7.18 There are various applications such as the freezing of food, combustion of small particles, or some chemical reactions in which a fluid flows through a matrix of particles, called a fluidized bed. The fluid pressure drop is a function of the diameter of the particles

d, the flow length of the bed L, the fluid velocity V, fluid density r, and fluid viscosity m. Use dimensional analysis to find the functional dependence of pressure drop on the other variables.