to me. @Get_Barried & @vgon_alves , any hints from your side?

Best,

Jousef


#3

Hi @raulab22,

What Jousef mentioned is correct. While it understandable that you want the top to be “exposed” to free air and act like its in the open, but you still have assign a boundary condition and enclose the top. Geometry wise, ensure that you have a cover at the top that allows the internal space to be watertight. The solver needs to be able to differentiate between internal and external flow so this is important. Once the meshing is done with the cover, you can assign the top Boundary Condition as custom boundary condition with all parameters set to zero gradient.

Hope this helps.

Cheers.

Regards,
Barry


#4

So as a followup, how exactly does one assign a boundary condition to enclose an open top of a container? I understand what you mean but being so new to program I am not sure how to go about this. The only options for B.C. is Velocity (inlet/outlet), Pressure (inlet/outlet), wall, symmetry, periodic, wedge, custom (which allows to customize options for those previously listed).

Thanks
@Get_Barried or @jousefm @vgon_alves


#5

Hi @raulab22!

To give more details about this it would be good to have a schematic drawing or something similar that shows how you want the flow to move because what I have seen from the setup it will be sort of “pumped” between the walls if I am not mistaken? Once you tell us how you intend to do the simulation we can give you further tips on how to efficiently improve the geometry.

Cheers,

Jousef


#6

Hi @raulab22,

Apologies for the delayed reply. Sometimes the weekend vibes get the jump on me and I don’t reply till Monday :stuck_out_tongue:.

To assign a top BC, you first have to enclose the top in CAD. Just a simple surface that allows you to assign something to it will do. Nothing complex. However, what Jousef has pointed out is important observation. Where is your flow going to exit to simulation? Do you plan to let it “overflow”? What is the objective? There is a need to know this before deciding what to assign.

Cheers.

Regards,
Barry


#7

Completely understand, the weekend puts everything on pause.

To give more detail of how system should work:
The 4 inlets are super high pressure water (Flowrate larger in magnitude than a firefighter’s hose).
The idea is that the pressure in the fluid be dissipated by producing a “vortex” like flow inside that large tube in the center. After the vortex begins (This happens under 0.5 seconds), the fluid will exit into a box containment device to be emptied. The valves will only be on for approx. 4-5 seconds so the containment box is enough for fluid.

-Inlet Flow rate at 500 000 in^3/sec (This is maximum)… I realize this is abnormally high, but I would like to test this with 1/4 flow rate, then 1/2 flow rate… and if the simScale servers can withstand the FULL flowrate I will make my team VERY happy as we have a deadline for this coming up in the next two days !! My full attention is on trying to make this work.

Let me know if that is clear or if you have further questions.

ALSO: Since we last spoke I added ‘LIDS’ to make the inlet and the top watertight for simulation. I just hope the system knows I would like to know if any water escapes through the top.


#8

The ‘objective’ of this simulation is to see how the water flows, how much of it is contained in the box without escaping out the top. I would like to generate an animation to show to my team and senior design instructors.

Since the flowrate (and consequently fluid pressure) are extremely high I would like to model this first with 1/4 flow rate and then up until reaching the full flowrate.

Deadline for this simulation is in the next day for my team. Hope to hear back soon! Appreciate all your help on this everyone.


#9

Hi @raulab22,

Then this would probably be a transient simulation and you will probably need to use some other analysis type such as multiphase.

Unfortunately, I do not have a lot of experience with multiphase, but your simulation is relatively simple so I suggest checking out some public projects to see how they setup the simulation.

Cheers.

Regards,
Barry