The basin factor is a hydrologic parameter that represents the overall impedance to flow of a watershed in the PC-Hydro peak discharge model for small ( < 10 mi2) semi-arid watersheds in Pima County, Arizona. To improve peak discharge estimates and provide validation of the basin factor as a physically-based parameter, basin factor values were "back-calculated" for return period and observed events on six undeveloped rangeland watersheds and correlated with Manning's n roughness coefficients, rainfall intensities, and hydraulic radii. Observed basin factor values displayed a positive trend with observed peak discharge. The results suggest that the correlated variables can predict the basin factor on small undeveloped sub-basins in Pima County and the basin factor is measurable as a physical parameter. Empirical models for basin factor prediction are proposed. The study may also be useful for estimating hydraulic roughness in hydrologic methods such as the kinematic wave time of concentration equation.

Designing monitoring networks that can discriminate among competing conceptual models is a key challenge for hydrologists. This issue is examined by considering the impact of network design on the utility of measurements for constraining hydrologic prediction uncertainty. Specifically, a three-staged approach was developed and is presented as a set of modeling case studies. The first case study presents a sensitivity analysis that examines conditions under which the proposed measurement method is likely to detect observations associated with the hydrologic process and properties of interest. This application is focused on the use of geomorphic information to estimate infiltration on arid alluvial fans.The second stage is an assessment of the likely utility of the measurement method to determine whether proposed measurements are likely to be useful for identifying hydraulic properties or hydrologic processes. This objective screening approach could reduce the number of unsuccessful uses of geophysical and other indirect measurement methods. A hypothetical site assessment examines whether the measurement method, temporal gravity change, is likely to detect signals associated with drawdown in an unconfined aquifer that occurs in response to pumping. Also, the utility of these measurements for identifying hydraulic conductivity and specific yield was considered.The third stage, an analysis of optimal network design, compares the projected measurement costs with the expected benefits of constraining hydrologic prediction uncertainty. The final case study presents a network design approach for a feasibility assessment of a proposed artificial recharge site. Predefined sets of proposed measurements of temporal gravity change were considered for various measurement times. An ensemble approach was used to assess the likely impact of measurement error on prediction error and uncertainty for different combinations of measurement sets. The ensemble of prediction errors was translated to probability-weighted performance costs for each measurement set using a cost function. Total cost was calculated as the sum of the performance and measurement costs. The optimal measurement set, defined as the set with the lowest total cost, depends on the prediction of interest, the per measurement cost, the maximum risk-based cost associated with the hydrologic prediction, and the treatment of uncertainty in defining performance costs.

Sediment erosion is a major challenge for run-of-river power plants, especially during flood periods. Due to the high content of hard minerals such as quartz and feldspar carried in the river, substantial damage is observed on the turbine components. Material is gradually removed, thus the efficiency of the turbine decreases and the operating time of the turbine reduces. Hydro power plants situated in areas with high sediment concentration suffer under hard conditions, where turbine components could be worn out after only a short period of three months. This short life expectation causes trouble for energy production since the replacement of new turbine parts is a time consuming and costly procedure. It is desirable to design a Francis runner which will withstand sediment erosion better than the traditional designs. The literature states that an expression for erosion is velocity to the power of three. By reducing the relative velocities in the runner by 10%, the erosion will decrease almost 30%. The objective is to improve the design of a Francis turbine which operates in rivers with high sediment concentration, by looking at the design parameters in order to reduce erosion wear. A Francis turbine design tool was developed to accomplish the parameter study. In the search for an optimized Francis runner, several design proposals were compared against a reference design by evaluating the turbine’s performance. The hydraulic flow conditions and the prediction of erosion on the turbine components are simulated by analyzing the models with a Computational Fluid Dynamic (CFD) tool. A Fluid Structure Interaction (FSI) analysis ensures that the structural integrity of the design is within a desired value. Results from this research show that it is feasible to design a runner with an extended lifetime, without affecting the main dimensions and hydraulic efficiency.

Lietuvoje įrengta 1590 tvenkinių, pastatyta daug kitokių hidrotechnikos statinių ir beveik kiekviename iš jų yra gelžbetoninių elementų ar konstrukcijų. Naudojami statiniai patiria įvairių apkrovų ir agresyvios aplinkos poveikį, dėl to jie ilgainiui nusidėvi, formuojasi pažaidos, statiniai genda ir tampa nebetinkami naudoti. Darbo tikslas – įvertinti defektų ir pažaidų įtaką naudojamų hidrotechnikos statinių gelžbetoninių konstrukcijų techninei būklei. 2006 metais tyrinėtos Marijampolės rajono naudojamų hidrotechnikos statinių gelžbetoninės konstrukcijos. Nustatyta pagrindinė konstrukcijų stiprum���� apibūdinanti charakteristika – gniuždomojo betono stipris. Užfiksuoti konstrukcijų defektai bei pažaidos, aptariamos galimos jų atsiradimo priežastys, konstrukcijų būklė įvertinta balais. Nurodyti dažniausiai pasitaikantys konstrukcijų defektai bei pažaidos, kurie atsirado dėl netinkamų sudėčių bei savybių betono, naudojimo trūkum��. / There are approximately 1590 dams and many other hydraulic structures constructed in Lithuania. Most of them have reinforced concrete elements or constructions. Due to different loads and environmental impact, condition of operational structures gets worse in time. Therefore, some deterioration may occur which leads structures to failure and makes them no longer useful for exploitation. The purpose of this work is to evaluate the influence of defects and deteriorations to the technical state of reinforced concrete hydraulic structures. In 2006, reinforced concrete constructions of hydraulic structures were investigated in Marijampole district. Compression strength is determined as the main characteristic of these constructions. Defects and deteriorations of constructions are noticed; main reasons that influence deterioration are discussed; and condition of constructions is estimated by points. It is established that most common defects and deteriorations are caused because of the use of unfit manufactured concrete and its shortage.

Condition monitoring of hydraulic systems is an area that has grown substantially in the last few decades. This thesis presents a scheme that automatically generates the fault symptoms by on-line processing of raw sensor data from a real test rig. The main purposes of implementing condition monitoring in hydraulic systems are to increase productivity, decrease maintenance costs and increase safety. Since such systems are widely used in industry and becoming more complex in function, reliability of the systems must be supported by an efficient monitoring and maintenance scheme. This work proposes an accurate state space model together with a novel model-based fault diagnosis methodology. The test rig has been fabricated in the Process Automation and Robotics Laboratory at UBC. First, a state space model of the system is derived. The parameters of the model are obtained through either experiments or direct measurements and manufacturer specifications. To validate the model, the simulated and measured states are compared. The results show that under normal operating conditions the simulation program and real system produce similar state trajectories. For the validated model, a condition monitoring scheme based on the Unscented Kalman Filter (UKF) is developed. In simulations, both measurement and process noises are considered. The results show that the algorithm estimates the iii system states with acceptable residual errors. Therefore, the structure is verified to be employed as the fault diagnosis scheme. Five types of faults are investigated in this thesis: loss of load, dynamic friction load, the internal leakage between the two hydraulic cylinder chambers, and the external leakage at either side of the actuator. Also, for each leakage scenario, three levels of leakage are investigated in the tests. The developed UKF-based fault monitoring scheme is tested on the practical system while different fault scenarios are singly introduced to the system. A sinusoidal reference signal is used for the actuator displacement. To diagnose the occurred fault in real time, three criteria, namely residual moving average of the errors, chamber pressures, and actuator characteristics, are considered. Based on the presented experimental results and discussions, the proposed scheme can accurately diagnose the occurred faults.

Emergency braking of a vehicle is bound with many factors, such as the behaviour of the driver, the drive of the vehicle braking system, the braking mechanisms, the condition of the tyres, and the properties of the pavement. This process involves all parameters of the system “the driver – the vehicle – the road”. In order to investigate the efficiency of braking process upon specific conditions, it is necessary to examine all physical processes that take place in the vehicle on pressing the brake pedal. Upon the completion of the experimental and theoretical investigation on emergency braking of vehicles a general mathematical model of vehicle with hydraulic braking system on its emergency braking had been developed. The dynamic, thermodynamic in solid systems and fluid hydrodynamic processes were assessed. The model enables to examine various cases of emergency braking with assessment of the driver’s reaction, parameters of the vehicle’ technical condition and the pavement condition. A general mathematical model of vehicle with hydraulic braking system that’s computing is realized in the system of the applied software Compaq Visual Fortran Professional system provides possibilities for research the hydrodynamic processes that take place in the system of braking; enables to define more closely the movement parameters of the vehicle in the emergency braking mode and may be applied for analysis of traffic events, improvement of vehicle braking systems as well as a manual for... [to full text]

Emergency braking of a vehicle is bound with many factors, such as the behaviour of the driver, the drive of the vehicle braking system, the braking mechanisms, the condition of the tyres, and the properties of the pavement. This process involves all parameters of the system “the driver – the vehicle – the road”. In order to investigate the efficiency of braking process upon specific conditions, it is necessary to examine all physical processes that take place in the vehicle on pressing the brake pedal. Upon the completion of the experimental and theoretical investigation on emergency braking of vehicles a general mathematical model of vehicle with hydraulic braking system on its emergency braking had been developed. The dynamic, thermodynamic in solid systems and fluid hydrodynamic processes were assessed. Model enables to examine various cases of emergency braking with assessment of the driver’s reaction, parameters of the vehicle’ technical condition and the pavement condition. A general mathematical model of vehicle with hydraulic braking system that’s computing is realized in the system of the applied software Compaq Visual Fortran Professional v 6.3 system provides possibilities for research the hydrodynamic processes that take place in the system of braking; enables to define more closely the movement parameters of the vehicle in the emergency braking mode and may be applied for analysis of traffic events, improvement of vehicle braking systems as well as a manual... [to full text]

The effect of coupled thermo-poroelastic behavior on hydraulic fracture propagation is of much interest in geothermal- and petroleum-related geomechanics problems such as wellbore stability and hydraulic fracturing as pore pressure and temperature variations can significantly induce rock deformation, fracture initiation, and propagation. In this dissertation, a two-dimensional (2D) boundary element method (BEM) was developed to simulate the fully coupled thermo-poroelastic fracture propagation process. The influence of pore pressure and temperature changes on the fracture propagation length and path, as well as on stress and pore pressure distribution near wellbores and fractures, was considered in isotropic and homogeneous rock formations. The BEM used in this work consists of the displacement discontinuity (DD) method and the fictitious stress (FS) method. Also, a combined FS-DD numerical model was implemented for the hydraulically or thermally-induced fractures in the vicinity of a wellbore. The linear elastic fracture mechanics (LEFM) theory was adopted to numerically model within the framework of poroelasticity and thermo-poroelasticity theory. For high accuracy of crack tip modeling, a special displacement discontinuity tip element was developed and extended to capture the pore pressure and temperature influence at the tip. For poroelastic fracture propagation, a steadily propagating crack driven by fluid pressure was modeled to find the effect of pore pressure on crack path under the two limiting poroelastic conditions (undrained and drained). The results indicate that the pore pressure diffusion has no influence on the crack growth under the undrained condition because the crack propagation velocity is too fast for the diffusion effect to take place. On the other hand, its influence on the crack path under the drained condition with its low propagation velocity has significance because it induces a change in principal stress direction, resulting in an alteration of fracture orientation. For the thermal fracturing, when the rock around a wellbore and a main fracture is cooled by injecting cold water in a hot reservoir, the rapid decrease in temperature gives rise to thermal stress, which causes a crack to initiate and propagate into the rock matrix. The single and multiple fracture propagation caused by transient cooling in both thermoelastic and poro-thermoelastic rock were numerically modeled. The results of this study indicate that the thermal stresses induced by cooling may exceed the in-situ stress in the reservoir, creating secondary fractures perpendicular to main fracture. Furthermore, the faster cooling rate produces longer crack extension of the secondary thermal fractures. This implies that the faster cooling induces a higher tensile stress zone around the fracture, which tends to produce larger driving forces to make the secondary fractures penetrate deeper into the geothermal reservoir.

No description available.

No description available.