Session: 03-02-02 Bio-Inspired and Biomedical Fluid Mechanics

Paper Number: 87916

87916 - Aerodynamics of Straight Rods at Low Reynolds Numbers in a Quiescent Fluid to Model Settling of Microfibers in the Atmosphere 

Authors Daniel Daramsing¹, Amirhossein Hamidi¹, Roozbeh Alishahian¹, Ronald E. Hanson¹, Eric Ward², Mark Gordon², Liisa Jantunen³

¹York University, Department of Mechanical Engineering, Toronto, Canada

²York University, Department of Earth and Space Science Engineering, Toronto, Canada

³Air Quality Processes Research Division, Environment and Climate Change Canada (ECCC), Ontario, Canada 

Introduction: Evidence of atmospheric transportation and deposition of Microplastics (MPs) has been observed across the globe, including remote areas, which underscores the important role of long-range atmospheric transportation of these particles. Compared to water, air currents are known to distribute atmospheric particles very quickly. To predict and model the dispersion of MPs by the atmosphere, the aerodynamic characteristics are required. In the present work, we focus on the determination of the aerodynamic drag of cylindrical rods falling in a quiescent fluid to quantify the settling velocity of microfiber particles, a subset of MPs pollution found globally. Results will support simulations of atmospheric transport.

Methods: Experiments are performed using a particle tracking velocimetry (PTV) technique to record the motion of straight cylindrical rods falling through glycerin and water mixtures composed of 80% or higher glycerin ratio. The rods have diameters between 0.5 to 2 mm with aspect ratios 3 to 30. Dual monochromatic cameras (Iron CXP 250) view the fall chamber at two orthogonal planes. A backlighting technique using a 10-Watt LED light projected onto an acrylic diffuser plate behind the chamber is used to capture the outline of the particles from the two viewing angles of the cameras. A thermocouple is mounted inside the chamber to record the temperature of the glycerin solution. The viscosity of the fluid is computed using a Discovery Hybrid Rheometer. Cameras are synchronized using a frame grabber connected to a computer. The system is calibrated using a grid placed inside the chamber. Knowing the time between images, the instantaneous velocity (both in terms of translation and rotation) can be determined as well as the Reynolds number and drag coefficient. Relationships between these non-dimensional parameters form the basis for models of the spectrum of complex fiber geometries typical of microfiber atmospheric deposition samples.

Discussion: The results obtained from our experimental setup will be compared to non-spherical models available in current literature. We plan on replicating the same Reynolds number regime (0.1 - 10) as microplastics and fibers falling in the atmosphere determined from non-spherical models. We will quantity our results based of drag coefficients with Reynolds numbers. We observe angular rotation and oscillation to quantify instantaneous velocities and influence on settling motion. Results will include a range of different aspect ratios and rod diameters within fluids of varying viscosities to achieve Reynolds numbers from 0.1 to 10.

Presenting Author: Daniel Daramsing York University - MECH Department