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Showing results 1 to 25 of 36 Search took 0.01 seconds. Search: Posts Made By: ghorrocks

Forum: CFX February 6, 2024, 17:06

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks CFX has only very simple models for particles... CFX has only very simple models for particles impacting surfaces. The wall film model is intended for fuel droplets and how they behave on walls. I do not think that will be very useful for your soot...

Forum: CFX February 9, 2023, 16:56

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Let's make some educated guesses: If the pore... Let's make some educated guesses: If the pore area of the filter is 50%, then the average velocity of the fluid in the filter is 2x the incoming duct. And if the pore size is 1% of the incoming duct...

Forum: CFX February 9, 2023, 02:06

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Make sure you know the definition of turbulence -... Make sure you know the definition of turbulence - you cannot tell turbulence from velocity vectors, and a common misunderstanding for people who do not know fluid mechanics is that recirculations are...

Forum: CFX February 8, 2023, 17:00

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks The length scale of the filter is going to be... The length scale of the filter is going to be much smaller than the length scale of the main flow. This means the Reynolds number in the filter is going to be much smaller than the main flow. So if...

Forum: CFX August 16, 2022, 18:33

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Make sure you are OK with those "exceeded time... Make sure you are OK with those "exceeded time limit" particles. They are probably stuck in a recirculation - so if you want to know what happens to them you will need to make the particle time...

Forum: CFX July 19, 2022, 21:46

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks It has been archived so will take me a bit to get... It has been archived so will take me a bit to get it back. But it is very simple, just open the file and use a regular expression to find the right bit of the output file (or even just a simple...

Forum: CFX July 19, 2022, 20:55

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks I am doing some work on particle capturing as... I am doing some work on particle capturing as well at the moment. I found the easiest way to get particle fates is to parse the output file. I have a python script which extracts the particle fates...

Forum: CFX July 19, 2022, 19:14

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Are you using the output file to get your... Are you using the output file to get your particle fates or CFD-Post? I get it from the output file as it is much easier.

Forum: CFX July 18, 2022, 21:07

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks By excluding the ones labelled as "Waiting for... By excluding the ones labelled as "Waiting for next time step".

Forum: CFX July 17, 2022, 21:34

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Yes, you only count the particles which are... Yes, you only count the particles which are relevant to what you are trying to measure.

Forum: CFX July 13, 2022, 23:49

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Make sur eyou understand what the categories are:... Make sur eyou understand what the categories are: Continue from last time step : These are the number of particles in the flow and carrying over from the previous time step. Left domain : These...

Forum: CFX July 13, 2022, 21:52

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks I use the particle fate summary at the end of the... I use the particle fate summary at the end of the simulation. You can also use the per-time step summaries as well. But if you run it transient you are going to have to run it for quite a while...

Forum: CFX July 13, 2022, 19:13

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks You can see the velocity field flapping about. So... You can see the velocity field flapping about. So it definitely is transient. Whether that transient nature is significant for your model is another question, but the flow definitely has a major...

Forum: CFX July 12, 2022, 01:32

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Do a transient animation of that plane for... Do a transient animation of that plane for velocity and/or pressure to see if it is transient. The parameters you need to check you have set accurately are mesh size, convergence tolerance and...

Forum: CFX July 11, 2022, 23:33

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks I cannot say anything definite about that. You... I cannot say anything definite about that. You will have to do some animations of it. The mesh artefacts suggest you are still running quite a coarse mesh. Have you done a mesh refinement study...

Forum: CFX July 11, 2022, 23:07

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Those images do not show much. You will have to... Those images do not show much. You will have to zoom in much closer to the infill section.

Forum: CFX July 11, 2022, 07:41

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks There is quite a lot there.... Firstly, I... There is quite a lot there.... Firstly, I would not look for transient flow in the particle tracks. It is more likely to be in the velocity or pressure field. So do a plane through the middle and...

Forum: CFX July 10, 2022, 19:25

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Have you had a look? It might be obvious. If not... Have you had a look? It might be obvious. If not post some images here and we can help. Also, generating some transient animations of the flow might help as well (only for the last third of the...

Forum: CFX July 10, 2022, 19:10

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Use either. But compare the 1E-4 run to the... Use either. But compare the 1E-4 run to the 1E-5 run to see if you can see significant differences. It is probably too early to be sure in your case as the significant thing in your case is how...

Forum: CFX July 10, 2022, 19:02

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks These results are suggesting it definitely is... These results are suggesting it definitely is transient, and quite strongly so. You should have a look at the post processor for the last third of the run to see if you can spot where the transient...

Forum: CFX July 9, 2022, 23:07

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks There are a few ways you can tell if a transient... There are a few ways you can tell if a transient simulation is required: 1) Run it SS and converge as tight as you can. Then look at the resulting flow field in CFD-Post and see if you can see...

Forum: CFX July 9, 2022, 23:00

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Note that y+ is meaningless in a laminar flow.... Note that y+ is meaningless in a laminar flow. You need to work out mesh settings in laminar flow with a sensitivity analysis.

Forum: CFX July 9, 2022, 22:43

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks Yes, they look like good settings for a... Yes, they look like good settings for a convergence tolerance = 1E-4 run.

Forum: CFX July 9, 2022, 22:42

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks If the time step size spirals to nothing it is... If the time step size spirals to nothing it is showing that it is having a hard time converging, no matter what you do. You should then think about what can you do to improve the numerical stability...

Forum: CFX July 9, 2022, 22:05

Replies: 98 Particles captured on walls Views: 3,522 Posted By ghorrocks No, that is not the correct approach. When you... No, that is not the correct approach. When you run adaptive time steps with 3-5 coeff loops it automatically adjusts the time step size depending on the mesh and physics, but also the convergence...

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