OpenUCT :: Browsing by Author "Kilner, F A"

Browsing by Author "Kilner, F A"

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Open Access
Beach development and movement as a function of water waves
(1978) Menné, Raymond Louis; Kilner, F A
This thesis consists of three parts. In Part One a literature study is made of available knowledge regarding wave theory and sediment transport in the nearshore zone, with special emphasis on littoral drift. The linear Airy theory for water waves is developed for the computation of longshore current, utilizing certain exact relationships for momentum flux. The near shore beach environment is discussed in detail with regard to the wave forces acting on it, beach forms, and three-dimensional circulation patterns. Part Two deals with experiments conducted in the hydraulics laboratory, Department of Civil Engineering, University of Cape Town, using the existing model wave basin. The experimental programme covers the development of equilibrium beach profiles as a function of certain wave characteristics, and seeks the relationship between different profiles in terms of the wave characteristics that formed them. Both normal and oblique wave attack programmes are reported on, the latter in terms of existing known relationships for littoral drift. Part Three deals with experiments conducted in the field off the South West African coast. Beach profile changes are compared to the local wave climate and relationships are sought between these changes and certain wave characteristics. A fluorescent tracer study on the swash zone is reported on as a method of gauging littoral drift.
Open Access
A critical review of measurement techniques in coastal hydraulics
(1990) Smith, G G; Kilner, F A
This thesis reviews measurement techniques in the field of coastal hydraulics. Techniques of wave measurement are studied in detail 1 and the analysis of wave measurements is then dealt with. Particular attention is paid to the analysis of one-dimensional wave energy spectra. Two computer programs were adapted for use on a microcomputer for the analysis of these spectra by the autocorrelation and the Fast Fourier Transform techniques. Experiments were conducted to determine the effect of input parameters on the analysed spectrum; the sensitivity of the one-dimensional wave energy spectrum to the number of data points, the sampling interval' and the maximum lag number (for autocorrelation analysis), is illustrated. Guidelines and examples are included for the selection of appropriate parameters.
Open Access
Design sea levels for Southern Africa : a probabilistic approach
(1993) Wijnberg, Allan Richard; Kilner, F A; Brundrit, Geoff
This thesis describes the development of a methodology for the quantitative assessment of design sea levels for southern Africa. In order to achieve this objective it was necessary to establish which ocean processes affected sea level in the sub-continent and develop a probabilistic model for the combination thereof. The methodology, is used to characterize regional design sea levels in terms of the west, south and east coasts. A site specific application is undertaken to demonstrate the model's capabilities with regard to the design of depth limited structures. The ultimate objective of this study is to provide a practical approach to the quantification of the sea level component of loading in the full probabilistic design assessment. Data analysis considers all available sea level and wave data for three ports around the coast. A three parameter threshold analysis technique is used to define independent identically distributed events. The distinction between the major processes affecting sea levels in southern Africa may be related to the differences in both the time and space scales of their response to the forcing mechanisms. The data analysis procedure is used to defined the primary statistical characteristics of the observed events in each data set as they relate to sea level. A stochastic simulation model is developed which reproduces a synthetic hourly sea level record displaying the same statistical characteristics as the observed data. Annual maximum values are extracted from the model output with a view to estimating extreme sea levels. The model may be run over any number of periods until satisfactory convergence in the results is obtained. The theoretical basis of the model is described and the results compared with the Gumbel method. A regional assessment of design sea levels for southern Africa indicated that the south coast experienced larger fluctuations in the stochastic component of sea level than the east and west coasts. Sea levels throughout the sub continent are primarily affected by tide, shelf waves, wind waves and edge waves. These processes were found to be statistically independent of one another for the areas evaluated. Design sea level would appear to be determined by a combination of a number of moderate magnitude events rather than one single process. The application of the model illustrates the importance of considering both wave height and sea level conditions as stochastic variables for the design of depth limited structures. The relative influence of stochastic sea level is shown to increase from deep to shallow water.
Open Access
An experimental investigation into the components of ship resistance
(1986) Cooke, Robert; Kilner, F A
This thesis is an experimental investigation into the components of ship resistance. The traditional Froude method of scaling is investigated with reference to the measurement of skin friction and viscous pressure resistance. A literature review is given on the theoretical background and experimental measurement techniques. Two models are used for the experimental work, which sizes are in the geometric ratio of 2,7 to 1. The model form is half a body of revolution with a vertical sided superstructure. The block coefficient of the model is 0,621 and the length to beam ratio is 7. Two surface models and one reflex model are tested. One of the models has 40 pressure tappings located on its hull which are used to measure the total pressure resistance of the model. The components of resistance directly measured are total resistance, total viscous resistance and total pressure resistance. The resistance components inferred are skin friction resistance and wave-making resistance. The deduced skin friction is found to deviate from the Prandtl-von Karman skin friction formulation. The wave-making resistance agrees favourably with the predicted values using Mitchell's integral. The total viscous resistance increases sharply at Reynolds numbers greater than 3 x 10⁶.
Open Access
The field measurement of suspended sediment in the surf zone
(1978) Heidstra, N N; Kilner, F A
Suspended sediment concentrations were measured in the nearshore environment at the site of the proposed breakwater of the Koeberg Nuclear Power Station. Reference concentrations are evaluated from the field data. Two sampling systems to obtain these concentrations were designed and constructed. The Mark I sampler was used to collect the field data, whilst the Mark II sampler was extensively tested in the laboratory and the proposed operational system was tested in the field. Difficulties were experienced in the operation of the Mark II sampling system, and are described. Recommendations for the improvement of the sampling systems are given, based on the experience gained using the sampling systems.
Open Access
Friction equation for uniform flow in channels of large relative roughness
(1989) Lillie, Edwin; Kilner, F A
This thesis is an experimental investigation of the roughness problem in open channel flow. A literature review is given on the previous research done on friction factors. It is done in chronological order, so that the historical development of the friction equation can be seen.
Open Access
Hydraulic conveyance of solid capsules
(1972) Lazarus, John Henry; Kilner, F A
The hydraulics of two phase flow of capsule - liquid mixtures is investigated experimentally and analytically. The technology of hydraulic transportation of solid capsules in pipes is advanced to the point of practical feasibility by the development and successful operation of experimental equipment in the laboratory. This involves the innovation of aspects of the technology concerned, such as novel booster pumps, injectors and metering equipment. The effect of independent variables such as capsule geometry, density, roughness and concentration as well as mean water velocity and pipe inclination are investigated. It is shown to what extent these variables affect the dependent variables. A theoretical analysis is presented for the determination of dependent variables, such as capsule velocity, excess energy and power dissipation. Flow conditions around static capsules are shown to be amenable to analysis, supplemented by experimentally determined coefficients. Energy dissipation at the inlet and outlet of static concentric and eccentric capsules is investigated for the first time, and empirical formulations are presented, which are simple and consistent with all the data. A correlation involving a pseudo hydraulic mean radius for analysing the friction head loss in eccentric annuli is presented. There have been numerous investigations concerned with friction head losses in concentric annuli. However, the correlation presented in this thesis is simpler than those given by other investigators and incorporates a wide range of experimental data satisfactorily. A theoretical analysis for flow in annuli of varying eccentricity is also presented in a novel manner and agreement with experiment is evidenced. A study is presented of incipient conditions of capsule motion which indicates a form of empirical equation for excess energy dissipation when capsules are moving.
Open Access
In-line and transverse forces on a cylinder near a boundary in oscillatory flow
(1991) Tucker, Gregory James; Kilner, F A
It was endeavoured to measure the in-line and transverse forces that act on a cylinder placed near a plane boundary in oscillatory flow. The value of performing such work is that it provides information on the forces that may be exerted by surf ace waves on a pipeline or cable mounted near the sea bed. Investigations were carried out in a laboratory, using a water filled flume. The test cylinder was attached to a plywood surface which was fastened to an hydraulic ram which could oscillate horizontally in a sinusoidal mode. Furthermore, this plywood surface, which acted as the boundary, was in contact with the upper free surface of the water in the flume, with the test cylinder submerged in the water under the plywood surf ace. The situation as it occurs in the field has therefore been inverted for this work, and the test cylinder is oscillated while the water remains stationary. Instead of measuring the lift and drag forces directly, pressure transducers were used to obtain the pressure distribution around the circumference of the test cylinder. An integration of these pressures then yielded the lift and drag forces.
Open Access
The influence of rainfall on the mechanics of soil erosion : with particular reference to Southern Rhodesia.
(1965) Hudson, Norman Webster; Kilner, F A
Today soil erosion is almost universally recognised as a serious threat to man's well-being, if not to his very existence, and this is shown by the fact that most Governments outside Europe give active support to programmes of soil conservation. But it is relevant, before making any assessment of present knowledge of erosion, to consider the development of this science which was almost unknown eighty years ago, and now enjoys world wide attention.
Open Access
Lift and drag forces on a submarine pipeline in steady flow
(1988) Kok, Nicolaas Johannes; Kilner, F A
This thesis describes an experimental investigation into the hydrodynamic forces induced on a cylinder placed transversely to a steady stream. Various cylinder locations near the bed of a water flume were considered. The work relates to pipeline design. The various flow phenomena around a cylinder are theoretically analysed and an explanation of the phenomenon of lift provided. A thorough literature review was undertaken regarding the classical theory, as well as experimental and theoretical studies carried out on the subject. This revealed that theoretical studies are virtually non-existent. Measurements have been done in intermediate water depths with both smooth and rough beds. Two different methods, comprising very simple yet novel techniques, were utilised in a water flume 18 m long x 600 mm wide x 450 mm deep. The methods involved a unique pressure determination method as well as the direct measurement of hydrodynamic forces, using a "weighing" method. Very ' accurate flow velocities were measured using a unique differential manometer. Experiments were performed in the Reynolds number range 6 000 to 26 000, using 30 and 50 mm diameter cylinders. comprehensive tests on cylinder roughening were carried out in a flow region which had not been well researched regarding this aspect. Cylinder locations were varied from a gap-to-cylinder diameter ratio of zero to 2,67. Results revealed that the force coefficients are not appreciably affected by bed roughness. Cylinder roughening produced somewhat contradicting results for the two different cylinders used. The influence on the lift coefficient was inconclusive, but the "rougher" 30 mm cylinder produced a slightly higher drag coefficient. Although the lift force was predominantly away from the bed, a downward lift force was measured on a few occasions with the cylinder situated further than one cylinder diameter away from the bed. A possible explanation is offered for this and other unexpected results. Flow visualisation tests were performed to confirm certain features of the flow around the cylinder. These as well as all the other results have been related to published work.
Open Access
Overtopping of coastal structures caused by irregular waves
(1991) Luger, Stephen; Kilner, F A
This thesis is an experimental investigation into the average rate of overtopping caused by irregular waves. A literature review is given which describes the previous research done in the field of overtopping. This research included a number of model studies using both regular and irregular waves. The literature review emphasises the dimensionless parameters which were developed by the various researchers in order to present their experimental results. The overtopping experiments were conducted in a 30m long, 0,75 m wide and 1,0 m deep wave flume equipped with an irregular wave generator. The flume was divided by two walls into three channels and the model structure was placed in the centre channel while the two side channels were used to measure the incident wave conditions. Irregular waves with a Jonswap spectrum were generated and the water which overtopped the model structure was collected in a calibrated tank located behind the structure. A wide range of wave conditions including waves which broke offshore of the structure, at the structure and beyond the structure were tested. The model structures tested were a 100 mm high vertical wall, a 200 mm high vertical wall and a 100 mm high wall with the seaward face inclined at 45°. It was found that the mechanism of overtopping was different for unbroken and broken waves. In order to model the kinematics of the water particles involved in the overtopping process, the concept of the total energy level or total head associated with the incoming waves was introduced.
Open Access
Scour at bridge piers and abutments
(1978) Little, Patrick Robert; Kilner, F A
In this thesis several of the formulae that have been put forward to predict scour are examined and some of their limitations pointed out in an attempt to clarify some of the research work that has been done on scour. The formulae are applied to two known bridge failures and their accuracy in those particular situations examined. The usual methods of scour prevention and protection are discussed.
Open Access
Shear stresses in turbulent flow through concentric annuli
(1977) Kennedy, Angus Lister; Kilner, F A
A novel experimental approach to the direct measurement of wall shear stresses in fully developed turbulent flow in concentric annuli is presented. By means of a specially constructed 6 m test rig known as the 'floating sleeve', results of individual wall shear stresses, friction factors and shear stress distributions were obtained for Reynolds numbers from 25 000 to 220 000 with radius ratios from 0,091 to 0,376. Tests were conducted using both smooth and rough annuli. A summary of previous investigations and an examination of the measuring devices most commonly used in annular flow are also presented.
Open Access
Side channel spillways
(1977) Timm, Trevor Dale; Kilner, F A
The design of side channel spillways has been discussed in detail by a number of investigators. In this thesis the most important works have been summarised, discussed and in some cases expanded in an attempt to give a concise account of the existing theories. Model tests were carried out on a side channel spillway of general type, as well as on the proposed Mtata dam spillway and the results are presented and discussed. Charts were drawn up and a procedure was recommended for the design of side channel spillways in an attempt to provide a designer with a simple method of design which he can use with confidence.
Open Access
A study of breakwater gap wave diffraction using close range photogrammetry and finite and infinite elements.
(1984) Pos, John Daniel; Kilner, F A; Adams, L P
In this thesis the diffraction of water waves passing through a gap in a breakwater is investigated experimentally, using close range photogrammetry, and numerically, using finite and infinite elements. The author was particularly interested in validating specific breakwater gap diffraction diagrams given in popular coastal engineering design manuals. Breakwater gap configurations with the following gap width to wave length ratios (B/L ratios) were analysed, both experimentally and numerically, namely: B/L = 1,64; 1,41; 1,2; 1; 0,75; 0,5. These configurations are symmetrical, i.e. both breakwater arms lie on the same straight line. An asymmetrical B/L = 1,64 breakwater gap configuration was also analysed. Previous experimental breakwater gap diffraction investigations are reviewed leading to the conclusion that the reported results are inconclusive due to (1) the relatively poor accuracy with which the wave heights were measured and (2) secondary basin effects which were superimposed upon and thus distorted the pure diffraction phenomena. In the experimental breakwater gap configurations investigated by the author, splitter plates were used to eliminate the reflection problems on the seaward side of the breakwaters, whilst a novel photogrammetric wave height measurement technique was used to measure accurately the wave heights in the entire basin, before they could be distorted by reflecting waves, basin resonance effects, etc. This "infinite basin technique" was used to simulate experimentally and measure the diffraction of a continuous wave train entering an infinite basin via a gap in an approximate totally absorbing breakwater. A number of different photogrammetric wave height measurement techniques based on analogue procedures, the theory of projective transformations, and the theory of the deformed reference plane, are investigated and developed. It was found that the technique based on the projective transformation theory, and in which the plates are analysed using a stereo-comparator linked to a microcomputer, is the most accurate. Using this technique it was found that, with the cameras situated approximately 5 m above the water surface, the wave heights in the basin can be measured with an accuracy of better than 2 mm. The above method, in conjunction with the infinite basin technique, was used to analyse the experimental breakwater gap configurations. The basic linear wave theory is described leading to the derivation of the Helmholtz diffraction equation. The classical diffraction theories for the semi-infinite breakwater and breakwater gap configurations are reviewed and compared. The Better-off refraction - diffraction equation is then briefly derived. A review of previous numerical refraction - diffraction investigations, and also of modern numerical methods for water wave diffraction and refraction-diffraction, is given. This review led to the adoption of the finite and infinite element program "WAVE", developed at the University College of Swansea, to model numerically the experimental breakwater gap configurations. The use of the "WAVE" program to model breakwater gap wave diffraction is novel and certain conceptual problems had to be overcome. Finally, the experimental and numerical diffraction diagrams obtained were compared to analytical diagrams where these were available. The correlation between the finite element and analytical results is excellent. When comparing the experimental and finite element results the general conclusions are : 1) in regions outside the shadow zones the linear diffraction theory is conservative except close to small gaps (B/L ≤ 1); and 2) within the shadow zones the linear theory is not conservative and one will have to allow for non-linear effects such as radiating second-order waves generated at the breakwater tips, and increased wave orthogonal spreading near the gap centre line and subsequent orthogonal bunching in the shadow zones caused by wave steepness differences along the crests. Other conclusions drawn are : 1) the photogrammetric techniques described are the best available for the experimental simulation and analysis of infinite domain diffraction and refraction - diffraction problems; and 2) the finite and infinite element program "WAVE" is a very useful tool for the prediction of wave heights in large harbour basins.
Open Access
A study of ship wave resistance from an analysis of the wave pattern using close range photogrammetry
(1986) Paterson, Angus John Cawood; Kilner, F A; Adams, L P
In this thesis the wave pattern generated by a moving ship is investigated experimentally using close range photogrammetry. The author has been primarily interested in validating a new approach in the determination of the wave making resistance of a ship by means of the energy contained within the wave pattern. Secondary considerations were the measurement of the total ship resistance and other dynamically related applications; squat and trim, bow and stern wave profiles and their interactive effects. The proposed theoretical approach in this analysis of the wave resistance from the wave pattern is essentially phenomenological. As a ship proceeds through the fluid, it generates a set of waves radiating from the bow and stern due to the pressure differences along the hull. Energy is needed to maintain this system and is supplied at a constant rate by the ship, this being the energy required to overcome wave-making resistance. If the total change in energy within the wave pattern can be evaluated over a time interval associated with a known ship movement, then the energy difference will be a related to the wave making resistance.
Open Access
A study of water wave reflection using close range photogrammetry
(1989) Petzer, J M; Kilner, F A; Rüther, Heinz
The intention of this investigation is to investigate the various forms of water wave reflection to a high degree of accuracy. Close range photogrammetry is the technique that is used to measure the water surface profile, as it produces an accurate and comprehensive analysis of the water surface profiles. Conventional photogrammetry techniques (photography) were used in preference to near real time photogrammetry (digital). Although near real time photogrammetry has the advantage of a far higher rate of data acquisition, it does not achieve the same degree of accuracy as can be achieved by conventional photogrammetry, the technique finally used for this investigation. For the generation of the desired wave patterns, certain equipment was developed and modified. To test the various angles of incidence a moveable reflecting wall was built. Due to the small size of the wave basin, an efficient wave absorber was required to absorb the reflected wave generated when oblique wave reflection was investigated. It was observed that a very poor quality wave was being generated by the wave generator, as a result of its flexibility. Consequently the wave generator was stiffened considerably which improved the wave generated. Interesting information was obtained from the analysis of the standing wave. A coefficient of reflection of 1,6 at the reflection wall was obtained, this places new emphasis on the relationship between the standing wave and overtopping. The oblique wave reflection resu1ts corresponded well with theoretical predictions, while no well-defined trends were established for the mach wave. The data for the mace wave did however suggest that previously established trends for the mach wave may not be correct. Close range photogrammetry produced accurate results, and is an excellent method for water surface profile measurement. The results obtained showed that the wave generator was not generating a pure wave, which lead to unknown errors in the results of spot heights. Conventional photogrammetry is a slow process, so not enough data was acquired to adequately analyse the reflection trends. This suggests that in order for the trends to be well-established, near real time photogrammetry should be used once these systems have developed sufficient accuracy.
Open Access
The underscour of rubble mound breakwaters by wave action
(1978) Allardice, Keith; Kilner, F A
Rubble mound seawalls, groins and breakwaters are still the most common type of shore-protection structures currently in use. Major reasons include: easiness to construct and repair, flexible with respect to settlement, favourable wave energy dissipation, fitness for any water depth and foundation, and because of their economical nature if rubble-stones are readily available. A complete failure of the rubble mound structure can be expected if the stone gradation is improper or if filters are not provided, or are improperly constructed to specification. Many failures have been attributed to internal erosion whereby beach materials are removed by percolating water, such as that due to water waves and surface run-off. Washing-out of the backfills, settlement of the main structure and overtopping of the subsequent waves will follow eventually. Two-dimensional model experiments have been conducted in order to clarify the basic characteristics of sand scour under dolos-protected rubble mound breakwaters, and to investigate some preventive measures against the scouring process. The inter-relationships of parameters associated with the scouring process have been investigated. Sand scour in a three-dimensional model has been discussed, and design procedures associated with Rubble Mound Breakwater and Dolos concrete armour units have also been included. This thesis is also intended to call the attention of researchers to consider foundation erosion, and protection by filter systems, in their future experimental studies on stability of rubble mound structures.
Open Access
Vertical ship motions in shallow water
(1986) Blake, Kevan Richard Kenilworth; Kilner, F A
With the increase in ship sizes, there has been an increased interest in the prediction of ship motions in shallow water, where the possibility of grounding becomes a problem. Theoretical equations governing the ship's motions have been formulated involving various hydrodynamic coefficients. In this thesis these coefficients have been found experimentally for a range of water depths and wave periods. The methods for solving the equations of motion theoretically are introduced and discussed. The equations of motion are solved using the coefficients, found experimentally, to give results in the form of motion response amplitude operators. These are compared against other authors' results derived either theoretically or experimentally. It was found that the hydrodynamic coefficients increase rapidly with decrease in water depth. Relatively good agreement between the empirical results of this thesis and results of other authors would indicate that the theoretical formulae do represent the coefficients to which they are claimed to approximate, for at least the case of zero or low forward speeds.
Open Access
Water surface profiles in side channel spillways : comparisons between computed and experimental values
(1989) Cullen, James; Kilner, F A
This thesis is an investigation into the water surface profiles found in side channel spillways. The classical method proposed by Hinds is investigated, with specific reference to the water surface slope equation. A literature review is given on the evolution of the theory, from the conceptual ideas of Hinds through to a systematic method of analysis. Experimental methods used over the years are also discussed. A computer program called WSPISCS (Water Surface Profiles In Side Channel Spillways), is developed to calculate the water surface profile. This in turn alleviates the laborious and tedious hand calculations necessary in the past. An iterative, step by step calculation of the water surface profile from .a known control point is conducted. A Runge Kutta fourth order algorithm is employed for the numerical integration. The program is verified with previous hand calculated examples, including the classical example calculated by Hinds. A thorough sensitivity analysis is conducted with regard to the magnitude of the step length, and also to the location of the starting point. Comparisons are made with experimental results obtained over a number of years of undergraduate research. The correlation between the calculated and experimental profiles is generally good. The only exception is a horizontal receiving channel with a hydraulically steep outflow chute, where the experimental profile falls below the calculated one as the inflow rate increases.