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boundary condition for streamline func and vorticity

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Old   June 16, 2018, 12:25
Default boundary condition for streamline func and vorticity
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A. Min
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Hi all
I have a solved domain (2D flow around a circular cylinder) with U field. Now I want to calculate stream function with this formulation:
Code:
omega = dv/dx - du/dy
solve (laplacian (sai) = - omega)
But at last the results are wrong!
The BC for sai are:
for top and bottom sai is calculated from the volumetric flux (Q = A.U_in) that is:
Quote:
sai_top - sai_bottom = U*delta(y) = 1*20 = 20, so:
top boundary: sai = 10
bottom boundary: sai = -10
cylinder surface boundary: sai = 0
inlet and outlet boundaries: d(sai)/dn = 0
and for omega:

Quote:
top, bottom, outlet boundaries: zero Gradient
inlet and cylinder : omega = 0
But the constant sai lines are not the same as stream lines:



Could you please help me?

Are the equations and boundary C. correct?
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Old   June 16, 2018, 14:42
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Filippo Maria Denaro
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but vorticity is not zero on the wall of the cylinder!
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