Mechanical Engineering Commons^™

Effect Of Thin Film Confined Between Two Dissimilar Solids On Interfacial Thermal Resistance, Zhi Liang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Non-Equilibrium Molecular Dynamics Model is Developed to Investigate How a Thin Film Confined between Two Dissimilar Solids Affects the Thermal Transport Across the Material Interface. for Two Highly Dissimilar (Phonon Frequency Mismatched) Solids, It is Found that the Insertion of a Thin Film between Them Can Greatly Enhance Thermal Transport Across the Material Interface by a Factor of 2.3 If the Thin Film Has One of the Following Characteristics: (1)a Multi-Atom-Thick Thin Film of Which the Phonon Density of States (DOS) Bridges the Two Different Phonon DOSs for the Solid on Each Side of the Thin Film; (2)a Single-Atom-Thick …

Optimization Of A Low Reynold's Number 2-D Inflatable Airfoil Section, Todd A. Johansen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A stand-alone genetic algorithm (GA) and an surrogate-based optimization (SBO) combined with a GA were compared for accuracy and performance. Comparisons took place using the Ackley Function and Rastrigin's Function, two functions with multiple local maxima and minima that could cause problems for more traditional optimization methods, such as a gradient-based method. The GA and SBO with GA were applied to the functions through a fortran interface and it was found that the SBO could use the same number of function evaluations as the GA and achieve at least 5 orders of magnitude greater accuracy through the use of surrogate …

Direct Numerical Simulation Of Hypersonic Turbulent Boundary Layers. Part 4. Effect Of High Enthalpy, L. (Lian) Duan, M. P. Martín

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper we present direct numerical simulations (DNS) of hypersonic turbulent boundary layers to study high-enthalpy effects. We study high-and low-enthalpy conditions, which are representative of those in hypersonic flight and ground-based facilities, respectively. We find that high-enthalpy boundary layers closely resemble those at low enthalpy. Many of the scaling relations for low-enthalpy flows, such as van-Driest transformation for the mean velocity, Morkovin's scaling, and the modified strong Reynolds analogy hold or can be generalized for high-enthalpy flows by removing the calorically perfect-gas assumption. We propose a generalized form of the modified Crocco relation, which relates the mean temperature …

3d Simulation Of Wind Turbine Rotors At Full Scale. Part Ii: Fluid–Structure Interaction Modeling With Composite Blades, Y. Bazilevs, Ming-Chen Hsu, J. Kiendel, R. Wuchner, K. U. Bletzigner

Ming-Chen Hsu

In this two-part paper, we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The fluid mechanics formulation and its suitability and accuracy for rotating turbulent flows; 3. The coupling of air flow and a rotating rigid body. In Part 2, we focus on the structural discretization for wind turbine blades and the details of the fluid–structure interaction computational …

High-Performance Computing Of Wind Turbine Aerodynamics Using Isogeometric Analysis, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs

Ming-Chen Hsu

In this article we present a high-performance computing framework for advanced flow simulation and its application to wind energy based on the residual-based variational multiscale (RBVMS) method and isogeometric analysis. The RBVMS formulation and its suitability and accuracy for turbulent flow in a moving domain are presented. Particular emphasis is placed on the parallel implementation of the methodology and its scalability. Two challenging flow cases were considered: the turbulent Taylor–Couette flow and the NREL 5 MW offshore baseline wind turbine rotor at full scale. In both cases, flow quantities of interest from the simulation results compare favorably with the reference …

Effective Approach For Estimating Turbulence-Chemistry Interaction In Hypersonic Turbulent Boundary Layers, L. (Lian) Duan, M. P. Martín

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An effective approach for estimating turbulence-chemistry interaction in hypersonic turbulent boundary layers is proposed, based on "laminar- chemistry" Reynolds-averaged Navier-Stokes mean flow solutions. The approach combines an assumed probability density function with a temperature fluctuation scaling, which provides the second moment for specifying the shape of the probability density function. As a result, the effects of temperature fluctuation on chemical production rates can be estimated without solving an additional moment evolution equation. The validity of this method is demonstrated using direct-numerical-simulation data. This approach can be used to identify regions with potentially significant turbulence-chemistry interaction in hypersonic boundary layers and …

A Multi-Regulator Sliding Mode Control Strategy For Output-Constrained Systems, Hanz Richter

Mechanical Engineering Faculty Publications

This paper proposes a multi-regulator control scheme for single-input systems, where the setpoint of a regulated output must be changed under the constraint that a set of minimum-phase outputs remain within prescribed bounds. The strategy is based on a max–min selector system frequently used in the aerospace field. The regulators used for the regulated and limited outputs are of the sliding mode type, where the sliding variable is defined as the difference between an output and its allowable limit. The paper establishes overall asymptotic stability, as well as invariance properties leading to limit protection. The design methodology is illustrated with …

Vortex Shedding From Elongated Bluff Bodies, Zachary J. Taylor

Electronic Thesis and Dissertation Repository

As the spans of suspension bridges increase, the structures become inherently flexible. The flexibility of these structures, combined with the wind and particular aerodynamics, can lead to significant motions. From the collapse due to flutter of the Tacoma Narrows Bridge to the case of vortex-induced vibrations (VIV) of the Storebælt Bridge, it is evident that a better understanding of the aerodynamics of these geometries is necessary. The work herein is motivated by these two problems and is presented in two parts.

In the first part, the focus is on the physical mechanisms of vortex shedding. It is shown that the …

Effect Of The Thickness Of Undoped Gan Interlayers Between Multiple Quantum Wells And The P-Doped Layer On The Performance Of Gan Light-Emitting Diodes, T. Lu, S. Li, K. Zhang, C. Liu, Y. Yin, L. Wu, H. Wang, Xiaodong Yang, G. Xiao, Y. Zhou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

InGaN based light-emitting diodes (LEDs) with undoped GaN interlayer of variant thicknesses grown by metal-organic chemical vapor deposition technique have been investigated. It was found that the thickness of undoped GaN interlayers affected LEDs' performance greatly. The LED with 50 nm undoped GaN interlayer showed higher light output power and lower reverse-leakage current compared with the others at 20 mA. Based on electrical and optical characteristics analysis and numerical simulation, these improvements are mainly attributed to the improvement of the quality of depletion region by inserting an undoped GaN layer, as well as reduction of the Shockley-Read-Hall recombination in InGaN/GaN …

Vibration-Based Health Monitoring Of Multiple-Stage Gear Train And Differential Planetary Transmission Involving Teeth Damage And Backlash Nonlinearity, Andrew Patrick Sommer

Master's Theses

The objective of this thesis is to develop vibration-based fault detection strategies for on-line condition monitoring of gear transmission systems. The study divides the thesis into three sections. First of all, the local stresses created by a root fatigue crack on a pinion spur gear are analyzed using a quasi-static finite element model and non-linear contact mechanics simulation. Backlash between gear teeth which is essential to provide better lubrication on tooth surfaces and to eliminate interference is included as a defect and a necessary part of transmission design. The second section is dedicated to fixed axis power trains. Torsional vibration …

The Biglobal Instability Of The Bidirectional Vortex, Joshua Will Batterson

Doctoral Dissertations

State of the art research in hydrodynamic stability analysis has moved from classic one-dimensional methods such as the local nonparallel approach and the parabolized stability equations to two-dimensional, biglobal, methods. The paradigm shift toward two dimensional techniques with the ability to accommodate fully three-dimensional base flows is a necessary step toward modeling complex, multidimensional flowfields in modern propulsive applications. Here, we employ a two-dimensional spatial waveform with sinusoidal temporal dependence to reduce the three-dimensional linearized Navier-Stokes equations to their biglobal form. Addressing hydrodynamic stability in this way circumvents the restrictive parallel-flow assumption and admits boundary conditions in the streamwise direction. …

Continuously Variable Rotorcraft Propulsion System: Modelling And Simulation, Naveen Kumar Vallabhaneni

Masters Theses

This study explores the variable speed operation and shift response of a prototype of a two speed single path CVT rotorcraft driveline system. Here a Comprehensive Variable Speed Rotorcraft Propulsion system Modeling (CVSRPM) tool is developed and utilized to simulate the drive system dynamics in steady forward speed condition. This investigation attempts to build upon previous variable speed rotorcraft propulsion studies by:

1) Including fully nonlinear first principles based transient gas-turbine engine model

2) Including shaft flexibility

3) Incorporating a basic flight dynamics model to account for interactions with the flight control system.

Through exploring the interactions between the various …

Thermal Expansions In Wurtzite Aln, Gan, And Inn: First-Principle Phonon Calculations, L.-C. Xu, R.-Z. Wang, Xiaodong Yang, H. Yan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Using the first-principle phonon calculations under the quasiharmonic approximation, thermal expansions in III-nitrides with wurtzite AlN, GaN, and InN are reported. The results showed that it is different for each thermal expansion of three III-nitrides at low temperatures, which is consistent with their Grneisen parameters as the function of temperature. Below 50 K, negative thermal expansions occur in InN, while GaN and AlN follow the rule of positive thermal expansion. To seek the origin of positivenegative thermal expansion distinction, the mode Grneisen parameters and the phonon spectra are investigated. They indicate that different low-frequency phonon vibration modes correspond to the …

Effects Of Supercooled Water Ingestion On Engine Performance, Rick Hutchings

Masters Theses

An aircraft will encounter freezing rain, snow, and ice during ground operation and flight. In cold conditions, ice may form on th einlet and internal stators and rotors of the gas turbine engine. When ice accumulates on blades (and/or stators), the aerodynamic characteristics of the blades change due to the altered size, shape, and roughness. This change causes the blade to no longer operate at its design point and decreases compressor performance. Therefore, characterization of the aerodynamic performance is required to define the associated losses due to the effects of supercooled liquid water ingestion. This characterization can be accomplished through …

Astro Camp Presentation, Get Away Special Team 2011

Education and Outreach

No abstract provided.

A Study On Facility Planning Using Discrete Event Simulation: Case Study Of A Grain Delivery Terminal., Sarah M. Asio

Department of Industrial and Management Systems Engineering: Dissertations, Theses, and Student Research

The application of traditional approaches to the design of efficient facilities can be tedious and time consuming when uncertainty and a number of constraints exist. Queuing models and mathematical programming techniques are not able to capture the complex interaction between resources, the environment and space constraints for dynamic stochastic processes. In the following study discrete event simulation is applied to the facility planning process for a grain delivery terminal. The discrete event simulation approach has been applied to studies such as capacity planning and facility layout for a gasoline station and evaluating the resource requirements for a manufacturing facility. To …

Interface Circuit For A Multiple-Beam Tuning-Fork Gyroscope With High Quality Factors, Ren Wang

Mechanical & Aerospace Engineering Theses & Dissertations

This research work presents the design, theoretical analysis, fabrication, interface electronics, and experimental results of a Silicon-On-Insulator (SOI) based Multiple-Beam Tuning-Fork Gyroscope (MB-TFG). Based on a numerical model of Thermo-Elastic Damping (TED), a Multiple-Beam Tuning-Fork Structure (MB-TFS) is designed with high Quality factors (Qs) in its two operation modes. A comprehensive theoretical analysis of the MB-TFG design is conducted to relate the design parameters to its operation parameters and further performance parameters. In conjunction with a mask that defines the device through trenches to alleviate severe fabrication effect on anchor loss, a simple one-mask fabrication process is employed to implement …

Effect Of Molecular Film Thickness On Thermal Conduction Across Solid-Film Interfaces, Zhi Liang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Brownian Motion and Aggregation of Particles in Nanofluids Often Lead to the Formation of Solid-Film-Solid Structures. the Molecular Thin Film Confined between Nanoparticles May Have Non-Negligible Effects on Thermal Conduction among Nanoparticles. using Nonequilibrium Molecular Dynamics Simulations, We Study Thermal Conduction Across the Ag Particle-Ar Thin-Film Interface. If the Film Contains Only One Molecular Layer, We Find that the Solid-Film Interfacial Thermal Resistance RSF is About 1 Order of Magnitude Smaller Than the Solid-Liquid (Bulk) Interfacial Thermal Resistance RSL. If There Are Two or More Molecular Layers in the Film, It is Shown that RSF Increases Rapidly toward RSL …

Port Flow Test System, Daniel Chairez, Chelsea E. Crawford, Daniel S. Welch

Mechanical Engineering

Solar Turbines Gas Compressor Engineering Division of San Diego, California called upon the Mechanical Engineering students of California Polytechnic University, San Luis Obispo to provide recommendations for optimization of compressor end cap port design. Various sizes of compressors have end caps with numerous ports that exchange fluids between the inside and outside of the working fluid pressure vessel. Because so many ports must exist on the end caps, unusual flow paths are created to supply the appropriate location within the compressor. These flow paths commonly consist of a drilled inlet hole which intersects with a sudden expansion. The sudden expansion …

Cal Poly Human Powered Helicopter, Josiah Auer, Eric Behne, Dave Berry, Rebecca Hennings, James Koch, Ian Marquardt, Josiah Mayfield, Sean Miller

Mechanical Engineering

The following report encompasses the Cal Poly Human Powered Helicopter team’s efforts during the 2010-2011 academic year. The intention of this project is to further the knowledge of human powered helicopter design and to validate an ideal configuration through experimental tests and analysis.

A. Background

The Sikorsky Prize offered by the American Helicopter Society has been the catalyst for many attempts at Human Powered Helicopter (HPH) flight. The requirement to win the prize is a continuous, human powered flight of more than 60 seconds that stays within a 10 meter square box and reaches an altitude greater than 3 meters …

Rayleigh Test Apparatus Design Report, Josef Duller, Owen Raybould, James Nicovich

Mechanical Engineering

The Rayleigh Test Apparatus is a device that will be used to test the thermodynamic properties of Nitrous Oxide to assess the feasibility of using this fluid as a coolant for a hybrid rocket aero spike. The aero spike is intended to redirect the propulsion flow as it leaves the engine to create a more efficient flow pattern at low and high altitudes. However, there are issues of overheating which leads to melting of the aero spike. For this reason, the use of nitrous oxide (N2O) as a coolant is being explored. N20 is being considered because it is already …

Development Of A Cubesat Instrument For Microgravity Particle Damper Performance Analysis, John Trevor Abel

Master's Theses

Spacecraft pointing accuracy and structural longevity requirements often necessitate auxiliary vibration dissipation mechanisms. However, temperature sensitivity and material degradation limit the effectiveness of traditional damping techniques in space. Robust particle damping technology offers a potential solution, driving the need for microgravity characterization. A 1U cubesat satellite presents a low cost, low risk platform for the acquisition of data needed for this evaluation, but severely restricts available mass, volume, power and bandwidth resources. This paper details the development of an instrument subject to these constraints that is capable of capturing high resolution frequency response measurements of highly nonlinear particle damper dynamics.

Design And Fabrication Of An Autonomous Solar Powered Airship, Mitchell Van Lee

Honors Theses

The purpose of the project was to design and build a prototype small scale photovoltaic (PV) powered autonomous airship. The principle reason for the construction of the unmanned airship was to investigate the possibility of using self-guided, lighter-than-air aircraft as an alternative to earth observational satellites for the purposes of terrain mapping and imaging. The necessary electrical energy was produced by single crystal photovoltaic solar cells. The airship was designed to carry an onboard battery in order to provide power generation in the case of intermittent cloud coverage. It was also designed to interface with an Arduino prototyping board which …

Sae Aero Design Project, Angela N. Mclelland

Honors Theses

The Union College Flying Dutchmen Team aims to compete in the spring 2011, SAE Aero Design® East Competition. This regional event, hosted by the Society of Automotive Engineers International, is a threefold opportunity for teams from around the globe to showcase their understanding of engineering fundamentals. Competing in the SAE Aero Design® competition creates an arena for students to participate in hands-on design, to emphasize technological innovations in a competition setting, and to cooperate in a unique atmosphere where intellectual advancement and teamwork are championed above success. The underlying goal of the SAE Aero Design® competition is to design and …

Effect Of Unsteady Combustion On The Stability Of Rocket Engines, Tina Morina Rice

Doctoral Dissertations

Combustion instability is a problem that has plagued the development of rocket-propelled devices since their conception. It is characterized by the occurrence of high-frequency nonlinear gas oscillations inside the combustion chamber. This phenomenon degrades system performance and can result in damage to both structure and instrumentation.

The goal of this dissertation is to clarify the role of unsteady combustion in the combustor instability problem by providing the first quantified estimates of its effect upon the stability of liquid rocket engines. The combination of this research with a new system energy balance method, accounting for all dynamic interactions within a system, …

Cross-Flow, Staggered-Tube Heat Exchanger Analysis For High Enthalpy Flows, Gary L. Hammock

Masters Theses

Cross flow heat exchangers are a fairly common apparatus employed throughout many industrial processes. For these types of systems, correlations have been extensively developed. However, there have been no correlations done for very high enthalpy flows as produced by Arnold Engineering Development Center’s (AEDC) H2 facility. The H2 facility uses a direct current electric arc to heat air which is then expanded through a converging-diverging nozzle to impart a supersonic velocity to the air. This high enthalpy, high temperature air must be cooled downstream by the use of a cross flow heat exchanger.

It is of interest to evaluate the …

Airplane Landing Flare-The Last 5 Seconds, Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

Modeling And Analysis Of Turbojet Compressor Inlet Temperature Measurement System Performance, Brian A Binkley

Masters Theses

Accurate measurement of turbine engine compressor inlet total temperature is paramount for controlling engine speed and pressure ratio. Various methods exist for measuring compressor inlet total temperature on turbojet engines with hydromechanical control. One method involves the use of an ejector-diffuser system (eductor) to pull air from the engine inlet in order to measure the incoming total temperature. Analysis of historical test data has revealed that the inlet temperature measurement can be biased at certain flight conditions causing engine mis-scheduling and off-nominal engine operation. This bias is characterized primarily by adverse heat transfer effects and secondly by poor flow quality …

Direct Numerical Simulation Of Hypersonic Turbulent Boundary Layers. Part 3. Effect Of Mach Number, L. (Lian) Duan, I. Beekman, M. P. Martín

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, we perform direct numerical simulations (DNS) of turbulent boundary layers with nominal free-stream Mach number ranging from 0.3 to 12. The main objective is to assess the scaling's with respect to the mean and turbulence behaviors as well as the possible breakdown of the weak compressibility hypothesis for turbulent boundary layers at high Mach numbers (M > 5). We find that many of the scaling relations, such as the van Driest transformation for mean velocity, Walz's relation, Morkovin's scaling and the strong Reynolds analogy, which are derived based on the weak compressibility hypothesis, remain valid for the range …

Surface Geometry And Heat Flux Effect On Thin Wire Nucleate Pool Boiling Of Subcooled Water In Mictrogravity, Troy Munro, Heng Ban

Presentations

No abstract provided.