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Old   September 13, 2012, 14:57
Question Mean coefficients
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Hello,

I am simulating unsteady laminar flow over an airfoil for the Reynolds number 70,000 for different AoA. the reason why i am performing this is to check whether the airfoil stall's or not.i am getting convergence in the solution, but my main concerns are coefficients(drag, lift and moment). HERE, i am enabling "data sampling for time statistics" option (DSTS) under iterate window, which according to the description, will give the root mean square of the coefficients (now, i assume that it will converge after sometime and becomes constant, which i assume a constant value for further "n" number of iterations).but that's not the case, even i select the DSTS my coefficient plots are still oscillating, since my main aim is to compare the coefficients with different AoA's). i am posting a plot for Cl for the reference. one more thing, i am using very fine mesh.

PLEASE HELP .

Bharat
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Old   September 13, 2012, 15:48
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What does the flow field look like? Is that oscillating? There may be some vortex shedding.
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Old   September 13, 2012, 22:26
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Hey,

Thanks for your kind attention .

Certainly, there is vortex shedding in the flow field. here i post you one picture. please have a look.
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Old   September 16, 2012, 04:07
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you want to find out the fluctuating and mean coefficients?
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Old   September 16, 2012, 04:32
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Sir,

I am glad that you've replied.

My main concern is to get the mean coefficient value(lift, drag and moment for unsteady laminar flow), which i can compare with turbulent flow.

bharat
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Old   April 28, 2014, 11:11
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Quote:
Originally Posted by Bharatt View Post
Sir,

I am glad that you've replied.

My main concern is to get the mean coefficient value(lift, drag and moment for unsteady laminar flow), which i can compare with turbulent flow.

bharat
I suppose you have solved the problem already. One easy way is to copy periodic Cl output values to Excel and get a mean value from there, assuming constant time steps.
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