$v_{3}[2]$ with different $|\Delta\eta|$ gaps is presented in Pb--Pb collisions at $\sqrt{s_{_{\rm NN}}} = 2.76$ TeV. $v_{3}[2, |\Delta\eta|> 0]$, $v_{3}[2, |\Delta\eta|> 0.4]$, and $v_{3}[2, |\Delta\eta|> 0.8]$ are represented by circles, diamonds, and squares, respectively. The different panels show the centrality evolution of the measurements Hydrodynamic calculations with MC-Glauber initial conditions and $\eta/s =$ 0.08  and with MC-KLN initial conditions and $\eta/s =$ 0.20 , with Trento initial conditions and temperature dependent $\eta/s$  and AMPT initial conditions and $\eta/s =$ 0.08  are shown in green dot-dash, orange dashed curves, and magenta and grey shaded areas, respectively.