Coefficient of drag and lift values for flow around a flat plate

Project Support
1

I am working on a simple case of a laminar flow around a flat plate airfoil. Following are the specifications:

Flat Plate :

Length =100mm=0.1m

Thickness(ideally infinitesimally thin), here 1mm

Flow:

u=1 m/s, kinematic visc =1e-5, density =1 kg/m^3, thus Re=1e4

Expected Cd= 0.0138
Simulated Cd = 0.0119
Error % = 13%.

Please take a look at the present set up :

However, I am getting a value for Cl be negative -0.02, when it is actually supposed to be 0. Are these values of Cd and Cl considered okay or is there anything which I am still supposed to rectify in the simulation set up ?

Thanks,
Athira

2

Hi there,
Thank you for posting on the Forum :slight_smile:
We will go through your project and get back to you soon!

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3

Aha, you must be working on a common class?? project as others :wink:

You might find some help in my post to this topic: To capture the mesh better around sharp edges - #8 by DaleKramer

EDIT: If I were you, the first thing I would investigate is whether your expected Cd value of 0.0138 comes from a reliable and trusted (peer reviewed etc) source. A lot of NASA NACA real world studies have been found to be not reliable. If it is a reliable number to verify against with CFD, you still need to need to know all of the conditions and assumptions that were made in determining 0.0138. Only then can you determine which CFD ‘best practices’ to implement in your CDF study to even expect to get close CFD results. Otherwise you will just be forcing your CFD results to match a given result which is sorta useless in my book :wink:

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4

Hey,

Thanks for the response. The value of Cd calculated here is for a flat plate airfoil in laminar flow, for which there is a direct formula for Cd=1.38/sqrt(Re) in flat plate theory.

Will continue working through this, and keep you posted.

Thanks,
Athira

5

And remember NOTHING is simple :slight_smile:

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