Hydraulic conductivity (K) is a key parameter required for the accurate prediction of contaminant transport in an aquifer. Traditionally, pump tests, slug tests, grain size analysis and, to a lesser extent, tracer tests have been employed to estimate the K of an aquifer. These methods have disadvantages in respect to assessing the K of a contaminated aquifer, for example, pumping tests generate large quantities of potentially contaminated water, slug tests interrogate only a small portion of aquifer to generate K values, and tracer tests are costly to perform. The recirculating well pair (RWP) system, assessed in this study, attempts to minimise these disadvantages while producing accurate estimates of K. The RWP system uses two wells, each screened in two positions; one screen injects water and the other extracts water from the aquifer. One well extracts water from the lower screen and injects it into the aquifer via the upper screen, whereas the second well extracts water from the upper screen and injects it through the lower screen. When these two wells are pumped in tandem a recirculation system is created within the aquifer. No water is lost or gained from the aquifer in this system. Hydraulic conductivity can be estimated from a RWP system by either the multi dipole or the fractional flow methods. The multi dipole method estimates K by measuring steady state hydraulic heads, whereas the fractional flow method uses a tracer test to obtain steady state concentrations at the four screens to estimate K. Both methods utilise a 3D flow model to simulate the aquifer system. Inverse modelling in conjunction with a genetic algorithm simulate the hydraulic head values obtained from the multi dipole experiments or the tracer steady state values obtained from the fractional flow method. Hydraulic ii conductivity estimates are obtained by matching the simulated and observed steady state hydraulic head, or tracer steady state values. An investigation of the accuracy of the two RWP methods, when system parameters are varied, in estimating K values was undertaken. Five multi dipole experiments were undertaken with varying dipole flow rates to assess the effect of altering dipole flow rate on estimates of K. Two experiments were also undertaken to assess the effect of altering the pumping well incidence angle as compared to the regional flow on the accuracy of K estimates. Five fractional flow experiments were conducted, four to assess the effect of changing dipole pumping rates and one to assess the influence of altering the incidence angle of the pumping wells on estimation of K. All experiments were undertaken in an artificial aquifer that allowed control of hydraulic parameters and accurate measurement of aquifer K by independent methods. Experimental results were modelled with the two RWP methods. Results indicate that both the multi dipole and fractional flow methods provide accurate estimates of the K of the artificial aquifer (5 % to 57% greater than the actual K and -14% to 17% of the actual K, respectively). Altering the ratio between the pumping well and regional aquifer flow rates had no effect on the estimated K results in both methods. Although preliminary results were positive, further work needs to be undertaken to determine if changing the orientation of the well pairs affects the estimation of K.

Wind/wave interactions in the surf zone are studied using a wave tank and environmental wind tunnel. The wind simulation is achieved over a relatively short fetch using accelerated growth techniques at a scale of roughly 1:100. Waves are scaled at approximately 1:50, and consequently there is some scaling mis-match between the wind and wave simulations. Results show that wind has a significant effect on the breaking of the waves. Both breaker location and breaker type are shown to be affected by the wind. Results are in agreement with those of Douglass (1989 & 1990), who used a wind/wave flume to simulate the prototype conditions, but made no attempt to correctly simulate the turbulence in the air flow. The main findings, are that onshore winds promote spilling waves and increase the surf zone width, whereas offshore winds promote plunging waves, decreasing surf zone width. Hot-film measurements of the air flow over the waves show that there exists significant differences between the air flow structure of offshore and onshore winds over the surf zone. Under offshore winds, the surf zone exerts a large drag on the air flow, dramatically increasing turbulence intensities aerodynamic roughness z0, and friction velocity, u*, near the point of wave breaking. Under onshore winds the air flow is less affected and at the point of wave breaking, z0 for onshore winds is an order of magnitude lower than the value under offshore winds. Phase-averaging techniques indicate large wave-induced perturbations to the mean velocity over the waves, and these are present to heights of up to 5 or 6 times the breaker height over the point of wave breaking. Spectra indicate that for onshore winds large wave-frequency fluctuations are present at the shore. Additionally, studies of particle motion offshore of the surf zone indicate wind effects on the drift velocities of suspended particles, although the precise nature of the wind effect was not clear.

The research into hydrodynamic loading on ocean structures is concentrated mostly on circular cross section members and relatively limited work has been carried out on wave loading on rectangular sections, particularly in waves and currents. This research work is therefore carried out focussing on the evaluation of hydrodynamic force coefficients for sharp edged rectangular cylinders of various cross-sections (aspect ratios), subjected to waves and currents. Three cylinders with three different cross-sections are constructed and tested vertically, as surface piercing and horizontally, as fully submerged with the cylinder axis parallel to the wave crests. The aspect ratios considered for this investigation are 1.0, 112, 2/1, 3/4 and 4/3. The length of each cylinder is 2000mm. The sectional loadings are measured on a 100mm section, which is located at the mid-length of the cylinder. The forces are measured using a force measuring system, which consists of load cells, capable of measuring wave and current forces. The in-line & transverse forces (for vertical cylinders) and horizontal & vertical forces (for horizontal cylinders) have been measured. For horizontal cylinder, to study the effect of depth of variation on submergence of the cylinder, the tests are carried out for two depths of submergence. The experiments are carried out at the Hydrodynamic Laboratory, Department of Naval Architecture and Ocean Engineering, University of Glasgow. The tests are carried out in a water depth of 2.2m with regular and random waves for low Keulegan-Carpenter (KC) number up to 4.5 and the Reynolds number varied from 6.397xl03 to 1.18xl05 • The combined wave and current effect has been produced by towing the cylinders in regular waves, along and opposite to the wave direction at speeds of ± 0.1 mis, ± 0.2 mls and ± 0.3 mls. Based on Morison's equation, the relationship between inertia and drag coefficients are evaluated and are presented as a function of KC number for various values of frequency parameter, {3. For the vertical cylinders, the drag coefficients decrease and inertia coefficients increase with increase in KC number up to the range of KC tested for all the cylinders. For the horizontally submerged cylinders, the drag coefficients showed a similar trend to vertical cylinders, whereas the inertia coefficients decrease with increase in KC number for all the cylinders. This reduction in inertia force is attributed to the presence of a circulating flow [Chaplin (1984)] around the cylinders. The random wave results are consistent with regular wave results and the measured and computed force spectrum compares quite well. While computing the force coefficients in the case of combined waves and currents, only the wave particle velocity is used, as the inclusion of current velocity tends to produce unreliable drag force coefficients. For vertical cylinders, the drag and the inertia coefficients in combined waves and currents are lower than the drag and the inertia coefficients obtained in waves alone. For horizontal cylinders the drag coefficients are larger than those obtained for waves alone and the inertia coefficients are smaller than those measured in waves alone. The Morison's equation with computed drag and inertia coefficients has been found to predict the measured forces well for smaller KC numbers. However, the comparison between measured and computed positive peak forces indicate that the computed forces are underestimated. It is suggested that if the wave particle kinematics are directly measured, this discrepancy between measured and computed forces might well be reduced. Wave excitation forces are also reported in non-dimensional forms in the diffraction regime, using 3D-Green function method. Wave induced pressure distribution around the cylinder in regular waves have been measured and are reported as normalised pressures. Wave run-up on the cylinder surfaces has been measured and simple empirical formulae are presented for run-up calculations on the cylinder surfaces. The results of this investigation show that the cylinder aspect ratio plays major role on hydrodynamic force coefficients, dynamic pressure distribution and on wave run-up on cylinder surfaces.

No description available.

The majority of the world's river basins remain ungauged and, therefore, the triedand- tested empirical techniques for predicting floods and droughts cannot be applied. An alternative approach, which is currently receiving a great deal of attention from research hydrologists, is to develop continuous simulation models whose parameters pertain to physical or hydrological properties of the river basins. However, difficulties related to scale, heterogeneity and complexity of real river basins have made a priori estimation of such parameters impossible: their estimation has always required calibration using river flow data. Therefore, estimating hydrological model parameters in ungauged river basins is one of the greatest challenges currently facing research hydrologists. In this thesis research advances towards this goal have been made at three different levels. First, at a conceptual level, a novel method for classifying river basins according to their physical properties is proposed. It is specifically designed for transferring hydrological model parameters from gauged river basins, where calibration is possible, to ungauged river basins. This approach relies on recognising that river basins can be similar in parts of their hydrological cycle but not in others. Thus, basins go through three independent classifications, one relative to each of the major components of the land phase hydrological cycle: interaction of soil water/vegetation and atmosphere; surface flow; and groundwater flow. This requires the ability to characterise the response of the components of the hydrological cycle independently, which leads to a second conceptual advance; rather than relying entirely on measured river flow data, from which it is difficult to separate out the effects of the three components, classification rules are devised on the basis of synthetic data produced by comprehensive, distributed, physically-based models. This thesis focuses on the surface flow component, applying the methodology to the identification of the best classifiers for surface flow through river networks. This required simulating river flow through a large number of Scottish river basins, which led to more practical research advances; all available commercial flow routing models were too cumbersome and required an impractical level of detail to be applied in such a large study. Therefore, a new flow routing modelling system was developed that extracts river network detail from digital databases and numerically solves a distributed flow routing model. Finally, on a detailed scientific level, significant insights have been made into the relationship between river network geomorphologic structure and stream flow response. In particular, it is shown that: a downstream hydraulic geometry relationship exists for Scottish rivers; although channel conveyance is a key factor in dictating network response, the features of the response hydro graph - namely the percentage attenuation of the flood peak and the lag in time to peak - scale linearly with both roughness and hydraulic geometry coefficients; much publicised invariant power law scaling rules for flood peaks in fact vary as a function of storm duration; statistical multivariate analysis of the simulated network flow responses demonstrated the low capacity of the network descriptors commonly used in regionalisation studies for characterising flow response. Four variables are shown to have significantly higher classifying power than the majority of the commonly used classifiers. Of these, two are entirely new to this thesis.

Hydraulic systems are complex dynamical systems whose performance can be degraded by certain faults, specifically internal or external leakage. The objective of this research is to develop an appropriate signal processing approach for detection and isolation of these faults. By analyzing the dynamics of the hydraulic actuator, an internal leakage is shown to increase the damping characteristic of the system and change the transient response of the pressure signals. An external leakage, on the other hand, drops the pressure signals without having a significant effect on transient responses. Offline detection of internal leakage in hydraulic actuators is first examined by using fast Fourier, wavelet and Hilbert-Huang transforms. The original pressure signal is decomposed using these transform methods and the frequency component which is sensitive to the internal leakage is identified. The root mean square of the processed pressure signal is used and a comparison of the three transforms is made to assess their ability to detect internal leakage fault, through extensive validation tests. The wavelet transform method is shown to be more suitable for internal leakage detection compared to the other two methods. The wavelet based approach is then extended to an online detection method of internal leakage fault. The online approach considers the more realistic case of an actuator that is driven in a closed-loop mode to track pseudorandom position reference inputs against a load emulated by a spring. Furthermore, the method is shown to remain effective even with control systems which are tolerant to leakage faults. Next, the application of wavelet transform to detect external leakage fault using both offline and online applications in hydraulic actuators is described. The method also examines the isolation of this fault from actuator internal leakage in a multiple-fault environment. The results show that wavelet transform is a fast and easily-implementable method for leakage detection in hydraulic actuators without any need to explicitly incorporate the model of actuator or leakage. Internal leakages as low as 0.124 lit/min, are shown to be detectable, for 80% of the times using structured input signal. For online application, internal leakages in the range of 0.2-0.25 lit/min can be identified. External leakages as low as 0.3 lit/min can be detected in all offline and online applications. Other methods such as observer based and Kalman filter methods, which require the model of the actuator or leakage fault, cannot report leakage detection of magnitudes as low as that reported in this work. The low leak rate detection and not requiring a model of the actuator or leakage make this method very attractive for industrial implementation.

Cracks in reinforced concrete structures can occur as a result of many phenomena such as fresh concrete bleeding, restrained shrinkage, thermal gradients, freeze-thaw cycles, alkali-aggregate reactions, and can also be induced by external loading. Thus, concrete becomes more vulnerable to the processes of deterioration by corrosion of reinforcement. The corrosion rate of cracked reinforced concrete in different exposure conditions has been studied by some researchers. However, it is not clear how the presence of cracks affects the corrosion-determining factors, which control the corrosion pattern at the crack. The objective of this project was to develop an understanding of the effects of cracking on the transport characteristics under wetting and drying cycles. In this project, flexural loading induced natural cracks, and parallel-wall artificial cracks were studied. The infiltration properties of those cracks were evaluated by the tension infiltrometry technique. The saturation conditions around the crack were monitored with the Time Domain Reflectometry (TDR) technique. A numerical simulation was carried out to model the evolution of saturation in the cracked beams; in the model two crack modeling approaches were employed and compared. The infiltration test showed that the presence of both artificial and natural cracks (0.3 mm and 1.0 mm) dramatically increased the permeability of concrete. The value of hydraulic conductivity was increased by up to 5 orders of magnitude at the location of the crack. The evolution of water saturation of the cracked concrete under wetting and drying conditions was analyzed as colour-scaled images and the water saturation contours were compared for different crack openings. For the artificial crack samples, a deviation from the expected “perfectly symmetric” flow regime around a straight crack was observed. This was probably caused by the micro cracks induced during the shim pull-out process or a non-uniform compaction around the shim insertion. For the natural cracks, in the drying phase, smaller cracks seemed to have better water storage. Hence, the water saturation decreased at a slightly slower rate. The crack behaved like an open surface that was exposed to the environment. Application of the same material properties to the open surface and the crack surface did not bring a large error for the water flow simulations. A hysteresis phenomenon has been found during the identification of the Van Genuchten material parameters using an inverse modelling approach, with Ks=5×10-10 m/s, α =4.33×10-4, for the wetting phase, n=1.32 and for the drying phase, n=2.0. The simulation results suggest that for the simple flexural crack, the 1D crack line averaged from the front and back crack lines is capable of representing the crack in the wetting and drying scenario. The crack could be modelled as “free surface” or “equivalent porous medium”.

The accurate prediction of stress concentration factors (SCF) at weld toes is recognised as one of the most important factors in the design, against fatigue failure, of welded tubular joints in offshore structures. The objectives of this work are i) to study the influence of some important tubular joint and weld profile geometric parameters on the elastic SCFs at weld toes, ii) compare these values with strains which could be measured by strain gauges, and iii) to determine plastic-elastic strain distributions after local yielding has occurred in the weld. Using 3-d frozen-stress, photoelastic techniques elastic SCFs were determined in non-overlapped corner K joints in balanced axial loading and in X joints in axial loading. For typical tube parameters, results have been obtained for different brace angles, brace spacings, weld size, weld angle and weld toe radii in the crown and saddle planes at the brace and chord wall ends of the weld. They have been presented as the product of a shell SCF Ks and a notch SCF Kn . Ks, which was measured at the weld toe, depends on position in the brace intersection, brace angle, brace spacing and weld size. Kn depends on weld toe radius, weld angle and weld size. Large scale 2-d photoelastic and finite element models were used to study the influence of weld profile "qualities" on Ks and Kn. Weld shapes conforming with minimum profiling requirements are called "uncontrolled". Improved weld shapes wi th concave profiles are called "controlled". The reductions in SCFs, due to the different profiles, depend on position (crown or saddle) when the results are presented for identical weld geometry. Plastic-elastic and residual plastic strains were obtained in 2-d steel weldments using reflection photoelasticity and moire interferometry experimental techniques. A moire interferometer, using Helium-Neon laser light and high sensitivity diffraction gratings was designed and built for this purpose. Strains were measured in the range 20µε to 2%. Strain concentration factors of between 13 and 17 were determined in models in which the corresponding elastic values were 3.6 and 4.6 respectively.

Wave overtopping is one of the most important processes for the design of seawalls. During the past 50 years methods for predicting wave overtopping of coastal structures have continuously been developed. However, it is evident from the existing literature that additional investigations into overtopping of small positive, zero and negative freeboard are needed. The present thesis describes numerical investigations based in this background. Wave overtopping is dependent on the processes associated with wave breaking. Therefore, a two dimensional breaking wave numerical model has been developed and used to study the phenomena of wave overtopping. The model is based on the Reynolds averaged Navier-Stokes equations for the mean flow and k-epsilon equations for turbulent kinetic energy, k, and the turbulence dissipation rate, epsilon. The model accuracy in simulating propagation of linear and irregular waves has been evaluated. The overall performance of the model is considered satisfactory. The development of guidelines for calculating overtopping discharge for different seawall slopes is presented. All slopes have been subjected to a wide range of irregular waves. The influence of how the slopes of seawalls, wave type (breaking and non-breaking) and crest freeboard affect the overtopping discharges has been investigated. Based on the numerical data, a new expression for breaking and non-breaking waves on smooth impermeable slopes is proposed. With the new expression it is possible to predict overtopping discharges of smooth seawalls in small positive, zero and negative freeboard.

No description available.