Or that's what I'm expecting (from matching conditions)

Now that I know about turbulent boundary conditions

How do I know what I should set them as? For walls, outlets, inlets and empty.

Which Solver are you using? Are you running a "non-dimensional" case (that is, nu as Reynolds)? Steady-State (Co > > 1 or SIMPLE)?

Hello!, thank you for ur reply, I'm actually using the SimpleFoam solver, Steady State simulation, sorry for my lack of knowledge but what do u mean by a non-dimensional case ? and ¿what purpose has to run a non-dimensional simulation?, Thank you very much in advance! 🙂

It mostly depends on whether you're resolving the boundary layer or using wall functions. I.e is your Yplus less than ~5, or >30

If using wall functions, just copy the setup in the motorbike tutorial case

If resolving the boundary layer, off the top of my head you set k to fixed value 0 (or like 1e-12 to prevent any divide by 0 issues) and epsilon/omega to zeroGradient, and set nut to calculated

but don't quote me on that

I almost always use wall functions

actually for omega just use omegaWallFunction anyway, it's coded to recognise if y+ is low and do the right thing anyway

k: kLowReWallFunction will compute k based on y+ (works also for High Re) and fit to one of the other curvem breaking point at 11.25

Ah there you go then

Great info

and for espilon, there is now another thing to add on the boundary if you want to use the lowRe form

How come it seems to be standard to use kqRWallFunction instead of the lowRe one then?

I haven't really looked into k wall functions much tbh

Ah nice one. For which version is this available?

someone did the work for us 😄 http://www.tfd.chalmers.se/~hani/kurser/OS_CFD_2016/FangqingLiu/openfoamFinal.pdf Page 27 is a resume. But names may have changed, for example epsilonLowReWallFunction doesnt exist anymore (in ESI version atleast)

atleast 2012, you should check the doc of the version you use though

Hmm I actually remember coming across that document not long ago and having the same thought then haha. I'd be interested to know if anyone here has a good explanation of the merits of zeroGradient (kqRWallFunction) vs kLowRe

I've spent much more time looking into the nut functions

please answer

i believe the above conversation of @User and @User were about your question. At least for the wall boundary conditions.

@User and @User thank you very much for your comments I got a lot to work on and u both helped a lot to clarify the way 😁

please go over the wiki openfoam tutorials which was suggested 1546151 times to you and has ALL the answers to all questions you ever asked here. You get few/no answers because you ask repeatedly basic things answered there, it feels like you ask before trying yourself to find out, and lazy questions call for lazy answers. In that case, no answer at all.

ok thanks

ok i learned greatly regarding turbulent boundary conditions

k can be zero, it's never dividing, unlike omega.

I'd argue exactly the opposite. Why running three cases with three different grids, and different values for the BCs, and where it's more difficult to interpret results when you can non-dimensionalize ("homogenize") your problem into one single case run three times just with different Reynolds Numbers.... Anyway, going back to your question, the length of your recirculation region is determined not only by the height of the obstacle, but also by its width (Martinuzzi & Tropea, 1993), Is this a 2D simulation (as opposed to an infinitely wide obstacle)? The second thing you need to have in mind is that shedding vortices from the 'roof' of your obstacle are not going to be resolved in SIMPLE, because they are "shed" (function of time). The shedding of vortices in the roof, when the obstacle is "small enough", opaque the lateral "karman vortices" which shorten the recirculation region...