Aerospace Engineering Commons^™

Solution To Incompressible Navier Stokes Equations By Using Finite Element Method, Wanchai Jiajan

Mechanical and Aerospace Engineering Theses - Archive

The finite element method has become a popular method for the solution of the incompressible Navier-Stokes equations. High Reynolds number cases require fine meshes so computational efficiency becomes an important factor in algorithm and code development. In this work, a Galerkin finite element method is proposed to solve the two dimensional incompressible Navier-Stokes equations. This approach typically leads to a sparse and indefinite matrix that is difficult to solve efficiently. The formation of an indefinite matrix is avoided in the present work by introducing an artificial compressibility term in the continuity equation. The concept of this method is to transform …

Finite Element Analysis Of Stresses In Involute Spur & Helical Gear, Shreyash D. Patel

Mechanical and Aerospace Engineering Theses - Archive

Developing an analytical approach and modeling procedure to evaluate stress distribution under velocity and moment would provide a useful tool to improve spur gear design with high efficiency & low cost. The purpose of this work is to analyze and validate the stress distribution in spur & helical gears using contemporary commercial FEM program ANSYS coupled with the Pro/E solid modeler. Gear profiles are created in Pro Engineer using the Relation and Equation modeling procedure so as to make it a general model, dependant on certain key features like number of teeth, diametral pitch, and pressure and helix angle. These …

Effects Of Curvature On The Stresses Of A Curved Laminated Beams Subjected To Bending, Thien Nguyen

Mechanical and Aerospace Engineering Theses - Archive

In aircraft structural applications, curved laminated beam structures are often used as part of the internal structure. If the curved composite structure is subjected to bending that tends to flatten or compress the composite structure, interlaminar stresses can be generated in the thickness direction of the composites. These interlaminar stresses are the major factor of delamination failure. Besides these stresses, the in-plane stresses can be also affected by the pre-existence of the beam curvature. This research has studied the variation of both tangential and radial stresses with respect to the changing in curvature, stacking sequence, and fiber orientation in a …

A Micromechanics Model Of Thermal Expansion Coefficient In Fiber Reinforced Composites, Nittapon Srisuk

Mechanical and Aerospace Engineering Theses - Archive

Fiber reinforced composites are widely used for the various applications in the aerospace, automotive, infrastructures and sporting goods industries. The evaluations of its mechanical and thermal properties are needed for accurate estimation of their structural response. In this study, a mathematical closed-form expression of unit cell model was developed to estimate the coefficient of thermal expansion (CTE) along longitudinal and transverse directions of unidirectional lamina. Unlike the previous models, the present model takes into consideration of the fiber configuration and volume fraction of each constituent in the unit cell. In addition, the model is also able to obtain the stresses …

Dynamic Thermal Management Of Multi Core Processors Using Core Hopping, Avinash Raghu

Mechanical and Aerospace Engineering Theses - Archive

Multi core processors are the order of the day today. The demand for greater levels of performance and the consequent increase in design complexity have rendered the single core processor obsolete and resulted in more cores being put onto a single chip. Processors incorporating more than 4 cores on a chip are dubbed many core processors. This, while improving performance, has lead to increased power densities. Also, the power distribution across the die surface is not uniform. These factors together, result in heat being concentrated at specific points on the die surface, called `hot spots'.The increase in die temperature results …

Mean Pressure Measurements Of Micro-Vortex Generator At Mach 2.5, Yusi Shih

Mechanical and Aerospace Engineering Theses - Archive

Shock wave/boundary layer interactions (SBLIs) are always an important issue for high-speed vehicles. SBLIs reduce the performance of aerodynamic surfaces and engine inlets, amongst a number of adverse effects. Micro-vortex generators (MVGs) are a potential flow control method that has seen intense investigation recently and have even been implemented in actual configurations at low speeds. The present research is focused on the mean pressures at Mach 2.5 around an MVG. Experiments were performed with a baseline flat plate and also with two MVG configurations (70 and 45 trailing edge) mounted ahead of a 5° ramp. In the present study MVGs …

Axial Wave Propagation In Truncated Cones, Bhumil A. Diwanji

Mechanical and Aerospace Engineering Theses - Archive

While dealing with problems of impact analysis, where the force is dependent on the time, one can use the transient analysis to compute the response. Transient wave propagation has drawn interest from a long time mainly because of the way structural members behave when subjected to high rates of loading. Solutions to these problems find applications in the design of various mechanical equipments, or any situation where rigid objects are impacting on structural members.The first part of this study deals with the axial wave propagation in cones of different apex angles using transient analysis in ANSYS. The results from the …

Fiber-Optic Pressure Sensor For Time-Of-Flight Measurements In A Shock Wave, Karthikeyan Jagadevan

Mechanical and Aerospace Engineering Theses - Archive

Fiber-optic sensors are widely employed to detect pressures and temperatures precisely. In particular, MEMS-based Ber-optic sensors are immune to electromagnetic interference but may have limitations at high temperatures as encountered in combustors. To ensure high-temperature survivability, such sensors may be bondedanodically. This project explains the development of a Ber-optic pressure sensor utilizing intensity based principle whereby a fused silica optical window was glued to the tungsten carbide enclosure. The development was estimated to determine high pressures of up to at least 3.5 MPa (507 psi). The sensor is designed to capture the pressure pulse and the time-of-flight (TOF) of a …

Peak Stress Of Composite Multiple-Hole Laminates With And Without Patch, Sakthivel Selvaraj

Mechanical and Aerospace Engineering Theses - Archive

In repairing of composite structures, the damage in the composite laminate is usually removed in the form of circular cutouts which results in holes in the laminate. Then a patch laminate is adhesively bonded to the damaged composite laminate. The presence of holes in any structures creates a high stress concentration at the edge of the hole which indeed reduces the life of the structure. The primary objective of this study is to investigate the high stress of the damaged laminate with different hole patterns and the effect of having single and double patches with various configurations on these hole …

Computational Model For Transient And Steady State Analysis Of A 1-Dimensional Auto-Thermal Reformer, Srikanth Honavara Prasad

Mechanical and Aerospace Engineering Theses - Archive

This study presents a 1-dimensional mathematical model of steam reformer to be used with high temperature solid oxide fuel cell (SOFC). Steam reforming (SR) is widely used in industries to produce hydrogen from hydrocarbons. There are various physical processes associated with chemical reactions in the SR of methane such as mass, heat and momentum transport. In this study a one-dimensional SR reactor with built-in preheater and mixing chamber connected to fuel gas and steam reservoirs is modeled and analyzed. The main part of the reformer is a metallic tube with catalyst coating on the inner walls, and it can be …

Alternative Cooling Technologies For Telecommunication Data Centers: Air Cooling And Rear Door Heat Exchangers, Venkata Naga Poornima Mynampati

Mechanical and Aerospace Engineering Theses - Archive

Telecommunication industry is currently emphasizing to a miniaturization and convergence. The need for smaller, smarter and faster devices is leading drastic increment in power density and accordingly, thermal management of such devices has become a challenge. The heat generated by the devices has to be dissipated in order to ensure proper and efficient functioning of the electronics. Electronics cooling ranges from device level to the room level cooling. Data Center is a facility (room) consisting of servers used for managing and transferring data or information. The thermal management of this facility is challenging due to the huge decrease in floor …

An Uncertainty Quantification Of The Variation Of Internal Heat Transfer Coefficients And The Effect On Airfoil Life, Jan H. Marsh

Electronic Theses and Dissertations

Uncertainty in accurately knowing applied internal heat transfer coefficients inside of a cooling passage can lead to variability in predicting low cycle fatigue life of a turbine vane or blade. Under-predicting a life value for a turbine part can have disastrous effects on the engine as a whole, and can negate efforts in innovative design for advanced cooling techniques for turbine components. Quantification of this fatigue life uncertainty utilizing a computational framework is the primary objective of this thesis. Through the use of probabilistic design methodologies a process is developed to simulate uncertainties of internal heat transfer coefficient, which are …

Overnight Atmospheric Transport And Chemical Processing Of Photochemically Aged Houston Urban And Petrochemical Industrial Plume, Rahul A. Zaveri, Paul B. Voss, Carl M. Berkowitz, Edward Fortner, Jun Zheng, Renyi Zhang, Ralph J. Valente, Roger L. Tanner, Daniel Holcomb, Thomas P. Hartley, Leslie Baran

Engineering: Faculty Publications

Overnight atmospheric transport and chemical evolution of photochemically aged Houston urban and petrochemical industrial plume were investigated in July 2005. We report here on the 26 July episode in which the aged plume was tagged 1.5 h before sunset with a pair of free-floating controlled meteorological balloons, which guided quasi-Lagrangian aircraft sampling in the plume as it was advected 300 km to the north over 8 h. The aged plume around sunset was well mixed within a 1600 m residual layer, and was characterized by enhanced levels of aerosol, O3, CO, olefins, acetaldehyde, total odd nitrogen compounds (NOy), and relatively …

Chemical Evolution Of Volatile Organic Compounds In The Outflow Of The Mexico City Metropolitan Area, E. C. Apel, L. K. Emmons, T. Karl, F. Flocke, A. J. Hills, S. Madronich, J. Lee-Taylor, A. Fried, P. Weibring, J. Walega, D. Richter, X. Tie, L. Mauldin, T. Campos, A. Weinheimer, D. Knapp, B. Sive, L. Kleinman, S. Springston, R. Zaveri, J. Ortega, Paul Voss, D. Blake, A. Baker, C. Warneke, D. Welsh-Bon, J. De Gouw, J. Zheng, R. Zhang, J. Rudolph, W. Junkermann, D. D. Riemer

Engineering: Faculty Publications

The volatile organic compound (VOC) distribution in the Mexico City Metropolitan Area (MCMA) and its evolution as it is uplifted and transported out of the MCMA basin was studied during the 2006 MILAGRO/MIRAGE-Mex field campaign. The results show that in the morning hours in the city center, the VOC distribution is dominated by non-methane hydrocarbons (NMHCs) but with a substantial contribution from oxygenated volatile organic compounds (OVOCs), predominantly from primary emissions. Alkanes account for a large part of the NMHC distribution in terms of mixing ratios. In terms of reactivity, NMHCs also dominate overall, especially in the morning hours. However, …

Measurement Sensitivity In Tapping-Mode Atomic Force Microscopy Using A Bi-Harmonic Drive Signal, Santosh R. Kodandarama, Douglas A. Bristow

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In tapping mode atomic force microscopy, surface features are measured indirectly via the amplitude of the tapping cantilever. a change in surface profile is detectable only if it results in an amplitude change that is significant enough to be measured by the optics. Previous works have focused on improving sensitivity through the system's Q-factor, either by changing physical cantilever properties or using feedback control, but those approaches undesirably slow down the dynamic response. in this work we take a novel approach to sensitivity amplification by reshaping the tapping trajectory. by shaping the trajectory so that the probe spends a greater …

An Investigation On Pulsing Performance Of Mn Class Bi-Propellant Thrusters, Carlos Francisco Gomez

Open Access Theses & Dissertations

With the advancement of technology and machining methods, considerable attention has been focused in manufacturing micro thrusters for micro spacecraft applications (Yetter et al, 2003). Micro propulsion systems are currently being investigated for Miniature Kill Vehicles (MKV) and Micro Satellite Systems (MSS) with an emphasis in reducing weight and cost but without affecting performance. Reducing the weight seems practical when reducing the size of the propulsion system, but problems are encountered with system design.

In addition, propulsion requirements strongly influence choice in propellant and complexity. A thorough understanding of stabilizing thrust levels and the ability to control the propulsion system …

Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha, Florin Bobaru

Department of Engineering Mechanics: Faculty Publications

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …

Influence Of Interactions Between Turbulence And Radiation On Transmissivities In Hypersonic Turbulent Boundary Layers, A. M. Feldick, L. (Lian) Duan, M. F. Modest, M. P. Martín, D. A. Levin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In the current paper, a high-fidelity large eddy simulation solver is coupled to our modified line-by-line radiative transport equation solver to study the effects of absorption turbulence-radiation interations in a hypersonic turbulent boundary layer, representative of the Orion CEV entering Earth's atmosphere, at peak heating condition. The turbulent and radiation fields represent extreme conditions typical of Orion, as the simulated boundary layer represents the region of high turbulence coupled to region of highest incident radiation. A simplification in the calculation of molecular spectra with a single temperature property database in allows for tractable calculation of spectral properties. A comparison of …

Direct Numerical Simulation Of Hypersonic Turbulent Boundary Layers. Part 2. Effect Of Wall Temperature, L. (Lian) Duan, I. Beekman, M. P. Martín

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, we perform direct numerical simulation (DNS) of turbulent boundary layers at Mach 5 with the ratio of wall-to-edge temperature T w/T ℘ from 1.0 to 5.4 (Cases M5T1 to M5T5). The influence of wall cooling on Morkovin's scaling, Walz's equation, the standard and modified strong Reynolds analogies, turbulent kinetic energy budgets, compressibility effects and near-wall coherent structures is assessed. We find that many of the scaling relations used to express adiabatic compressible boundary-layer statistics in terms of incompressible boundary layers also hold for non-adiabatic cases. Compressibility effects are enhanced by wall cooling but remain insignificant, and the …

Direct Detection Of No Produced By High-Temperature Surface-Catalyzed Atom Recombination, Dušan A. Pejaković, Jochen Marschall, Lian Duan, Maria P. Martin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The surface-catalytic recombination of oxygen and nitrogen atoms to form nitric oxide was confirmed by the direct detection of product NO molecules, using single-photon laser-induced fluorescence spectroscopy. Experiments were performed from room temperature to 1200 K in a quartz diffusion-tube sidearm reactor enclosed in a high temperature tube furnace. Atomic nitrogen was generated using a microwave discharge, and atomic oxygen was produced via the rapid gas-phase titration reaction N + NO → O + N2. The use of isotopically labeled titration gases 15N16O and 15N18O allowed for the unambiguous identification of nitric oxide produced by the O + N surface …