Measurements of relative particle velocity and preferential concentration:
Towards a measurable collision kernel for inertial particles in turbulence
Alberto Aliseda
Department of Mechanical Engineering
University of Washington
Seminar Host: Ted Heindel
Abstract
Turbulent multiphase flows encompass some of the biggest open questions in modern fluid mechanics. The dynamics of solid particles, liquid droplets and gas bubbles represent significant gaps in our fundamental understanding, while at the same time, being of great relevance in many industrial and environmental applications. There are multiple examples of the relevance of these problems, but I will focus on the formation of rain in warm clouds as a classical example where the poor basic understanding hinders progress in accurate modeling and prediction of the underlying geophysical, or engineering, process.
I will discuss laboratory experiments in which we probe the inertial effects in the dynamics of heavy particles in a homogeneous isotropic turbulent flow. The interaction of the inertial particles with the turbulent vortical structures results in accumulation of droplets in regions of high strain and the modification of the drift velocity of droplets due to gravity. Both of these effects lead to a higher probability of collisions due to smaller inter-droplet distance and higher relative velocities. We have found evidence of strong coupling of the particle dynamics with the underlying turbulence, and through this coupling of a significant enhancement of the relative velocity leading to collisions. A novel formulation for the collision kernel is proposed that, unlike previous efforts, is based on measurable droplet statistics.
Dr. Alberto Aliseda‘s research and teaching focuses on fluid mechanics with applications to Energy, Environmental and Biomedical Flows. In particular, he is interested in the dynamics of multiphase flows, such as bubbles in water and droplets in air. This type of flows arise in many engineering and environmental problems such as the exchange of gases between the atmosphere and the ocean, the formation of rain drops in clouds, the atomization of liquids in combustion and manufacturing processes and the dynamics of microbubbles injected in the human circulation to enhance ultrasound imaging and therapeutic use. He uses a large number of experimental techniques (Laser Doppler Velocimetry, Laser Induced Fluorescence, Particle Image Velocimetry, Hot-Wire Anemometry, Phase Doppler Particle Analysis, etc.) to gain insight into the fundamental physics of these complex flows. He complements these experimental studies with mathematical analysis and modeling in order to extract useful information that can be applied outside the laboratory in real world problems.
This seminar counts towards the ME 600 seminar requirement for Mechanical Engineering graduate students