This research includes a sensitivity analysis of channel geometry and model assumptions in 1 dimensional (1D) dam break analysis. The specific modeling assumptions that are analyzed include, breach development time, breach width, and breach side-slopes. The question always arises when doing 1D dam break modeling of how detailed does the geometry data need to be to answer the subject question within an acceptable tolerance. LIDAR data and bathymetric data used for channel characteristic add significant detail to the model geometry as opposed to using course gridded data such as the USGS 10 meter Digital Elevation Models (DEMs). However, as geometry detail increases so does model development time, model run time, and cost to retrieve data. This research analyzes the level of error introduced in model results from accuracy of channel geometry as compared to the level of error introduced from assumption made in breach characteristic.

M.Phil. / This study identifies and evaluates dynamic models used to characterise the dynamic stiffness and phase angle of hydraulic elastomeric mounts that are primarily used as engine and operator cab isolators in vehicular applications. Linear models developed for hydraulic elastomeric mounts are analysed for their suitability to be used to characterise the dynamic stiffness and its phase angle in the low and high frequency range. A sensitivity analysis provides insight into the parameters with a high level of sensitivity to changes in model parameters. The models selected from the linear analysis are enhanced and updated by performing a quasi-linear analysis to compensate for the dynamic behaviour of certain parameters. Non-linear dynamic behaviour of the decoupler is also investigated. These models are then verified experimentally. To set-up an analytical model that can be used to predict the dynamic characteristics of the hydraulic elastomeric mount it is necessary to develop a physical model from which the system differential equations are extracted. From the physical model flow continuity equations and fluid momentum equations are developed to obtain an expression that describe the fluid response in the inertia track and decoupler respectively. Lumped parameter mechanical models are developed next from which equivalent differential equations are derived to describe the internal dynamics of the hydraulic mount. These differential equations along with the transmitted force equation directly derived from the physical model are used to develop the dynamic stiffness transfer function. Time domain input displacement and output transmitted force data are taken at a specific frequency and amplitude, and are used to generate hysteresis loops to extract the dynamic stiffness and phase angles. For most of the computational effort, both analytical and experimental, MATLAB programs are written to perform curve fitting, FFT calculation, numerical integration and dynamical simulation. Emphasis is placed on the dynamic considerations of hydraulic mount design in the automotive industry and where machines are subjected to shock and vibration. The results and techniques used to model and the mounts are useful to designers in the field of shock and vibration isolation. Finally, the aim of the work is to keep the dynamic models as simple as possible, to be used effectively in the identification of the structural dynamic characteristics of hydraulic elastomeric mounts. To avoid complexity two models are used to describe the dynamics of the mount, one model for the low frequency, large amplitude conditions and one for the high frequency, small amplitude conditions. The information is then used to determine how the mount will respond under certain dynamical conditions.

A mathematical model is derived to provide quasi-steady state predictions of the performance of a high pressure hydraulic supply system, using equations which govern the physical processes as opposed to equations which match input-output characteristics. Model equations are developed to describe the operation of the power source, control valves, energy source, gas side of the system, hydraulic accumulator, the motorpump, and hydraulic side of the system. The accuracy of the model is then checked by inserting known parameters from a previously developed control system and comparing model predictions with performance data from this system.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2015. / The propagation of hydraulic fractures with tortuosity is investigated. Tortuosity is the complicated fracture geometry that results from asperities at the fluid-rock interface and, if present, from contact regions. A tortuous hydraulic fracture can either be open without contact regions or partially open with contact regions. We replace the tortuous hydraulic fracture by a two-dimensional symmetric model fracture that accounts for tortuosity. A modified Reynolds flow law is used to model the tortuosity in the flow due to surface roughness at the fracture walls. In order to close the model, the linear and hyperbolic crack laws which describe the presence of contact regions in a partially open fracture are used. The Perkins-Kern-Nordgren approximation in which the normal stress at the crack walls is proportional to the half-width of the symmetric model fracture is used. A Lie point symmetry analysis of the resulting governing partial differential equations with their corresponding boundary conditions is applied in order to derive group invariant solutions for the half-width, volume and length of the fracture. For the linear hydraulic fracture, three exact analytical solutions are derived. The operating conditions of two of the exact analytical solutions are identified by two conservation laws. The exact analytical solutions describe fractures propagating with constant speed, with constant volume and with fluid extracted at the fracture entry. The latter solution is the limiting solution of fluid extraction solutions. During the fluid extraction process, fluid flows in two directions, one towards the fracture entry and the other towards the fracture tip. It is found that for fluid injection the width averaged fluid velocity increases approximately linearly along the length of the fracture. This leads to the derivation of approximate analytical solutions for fluid injection working conditions. Numerical solutions for fluid injection and extraction are computed. The hyperbolic hydraulic fracture is found to admit only one working condition of fluid injected at the fracture entry at a constant pressure. The solution is obtained numerically. Approximate analytical solutions that agree well with numerical results are derived. The constant pressure solutions of the linear and hyperbolic hydraulic fracture are compared. While the hyperbolic hydraulic fracture model is generally considered to be a more realistic model of a partially open fracture, it does not give information about fluid extraction. The linear hydraulic fracture model gives various solutions for di erent working conditions at the fracture entry including fluid extraction.

No description available.

Maximum equilibrium scour depths, equilibrium scour volumes, and induced equilibrium movements at isolated obstacles on river beds were investigated in clear-water scour. The research was achieved by a systematic flume study based on the results of dimensional analysis of local scour. The main tested obstacles for local scour were cubes. Local scour at a circular cylinder of aspect ratio 1 and a sphere were also examined for comparison with scour at cubes. Each obstacle was placed on a flat movable bed and oriented normal to the incident flow. Non-cohesive uniform medium sand and very fine gravel were used as movable beds. The tested flow conditions were controlled to give many combinations of the relevant dimensionless parameters for local scour: the flow Froude Number, relative obstacle size, and relative roughness of bed material. Water surface profiles and longitudinal velocity profiles along the plane of symmetry, as well as the horizontal velocities near the bed around isolated obstacles on a fixed bed were examined in several runs. For a slightly submerged cube, the path of maximum velocity downstream of the cube moves from the water surface into the lower part of the flow. At a greater distance downstream, the path of maximum velocity tends to move upward toward the water surface. An increase of flow Froude Number leads to a hydraulic jump behind the cube. The relative longitudinal velocity near the bed is increased in this region. The decrease of relative water depth or the increase of flow Froude Number can lead to increased average relative horizontal velocity (V/u) near a cube. The cube has the highest average V/u value, as compared to flow near a circular cylinder and a sphere. The local scour processes and equilibrium scour patterns at isolated cubes on movable beds were also examined. There is not a unique equilibrium scour pattern for clear-water scour at a cube on a movable bed. Equations were developed to predict the maximum equilibrium scour depth and scour volume and the critical condition for incipient motion of bed material at a cube in clear-water scour. As the water becomes relatively deep, the shape effect of the circular cylinder and the sphere become negligible. The major equilibrium movement of a cube on a movable bed due to scour involves longitudinal displacement, vertical settlement, and longitudinal inclination. Equations were developed to predict the equilibrium movement and the critical condition for incipient upstream movement of a cube in clear-water scour. / Graduation date: 1991

No description available.

Thesis (M.S.)--Baylor University, 2008. / Includes bibliographical references (p. 61-67)

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 73-74.

No description available.