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Old   July 19, 2011, 18:53
Default Coherent structures
M. Nabi
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Hi all;

In order to plot the coherent structure of turbulence, I use the formulation proposed by Hunt et al. (1988) as

Q=-\frac{1}{2} \frac{\partial u_i}{\partial x_j} \frac{\partial u_j}{\partial x_i} = -\frac{1}{2} \left( |S|^2 - |\Omega|^2 \right)

Q will include positive and negative values. Can anybody explain it to me, what is different between positive Q and negative values of Q? Does it have a physical meaning?

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