Hello,
I am designing a contraction for a water tunnel. I have attached the model in the post.
I am running into the error: unresolved boundary condition at inlet flow boundary condition. Can someone please tell me what I am doing wrong?
I have meshed half the contraction and have assumed symmetry in x-axis for the other half. Is that ok?
My initial conditions are set to zero. Is that ok?
Sorry, I am fairly new to this. The tutorials and online help has got me this far, but now I am stuck.
several issues
1. start a bit simpler, merge all your bodies together, don't worry about the lids being separate
2. i think you're trying to apply pressure and volume flow rate on the same face, this isn't possible, lots of good posts about this. pressure pressure or volume/velocity and pressure are your options for inlet/outlet combos.
3. you have faces that aren't in the comp domain selected for your volume flow rate which is why you're getting the unresolved bc. (you have faces that aren't in the flow stream selected.
4. if you really have real walls, don't forget to select the radiused faces
Thank you for the reply. I appreciate it.
Thank you for 1, 2 and 4, will get working on that!
Regrading No. 3, I did the computational domain in order to utilize the symmetry at the middle plane. In that case, do I have to apply the constraints only to half of the inlet and outlet? Is there a way to do that?
Appreciate the help!
The symmetry faces are ok, they are in the comp domain.
It's the faces on the edge faces of the one part that aren't.
Thank you for that clarification.
I have added the updated part file.
I still can't add the top left (in the symmetry computational domain) to the real walls.
Also, the flow rate and the output velocity seem to be missing the symmetry aspect i.e. with the given flow rate, I should have got around 5 m/s, but I get 10 m/s, because the inlet flow only gets applied to half of the face. Am I understanding the symmetry of the computational domain in the wrong sense? I was trying to save computing time by only including the half model. I thought the final results would include the whole model.
Secondly, the Z-velocity shows no fluctuation at all! I find that hard to believe. There ought to be some variation, especially near the walls and corners. Am I missing something?
Your inlets have to compensated for in the bc magnitude. Ie half model, half flow rate.
Also results cannot be plotted on the comp domain that is cut out.
Is the error gone now? What error do you get adding the real wall?
As for the z results, what are you plotting and where?
The errors are gone! Thanks for that help!
The symmetry makes sense to me now. I might actually have to do a whole model analysis.
I am plotting the z-velocity at the outlet (i.e. the smaller opening). I created a surface plot at the LID 2 face. The z-fluctuations were non-existent. Is that because the flow has to follow continuum assumption (it is along flow stream) and water is incompressible? Maybe, the x and y velocities might show more fluctuations.
I just expected to get more fluctuation in z-velocity. The surface plot max and min were being shown as the same to the 6th decimal point.
What type of boundary condition do you have applied there?
What amounts if fluctuation are you expecting?
Is z the flow in/out of he unit?
Don't have access to a system to look at your files so screenshots would be very helpful.
Attached are the screenshots.
BC: 1. outflow volume flow of 2200 gpm
2. total pressure at inlet
3. four real walls (and fillets)
I was expecting at least a range of 0.5 m/s difference (but I could be wrong here)
In the velocity screenshot, you can see the legend does not show any change. It stays at 11.863 m/s. The decimal points after the shown digits were the same as well. So, there were no z-fluctuations at all. The color change represents a change in the 7th decimal point or lower.
Vorticity and TI makes sense. However, it is surprising that TI is not the minimum in the middle of the section, but the bottom wall.
Last question, should my computational domain be as big as I have used? Or should be just enough to cover the model?
By defining outlet flow rate, you set the velocity. So it will remain constant. Only a pressure outlet would have a different profile. This is more recommended by the developers.
Comp domain for internal analysis is automatically set so no need to change.
Have you reviewed the definition of ti? What do you have to compare it against?
Yeah, I realized my assumption for z-velocity did not really made sense. The plots are much more reasonable when I look at the complete Velocity value and the normal velocity vectors.
For TI, I was just basing it on the fact that the fluid in the center would supress the most; and, thus should have the lowest TI values. However, that could be a wrong line of reasoning.
Either way, the plots are looking much better
Thank you for all the help!
By defining outlet flow rate, you set the velocity. So it will remain constant. Only a pressure outlet would have a different profile. This is more recommended by the developers.
Comp domain for internal analysis is automatically set so no need to change.
Have you reviewed the definition of ti? What do you have to compare it against?