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Full-Text Articles in Engineering
Unified Theory Of Gas Damping Of Flexible Microcantilevers At Low Ambient Pressures, Rahul A. Bidkar, Ryan C. Tung, Alina A. Alexeenko, Hartono Sumali, Arvind Raman
Unified Theory Of Gas Damping Of Flexible Microcantilevers At Low Ambient Pressures, Rahul A. Bidkar, Ryan C. Tung, Alina A. Alexeenko, Hartono Sumali, Arvind Raman
School of Aeronautics and Astronautics Faculty Publications
No abstract provided.
Modeling Of Viscous Shock Tube Using Es-Bgk Model Kinetic Equations, S Chigullapalli, A Venkattraman, Alina A. Alexeenko
Modeling Of Viscous Shock Tube Using Es-Bgk Model Kinetic Equations, S Chigullapalli, A Venkattraman, Alina A. Alexeenko
School of Aeronautics and Astronautics Faculty Publications
The viscous effects on unsteady shock wave propagation are investigated by numerical solution of the Boltzmann model kinetic equations. The kinetic equations are solved for two unsteady non-equilibrium flow problems, namely, the one-dimensional Riemann problem and a two-dimensional viscous shock-tube. The numerical method comprises the discrete velocity method in the velocity space and the finite volume discretization in physical space using various flux schemes. The discrete version of H-theorem is applied for analysis of accuracy of the numerical solution as well as of the onset of non-equilibrium. Simulations show that the maximum entropy generation rate in viscous shock tube occurs …
Simulations Of Aerodynamic Damping For Mems Resonators, Xiaohui Guo, Alina A. Alexeenko
Simulations Of Aerodynamic Damping For Mems Resonators, Xiaohui Guo, Alina A. Alexeenko
School of Aeronautics and Astronautics Faculty Publications
Aerodynamic damping for MEMS resonators is studied based on the numerical solution of Boltzmann-ESBGK equation. A compact model is then developed based on numerical simulations for a wide range of Knudsen numbers. The damping predictions are compared with both Reynold equation based models and several sets of experimental data. It has been found that the structural damping is dominant at low pressures (high Knudsen numbers). For cases with small length-to-width ratios and large vibration amplitudes, the threedimensionality effects must be taken into account. Finally, an uncertainty quantification approach based on the probability transformation method has been applied to assess the …
Numerical Investigation Of Power Transmission Efficiency In A Rf Plasma, Akshay Ashok, William Stein, Alina A. Alexeenko
Numerical Investigation Of Power Transmission Efficiency In A Rf Plasma, Akshay Ashok, William Stein, Alina A. Alexeenko
School of Aeronautics and Astronautics Faculty Publications
Capacitively coupled radio frequency discharges are used in a variety of applications in which the power transmission efficiency of the discharge is an important performance parameter. While previous research addressed the discharge properties and discharge modeling, little analysis has been done on the dependence of the power transmission efficiency on main discharge paremeters such as applied voltage, operating frequency and pressure. To investigate the effects of a dual frequency waveform on the power transmission efficiency, Particle-InCell/Monte-Carlo Collison (PIC/MCC) methods are used to simulate RF co-axial plasma discharge. Plasma characteristics are studied for a range of operating pressures and radii, as …
Modeling Of Subcontinuum Thermal Transport Across Semiconductor-Gas Interfaces, Dhruv Singh, Xiaohui Guo, Alina A. Alexeenko, Jayathi Y. Murthy, Timothy S. Fisher
Modeling Of Subcontinuum Thermal Transport Across Semiconductor-Gas Interfaces, Dhruv Singh, Xiaohui Guo, Alina A. Alexeenko, Jayathi Y. Murthy, Timothy S. Fisher
School of Aeronautics and Astronautics Faculty Publications
A physically rigorous computational algorithm is developed and applied to calculate subcontinuum thermal transport in structures containing semiconductor-gas interfaces. The solution is based on a finite volume discretization of the Boltzmann equation for gas molecules (in the gas phase) and phonons (in the semiconductor). A partial equilibrium is assumed between gas molecules and phonons at the interface of the two media, and the degree of this equilibrium is determined by the accommodation coefficients of gas molecules and phonons on either side of the interface. Energy balance is imposed to obtain a value of the interface temperature. The classic problem of …
Simulations And Measurements Of Gas-Droplet Flows In Supersonic Jets Expanding Into Vacuum, A Venkattraman, Alina A. Alexeenko
Simulations And Measurements Of Gas-Droplet Flows In Supersonic Jets Expanding Into Vacuum, A Venkattraman, Alina A. Alexeenko
School of Aeronautics and Astronautics Faculty Publications
Simulations and measurements of gas-droplet multiphase flows in application to supersonic expansions into vacuum have been considered and compared with each other. The experiments involved exposing a control surface to a supersonic plume from two different nozzles and measuring the size distribution of droplets at various locations. The simulations are based on the direct simulation Monte Carlo modeling of vapor-phase flow with a one-way coupling of droplet momentum and energy. The droplet trajectories are computed for the experimental conditions for droplets originating at the throat and lip of two different nozzles. The maximum droplet radius reaching the control surface and …
Numerical Simulation Of Gas-Phonon Coupling In Thermal Transpiration Flows, Xiaohui Guo, Dhruv Singh, Jayathi Murthy, Alina A. Alexeenko
Numerical Simulation Of Gas-Phonon Coupling In Thermal Transpiration Flows, Xiaohui Guo, Dhruv Singh, Jayathi Murthy, Alina A. Alexeenko
School of Aeronautics and Astronautics Faculty Publications
Thermal transpiration is a rarefied gas flow driven by a wall temperature gradient and is a promising mechanism for gas pumping without moving parts, known as the Knudsen pump. Obtaining temperature measurements along capillary walls in a Knudsen pump is difficult due to extremely small length scales. Meanwhile, simplified analytical models are not applicable under the practical operating conditions of a thermal transpiration device, where the gas flow is in the transitional rarefied regime. Here, we present a coupled gas-phonon heat transfer and flow model to study a closed thermal transpiration system. Discretized Boltzmann equations are solved for molecular transport …