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Full-Text Articles in Aerospace Engineering
Liquid Phase Stability Under An Extreme Temperature Gradient, Zhi Liang, Kiran Sasikumar, Pawel Keblinski
Liquid Phase Stability Under An Extreme Temperature Gradient, Zhi Liang, Kiran Sasikumar, Pawel Keblinski
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Using Nonequilibrium Molecular Dynamics Simulations, We Subject Bulk Liquid to a Very High-Temperature Gradient and Observe a Stable Liquid Phase with a Local Temperature Well above the Boiling Point. Also, under This High-Temperature Gradient, the Vapor Phase Exhibits Condensation into a Liquid at a Temperature Higher Than the Saturation Temperature, Indicating that the Observed Liquid Stability is Not Caused by Nucleation Barrier Kinetics. We Show that, Assuming Local Thermal Equilibrium, the Phase Change Can Be Understood from the Thermodynamic Analysis. the Observed Elevation of the Boiling Point is Associated with the Interplay between the "Bulk" Driving Force for the Phase …
Kinetic Simulations Of Plasma Plume Potential In A Vacuum Chamber, Joseph J. Wang, Daoru Frank Han, Yuan Hu
Kinetic Simulations Of Plasma Plume Potential In A Vacuum Chamber, Joseph J. Wang, Daoru Frank Han, Yuan Hu
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Direct Simulation Monte Carlo and Particle-in-Cell simulations are carried out to study the potential of a mesothermal plasma plume in a vacuum chamber. The results show that the beam potential with respect to the ambient in a vacuum chamber is different from that in space because the facility plasma can prematurely terminate the plume expansion process. As a result, the plume potential measured in a vacuum chamber may be significantly lower than that under the in-space condition. This can lead to under estimation of the backflow of CEX ions and ionized contaminants in plasma thruster plume modeling.
Simulations Of Ion Thruster Plume Contamination With A Whole Grid Sputtered Mo Source Model, Daoru Frank Han, Joseph J. Wang
Simulations Of Ion Thruster Plume Contamination With A Whole Grid Sputtered Mo Source Model, Daoru Frank Han, Joseph J. Wang
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A particle simulation based source model is developed to calculate the density distribution of the sputtered Mo atoms for a whole ion optics grid. The source model is used in PIC simulation of ion thruster plume contamination for 3-grid and 2-grid ion thrusters. The results show that the commonly used point-source approximation for sputtered Mo atoms is oversimplified and would lead to over-prediction of contamination deposition.
Analysis Of Damage In Laminated Architectural Glazing Subjected To Wind Loading And Windborne Debris Impact, Mahesh S. Shetty, Jun Wei, Lokeswarappa R. Dharani, Daniel S. Stutts
Analysis Of Damage In Laminated Architectural Glazing Subjected To Wind Loading And Windborne Debris Impact, Mahesh S. Shetty, Jun Wei, Lokeswarappa R. Dharani, Daniel S. Stutts
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Wind loading and windborne debris (missile) impact are the two primary mechanisms that result in window glazing damage during hurricanes. Wind-borne debris is categorized into two types: small hard missiles such as roof gravel, and large soft missiles representing lumber from wood-framed buildings. Laminated architectural glazing (LAG) may be used in buildings where impact resistance is needed. The glass plies in LAG undergo internal damage before total failure. The bulk of the published work on this topic either deals with the stress and dynamic analyses of undamaged LAG or the total failure of LAG. The pre-failure damage response of LAG …
Equilibrium And Nonequilibrium Molecular Dynamics Simulations Of Thermal Conductance At Solid-Gas Interfaces, Zhi Liang, William Evans, Pawel Keblinski
Equilibrium And Nonequilibrium Molecular Dynamics Simulations Of Thermal Conductance At Solid-Gas Interfaces, Zhi Liang, William Evans, Pawel Keblinski
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The Thermal Conductance at Solid-Gas Interfaces with Different Interfacial Bonding Strengths is Calculated through Green-Kubo Equilibrium Molecular Dynamics (EMD) Simulations. Due to the Finite Size of the Simulation System, the Long-Time Integral of the Time Correlation Function of Heat Power Across the Solid-Gas Interface Exhibits an Exponential Decay, Which Contains the Information on Interfacial Thermal Conductance. If an Adsorbed Gas Layer is Formed on the Solid Surface, It is Found that the Solid-Gas Interface Needs to Be Defined at a Plane Outside the Adsorbed Layer So as to Obtain the Correct Result from the Green-Kubo Formula. the EMD Simulation Result …
Improvement Of Heat Transfer Efficiency At Solid-Gas Interfaces By Self-Assembled Monolayers, Zhi Liang, William Evans, Tapan Desai, Pawel Keblinski
Improvement Of Heat Transfer Efficiency At Solid-Gas Interfaces By Self-Assembled Monolayers, Zhi Liang, William Evans, Tapan Desai, Pawel Keblinski
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Using Molecular Dynamics Simulations, We Demonstrate that the Efficiency of Heat Exchange between a Solid and a Gas Can Be Maximized by Functionalizing Solid Surface with Organic Self-Assembled Monolayers (SAMs). We Observe that for Bare Metal Surfaces, the Thermal Accommodation Coefficient (TAC) Strongly Depends on the Solid-Gas Interaction Strength. for Metal Surfaces Modified with Organic SAMs, the TAC is Close to its Theoretical Maximum and is Essentially Independent from the SAM-Gas Interaction Strength. the Analysis of the Simulation Results Indicates that Softer and Lighter SAMs, Compared to the Bare Metal Surfaces, Are Responsible for the Greatly Enhanced TAC. © 2013 …
Numerical Study Of Pressure Fluctuations Due To A Mach 6 Turbulent Boundary Layer, Lian Duan, Meelan M. Choudhari
Numerical Study Of Pressure Fluctuations Due To A Mach 6 Turbulent Boundary Layer, Lian Duan, Meelan M. Choudhari
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Direct numerical simulations (DNS) are used to examine the pressure fluctuations generated by a Mach 6 turbulent boundary layer with nominal freestream Mach number of 6 and Reynolds number of Reτ ≈ 464. The emphasis is on comparing the primarily vortical pressure signal at the wall with the acoustic freestream signal under higher Mach number conditions. Moreover, the Mach-number dependence of pressure signals is demonstrated by comparing the current results with those of a supersonic boundary layer at Mach 2.5 and Reτ ≈ 510. It is found that the freestream pressure intensity exhibits a strong Mach number dependence, irrespective of …