Figure 7 shows the particle distribution of the horizontal-horizontal case at the downstream of the bend from t=1 s to t=2.5 s. At exit of the bend (x/D=0), the particle rope is strong, and the particles distribute in a small area. The particles distribute around the whole circum of the pipe at x/D=5, and keep close to the inside of the pipe. Note that the particles distribute the whole circum during t=1 s to t=2.5 s, but they concentrate in a particular area at each moment. It indicates that the rope is weak and unstable, but does not completely disperse. The particles distribution is not a full circum at x/D=10, as the particles are difficult to approach to the top of the pipe because of gravity. The particles gradually deposit at the bottom of the pipe, and the rope almost disperses.