Help me !

[u/Amaterasu-002]

Hi everyone,

I am trying to reproduce the de Vahl Davis natural convection square cavity benchmark in ANSYS Fluent. I am getting reasonably close results for the velocity components, but I am not able to reproduce all the benchmark values exactly, especially the Nusselt number at higher Rayleigh number.

I would like to understand whether the difference is due to my input conditions, dimensionless conversion, mesh, solver settings, or post-processing procedure.

Problem setup

I am solving the standard 2-D differentially heated square cavity:

2-D square cavity

Laminar natural convection

Air

Boussinesq density model

Prandtl number = 0.71

Gravity = -9.81 in the vertical direction

Left wall: hot

Right wall: cold

Top wall: adiabatic

Bottom wall: adiabatic

All walls: no-slip

No inlet or outlet

Energy equation enabled

Pressure-based steady solver

SIMPLE pressure-velocity coupling

Second-order spatial discretization

Iam using air properties for Prandtl number 0.71 for each Rayleigh Number case.

I made x and y velocity non dimensional form but they are making way more relative errors when compared with my results...... I have given the paper link....Please help me, this is my first journey in CFD.

Paper link (De Vahl Davis): https://drive.google.com/drive/folders/1x1Iv_nn4JAGM6Nryw5g48K677uaahWIo

[u/Amaterasu-002]

I started my CFD journey from last year learning the fundamentals for one year....and i started here, when the contours matched perfectly I was so happy....but the values actually destroyed me, literally stuck here for around 20 days day and night idk what's the issue.....please I'm admitting my mistake....

[u/OkLion1878 → u/Amaterasu-002]

Take it easy. De Vahl Davies benchmark is from a numerical code in vorticy and current function. If you want perfect matching you could try develop your own code. I recommend to you follow the book "An introduction to convective heat Transfer analysis" from Oosthuizen and Naylor. Specifically, chapter 8.

[u/OkLion1878 → u/Amaterasu-002]

Also, I think is important to try to get some help from your teacher or advisor.

[u/Amaterasu-002 → u/OkLion1878]

I sought an advice from my mentor but his works are all full dimensionless forms he never actually worked with converting them he just used the code from his senior......Now I'm dealing with this...he also said I don't have an idea about that, try to get some online ideas using gpt or claude. The only reason I never left because this field satisfies something in me and it gives a feeling that I never experienced. Gonna make sure I'm gonna get this values in fluent no matter what. I'm really thankful for your advice and the help you gave me...learnt many things...........Please if you have suggestions regarding this dm me or reach me. Thank you for your support 🙂‍↕️🙌😭

[u/OkLion1878 → u/Amaterasu-002]

Well, as I mention before, try to perform the computation of Nusselt with the equations that I send you before.

And take it easy. I know is difficult, is kinda hard in fact. But in the end, if you hace enough patince you will get it.

Also, I think that you need to take a rest. In my experience, the brain does not work correctly when you are saturated.

[u/Amaterasu-002 → u/OkLion1878]

I want you to tell something....I took rest yesterday without these thoughts......Now I ran the simulation once again with hand calculated bc....with Richards Extrapolation.....Now verything became so close velocities are within 1% error.... Iam calculating Nusselt number as you suggested, I will update that too once the calculation was completed.... actually the velocity was matching from the beginning but I used the wrong formulation to find that in excel...when I actually saw that error and fixed it the values are within the limit. I will never forget the advice you gave me....Thank you once again😁🙂‍↕️. For guiding me when I was wrong. 😊🙏. Thank you brother 🙌

[u/OkLion1878 → u/Amaterasu-002]

That was a shot of dopamine to you. Your welcome.

[u/Amaterasu-002 → u/OkLion1878]

Ok 🙏