Mechanical Engineering Commons^™

Effect Of Perturbations On The Dominant Flow Structures In A Rectangular Lid-Driven Cavity With Particle Suspensions, Siva Bolisetty

Graduate Research Theses & Dissertations

The lid-driven cavity is a canonical problem in the field of analytical and computational fluid dynamics. This work is focused on a 2-D rectangular cavity with a length twice the size of its width and consists of an incompressible fluid with a moving upper wall/lid while the rest of the wall boundaries are subjected to fixed, no-slip, zero-velocity boundary conditions. The objective is to investigate the effect of perturbations resulting from particle drag and particle collisions on dominant flow structures of the fluid within this cavity. The dominant flow structures in a rectangular lid-driven cavity constitute a primary vortex, a …

Studying The Effect Of Vacancies On The Thermal Conductivity Of Metal-Coated Carbon Nanotubes Using Molecular Dynamics Atomistic Simulations, Ravindra Sunil Dhumal

Graduate Research Theses & Dissertations

Breakthroughs in nanotechnology have made it possible for the size of electronic gadgets to be scaled down to micro/nano level. What follows however, is the side effect of high power densities and overheating as the heat dissipation is restricted to very small surface area. Thus, the need of an effective thermal management system is central to these developments. One way to counter this problem is to use Thermal Interface Materials (TIMs) which promote heat transfer between heat source and sink.

Owing to their high thermal conductivity (up to 6000 W/mK), Carbon Nanotubes (CNTs) are thought of as strong candidates for …

Steady Flows In Annular Wedge Lid-Driven Cavities, Anandan Ganapathy

Graduate Research Theses & Dissertations

The lid-driven cavity is a well-known canonical problem in the field of analytical and computational fluid dynamics. It is comprised of a square domain of an incompressible fluid with its upper lid has a specified velocity and the remaining wall boundaries are subjected to fixed, no-slip, zero-velocity constraints. There are numerous examples found in the literature that address the well-known, stable behavior of this system, which includes a primary recirculating vortex, secondary corner vortices, and a velocity profile through the center midpoint y-axis that is shown to be dependent on the Reynolds number. In this investigation, the shape of the …

Proper Orthogonal Decomposition Analysis Of Lid-Driven Cavity Flows Containing Particle Suspensions., Nitin Katiki

Graduate Research Theses & Dissertations

Previous experiments done on the square lid driven cavity have shown that its stability and transitional behavior, and by extension the behavior of more complex flows, can be greatly modified by introducing systematic disturbances called perturbations to its flow field. In this study, a square lid driven cavity is calculated in two-dimensional space and perturbed by means of particles suspended in the flow. The perturbations manifest as subtle changes in the flow field velocity and overall flow structure, these are caused by the particle-fluid drag interaction and the particle-particle collision interaction. To understand the nature of these changes and their …

Temporal Dynamics Of Human Emotional Response To Aversive Stimuli, Joseph Lawence Kempel

Graduate Research Theses & Dissertations

Emotions are an integral part of human expression and are often communicated nonverbally through behavioral actions. With advancements in electroencephalography (EEG) technology it is now possible to measure the dynamics of emotion generation in an individual on the basis of patterns in their brain activity. This thesis aims to model the temporal dynamics of human emotion generation upon exposure to aversive stimuli and measure the effect of external distractions as a viable emotion regulation strategy.

This research builds on previous work in the literature that has shown that the ability of humans to regulate their emotions intrinsically (based on their …

Direct Polymer Grafting As A Method Of Maintaining The Mechanical Properties Of Cellulose Nanocrystals In The Presence Of Moisture, Mary Elizabeth Breen-Lyles

Graduate Research Theses & Dissertations

Cellulose nanocrystals (CNCs) are a distinctive nanomaterial derived from cellulose, the most abundant natural polymer on Earth, and the primary reinforcing structural component of cellulose fibrils found within the plant cell wall. These nanocrystals exhibit mechanical properties comparable to synthetic aramid fibers but are advantageous as they are biodegradable, renewable, and can be produced sustainably as they are predominantly extracted from naturally occurring cellulosic materials. These qualities make it a sustainable, highly renewable and environmentally friendly material to be used in place of synthetic materials in a variety of applications. With their high surface area to volume ratio, low level …

Implementation Of The Shpb System For Material Property Test Under High Strain Rate Deformation, Jiaqi Zhu

Graduate Research Theses & Dissertations

Since Bertram Hopkinson first raised the concept of Hopkinson pressure bar in 1914, many efforts have been taken by engineers and scholars for developing the system to measure the stress pulse propagation in metal bars for studying the properties of different materials under high strain rate deformation. The Northern Illinois University Material’s Lab has also built two generations of the split Hopkinson pressure bar (SHPB) system with the effort of several senior design teams in history.

The aim of this study is to develop the existing SHPB system of NIU to make it function properly. By redesigning the gun barrel, …

Numerical And Experimental Validation For The Optimization Of Directed Energy Deposition Processing Parameters, Luis Nunez

Graduate Research Theses & Dissertations

In order to capitalize on the cost effectiveness of Metal Additive Manufacturing (MAM) it is critical to understand how to build components with consistency and high quality. Directed Energy Deposition (DED) is a MAM method for creating parts layer by layer through the use of a moving heat source and powder material inserted into the melt pool generated on the substrate. DED like most MAM processes are highly complex due to the rapid thermal gradients experienced during processing. These thermal gradients are determined by a variety of processing parameters which include laser power, powder feed rate, travel speed, layer height …

A Computational Fluid Dynamics Analysis Of The Aerodynamic Performance Of Wind Turbine, Ashkan Ostovari

Graduate Research Theses & Dissertations

Renewable energy resources are likely to be a future energy solution. Among them, the wind has gained a lot of interest. Despite the theoretical limitation in wind energy harnessing efficiency, it is, still, one of the most promising renewable resources with utilizing turbines to extract this energy. Wind turbines, based on their axis of rotation are categorized into vertical axis wind turbine (VAWT) and horizontal axis wind turbine (HAWT), which HAWT’s have shown relatively higher efficiency than VAWT’s. The aim of this thesis is first to develop a scaled-down model of a wind turbine in Computational Fluid Dynamics (CFD) environment …

Energy Analysis For Process Parameter Prediction Of Direct Energy Deposition Metal Additive Manufacturing, Daniel John Pulscher

Graduate Research Theses & Dissertations

Metal Additive Manufacturing with the Direct Energy Deposition (DED) process allows for rapid prototyping and low-volume custom manufacturing of complex geometries at a lower cost than traditional manufacturing methods. Direct energy deposition is a complex process having many inter-related process parameters that effect the overall quality and mechanical properties of the build. When new powder feedstocks are used, calibrating these process parameters is typically done empirically in trials that can contain more than a hundred different combinations of parameters. This time-consuming process can be reduced by performing an analytical analysis on how the energy from the laser transfers into the …