ABSTRACT
Gravity flows of loose-matter particles are accompanied with aerodynamic forces that produce ejection of air in the loading and unloading chutes. A flow of loose matter acts like a blower. Head created by this blower (that we choose to call ejection head) comprises a sum total of aerodynamic forces of falling particles divided by the cross-sectional area of the flow [213]. Aerodynamic force may be expressed using the drag coefficient
R F
v u v u m=
( )ψ − − ρ 2
, (7.1)
where R is the aerodynamic force of a single particle (N) ψ is the drag coefficient Fm is the midsection area of a particle (m2) v is the velocity of falling particles (m/s) u is the velocity of ejected air (m/s) ρ is the density of air (kg/m3)
Absolute value of relative velocity |v−u| had to be isolated into a dedicated variable due to the need to vectorize the square of relative velocity for the case involving unidirectional motion of a two-component particle-air medium. This notation means that at v > u, R is positive and directed parallel with the leading motion of solid particles. At v < u, this force is negative, that is, opposite to the falling particles.
