Drag Coefficient and Movement Phenomena of Free-rising Spherical Particles
Abstract
Light particles are commonly utilized as the solid phase in reverse fluidized bed reactors, especially for applications in wastewater treatment and other chemical or biochemical processes. This is primarily due to their favorable buoyancy characteristics and their ability to enhance mass transfer and mixing within the reactor. The drag coefficient related to the particle terminal velocity is one of the vital parameters for fluidized bed operation and design. However, traditional drag coefficient models are mostly based on heavy particle settling experiments. The few free-rising particle experiments have only justified the constant drag coefficient values in the high Reynolds number region, but the drag coefficient predictions for the low Reynolds number region have been assumed to be the same as for heavy particles.
Thus, this study investigates the drag coefficient and movement phenomena of free-rising spherical particles in various fluid mediums. It focuses on understanding the complex interactions between spherical particles and fluid dynamics, particularly under different conditions of density differences and fluid types. The research encompasses experimental setups using spherical particles of various materials and sizes in fresh and salted water. High-speed video imaging and advanced tracking software were employed to analyze the particles' terminal velocities and movement behaviors. A new drag coefficient model for free-rising spherical particles was developed, offering improved accuracy over traditional models, especially at lower Reynolds numbers. The study's findings provide valuable insights into particle-fluid interactions, which have significant implications for fluidization technology and related industrial applications.