support by the National Science and Technology Major Project(grant No.2011zx06901-003);the fund of the Nuclear Power Technology Innovation Centre(grant No.HDLCXZX-2021-ZH-024).
Voidage(porosity or void fraction)in packed particles(or pebbles)is of fundamental importance in calculating the pressure drop,obtaining the drag,predicting the bed permeability,estimating the neutron streaming,etc.Fo...