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1994

Departmental Papers (MEAM)

Articles 1 - 4 of 4

Full-Text Articles in Mechanical Engineering

Gas Flow In Micr-Channels, John C. Harley, Yufend Huang, Haim H. Bau, Jay N. Zemel Sep 1994

Gas Flow In Micr-Channels, John C. Harley, Yufend Huang, Haim H. Bau, Jay N. Zemel

Departmental Papers (MEAM)

An experimental and theoretical investigation of low Reynolds number, high subsonic Mach number, compressible gas flow in channels is presented. Nitrogen, helium, and argon gases were used. The channels were microfabricated on silicon wafers and were typically 100 μm wide, 104 μm long, and ranged in depth from 0.5 to 20 μm. The Knudsen number ranged from 10-3 to 0.4. The measured friction factor was in good agreement with theoretical predictions assuming isothermal, locally fully developed, first-order, slip flow.


Direct Simulation Of Initial Value Problems For The Motion Of Solid Bodies In A Newtonian Fluid. Part 2. Couette Adn Poiseuille Flows., James Feng, Howard H. Hu, Daniel D. Joseph May 1994

Direct Simulation Of Initial Value Problems For The Motion Of Solid Bodies In A Newtonian Fluid. Part 2. Couette Adn Poiseuille Flows., James Feng, Howard H. Hu, Daniel D. Joseph

Departmental Papers (MEAM)

This paper reports the results of a two-dimensional finite element simulation of the motion of a circular particle in a Couette and a Poiseuille flow. The size of the particle and the Reynolds number are large enough to include fully nonlinear inertial effects and wall effects. Both neutrally buoyant and non-neutrally buoyant particles are studied, and the results are compared with pertinent experimental data and perturbation theories. A neutrally buoyant particle is shown to migrate to the centreline in a Couette flow, and exhibits the Segré-Silberberg effect in a Poiseuille flow. Non-neutrally buoyant particles have more complicated patterns of migration ...


Effect Of Negative Ions On Electrical Breakdown In A Nonuniform Air Gap Between A Wire And A Plane, K. Ramakrishna, Ira M. Cohen, Portonovo S. Ayyaswamy Jan 1994

Effect Of Negative Ions On Electrical Breakdown In A Nonuniform Air Gap Between A Wire And A Plane, K. Ramakrishna, Ira M. Cohen, Portonovo S. Ayyaswamy

Departmental Papers (MEAM)

Electrical breakdown of an axisymmetric, atmospheric pressure air gap between a wire and a plane has been investigated for a gap length of 0.5 mm. 0- and 02- have been identified as the negative ions affecting the discharge development in air, besides electrons and positive ions, and have been included in the electrical breakdown model. Five coupled two-dimensional transient partial differential equations describing the discharge evolution in the air gap have been solved using a finite difference algorithm developed earlier. Temporal development of the charged particle number densities, electrostatic potential, electric field, and current at both the electrodes ...


Direct Simulation Of Initial Value Problems For The Motion Of Solid Bodies In A Newtonian Fluid Part 1. Sedimentation, James Feng, Howard H. Hu, Daniel D. Joseph Jan 1994

Direct Simulation Of Initial Value Problems For The Motion Of Solid Bodies In A Newtonian Fluid Part 1. Sedimentation, James Feng, Howard H. Hu, Daniel D. Joseph

Departmental Papers (MEAM)

This paper reports the result of direct simulations of fluid-particle motions in two dimensions. We solve the initial value problem for the sedimentation of circular and elliptical particles in a vertical channel. The fluid motion is computed from the Navier-Stokes equations for moderate Reynolds numbers in the hundreds. The particles are moved according to the equations of motion of a rigid body under the action of gravity and hydrodynamic forces arising from the motion of the fluid. The solutions are as exact as our finite-element calculations will allow. As the Reynolds number is increased to 600, a circular particle can ...