Anisotropic Flow and Viscous Hydrodynamics

We report part of our recent work on viscous hydrodynamics with consistent phase space distribution f(x, p) for freeze out. We develop the gradient expansion formalism based on kinetic theory, and with the constraints from the comparison between hydrodynamics and kinetic theory, viscous corrections to f(x, p) can be consistently determined order by order. Then with the obtained f(x, p), second order viscous hydrodynamical calculations are carried out for elliptic flow v₂.