Settling Velocity of Straight and Curved Rods at Low Reynolds Numbers in a Quiescent Fluid

The present thesis is aimed towards understanding the effects of microfibre geometry on the settling velocity. Microfibres have been mathematically modelled as simple straight rods in the past to estimate their settling velocity; however, samples collected demonstrate complex geometries. One common geometric parameter of realistic microfibres is curvature, and the effect of this parameter on the settling velocity is the focus of the present thesis. A new drop tank and particle tracking system were designed to measure the settling velocity of curved rods at low Reynolds numbers typical of microfibres found in atmospheric samples. An experimental model was developed to relate the Reynolds number at terminal velocity and drag coefficient for both straight and curved rods. Non-ideal effects can significantly affect the estimation of travel of microfibres in comparison to other existing models, which emphasizes the importance of improved models that are tuned to predict the settling velocity of microfibres.