Computational modeling of multiphase fibrous flows for simulation based engineering design

This dissertation develops a modeling framework for predicting the behavior of fibrous bulk solids in pneumatic conveyance systems that are currently not possible with conventional computational models. The developed framework allows designers to computationally predict flow characteristics of fibrous bulk solids, which impacts pneumatic conveyance system performance. These performance characteristics include air and fibrous bulk solids velocity profiles, fibrous bulk solids concentrations, pressure loss, and general system behavior. The motivation for this research is to expand the capabilities of computational models within in the engineering design process, rather than relying solely on generalized experimental correlations and previous design experience. This framework incorporates the primary characteristics of fibrous biomass-based bulk solids including low density, large characteristic length, and non-spherical shape. The main features of the developed modeling framework are (1) the effects of the particle drag on the flowing air and (2) the resistive effects of the interconnected fibers between the particles. The models are implemented within a commercially available CFD solver package with user-defined functions. Velocity profiles, bulk solids concentration, and air pressure are modeled with the differential conservation equations for mass and momentum based on the Eulerian-Eulerian multiphase modeling approach. The inter-particle and the particle-air interactions result in momentum exchanges, and these exchanges are incorporated into the model through a series of externally defined user functions that account for the momentum exchange due to drag of the particles and the resistance of the connected fibers. These user-defined functions allow the user to set a series of parameters specific to the transported bulk solids and to the loading conditions. The model is applied to two specific studies, which include (1) cotton-air flow through a positive pressure pneumatic conveyance system and (2) biomass-air flow through a negative pressure (vacuum) conveyance system. The model parameters are chosen to match existing experimental data obtained from their corresponding lab tests

Incorporating computational fluid dynamics into a virtual engineering environment

This thesis develops a process for integrating computational fluid dynamics (CFD) models into a virtual engineering environment. The goal of this research is to enable a non-CFD expert to readily incorporate changes to a reduced CFD model and to view the results of those changes in an intuitive and natural manner. There are five steps in this process. These steps are (1) construct the complete CFD model, (2) validate the complete model, (3) reduce the model by focusing on the questions that the model needs to answer, (4) integrate the model into an interactive virtual environment, and (5) validate the reduced model with the complete model. This thesis elaborates on the third and fourth steps, specifically model reduction, by examining the questions being answered and addressing the integration of the CFD model into an interactive virtual engineering environment. These methods are implemented on a complex CFD model used for practical engineering decision making. The CFD model is of an underhood engine compartment of a vehicle. The complete CFD model consists of approximately eight million cells and requires approximately three days of computational time to determine the results of a design change. The complete CFD model of the vehicle is reduced to encompass the underhood engine compartment. Boundary conditions are then mapped to the outside surface of the reduced model to replicate the flow conditions of the complete model. The reduced model is able to develop a converged solution in approximately five percent of the original model\u27s time, thereby making the model more feasible for interactive design. This reduced model is then integrated with a virtual engineering software package which allows the user to add a flow-deflecting baffle into the model, run the model, and view the results in a virtual environment. This environment allows human interaction with the CFD models and the associated geometric representations. The integration of the model with interactive design tools creates a more holistic approach to engineering and brings CFD results of a design change into a more collaborative tool in the design process

Engineering the Future: A Workshop for High School Teachers

The framework guiding the development of Next Generation Science Standards (NGSS) identifies eight science and engineering principles essential for all students to learn. The Engineering the Future workshop, offered by South Dakota State University (SDSU) in the summer of 2012, focused on helping teachers better understand those principles and how to employ them effectively in their classrooms. Each day of the week-long workshop, teachers participated in a variety of engineering-related activities, accessed low and high-end instrumentation, took tours of engineering-related facilities in the region, and developed lesson plans to incorporate what they learned into their science classrooms. We used pre- and postworkshop surveys to assess the participants’ understanding and attitudes regarding science and engineering. Results of the survey showed participants had a narrow view of engineering prior to the workshop but by the end of the workshop, they were more aware of the nature of engineering, the various types of engineering, and they better understood how they could incorporate engineering principles into their current curriculum

Examination of near-wall hemodynamic parameters in the renal bridging stent of various stent graft configurations for repairing visceral branched aortic aneurysms

ObjectiveThis study examined the flow behavior of four stent graft configurations for endovascular repair of complex aneurysms of the descending aorta.MethodsComputational fluid dynamics models with transient boundary conditions and rigid wall simplifying assumptions were developed and used with four distinct geometries to compare various near-wall hemodynamic parameters.ResultsGraphic plots for time-averaged wall shear stress, oscillating shear index, and relative residence time were presented and compared among the four stent graft configurations of interest.ConclusionsAbrupt 90° and 180° changes in stent geometry (particularly in the side branches) cause a high momentum change and thus increased flow separation and mixing, which has significant implications in blood flow characteristics near the wall. By comparison, longer bridging stents provide more gradual changes in momentum, thus allowing blood flow to develop before reaching the target vessel.Clinical RelevanceRenal vessel patency is a well-known but rarely talked about challenge with complex aneurysm repair. Many factors need to be optimized to ensure branch vessel patency in aneurysms of the visceral segment, including bridging stent compliance transition, bridging stent material selection and design, and main body graft alignment. One topic that has not been discussed much is the flow characteristics entering the branch. Here we propose a technique to evaluate device configurations and their associated flows for their ability to maintain branch vessel patency

The reputation trap of NGO accountability

In this paper we examine the role of reputation in the behavior of nongovernmental organizations (NGOs). Can the pursuit and maintenance of a reputation cause NGOs to change their behavior in meaningful ways? Or are the norms and institutions that motivate and govern NGOs the sole drivers of behavior? To answer these questions, we focus on the relationship between NGOs and their donors. Our theoretical model reveals that reputation can be a key piece of information in the decision to fund the activities of a non-governmental organization. Indeed, reputation can become so important to the survival of the NGO that it interferes with the long-term policy goals of the organization. The resulting short-term NGO behavior is often misconstrued as incompetent or inefficient, but it is actually motivated by the structural constraints of the relationship with donors. We illustrate this strategic dynamic here with a focus on three types of NGO activity: international crisis mediation, ameliorating poverty, and water improvement

Enhancing Undergraduate Engineering Education of Lean Methods using Simulation Learning Modules Within a Virtual Environment

This paper highlights the use of an integrated user-centered virtual learning environment throughextensible simulation learning modules that is currently being developed to enhance undergraduate curricula to meet the industrial needs for engineers with education in lean. The purpose of the research is to address these expectations by developing learning modules that incorporate lean simulation models into various Engineering Management, Industrial Engineering, and Mechanical Engineering courses at Missouri S&T, Texas Tech, and South Dakota State, respectively. In recent years, increasing global competition, rapidly changing technology, and a deficit of U.S. engineering graduates have intensified the need to produce graduating engineers who are effective problem solvers and analytical thinkers, yet who can also collaborate on interdisciplinary teams to address complex, real-world systems. A key area of competence for many engineering undergraduate, as well as graduate, disciplines is the application of structured problem solving methods, e.g., lean, to improve the performance of organizational processes. This virtual learning environment will enhance undergraduate engineering education by utilizing technology as a learning tool in lean, by fostering student development through active learning in the classroom, and through projects based on current real-world challenges, thus improving student learning, motivation, and retention. The paper highlights the learning modules to be developed in the virtual learning environment. The long-term goal is to evaluate the impact of the curriculum changes on student learning, outreach, and industrial collaboration

Armed Intervention and Civilian Victimization in Intrastate Conflicts

Abstract Research has begun to examine the relationship between changes in the conflict environment and levels of civilian victimization. We extend this work by examining the effect of external armed intervention on the decisions of governments and insurgent organizations to victimize civilians during civil wars. We theorize that changes in the balance of power in an intrastate conflict influence combatant strategies of violence. As a conflict actor weakens relative to its adversary, it employs increasingly violent tactics toward the civilian population as a means of reshaping the strategic landscape to its benefit. The reason for this is twofold. First, declining capabilities increase resource needs at the moment that extractive capacity is in decline. Second, declining capabilities inhibit control and policing, making less violent means of defection deterrence more difficult. As both resource extraction difficulties and internal threats increase, actors' incentives for violence against the population increase. To the extent that biased military interventions shift the balance of power between conflict actors, we argue that they alter actor incentives to victimize civilians. Specifically, intervention should reduce the level of violence employed by the supported faction and increase the level employed by the opposed faction. We test these arguments using data on civilian casualties and armed intervention in intrastate conflicts from 1989 to 2004. Our results support our expectations, suggesting that interventions shift the power balance and affect the levels of violence employed by combatants

Interactions of Host Proteins with the Murine Leukemia Virus Integrase

Retroviral infections cause a variety of cancers in animals and a number of diverse diseases in humans such as leukemia and acquired immune deficiency syndrome. Productive and efficient proviral integration is critical for retroviral function and is the key step in establishing a stable and productive infection, as well as the mechanism by which host genes are activated in leukemogenesis. Host factors are widely anticipated to be involved in all stages of the retroviral life cycle, and the identification of integrase interacting factors has the potential to increase our understanding of mechanisms by which the incoming virus might appropriate cellular proteins to target and capture host DNA sequences. Identification of MoMLV integrase interacting host factors may be key to designing efficient and benign retroviral-based gene therapy vectors; key to understanding the basic mechanism of integration; and key in designing efficient integrase inhibitors. In this review, we discuss current progress in the field of MoMLV integrase interacting proteins and possible roles for these proteins in integration