  We report on the application of a cascade + viscous hydro + cascade model for
heavy ion collisions in the RHIC Beam Energy Scan range, $\sqrt{s_{\rm
NN}}=6.3\dots200$ GeV. By constraining model parameters to reproduce the data
we find that the effective(average) value of the shear viscosity over entropy
density ratio $\eta/s$ decreases from 0.2 to 0.08 when collision energy grows
from $\sqrt{s_{\rm NN}}\approx7$ to 39 GeV.
