The logarithmic values of the gas (top) and Ωt_stop = 1 particle density (bottom) at the end of simulations with various cooling time as shown in the top panels of each column. Colour bars are on the left of each row. As t_cool increases, the fluctuation of gas density becomes weaker, the tilt angle of shearing waves also gets smaller, both indicates relatively weaker angular momentum transport as the cooling time-scale gets longer. However, stronger clustering effects are found for longer cooling cases as the velocity dispersion from the gas gets weaker.