... speed and turbulent velocity on bulk yard. When the strong wind is coming, only part of it can go ... , the opening rate of wall is zero.When Pa> Pb, Pc> Pd, in area A and B, low pressure areas ... forms a vortex area at the back of storage pile in area B which uptakes dust.When windbreak wall is used, ... such wall has some open holes; wind can go through the wall. In area A, ...