This research examines different techniques and proposes a Computational Fluid Dynamics (CFD) model as a robust tool for flow characterization of load leveling valves. The load leveling valve is a critical component of an air suspension system since it manages air spring pressure, a key function that directly impacts vehicle dynamic performance in addition to maintaining a static ride height. Efficiency of operation of a load leveling valve is established by its flow characteristics, a metric useful in determining suitability of the valve for application in a truck-suspension configuration and for comparison among similar products. The disk-slot type load leveling valve was chosen as the subject of this study due to its popularity in the heavy truck industry. Three distinct methods are presented to model and evaluate flow characteristics of a disk-slot valve. First is a theoretical formulation based on gas dynamic behavior through an orifice; second is an experimental technique in which a full pneumatic apparatus is used to collect instantaneous pressure data to estimate air discharge; and third is a CFD approach. Significant discrepancies observed between theoretically estimated results and experimental data suggest that the theoretical model is incapable of accurately capturing losses that occur during air flow. These variations diminish as the magnitude of discharge coefficient is altered. A detailed CFD model is submitted as an effective tool for load leveling valve flow characterization/analysis. This model overcomes the deficiencies of the theoretical model and improves the accuracy of simulations. A 2-D axisymmetric approximation of the real fluid domain is analyzed for flow characteristics using a Realizable k-ϵ turbulence model, scalable wall functions, and a pressure-based coupled algorithm with a second order discretization function. The CFD-generated results were observed to be in agreement with the experimental findings. CFD is found to be advantageous in the evaluation of flow characteristics as it furnishes precise data without the need to experimentally evaluate a physical model/prototype of the valve, thereby benefitting suspension engineers involved in the development and testing of load leveling valve designs. This document concludes with a sample case study which uses CFD to characterize flow in a modified disk-slot load leveling valve, and discusses the results in light of application on a heavy truck. / MS / A majority of heavy trucks in North America equipped with air suspensions use a device known as a load leveling valve. This is a mechanical control system which manages pressure in air springs to maintain a preset/constant static ride height irrespective of the payload, doing so by sensing the distance between the truck frame and the axle. The rate of airflow to/from air springs in response to a road disturbance or load shift is critical to the stability of the truck when on the road. This rate of airflow for a given set of conditions constitutes flow characteristics of a load leveling valve. Accurate measurement of flow characteristics is necessary to understand the actual effect of the use of a particular valve on a truck-suspension configuration. This research addresses that requirement by presenting three distinct methods to model and evaluate flow characteristics of a load leveling valve, conducted on the disk-slot valve for its popularity in the heavy truck industry. First is a theoretical formulation based on flow of gas through an orifice; second is an experimental technique in which a full pneumatic apparatus is used to collect instantaneous pressure data to estimate air discharge; and third is a Computational Fluid Dynamics (CFD) approach. Significant discrepancies observed between theoretically estimated results and experimental data suggest that the theoretical model is incapable of accurately capturing losses that occur during air flow. The disparities also justify the adoption of CFD as an alternate method. A comprehensive CFD model is proposed as a capable tool for load leveling valve flow analysis/characterization. This model overcomes the deficiencies of the theoretical model and improves the accuracy of simulations. CFD-generated results are found to be in agreement with the experimental findings, highlighting its effectiveness at flow characterization. The ability of a CFD model to furnish precise data without the need to experimentally evaluate a physical model/prototype of the valve promises to benefit suspension engineers involved in the development and testing of load leveling valve designs. This document concludes with a sample case study which uses CFD to characterize flow in a modified disk-slot valve, and discusses the results in light of application on a heavy truck.

This research provides a thorough flow characterization study to compare the functionality of two types of load-leveling valves that are commonly used for air suspension systems of commercial trucks. The first valve features a simple disk/slot design and is relatively compact for installation. The second type is larger and has a sophisticated, chambered design, which allows for considerably quicker fill and exhaust response times in the transient region. A new approach is introduced to estimate the transient mass flow rate of a load-leveling valve under different suspension pressures, without requiring a mass flow meter. An extensive series of dynamic tests are conducted to characterize and compare the two load-leveling valves. A generic heavy-truck pneumatic suspension, consisting of load-leveling valves, airspring, air tank, and air-hose fittings, is configured for testing. The test setup is used to evaluate the transient performance of each type of load-leveling valve in a typical truck suspension. The flow behavior of the system is validated by the force/pressure responses of the air spring due to various displacement excitations. The experimental results describe the detailed flow behavior of both valves. The flow characterization results can be incorporated as one of the most critical parameters for future model development of pneumatic systems. The tests indicate that the leveling valve with chambered design has a far faster transient flow response than the disk valve, although it is more complicated in its mechanical design and therefore costs more. To take advantage of the design simplicity of the disk valve, while also enabling it to have a faster transient response (compared with the chambered design), it is re-designed with larger flow openings and other elements to match the performance of the chambered valve for transient flow. A comparison of the experimental results and simulations validates that the re-designed rotary disk valve performs nearly the same as the chambered valve, but is simpler and costs less. The study's results are directly applicable to improving the transient dynamics of heavy truck air suspensions by providing a better understanding of how load-leveling valves can be used not only to provide ride-height control, but also to influence the roll and pitch dynamics of heavy trucks. / Master of Science / Heavy trucks are balanced using air suspension systems. These pneumatic controls provide stability when a truck undergoes a turn or other change in movement, including roll and pitch. As a truck experiences these changes, air is supplied or purged from the system to balance the truck. Load leveling valves control this flow of air that provides stability and are considered crucial elements in the overall design of a heavy truck. This study evaluates many different types of valves, namely a "chambered" valve and a "disk" valve. The chambered valve is large and has many parts, resulting in a heavy expense but high performance. The disk valve is a simpler design, making it much cheaper but at the expense of performance. The quality of performance that is evaluated here is the time it takes to fill or purge the air suspension, which is related to the mass flow. These characteristics were experimentally obtained and compared. The results showed the disk valve taking more time and having a lower flow rate, making its performance lower when compared to the chambered valve. The next aspect of this study is the modification of this disk valve design that is commercially available to make its performance comparable to the chambered valve. After a series of experiments, the modified design was verified to perform as well as the chambered valve. Overall, these results are important for the future design of heavy truck load leveling valves and clarify important characteristics to consider when designing them. The results from this study can lead to lower costs for heavy truck companies and a better ride for truck drivers.

This research will compare the transient response characteristics of a four-degree-of-freedom, roll-plane model, representing a class 8 truck, using passive and semiactive dampers. The semiactive damper control policies that are examined include the previously developed policies of on-off skyhook, continuous skyhook, and on-off groundhook control, along with a newly developed method of fuzzy logic semiactive control. The model input will include body forces and torques, as well as transient displacements at the tires. The model outputs include the vehicle body heave and roll displacements, the vertical displacement of the tire (wheel hop) and the vertical acceleration of the vehicle body. For each output, the maximum peak-to-peak and RMS values of the response are examined. The results of the study show that semiactive dampers have minimal effect on improving the vehicle body and tire transients due to forces or torques applied to the body, as compared to passive dampers. For road inputs, however, semiactive dampers are able to provide a more favorable compromise between the body and axle transient dynamics, when compared to passive dampers. The fuzzy logic semiactive control policy that is proposed in this research is better able to balance the body and axle dynamics than the conventional semiactive damping control policies that are investigated. Further research on the application of fuzzy logic semiactive control concepts is suggested, in order to fully investigate the potential of such control schemes for vehicle suspensions. / Master of Science

A digital controller was designed for a semiactive primary suspension for a class 8 highway truck. The controller used a skyhook policy (where the semiactive damper simulates a damper between the sprung mass and an inertial reference) to control magneto-rheological dampers placed on the truck 's primary suspension in response to measurements made by accelerometers placed on the axle and the truck frame. The completed system was then tested for both random noise (on highway driving) and impulse (speed bump) response. The test results showed that for the damping tuning and controller arrangements used in this study, semiactive dampers do not offer any significant benefits in reducing overall vibration levels at the truck frame or axles. The semiactive dampers, however, provided better control of the dynamic transients, such as roll and pitch induced by hitting speed bumps, as compared to passive dampers. Further assessment of the magneto-rheological damper's tuning and the skyhook control policy is needed to establish any definitive conclusions on the potential benefits of semiactive magneto-rheological suspensions for heavy trucks. / Master of Science

An Analysis of Suspension Days Among Students in Special Education and General Education in A Rural School District, is designed to look at those disciplinary trends that directly affect our most vulnerable population of students, with an emphasis on suspension, expulsions and the rates at which special education students are suspended and/or expelled as compared to their non-disabled peers in a rural district in Mississippi. As the Mississippi State Department of Education cited this district for its high rate of suspension and/or expulsions of students with Individualized Educational Plans, this study is of significant importance in identifying those factors that contribute to the disciplinary outcomes for special education students.

A description of a documentary produced about human flesh-hook suspension. This document covers the pre-production, production, and post production of the documentary film and the research behind it.

Les avantages de la gestion intégrée de l'eau sont connus depuis des années, mais ces approches sont devenues plus importantes que jamais. Cela est reconnu dans l'objectif 6 des 17 objectifs de développement durable des Nations Unies. En ciblant à la fois l'eau potable et l'assainissement, cet objectif demande une approche intégrée car il reconnaît leur interdépendance. Cette thèse vise à faire progresser le domaine de la modélisation intégrée de l'eau, et en particulier en ce qui concerne les matières en suspension. Les émissions globales de l'assainissement ont gagné en intérêt puisque les normes de qualité de l'eau sont étendues de la station de récupération des ressources de l'eau au réseau d'égout. La modélisation intégrée permet d'évaluer les interactions et d'estimer les émissions en plus des mesures de la qualité de l'eau (encore) rares. Les particules peuvent être considérées comme un indicateur de la qualité de l'eau couvrant la pollution particulaire, mais aussi les matières organiques, les nutriments et les substances telles que les micro-polluants hydrophobes. L'approche de modélisation choisie est conceptuelle, pour ses calculs rapides, et basée sur la distribution de la vitesse de décantation des particules, partout où la décantation et la remise en suspension sont les processus caractéristiques. L'approche est complétée par d'autres modèles pour couvrir le système du bassin versant jusqu'à la station de récupération des ressources de l'eau. Un modèle intégré nécessite de nombreuses données. Pour une collecte de données efficace, premièrement, une procédure est établie pour construire un modèle conceptuel d'égout à partir d'un modèle hydraulique détaillé. Deuxièmement, une méthodologie de conception expérimentale optimale est adaptée à l'environnement complexe des égouts pour une campagne de mesure de la qualité de l'eau. L'utilité de l'approche de la distribution de la vitesse de décantation des particules est ensuite démontrée en calibrant et en validant le modèle pour une site pilote. Une procédure est élaborée pour tenir compte de l'incertitude des paramètres et de la variabilité des données d'entrée an d'identifier des points de contrôle ables. La procédure est utilisée pour la réduction d'émission des particules, facilitée par le calcul rapide du modèle car plusieurs analyses de sensibilité sont demandées. Le dernier chapitre termine la thèse par l'évaluation pratique des stratégies visant à réduire les émissions globales. La thèse fait ainsi progresser le domaine de la modélisation intégrée des particules et fournit en même temps des procédures qui permettent de surmonter les obstacles généraux à la modélisation en mettant l'accent sur la collecte de données fiables et efficaces, la modélisation ainsi que l'optimisation. / The advantages of integrated water management have been known for decades, but are more than ever important. This is acknowledged in goal six of the 17 sustainable development goals of the United Nations. By targeting both clean water as well as sanitation, this goal is inherently asking for an integrated approach since it recognizes their interdependence. This dissertation aims at advancing the eld of integrated water systems modelling in general, and in particular with respect to suspended solids. Overall emissions from the integratedurban wastewater system have gained interest since water quality standards are increasing lyextended from the water resource recovery facility to the sewer system. Integrated modelling allows evaluating interactions and estimating overall emissions complementary to the not (yet) abundant water quality measurements. For this evaluation suspended solids can be seen asan indicator for the receiving water quality covering particulate pollution as such, but also undesired organic matter, nutrients and substances such as hydrophobic micropollutants. The modelling approach chosen is conceptual, due to its rapid calculations, and based on the particle settling velocity distribution wherever settling and resuspension are the characteristic processes of suspended solids. The approach is extended with complementary models to coverthe integrated system from the catchment down to the water resource recovery facility. The development of an integrated model however requires vast data sets. First, for efficient data collection a procedure is established to build a fast conceptual sewer model from its detailed hydraulic counter part. Second, an optimal experimental design methodology is adapted to the challenging sewer environment for the efficient planning of a water quality measurement campaign. The usability of the particle settling velocity approach is then shown by calibrating and validating the model for a case study. A procedure is developed to consider parameter uncertainty and input variability to identify reliable control handles. The procedure is appliedfor the abatement of total suspended solid, facilitated by the comparably low computational demand of the model, as the procedure asks for multiple global sensitivity analyses. The last chapter closes the dissertation with the practical application of evaluating different strategies to reduce the total suspended emissions to the receiving water. The dissertation thus advances the eld of integrated modelling for particulates and at the same time provides procedures which overcome barriers general to modelling focusing on reliable and efficient data collection,as well as optimization.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008. / Suspension seats are commonly used for earth moving machinery to isolate vehicle operators from vibrations transmitted to the vehicle body. To provide the required stiffness and damping for these seats, air-springs are typically used in conjunction with dampers. However, to eliminate the need for additional dampers, air-springs can be used in conjunction with auxiliary air volumes to provide both spring stiffness and damping. The damping is introduced through the flow restriction connecting the two air volumes. In this study, simplified models of an air-spring were derived followed by a model including the addition of an auxiliary volume. Subsequent to simulations, tests were performed on an experimental apparatus to validate the models. The air-spring models were shown to predict the behaviour of the experimental apparatus. The air-spring and auxiliary volume model followed the trend predicted by literature but showed approximately 27 % lower transmissibility amplitude and 21 % lower system natural frequency than obtained by tests when using large flow restriction diameters. This inaccuracy was assumed to be introduced by the simplified mass transfer equations defining the flow restriction between air-spring and auxiliary volume. The models however showed correlation when the auxiliary volume size was decreased by two thirds of the volume actually used for the experiment. This design of a prototype air-spring and auxiliary volume is presented for a suspension seat used in articulated or rigid frame dump trucks. The goal of this study was to design a suspension seat for this application and to obtain a SEAT value below 1,1. The design was optimised by varying auxiliary volume size, flow diameter and load. A SEAT value of less than 0,9 was achieved.

Au cours de ce travail, nous nous sommes attachés à prédire les caractéristiques rhéologiques de suspensions de particules dans des situations non newtoniennes. Nous avons tout d'abord étudié expérimentalement le comportement rhéologique de suspensions bidisperses de particules non colloïdales et non browniennes immergées dans un fluide à seuil dans les situations où les interactions entre particules sont hydrodynamiques (mécaniques). Nous avons montré que l'influence de la polydispersité des particules sur le module élastique et le seuil de contrainte de la suspension pouvait être décrit en utilisant un modèle d'empilement développé pour les matériaux granulaires secs. Deux relations analytiques simples permettant d'estimer le module élastique et la contrainte seuil d'une suspension non newtonienne polydisperse en fonction des caractéristiques des constituants ont alors été proposées et validées. Nous nous sommes ensuite intéressés à la prédiction des caractéristiques globales de suspensions contenant une forte concentration de particules de taille différente dans le cadre d'une approche par changement d'échelle. Pour cela, nous avons mis en uvre une approche par motifs morphologiques permettant la prise en compte de paramètres géométriques tels que la distribution de tailles des inclusions ou les distances entre particules voisines. Les résultats de ce modèle ont été validés par comparaison avec des données expérimentales de la littérature. Nous avons ensuite montré que les modèles morphologiques permettaient également de décrire l'évolution des modules complexes d'un matériau thixotrope subissant une transition de phase liquide-solide due à la croissance et la percolation d'un réseau de particules attractives. Dans la dernière partie de cette étude, nous avons étudié expérimentalement l'influence de l'histoire de cisaillement sur la structuration et la déstructuration d'une suspension colloïdale thixotrope / In this work, we aimed to predict the rheological properties of suspensions of particles in non-Newtonian fluids. We first studied experimentally the rheological behaviour of bidisperse suspensions of non colloidal particles and non-Brownian immersed in a yield stress fluid in situations where interactions between particles are hydrodynamic (mechanical). We showed that the influence of the polydispersity on the elastic modulus and yield stress of the suspension could be described using a packing model developed for dry granular materials.Two simple closed form estimates for both the elastic modulus and the yield stress of non-Newtonian polydisperse suspension as a function of the characteristics of the constituents were proposed and validated. This study was then extended in a micromechanical analytical framework to predict the macroscopic characteristics of suspensions containing highly concentration of particles with different size. Our ne w model, called a "Morphologically Representative Pattern - Based Approach" (MRP-based approach), successfully predicts the behaviour of such materials by taking into account some geometrical parameters such as the particle size distribution or the distance between the nearest-neighbour particles. This model has been validated by a comparison with the experimental data in the literature. We then showed that the MRP-based approach also allowed describing the evolution of complex modules of a thixotropic material undergoing a liquid-solid transition due to the growth and the percolation of an attractive particle network. In the last part of this work, we studied experimentally the influence of the flow history on the structure of a thixotropic colloidal suspension

The research work performed in this thesis has been carried out at the Production Tech-nology Centre where the Thermal Spray research group of University West has its work-shop and labs. This research work has been performed in collaboration with the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India. First of all, I would like to express my sincere thanks and gratitude to my supervisors Dr. Nicolaie Markocsan and Dr. Nicholas Curry for their guidance, great support and valuable suggestions without which this work could not have been possible. I would also like to thanks Prof. Per Nylén for keeping faith in me and providing me an opportunity to work at PTC, which is a great place to perform research. It is my pleasure being their student and I wish I would keep learning from all of them, both on academic and personal grounds. I would also like to thank my colleagues at PTC Mr. Mohit Gupta and Mr. Stefan Björklund, for their help and support during this work. I would like to acknowledge the H.C. Starck Company for its financial support for the pro-ject; Dr. Filofteia-Laura TOMA at Fraunhofer IWS, Dresden to help us in spraying suspen-sion sprayed YSZ top coats, G Shivkumar from ARCI to help us in spraying solution pre-cursor sprayed top coats and Toni Bogdanoff, Jönköping University to help us in conduct-ing the LFA experiment