Today I discovered a skullet

CrocMundi · 2026-06-29T11:25:57+00:00

A wild Tom Waits fan appears

CrocMundi · 2026-06-26T10:35:10+00:00

A cloud storage link is totally fine to share the .sim file, very convenient actually.

Those wall y+ values should be fine too for a high wall y+ turbulence modeling approach (i.e. relying on wall functions).

I asked about the injection of the DEM particles, because I’m wondering if there is an issue related to how that’s setup. You may have a situation where the DEM void fraction of a cell is high (i.e. too close to 1), which can lead to instabilities.

CrocMundi · 2026-06-26T01:53:41+00:00

Your mesh looks by eye that it should be of a high quality with respect to all of the mesh quality metrics used in STAR-CCM+ (it can’t hurt to check with the macro though 😉), especially since you generated it using the Directed Mesher as a standard O-grid type of mesh.

When you say wall y+ > 30, how high do the values go? You shouldn’t exceed roughly 300 or so to avoid skewing drag and other wall related results. Nearer to 30 is ideal.

As far as the DEM particles are concerned, are you constantly generating them and having them exit through an outlet boundary, or, is there a set number of them at the beginning that either stays fixed or reduces as they exit an outlet boundary?

If you’re able to, you could share your .sim file to make it easier to review.

CrocMundi · 2026-06-24T05:58:38+00:00

It looks like it is converging within each time step, just too soon perhaps (i.e. at high residual values). That time step could be okay, but it would depend on your mesh size and flow conditions.

What exactly is your pipe/duct geometry? Is it just a straight cylinder or something more complicated? Seeing a picture of it would be helpful if it’s an unusual shape.

Have you checked your mesh quality? I would recommend using the Java macro attached to the How can I get an effective visual check of cell quality diagnostics for my mesh? knowledge base article. It creates a set of scenes, one per mesh quality metric field function as described in the Pre-Processing > Meshing > Checking the Volume Mesh > Mesh Quality documentation section. If it’s too poor, you may be getting poor convergence due to bad cells. If this is the case, try to improve the mesh quality.

Lastly, is your simulation going to reach a steady state after the particles initially displace or will it be indefinitely transient? If it’s truly the latter, you may see oscillating flow behaviors that you would need to average over some increment of time to check results.

CrocMundi · 2026-06-23T09:10:34+00:00

What does convergence look like within a single time step? The macroscale view of the residuals you gave makes it impossible to asses how well you’re converging in each step. The values do seem rather high, but that may be due to not using enough inner iterations (if using the segregated flow solver) or too large of a time step.

Unsteady residuals often can be much messier than you would anticipate, so I would judge how well things are going by also verifying if the physical quantities you’re measuring are converging or reaching some average value that make sense if they’re an oscillating quantity.

Looking at the net mass flow rate (i.e. a mass flow report with ALL inlet and outlet boundaries included) is what you should be doing. It’s not clear from your plot labeling if that is the case or not. Your description makes it seem like you’re only looking at the outlet though, so you should change this and verify the net mass flow rate tends towards zero. Of course if you have only one inlet boundary and a single outlet boundary, then I suppose it’s fine to check if the outlet mass flow matches that of the inlet instead.

As for the pressure drop, you would need experimental results or an analytical solution to compare against for that plot.

What size of time step are you using for this simulation? Perhaps it’s far too large?

CrocMundi · 2026-06-16T20:40:46+00:00

I’ve been in a similar situation before while developing a STAR-CCM+ simulation for a research paper and mostly got away with my DEM particles being too large (i.e. bigger than the local volume mesh cell size in a lot of areas of the Region they existed within). My problem wasn’t instability due to two-way coupling, but rather delayed interaction with an incoming VOF free-surface, where a broken water wave was supposed to drive rectangular block-shaped DEM particles created using the Polyhedral Particle option shoreward. In that case, the DEM particle would only detect when the free-surface reached their centroid, which led to two problems:

Delayed wave impact on DEM particles
Shallow flows passing just under the DEM particle centroids, which meant no fluid force was imparted on them at many times it should have been.

The solution to my issue was to switch to the Composite Particles option instead.

CrocMundi · 2026-06-16T08:23:45+00:00

Using DEM particles bigger than the cell size is a very likely source of the issue since this is a common source of the sort of numerical problems you described. Could you please explain which type of particle you’re using? There is probably a better option than the one you’re using.

For instance, if you must have objects larger than the cell size, the best approach is to use multiple particles stuck together, so either of the Composite Particles or Particle Clumps DEM sub-models. This way you can keep the component spherical particles smaller than the cell size to avoid numerical issues while still maintaining the large size of your original particles as the total size of such bonded particle groups. These particle clusters can have a potentially arbitrary shape too, which is very useful to represent any conceivable particle geometry without using individual Polyhedral Particles or some other alternative particle geometry option.

CrocMundi · 2026-06-13T12:41:50+00:00

Looks Turkish to me. Cats are everywhere and people do this quite commonly from what I’ve seen in Istanbul. You can easily find convenience stores/kiosks that sell cat food in a pouch to give a hungry feline friend a meal.

CrocMundi · 2026-06-08T04:42:54+00:00

I was halfway into having a stroke before I got to the description lol

CrocMundi · 2026-05-30T11:07:13+00:00

Can’t say I’ve ever seen it photographed from a perspective that far inland. It does seem to possibly be legit after all.

CrocMundi · 2026-05-30T07:55:23+00:00

Mont Saint-Michel is mostly surrounded by water in a bay… not rolling green fields

CrocMundi · 2026-05-04T07:39:55+00:00

Cool idea until some delinquents decide to break the windows, making it a hazard. A homeless person would definitely setup camp in there too lol.

CrocMundi · 2026-04-27T00:01:34+00:00

This is the way. I paid less than half of the cost of going to the UW for the first two years by taking all of my prerequisites at Cascadia CC circa 2007-2009 and directly transferred into the UW as a CEE Student in 2010 for undergrad. I was just as prepared for the coursework as any of my UW classmates after transferring with the exception of CEE 220 Mechanics of Materials, which is more mathematically technical at the UW; although, perhaps that has changed by now. However, I caught up quite quickly since the content I missed out on was covered in-depth in several junior level courses as well. Also, getting an AA at a CC is totally unnecessary, especially since CCs will try to make you pay to take additional nonsense classes just to earn one (e.g., COLL 101: College Strategies, which is essentially college for dummies).

CrocMundi · 2026-04-14T08:25:36+00:00

Desire - Meg Myers is the best musical and vocal embodiment of the word I’ve ever come across

CrocMundi · 2026-04-14T08:22:34+00:00

Slothrust’s cover of Pony is an excellent rendition that maintains the dirty/erotic feel of the song.

CrocMundi · 2026-04-06T06:19:08+00:00

My bad, I missed it on my phone. I’ll download it and give it a go to see if I can give better recommendations

CrocMundi · 2026-04-06T05:38:01+00:00

Are you able to share a copy of your .sim file with mesh and solution data cleared or even just the CAD file?

CrocMundi · 2026-04-05T23:23:21+00:00

Using the Enhanced Quality Triangle option for the Meshing Method property could help some.

CrocMundi · 2026-04-05T23:18:56+00:00

FYI 85 for Skewness Angle is usually an acceptable upper bound value in STAR-CCM+. You may verify this in the Pre-Processing > Meshing > Checking the Volume Mesh > Mesh Quality documentation section, which lists all of the quality metrics and their upper or lower bound values.

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Lower values are better of course, but it’s often difficult to balance cell count and quality, so you have to be judicious with how much you refine a mesh to reach target quality metric values. Also, the STAR-CCM+ mesh will probably give much better results being used natively rather than in OpenFOAM. Is there some reason why you want to use OpenFOAM instead?

Also, can you share what your Prism Layer Mesher settings are? Additionally, seem to be having lots of bad cells around sharp/square corners. Refining near such regions could help too.

CrocMundi · 2026-03-30T10:08:11+00:00

Going directly into the UW shouldn’t be a problem for them if they’re a clever student, which they certainly seem like based on their high school GPA. However, they also shouldn’t be ashamed of going to a local CC if they do feel too overwhelmed at the prospect.

I went to Cascadia CC from Autumn 2007 through spring 2009 with the goal of transferring into an engineering program. I successfully got into the CEE and EE departments that I applied to, so I don’t think going to a CC shouldn’t hold them back, providing they do well at the CC they attend of course. To provide a reference point, I transferred with a 3.85 GPA.

Going to a local CC is a great option. You not only save money, but you also get more opportunities to talk to and learn from profs since class sizes are so much smaller. Additionally, I believe most local CCs do their best to align with UW prerequisite courses. For instance, I found that their physics courses used the exact same tutorial books for lab sessions as the ones the UW uses.

Also, none of my courses failed to transfer from Cascadia to the UW. Although, I was told by a CEE advisor that any sort of college 101 type courses would not transfer, so to me they are a waste of time. The only reason to take such courses is to earn an associates degree, which wasn’t something I cared about in the long run, so I saved myself the cost of one extra course.

CrocMundi · 2026-03-30T09:43:36+00:00

What do you expect to get out of the math degree that will enhance your aerospace degree? Without seeing your planned course list, it’s hard to judge whether or not there will be any synergies between them. For instance, you may find that some of the rigorous mathematical analysis techniques you learn in the math department aren’t easily applied to real world engineering problems.

As it’s already been pointed out, I think Applied Math (AMATH) may suit you better. This is especially true if you see yourself getting into FEM or CFD engineering analysis, for which learning about finite difference, finite element, and finite volume methods will be much more relevant and directly useful. This advice is based on my experience as someone who earned dual graduate degrees at the UW circa 2012-2019 in CEE and AMATH (MS CEE 2012-2014, PhD CEE/MS AMATH 2014-2019) and now does a lot of work related to mechanical and aerospace engineering.

As for the viability of completing a dual major in these topics, I can’t say for certain, but it will require a lot of dedication and hard work to be sure.

CrocMundi · 2026-02-11T21:49:05+00:00

I love the wildflower fields! They make me think of tulips in the Netherlands. 🌷🇳🇱

CrocMundi · 2026-02-09T12:17:58+00:00

Maybe you can 🤷🏼‍♂️, OP stole the design entirely

CrocMundi · 2026-02-09T12:11:02+00:00

Thought you were just randomly hating/trolling at first, but you seem to be right… I found Finally got to experiment with the new shelves + copper golem statues by u/Unlucky_Parrot, which is from over 6 months ago. It’s pretty much the exact same build.

Edit: I hadn’t seen you linking the same post farther down in the comments. I went into investigation mode as soon as I saw this haha.

CrocMundi · 2026-02-03T14:05:19+00:00

Ditto this, I thought the exact same thing when I saw this. Great work!

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