Bivariate probability density functions between the velocity (x-axis) and the decoupling in the velocity (y-axis) for the P′ case (top panels) and L2′ case (bottom panels), where the evolution of the background has been removed. In both cases, all velocity values over the last 50 s of each simulation, and at the vertical location between −2L₀ and 2L₀ have been considered. Left panels: bivariate probability density functions corresponding to horizontal velocity. Right panels: same, but for the vertical velocity. The vertical dotted line gives the location of zero velocity value.