Dear Mohamed,

based on the information you gave us, the problem could be related to the y+ around your profile. I think you use the same settings and turbulence models that are used in the papers/references.  You should ensure that the models that are used are similar. I am only an expert in OpenFOAM and do not know which toolbox you are using but the first guess could be the dimensionless wall distance y+ that is really influencing the drag coefficients. I already forgot how to calculate cd and cl but if there is the density somewhere and you calculate everything  based on incompressible, make sure that your values have the same units.

Kind regards,

Tobi

Dear Mohamed,

I hope you are doing great. I think the problem is related to the mismatch of properties because when you solve for wind turbine profiles you use the properties of air. The density and viscosity of air as well as the speed of sound are now known. So, when you specify the Mach number, the velocity is also known. In this case Reynolds number will change only by changing the chord of the airfoil and so on. So, before making any comparisons check the properties you use in your code and the dimensions in the two cases.

Best wishes and best regards,

Hamdy

Dear Tobias,

Thank you for your kindest respond. The y+ if not the problem because I calculated carefully and I am totally sure that is good. Yes I used the same turbulence model used in the references but I have also changed the turbulence mode but didn't help. I am using an developed code called FLOWer (developed by DRL with extensions done at the institute where I am working). So basically there are some defined parameters in FLOWer for the non-dimensionalisation of the Navier-Stokes equations and after struggling understanding them I found the problem. It was a matter of non-dimensional parameters defined in FLOWer.

So Thank you so much for your time and wish you all the best in your carrier.

Best regards

Mohamed

Dear Prof. Kandil,

First of all, I want to express my deepest greeting to you. I tried to call you but I couldn't reach you. Second, thanks for your response, As a student of you, I did that already and I discover the problem as I mentioned above. It is a problem of the non-dimensionalisation of the Navier-Stokes equations as defined by the deveolper.

kindest regards

Mohamed