It was a requirement since little information was available on the internet and was not clear enough. I think you will complete uncovering every piece of important concepts in CFD in the future. Thanks.
Great wrap-up! Even to me a CFD engineer with 25 years in the field it gave great tips for the results visualization! Thank you Aidan, will apply that.
Thanks very much doctor Aidan. Thank to you, I am capable of improving and enhancing my knowlegdes about CFD. I can apply these informations in my researchs and workings much more. You are really genius 😀😀😀
If I make a contour of turbulence intensity in Fluent, the contour typically use the reference velocity which is defined in the Reference Data Settings Page. But if I want the turbulence intensity based on the local velocity, the typical turbulence intensity in Fluent should be treated as a constant. And after that, multiply it with the velocity magnitude.
If I look at an ABL flow (6.44m/sec @10m and z0=1m) I see at 12.5m height;, a speed |U| of 7.2m/sec and a KTE of around 1.6m2/sec2. And this gives an I =sqrt(2KTE)/|U|=sqrt(21.6)/7.2=25% So your boundaries (1 and 5%) do not really work for an ABL environment. Do I misunderstand? Thanks for the feedback.
That's correct, the BC for turbulents fields (TKE, epsilon or omega) follows variable with height formulas according to the approach you want to use for the ABL: shear stress driven flow (Richard & Hoxey 1993) or pressure driven flow (Deaves and Richard & Norris 2018), taking aside if you want to model neutral or non-neutral ABL. So the standard theory we find in CFD courses to set a fixed value of TI or for the turbulent fields won't match with accurate inlet profiles, and so downwind results may differ a lot from your experimental data.
Excellent as usual! In 5:10 the 6th item in the list: "Sum and take the square root". Isn't 'sum' redundant since in step 5 the mean of x,y, and z components is calculated?
Hi. I might have the same doubt of yours, step 5 should be better a recall to also perform steps 1 to 4 for the other velocity components (y and z), and then finally go to step 6 for a unique urms value that involves all the fluctuating velocities
Good day dr. Aidan, from silide 4:25, the step 5 would be a recall to also solve (u'_y ^2) and (u'_z' ^2) as steps 1 to 4 solved (u'_x ^2), right? or is this step 5 an extra mean value to be computed over (u'_x^2) solved in step 4?
I appreciate the advice but, I am doing a PhD thesis and the truth as a researcher it does not look good to cite these videos. but I clarify that contain very interesting concepts and especially valid in the field of fluid mechanics, so if you have articles of scientific character would appreciate sharing the links and your credentials. especially I emphasize the academic value of your videos, regrettably as I said it does not look very good as a source of research; greetings.
Great content as always. I've never understood the pro/con of this same intuition when applied to Pressure&Temperature boundary conditions where the options exist to use TKE & ESP or Length Scale & Viscosity Ratio. Is there a reason you should employ one strategy over another when applied to a URANS sim for example?
Ultimately the value will be the same, so it doesn't really matter. If you are going to have to change the boundary condition (for example to investigate the effect of a range of different ambient turbulence conditions) then I would choose the option that makes it easiest for you to change, so that you don't have to re-do the calculation yourself (you might make an error).
I am confused with the definition of urms, isn't it the average of one fluctuating velocity component over time, eg: u' is instantaneous fluctuation along x-direction, urms is square root of u'^2 only? So that T.I is different along 3 different axis, Tx Ty and Tz
You could define it that way if you wanted. I think the important thing is to check the manual of the CFD code you are using, so that you know what is being reported. If you are doing the post-processing yourself, you can define Tx, Ty and Tz yourself, or any other quantity that you wanted! This is the art of good engineering, knowing what quantity is best to report and in what way, so that you can use it to make good decisions
![[CFD] Turbulence Intensity for RANS](/img/logo.svg){kind=logo}
