Tsunamis -- the propagation of long waves onto a shelf

The various aspects of the propagation of long waves onto a shelf (i.e., reflection, transmission and propagation on the shelf) are examined experimentally and theoretically. The results are applied to tsunamis propagating onto the continental shelf. A numerical method of solving the one-dimensional Boussinesq equations for constant depth using finite element techniques is presented. The method is extended to the case of an arbitrary variation in depth (i.e., gradually to abruptly varying depth) in the dirlection of wave propagation. The scheme is applied to the propagation of solitary waves over a slope onto a shelf and is confirmed by experiments. A theory is developed for the generation in the laboratory of long waves of permanent form, i.e., solitary and cnoidal waves. The theory, which incorporates the nonlinear aspects of the problem, applies to wave generators which consist of a vertical plate which moves horizontally. Experiments have been conducted and the results agree well with the generation theory. In addition, these results are used to compare the shape, celerity and damping characteristics of the generated waves with the long wave theories. The solution of the linear nondispersive theory for harmonic waves of a single frequency propagating over a slope onto a shelf is extended to the case of solitary waves. Comparisons of this analysis with the nonlinear dispersive theory and experiments are presented. Comparisons of experiments with solitary and cnoidal waves with the predictions of the various theories indicate that, apart from propagation, the reflection of waves from a change in depth is a linear process except in extreme cases. However, the transmission and the propagation of both the transmitted and the reflected waves in general are nonlinear processes. Exceptions are waves with heights which are very small compared to the depth. For these waves, the entire process of propagation onto a shelf in the vicinity of the shelf is linear . Tsunamis propagating from the deep ocean onto the continental shelf probably fall in this class

Structure of the internal boundary layer over a patch of pinnid bivalves (Atrina zelandica) in an estuary

Measurements of tidal-current boundary-layer flow over an experimental 2-m by 2-m patch of pinnid bivalves (Atrina zelandica) in a northern New Zealand estuary are presented. Previous work demonstrated a link between mesoscale (order 100 m) patchiness of the benthic biota and time-averaged boundary-layer dynamics. The aim in this new experiment was to describe the three-dimensional structure of turbulence at the patch scale (order 1 m). Flow over three densities of Atrina was investigated: 340 individuals per 4 m2, 50 individuals per 4 m2 and zero individuals. An internal boundary layer (IBL) grows downstream from the leading edge of the patch at the base of the ambient boundary layer. One meter in from the leading edge, the top of the IBL was ~ 12 cm above the bed for the high-density patch and ~ 6 cm for the low-density patch. Flow in the IBL was three-dimensional in that vertical and transverse mean velocities were nonzero, secondary Reynolds stresses were nonzero and comparable with the primary stress, and velocity spectra deviated from scaling relationships for two-dimensional flow. Thus, the observed IBL was still in its infancy, i.e., it consisted of a roughness sublayer only as the distance from the leading edge of the patch was not enough for development of a second, overlying logarithmic layer. In summary, the IBL that envelops the Atrina patch is a region of lower mean longitudinal velocities but more energetic turbulence relative to the ambient boundary layer. The former translates into shelter, which some organisms might take advantage of, and the latter translates into increased vertical exchange across the top of the IBL, which might enhance fluxes of nutrients, colonists and suspended sediments, and might have implications for deposition and resuspension of organically rich biodeposits. The results extend our knowledge of turbulence over patches of suspension feeders at the 1-m scale and therefore provide information needed to improve depiction of flow in models of suspension-feeder-flow interactions

Meteotsunami resulting from the propagation of synoptic-scale weather systems

a b s t r a c t From time to time in conditions of light swell and balmy weather, long waves of up to 1 m in height and several minutes period occur on the eastern seaboard of New Zealand. These waves are an insidious threat to navigation because they cause set-down in vessels navigating to berth, thus reducing their under-keel clearance. The events are strongly correlated with low-pressure systems that emerge from the tropics and propagate southwards 1000 km or more to the east of New Zealand. The speed of propagation of the weather systems is generally of the order of 20 km/h, which is well below the long wave speed of 800 km/h, but is close to the group velocity of swell waves in deep water

Amphiphilic polyethylene block copolymers and their application as wax crystal modifiers in middle-distillate fuels

Chapter 1 Reviews the synthesis of polyolefin block copolymers, focussing on strategies involving catalytic coordination polymerisation to produce end-functionalised polyolefins followed by the growth of a second block from the reactive end group using living/controlled techniques. The advantages and disadvantages of the various literature methods are discussed. Chapter 2 Discusses the utilisation of the Catalytic Hydride Insertion Polymerisation (CHIP) mechanism for the synthesis of low molecular weight polyethylene macromonomers by manipulating the relative concentrations of dihydrogen and ethylene in the reactions. The application of the mechanism is investigated further with the introduction of two non-styrenic comonomers 5-vinyl-2-norbornene and 5-ethylidene-2-norbornene. Observations made when we studied the effects of comonomer concentration and dihydrogen partial pressure on the products are discussed and some mechanistic insights for the copolymerisation between ethylene and norbornene derivatives in the presence of dihydrogen are proposed. Chapter 3 Focusses on the investigation of the mechanism for the copolymerisation between the PE-i-DIB macromonomer and n-butyl acrylate using a small-scale batch process and a larger scale starved feed semi-batch process. Observations are found to be consistent with a reversible cross-propagation mechanism between PE-i-DIB and the propagating P(n-BA) chain in which the continued availability of monomer is key to the lifetime of the process, as demonstrated by the difference in the evolution of molecular weight in the batch and semi-batch processes. The semi-batch process also provides superior control over the copolymerisation compared to the batch process. Chapter 4 Investigates the versatility of the PE-i-DIB macromonomer in copolymerisations with several other types of polar monomer. Copolymer products with vinyl esters, methacrylates and styrenes are synthesised and the challenges provided by the new monomer types are discussed. The products discussed here and in Chapter 3 are characterised by NMR, GPC, DLS and DSC and the evidence is found to be consistent with the presence of block copolymers. Chapter 5 Describes the testing of some of the block copolymers synthesised in Chapters 3 and 4 for their wax crystal modification properties in one type of diesel fuel. The block copolymers were tested as neat additives and in formulation with commercial nucleators and growth arrestors in the Cold Filter Plugging Point (CFPP) test to assess performance and to indicate mode of action. The mode of action was then investigated further by observing the effect of the additives on the crystallisation events using DSC. The performance in CFPP and the observations in DSC are consistent with the block copolymers generally acting as nucleating agents, though some also display single-shot activity. There is an observable trend in performance with the varying size of the polar block as well as varying the polar block itself. Chapter 6 Details the experimental procedures used to carry out the work in this thesis

Probabilistic modelling of bed-load composition.

NoThis paper proposes that the changes which occur in composition of the bed load during the transport of mixed-grain-size sediments are largely controlled by the distributions of critical entrainment shear stress for the various size fractions. This hypothesis is examined for a unimodal sediment mixture by calculating these distributions with a discrete particle model and using them in a probabilistic calculation of bed-load composition. The estimates of bed-load composition compare favorably with observations of fractional transport rates made in a laboratory flume for the same sediment, suggesting that the hypothesis is reasonable. The analysis provides additional insight, in terms of grain mechanics, into the processes that determine bed-load composition. These insights strongly suggest that better prediction methods will result from taking account of the variation of threshold within size fractions, something that most previous studies have neglected

Observations, effects and real time assessment of the March 11, 2011 Tohoku-oki Tsunami in New Zealand

The great Tohoku-oki earthquake of March 11, 2011 generated a devastating tsunami in the near field as well as substantial far-field effects throughout the Pacific Ocean. In New Zealand, the tsunami was widely observed and instrumentally recorded on an extensive array of coastal tidal gauges and supplemented by current velocity data from two sites. While the tsunami's first arrival was on the morning of March 12 in New Zealand, the strongest effects occurred throughout that afternoon and into the following day. Tsunami effects consisted primarily of rapid changes in water level and associated strong currents that affected numerous bays, harbors, tidal inlets and marine facilities, particularly on the northern and eastern shores of the North Island. The tsunami caused moderate damage and significant overland flooding at one location. The tsunami signal was clearly evident on tide gauge recordings for well over 2 days, clearly illustrating the extended duration of far field tsunami hazards. Real time analysis and modelling of the tsunami through the night of March 11, as the tsunami crossed the Pacific, was used as a basis for escalating the predicted threat level for the northern region of New Zealand. A comparison to recorded data following the tsunami shows that these real time prediction models were accurate despite the coarse near-shore bathymetry used in the assessment, suggesting the efficacy of such techniques for future events from far-field sources

Erratum to: Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition) (Autophagy, 12, 1, 1-222, 10.1080/15548627.2015.1100356

non present