The drag coefficients of single spheres moving in steady and accelerated motion in a turbulent fluid

Drag coefficients of aerodynamically smooth spheres having a density variation of from 0.252 to 1.91 g./cc. and a diameter variation from 1.56 to 3.21 mm. were obtained for acceleration rates varying from 103.5 ft./sec.2 to ‐30 ft./sec.2 and for relative intensities of up to 45%. The particle‐to‐Eulerian macroscale ratios varied from 0.50 to 0.16, and the diameter‐to‐Eulerian microscale ratios varied from 10 to 2. The drag coefficients were found to be a function of the particle Reynolds number and of the relative intensity but not of the acceleration and relative macro‐and‐microscale variations. A transition theory for the system investigated is presented, which predicts that the product of the critical Reynolds number and the square of the relative intensity should be a constant; it is supported by the experimental results obtained.