Hi Kareem, when you calculated the wall distance why did you put 0.01 as the boundary length and also, why is the wall distance you calculated on the website different to the one you put into Ansys. Thank You.
@cfdkareem4 ай бұрын
Hello, the characteristic length used to calculate the Y+ is the step height, 0.01 m. Good catch on the wall distance! The one calculated on the website should have been used as the first layer height of the inflation. It looks like I forgot to paste the value!
@abhishekbenny79304 ай бұрын
@@cfdkareemyh that was really baffling me, but thanks for clarifying
@LCucumidesC3 ай бұрын
Dear Kareem, I would like to know what the analytical equation is for the velocity profile. Thank you.
@cfdkareem3 ай бұрын
There are numerous equations for estimating the turbulent velocity profile. The most common for industrial flows is known as the Prandtl one seventh power law which takes the form: u/Umax=(y/R)^1/7. You can plug in Umax and R to solve for u over the range of y.
@joaquinbarawed90163 ай бұрын
Hi, I can’t seem to find where to download the experimental data, and the link I’m pressing only opens up a new tab with the data
@cfdkareem3 ай бұрын
Hello Joaquin, near the bottom of the NASA page there are two links to the Cf and Cp data. Clicking the links will open a new tab with the data displayed in text format. You can then copy the data and paste it into excel or a text document.
@haiderh20526 ай бұрын
Hi, can I just extend the upstream length for this case instead of creating a secondary simulation for inlet profile ? will that works the same
@cfdkareem6 ай бұрын
It will! You just have to make sure you extend it far enough for the flow to fully develop. It will also increase your solving time as the mesh will get much larger.
@benguerichezah4676Ай бұрын
I have problem i want to fill this geometry with fluid ,i try your vedio but i have problem in velocity contour is empty don't fill with fluide
@cfdkareemАй бұрын
Hello, are you trying to change the flow from air to water? Or trying to do a multiphase simulation with air and water?
@aliakbas73873 ай бұрын
hello sir, im trying to simulate a similar case but with small inlet lenght to see the vorticies at the top wall. However, nomatter which methods or solvers i use i can not get the same results with published articles."E. Ertürk, Numerical solutions of 2-D steady incompressible flow over a backward-facing step, Part I: High Reynolds number solutions, Computers & Fluids 37 (2008) ". Can you give me any hints to handle this simulation. Laminar case is easy but i can only get top vorticies with DES method but it is still not accurate. I can not get the 3third vortex for Re = 3000 and the other x/h values doesnt match with the reference.
@aliakbas73873 ай бұрын
Our teacher said u can use k-epsilon for turbulence but with that method you can only get the first vortex others only appears for the initial iterations then dissappear.
@aliakbas73873 ай бұрын
also, with very fine mesh (i have uniform 150k grids) DES methods takes almost 2k iterations to hit 10^-3 criteria and oscillations never stops as i see.
@ratuldas535211 ай бұрын
Hello, just a simple question, why did you divide x/0.1? I can't get my head around it.
@cfdkareem11 ай бұрын
Hello, in our analysis we divided the x variable by our step height, .01. This will make our variable "non-dimensional" since we divided X, with units meters, by the step height, also with units meters. It is common to report data as non-dimensional values so the output is not dependent on the size of the domain. In other words, we could use the reattachment point from our simulation and compare it directly to a simulation domain twice as big. It is similar to normalizing data in a statistical analysis which allows us to compare two data sets with a common ratio. Let me know if that answered your question!
@marstokrom Жыл бұрын
Hey! could you describe how to make the secondary simulation for defining the fully developed turbulent flow inlet condition in a bit more detail? what size does the mesh need to be etc? How do i know if the flow is fully developed? Thanks! this video is excellent
@marstokrom Жыл бұрын
my apologies, i see youve linked it already! legend!
@JamesAGBAJE-wg1yo4 ай бұрын
Hi Kareem, please I’m having issues with the secondary simulation can you share the file of the velocity profile?
@cfdkareem4 ай бұрын
Hey James, I've added the inlet velocity profile to the video description! Copy it to a .txt file. It can then be read in as a profile for the velocity inlet.
@aiwithhamzanaeem Жыл бұрын
Looking for topic "Backward step flow in transonic regime"
@cfdkareem Жыл бұрын
Hey Muhammad, thanks for the suggestion! I will add it to my list for future videos!
@marstokrom Жыл бұрын
Hi again kareem! just wondering, why opt for the coupled solution approach rather than SIMPLE or SIMPLEC? many thanks!
@cfdkareem Жыл бұрын
The coupled solver is more robust then the SIMPLE or SIMPLEC numerical approach, most of the time. SIMPLE is good for giving quick simulations if the boundary conditions are well defined and the pressure-velocity coupling is low. When in doubt I would always recommend the coupled solver, even if it may be a bit slower to compute.
@tomfindlay5652 Жыл бұрын
I can’t seem to find the data you have linked , I can only find data for skin friction coefficient and not wall shear stress
@cfdkareem Жыл бұрын
Hey Tom, the wall shear stress is a scalar multiple of skin friction coefficient, Cf = tao/(.5*rho*U^2). In this case we are looking at the second zero crossing of the graph. This point will be equivalent for wall shear and skin friction coefficient. You can plot either the wall shear stress or the skin friction coefficient to compare to the experimental data to simulation.
@tomfindlay5652 Жыл бұрын
@@cfdkareem my simulation data seems quite off, I didn't do the developed flow simulation for the inlet conditions, would this likely be the reason for the large difference or something else fundamentally wrong
@tomfindlay5652 Жыл бұрын
@@Syrsylo The X/h values on the graph are much lower than the experimental data, but the shape of the graph is the same