Three-dimensional water impact at normal incidence to a blunt structure

The three-dimensional (3D) water impact onto a blunt structure with a spreading rectangular contact region is studied. The structure is mounted on a flat rigid plane with the impermeable curved surface of the structure perpendicular to the plane. Before impact, the water region is a rectangular domain of finite thickness bounded from below by the rigid plane and above by the flat free surface. The front free surface of the water region is vertical, representing the front of an advancing steep wave. The water region is initially advancing towards the structure at a constant uniform speed. We are concerned with the slamming loads acting on the surface of the structure during the initial stage of water impact. Air, gravity and surface tension are neglected. The problem is analysed by using some ideas of pressure-impulse theory, but including the time-dependence of the wetted area of the structure. The flow caused by the impact is 3D and incompressible. The distribution of the pressure-impulse (the time-integral of pressure) over the surface of the structure is analysed and compared with the distributions provided by strip theories. The total impulse exerted on the structure during the impact stage is evaluated and compared with numerical and experimental predictions. An example calculation is presented of water impact onto a vertical rigid cylinder. Three-dimensional effects on the slamming loads are of main concern in this study

The Economic Value of Environmental Services on Indigenous-Held Lands in Australia

Australians could be willing to pay from $878m to$2b per year for Indigenous people to provide environmental services. This is up to 50 times the amount currently invested by government. This result was derived from a nationwide survey that included a choice experiment in which 70% of the 927 respondents were willing to contribute to a conservation fund that directly pays Indigenous people to carry out conservation activities. Of these the highest values were found for benefits that are likely to improve biodiversity outcomes, carbon emission reductions and improved recreational values. Of the activities that could be undertaken to provide the services, feral animal control attracted the highest level of support followed by coastal surveillance, weed control and fire management. Respondents' decisions to pay were not greatly influenced by the additional social benefits that can arise for Indigenous people spending time on country and providing the services, although there was approval for reduced welfare payments that might arise

Heat-flow anomaly and residual topography in the Mascarene hotspot swell (Indian Ocean)

We review the sea-bottom heat-flow determinations and present a new heat-flow observation on the Mauritius island, which is part of the long-lived Reunion hotspot track. The marine heat flow is on average 66 \ub1 11 mW m 122 and is consistent with the on-land value of 61 \ub1 18 mW m 122 found in Mauritius. Since these values do not significantly deviate from the reference cooling-plate model, lithosphere erosion does not seem a likely mechanism for the swell formation. The lack of significant reheating due to a mantle plume impacting the lithosphere base is confirmed by thermal modelling. Moreover, the coherency between on-land and marine data is argument against advective redistribution of heat near the axis of the swell. We also analyse the large-scale features of the ocean lithosphere, which are not simply a function of the plate cooling and can reflect variations in mantle dynamic topography. The predicted topography variation along the swell shows amplitude and wavelength comparable to other hotspots. Both the topographic swell magnitude and the wavelength increase northwards with the increase of the age of volcanism. The estimated flux of material from the mantle follows the same trend, being larger in the northern part of the swell. The result that residual topography and the buoyancy flux are smaller at the active volcano of Reunion could be evidence that the activity of the plume has decreased with time