My use of SimCFD is limited to fluids in closed volumes and I am always concerned about results accuracy. Mesh design is a key to good accuracy. I recently learned that the mass flow rate for the input and output is actually logged in one of the multitude of files the program generates. Since mass should to be conserved, the values should be very close.
I'd like to see this information as an output in the message window when the run of a study finishes so that a user doesn't need to go looking for it. It could be reported as a ratio to imply model accuracy and printed in a red font if outside of parameters (preferably user selectable). I can see the message suggesting that a study is really not complete, even if the study fully converged. It could direct the user to further iterations, tightening of convergence parameters or the addition of mesh. I could also see it being used to suggest that the user incorporate the adaptation features (perhaps to avoid starting the study from 0 with an all new mesh).
The majority of our CFD simulations are axisymmetric. The advantages of being able to analyze in 2D versus 3D are tremendous for us. Many of our parts are long tubes (40" to 100" long) with wall thicknesses from .031" to .062" and diameters from 1" to 4". Some tubes have a .0004" silver or copper plate on the OD or ID along its entire length. The plating has a significant impact on heat flow but the plating is impractical to model. This is because the plating is so thin compared to the tube wall thickness (77 to 155 times thinner) and because the plating is so long compared to its thickness (100,000 to 250,000 times longer), meshing causes the plating and the tube to have a godzillion elements.
The ability to select an edge and define it as a "surface part" and then to specify its thickness (example: .0004" thick) like we can do in 3D would be a great asset.
Often while checking the final meshcount I have to count the number of digits to make sure if the mesh is of the order of hundred thousands, millions or over 10 million. How about showing the number of elements by separating three digits with a comma? I know it's rather a trivial requiest but can come handy to quickly get the sense of enormity of mesh. There had been times where I have seen my colleagues submitting a job of 23 million mesh, thinking it was a 2.3 million mesh!
When we mesh our model, in the message window there is a sentence like this " creating volume mesh" i think loading bar (Percentage bar) must be in it so we can see when the mesh process will finish. Because sometimes meshing process takes too much time.
Ideally I'd like to have the surface meshing process to finish, even if it could not mesh a particular face, before the simulation aborts. So it could identify all surfaces with (mostly) too rough mesh sizes and put them into a geometry group which can finally be displayed and evaluated.
It is puzzling that while we are meshing, we have to give away a licence in solving, forcing us to stop the jobs running in the queue, just to be able to mesh. In most commercial CFD (or FEA) software packages that I know of, I see that meshing and solving are completely exclusive of each otherin a single licence.
Majority of time of every CFD engineer is occuppied in meshing at his workstation. At the same time, he can't finish his job unless these meshes are run, often in the remote cluster etc. Sorry if I sound rude, but is it me, or has Autodeksk really employed this unfair and unjust tactic to engage a solver licence in meshing, thereby indirectly forcing users to go for additional solver licences, so that they can continue both meshing and solving uninterrupted at the same time?
I know this may call for a major overhaul in code (or maybe not), but is it not reasonable to demand that "meshing" and "solving" be treated exclusive of each other?
In Simulation CFD 2013 we introduced mesh history in the design study tree. We're curious how this feature is working for you and what could make it better.
These are some of the suggestions we received prior to having the IdeaStation:
- Be able to add a surface/solid to a mesh history branch. I created the adjustment but forgot a surface/part that I wanted to include there. Drag and drop the branch onto a surface or part would be consistent with some of the other setup tasks.
- Reorder mesh history.. Right click > move up/move down
- When you delete the 'automatic size' level you do a rebuild you get a manual mesh. Interesting consequence, but you eliminate all your history. May want a warning when deleting the automatic size part of the history.
- When you right click on the surface/gap, length scale and go edit. Actually edit those. If you do it to surface it would switch it from false to true.. Length scale would open the diagnostics window.
Do you agree (+ kudos)? Do you have other ideas?
User Experience Designer
We require a good uniform mesh on fans and resistances, which can easily be forgotten by the user, causing poor results or poor convergence.
I tend to recommend 5 elements from inlet to outlet. Could this be automated in any way?
I can appreciate this would be a challenge for irregular resistances but for oblongs, possible?
I deal with a lot of circular geometries and thus I need to use cylindrical regions to refine small passageways in the model, these can be as small as 0.3mm. Hence I have the main fluid body at roughly 1mm manual mesh, and refine the small gap at 0.1mm. I use a cylindrical region for this.
However I do not need an entire cylinder at 0.1mm, and it would be great if I could refine just a disc shape to alleviate the density of the overall mesh. This is bearable for static runs, but for transient studies with motion as well, the computation time is seemingly infinite.
Rebuilding the mesh definition can be a useful workflow when you want to modify the mesh history and perform sensitivity studies. One issue that slows down this workflow is that if you have mesh refinment turned on before you rebuild the setting is lost.
I think it would reduce the chance of error if when if you rebuild it reuses this setting and when the edge sizing is finished the surface refinement is automatically applied as well so you don't have to click on refine again to eliminate the warning icon.
Could we have some more intellgence in the mesher so that if we have a large model and simply change a wall to a P=0 we are not required to carry out a 100% remesh - should we not have the exact same mesh but without a boundary layer?
Even with manual meshing we require a remesh, seems like time wasted.
Give the option of assigning mesh size scalars to volumes (fine to coarse) before auto-meshing. As a bonus, give the option of bulk assignment of mesh size scalars to material groups.
When doing 2D compressible analysis that include shocks, having adaptation would produce a more efficient and sharper result. Would also be a good test bed to test adaptation strategies before running a larger 3D model.
Certain applications involving both internal or external flow require accurate prediction of flow separation. The mesher and solver should provide new options for predicting the onset of flow separation as accurately as possible.
1- Assign a unique color to each mesh region, this would help adjusting the sizes and relocating the regions.
2- Show region number under Mesh History in Design Study Bar, also show that number on the graphic area.
3- When editing an existing region the old one is still in the design tree (the old one doesn't get updated somtime).
4- Under Mesh History in Design Study Bar, there should be a "Spread changes" check box for each individual region, but usually there is only one for all,...
5- Editing a region from the Mesh History (under Design Study Bar), the manu is different than the menu available in "Automatic Sizing" in the "Panel Buttons", and the spread changes button is missing!.
Also the mesh size text box is not responsive and won't get updated correctly.
My CPU is only operating at 3% during the meshing and pre-solve process. Sometimes this takes a long time (up to 2 hrs) on large models. Is there some way you can change the system so the computer uses all of its processing power during this time period.
It will be nice if we can mesh the geometries and check if meshing will be successful before setting up all the material properties, BCs, ICs.,..etc.
It will be nice to know where/how the mesh fails if meshing fails.
I turned on text alerts to let me know when my analysis was complete. The only issue is that the alert comes from a different number every time I get it. Its a simple sequential number but it is pretty irrelevant and comes up as a number I do not know. When I got the first text, I set up the number as a contact titled "CFD Alert". It would be nice if all the alerts came from the same number so I would know what they are just by looking at the contact.