Wave Generation in Open Channels by Vortex Shedding from Channel Obstructions

Transverse surface waves were produced in a rectangular open channel in the region where the otherwise steady, uniform, flow passed through a cluster of vertical circular cylinders. The cylinders could represent either naturally occurring obstacles such as vegetation or man-made structures such as a group of piles driven into the bed of a river. The waves were produced from the periodic forces created by the vortex shedding from the cylinders. These forces generated and then amplified transverse waves in the channel. In some experiments the waves had amplitudes of 35% of the mean flow depth. These resonance-generated waves produce a seiching that can occur in hydraulic models as well as prototype systems. Both laboratory experiments and a theory-based analysis were used to determine the relationship between the amplitude of the vortex-generated wave, average velocity of the approach flow, viscosity of the fluid, width of the rectangular channel, depth of flow, cylinder diameter, and cylinder placement configuration.     

LEFM size requirements for the fracture testing of sea ice

The stress-separation curve obtained for the in-situ response of first-year sea ice is used to obtain specimen size requirements for sea ice fracture tests. Issues of notch sensitivity and minimum size requirements for the applicability of linear elastic fracture mechanics are addressed. The role of time dependent deformations in studying sea ice fracture is examined.     

Mathematical modeling of river ice processes

River ice processes involve complex interactions between hydrodynamic, mechanical, and thermal processes. River ice research has largely been driven by engineering and environmental problems that concern society, including ice effects on flooding, hydropower, navigation, ecology, and the environment. Important findings on river ice research before 1980 have been summarized by Ashton (1986) and Donchenko (1987). Significant progress has been made in river ice research in the last three decades. Mathematical modeling has been an essential part of this progress. Mathematical models have been developed for various river ice processes. They not only helped to advance understanding of the physical processes by complementing field and laboratory studies, but also provided tools for planning and design of engineering projects. In this paper, models of various river ice processes during the winter, from freeze-up to breakup, are reviewed after a brief overview of river ice phenomena. Following the discussion of these ‘component’ models, a discussion on ‘comprehensive’ models and an analytical framework which links all river ice processes in a coherent manner is presented.     

Model selection, updating, and averaging for probabilistic fatigue damage prognosis

This paper presents a method for fatigue damage propagation model selection, updating, and averaging using reversible jump Markov chain Monte Carlo simulations. Uncertainties from model choice, model parameter, and measurement are explicitly included using probabilistic modeling. Response measurement data are used to perform Bayesian updating to reduce the uncertainty of fatigue damage prognostics. All the variables of interest, including the Bayes factors for model selection, the posterior distributions of model parameters, and the averaged results of system responses are obtained by one reversible jump Markov chain Monte Carlo simulation. The overall procedure is demonstrated by a numerical example and a practical fatigue problem involving two fatigue crack growth models. Experimental data are used to validate the performance of the method.     

Membrane and solution effects on solute rejection and productivity

Limited understanding of the physical and chemical processes involved in membrane processes affects their widespread application in drinking water treatment. Insight into these processes was attained through a systematic manipulation of solution chemistry in membrane filtration with three ‘loose’ nanofiltration membranes. Eighteen known solutions were created varying pH, ionic strength, and major cation valence in the presence of a commercial humic acid. The membrances varied as well, including a non-ionic hydrophobic, a non-ionic hydrophilic, and an anionic hydrophilic membrane surface. Specific membrane productivity and TOC and conductivity rejection were monitored.

In all cases, the presence of divalent cations decreased the rejection of both conductivity and organic matter. Divalent cations also greatly increased the rate of productivity decline over equivalent tests in solutions with monovalent cations. The most hydrophobic membrane had the greatest productivity decline rate under all solution conditions. The lowest ionic strength solutions showed the greatest TOC and conductivity rejection and the greatest rate of productivity decline for each of the membranes.     

Extraction of uranium from the concentrated brine rejected by integrated nuclear desalination plants

This work was carried out under the specific collaboration agreement between the Bhabha Atomic Research Centre (BARC) from India and the Commissariat à l'Energie Atomique (CEA) from France. This paper summarises first results of review and research on the possible extraction of uranium from the concentrated brine rejected by integrated nuclear desalination systems, which both partners are currently developing in the two organisations. Three innovative and efficient methods of uranium extraction have been proposed: 1) Resin grafted with calixarene: this method has the advantage of very high selectivity. Its performances, especially for large-scale extraction, still need further R&D and optimisation; 2) Magnetic separations: yet another method with high selectivity, easy separation and affording high degree of material recovery. The method, however, is in developmental stage; 3) Canal system with Braid adsorbents: high selectivity. Appears to be feasible in conjunction with existing technology. It would nonetheless require large amounts of adsorbents and adequate infrastructure.     

A brief study of the force balance between a small iceberg,the ocean,sea ice,and atmosphere in the Weddell Sea

Icebergs are an important source of freshwater to the Weddell Sea. A unique set of oceanographic and other observations made during the Maud Rise Nonlinear Equation of State Study around one of the small icebergs, ubiquitous in the winter Weddell Sea, give us the opportunity to examine the dynamics of the interaction between an iceberg and the ocean. The iceberg was mapped using radar ranges and bearings from our ship, the research icebreaker Nathaniel Palmer, and found to be about 200 m wide above the water with a draft estimated to be 219 m. For this size, form drag dominates skin friction in both the atmosphere and ocean. Sea ice was ridged against the upwind side of the iceberg and thin sea ice and open water were on the downwind side. The iceberg was drifting 0.14 m s^− 1, or about 3% of the wind speed and 23° to the left. An automated CTD operating through the ship's moon-pool was used to measure temperature and salinity profiles upstream, downstream, and to the side of the iceberg. These profiles show a mixed upper layer 150 m deep upstream and 60 m deep downstream of the iceberg. The difference in density across the pycnocline was 0.05 kg m^− 3, which for the average pycnocline depth of 105 m and size of the iceberg corresponds to an interfacial internal wave speed equal to 0.166 m s^− 1. This and the upstream–downstream difference in pycnocline depth are consistent with a ± 45 m internal wave wake being generated by the motion of the iceberg. We estimate the contributions to total water drag from form drag and generation of the internal wake to be about equal. Consistent with theory, a qualitative argument using the observed pycnocline displacements suggests that internal wake drag should be a maximum when iceberg drafts are near the pycnocline depth. The drift rate of the iceberg (and sea ice) relative to wind speed was near the relative drift rate for the Weddell Sea ice we encountered during MaudNESS, but three times greater than what would result from a pure balance of atmospheric form drag against ocean form drag on the iceberg. Therefore, the force of sea ice on the iceberg, evidenced by ridging on the upwind side was dominant in moving the iceberg with the sea ice drift speed. The force transmitted through the sea ice required to drive the ice at the observed rate would be equivalent to the wind stress acting on an area of sea ice of 7.5 km². Maximum ridging forces in the 0.5 m thick sea ice should be adequate to drive the iceberg with this 219-m draft at 0.56 m s^− 1, much more than the observed drift rate but similar to the sea ice velocities during Weddell Sea storms.     

Field-Scale In-Situ Compliance of Arctic First-Year Sea Ice

This paper presents the experimental results and analysis of the creep recovery and cyclic loading crack-opening-displacement measurements recorded on level first-year sea ice at Barrow, Alaska. This was the third of a three-trip program to track the seasonal evolution of the mechanical and physical properties of first-year S2 sea ice. Seven large-scale in-situ experiments were completed covering a size range of 1:30 with the largest test having dimensions of 30 m × 30 m. The creep recovery response from the largest test specimen is examined in this paper to determine the compliance of a precracked square-plate test geometry via a nonlinear viscoelastic∕viscoplastic formulation. This model is then applied to the cyclic loading, and a monotonic ramp to fracture, to quantify its ability to predict the behavior for a variety of loading paths.