 Research |
Students & Postdocs |
Courses |
Publications |
Melany L. Hunt Dotty and Dick Hayman Professor of Mechanical Engineering Division of Engineering and Applied Science Office: 265 Gates-Thomas Laboratory |
Contact
Holly Golcher Office: 262 Gates-Thomas Laboratory
|
|
|
Liquid-Solid Flows |
|
||
Liquid-saturated flows of particulate materials are ubiquitous in industrial and geophysical environments, including debris flows, slurries, mining and milling operations, sediment transport, and surface erosion on Mars. Unlike collision-dominated dry granular flows or sediment-laden liquid flows, this area of multi-phase flow research combines the mechanics of particle-to-particle interactions with the inertial effects of both phases and the effect of a viscous fluid.
We have designed a new particle-liquid rheometer to measure the shear and normal forces for a liquid-solid mixture. These experiments provide a unique opportunity to explore the transition from transport in a pure Newtonian fluid to transport occurring during a dense flow of particles. The measurements will show the dependence of the stresses on the Stokes and Reynolds number, concentration, and other experimental parameters (such as the stiffness of the particles, gap size relative to particle diameter, and density ratio). These results will also allow us to develop constitutive models for these flows.
Simulations of Collisions in a Liquid We are interested in developing computational methods to compute flows in which particle interactions and the inertia of both the liquid and solid phases are important. To calculate the flow field, we have been using the immersed boundary method is used to simulate the process of a rigid sphere settling and colliding with a non-deforming solid wall. By including a contact model, the numerical method captures the elasticity of the solid boundaries and mitigates the resolution problem when the particle is close to the wall. The axisymmetric numerical method has been validated through comparisons with experimental measurements of particle collisions. We are interested in developing a three-dimensional code that models the collision process and can include many particles.
|
|||
| Booming Sand Dunes In approximately 30 known locations around the world with large sand dunes, an avalanching of sand is accompanied by a loud droning or booming sound, which is not a noise composed of many frequencies but instead contains a dominant audible frequency and several higher harmonics. The sound can be heard after a naturally occurring slumping event or triggered by forcing sand down the leeward face of a large dune. In the later case, the dune will continue to boom and vibrate even after the sand has visibly stopped moving. Field measurements show that the frequency ranges from 75 to 110 Hz depending on the desert location and time of the year. Our measurements suggest that the physical features (such as a moisture barrier) of the sand dune plus the characteristics of the shearing on the surface may contribute to a wave-guide phenomena that results in a resonate behavior at a characteristic frequency. We have made extensive measurements in several dune locations using seismic refraction techniques and ground penetrating radar. In 2009, we were part of an episode of National Geographic's Wild Spaces: Death Valley , which can be viewed at http://channel.nationalgeographic.com/series/americas-wild-spaces/4296/Overview#tab-Videos/06912_00 America's Wild Spaces: Death Valley In 2005, NOVA Science NOW included our field studies in their premier episode, http://www.pbs.org/wgbh/nova/earth/booming-sands.html
|
|
||
| Granular Flows Granular flows occur in industry (for example: dry chemicals, pharmaceutical powders, plastic pellets, toner), agriculture (grains, food products), natural environments (sand and debris flows), and in lunar and Martian exploration. Dry flows of these materials are governed by the particle collisions, and the interstitial fluid has negligible effect on the momentum transport. These flows are often modeled analytically by exploiting ideas from dense-gas kinetic theory, and through discrete particle simulations. In addition, discrete element simulations are used to compute dry flows by modeling the inelasticity and friction of the particles, and computing the motion by integrating Newton 's equation. We have been interested in mixing and segregation of granular materials, the effects of vibration, wave propagation, heat and mass transfer within the materials, and a variety of related processes involving these complex materials.
|
|||
|
|
|||
Select Recent Publications
|
|||
Courses
|
|||
|
Former Graduate Students and Postdoctoral Scholars
Thesis: Rheological measurements in liquid-solid flows
Thesis: Surface Deformation in a Liquid Environment Resulting from Single Particle Collisions
Thesis: Interaction Law for a Collision Between Two Solid Particles in a Viscous Liquid
Thesis: Collisional Dynamics of Macroscopic Particles in a Viscous Fluid
Thesis: Couette Flows of Granular Materials: Mixing, Rheology, and Energy Dissipation
Thesis: Buoyant Flows in Vertical Channels Relating to Smoke Movement in High-Rise Building Fires
Thesis: Vibration of Granular Materials
Thesis: Material and Thermal Transport in Vertical Granular Flows
Thesis: An Investigation of Velocity and Temperature Fields in Taylor-Couette Flows
|
|||
