Search

Rapportage groep studenten van het Smart Solution Semester, in opdracht van onderzoeker R. Nijdam van het lectoraat Regio-ontwikkeling. Het deelproject van deze studenten behelst deel 1 van een onderzoeksproject naar de ontwikkeling van een beslissingsondersteunend systeem voor ondernemers in de verblijfsrecreatieve sector om hun bedrijfsvoering zo duurzaam en circulair mogelijk te organiseren. De rapportage is gepresenteerd aan een representatieve groep vertegenwoordigers uit het werkveld (ondernemers en branchevereniging).&nbsp

The Atlantic Multidecadal Oscillation (AMO) is a pronounced signal of climate variability in the North Atlantic sea-surface temperature field. In this paper, we propose an explanation of the physical processes responsible for the timescale and the spatial pattern of the AMO. Our approach involves the analysis of solutions of a hierarchy of models. In the lowest member of the model hierarchy, which is an ocean-only model for flow in an idealized basin, the variability shows up as a multidecadal oscillatory mode which is able to destabilize the mean thermohaline circulation. In the highest member of the model hierarchy, which is the Geophysical Fluid Dynamics Laboratory R30 climate model, multidecadal variability is found as a dominant statistical mode of variability. The connection between both results is established by tracing the spatial and temporal expression of the multidecadal mode through the model hierarchy while monitoring changes in specific quantities (mechanistic indicators) associated with its physics. The proposed explanation of the properties of the AMO is eventually based on the changes in the spatial patterns of variability through the model hierarchy.

Current is generated at the National Research Council, Institute for Marine Dynamics, Ocean Engineering Basin in St. John's, Newfoundland, using a pump thruster system where flow is conveyed under a false floor in the test basin. The objectives of this project were firstly, to quantify and assess the performance of the existing current generation system and to experimentally verify a design exit turning vane for improved current generation.

Results of computer simulations of the water motion in ship anti-roll tanks are compared with experimental data. The numerical computations are done with a Volume Of Fluid (VOF) based Navier-Stokes solver. Both free-surface anti-roll tanks and U-tube anti-roll tanks are considered. Calculated and measured results for the local wave heights, the sway force and roll moment are presented for both regular and irregular tank motions. A simple but effective simulation model for the active control of U-tube anti-roll tanks is introduced. Finally, the fully nonlinear time-domain coupling of the ship motion and the tank water motion is established.

From a computational point of view, fluid behaviour under micro-gravity conditions is more complicated than under terrestrial conditions: the fluid has a tendency to undergo large topological changes, requiring an accurate and robust method for free-surface advection. Moreover, the fluid is often contained in a cavity (e.g. satellite) that itself is moving; not only because of external forces (e.g. manoeuvring thrusters on a satellite), but also under influence of the fluid motion: the dynamics of the solid-body motion and the liquid motion are coupled. In the paper a method is presented for simulating coupled liquid-solid dynamics under micro-gravity conditions (although the method also works in a terrestrial environment). The liquid dynamics is solved by discretising the Navier-Stokes equations on a Cartesian grid. Transportation of the free surface is based on the VOF-method; however, slightly adapted in order to avoid the (numerical) creation of "flotsam" and "jetsam". The solid-body motion is governed by equations for its linear and angular momentum, in which terms appear that represent the force and torque induced by the sloshing liquid. Care has to be taken in solving these equations to keep the coupling numerically stable for arbitrary liquid/solid mass ratios.

Free-surface flows are difficult to simulate since the position of the free surface itself is part of the problem that needs to be solved. In the absence of gravity, simulation of free-surface flow is extra complicated because capillary effects dominate. In this case the shape of the interface drives the flow: the pressure at the free surface depends on the curvature of the surface. In our approach, the numerics is based on finite-volume discretization on a three-dimensional Cartesian grid. Special attention has been paid to the implementation of boundary conditions at non-gridaligned boundaries. The position of the fluid (and thus the free surface) is described by an Eulerian Volume-of-Fluid function F. Transportation of F is achieved using a local level-set function. Because the method is based on Cartesian grids, it is capable of simulating flows in arbitrary complex three-dimensional geometries. The method has already been used in a wide variety of (industrial) flow problems, such as green water loading on the foredeck of a ship and liquid sloshing aboard satellites.