Efficiency of a gyroscopic device for conversion of mechanical wave energy to electrical energy:Technical report from ESGI-83 workshop in industrial mathematics 2011

We consider a recently proposed gyroscopic device for conversion of mechanical ocean wave energy to electrical energy. Two models of the device derived from standard engineering mechanics from the literature are analysed, and a model is derived from analytical mechanics considerations. From these models, estimates of the power production, efficiency, forces and moments are made. We find that it is possible to extract a significant amount of energy from an ocean wave using the described device. Further studies are required for a full treatment of the device.Resulting from the interaction with Joltech A/S at ESGI-83 (European Study Group with Industry) workshop on industrial mathematics, Sønderborg Denmark, 2011.</p

ULTRASONIC VELOCITIES OF CHALK SAMPLES: INFLUENCE OF POROSITY, FLUID CONTENT AND TEXTURE

ABSTRACT The acoustic properties of the pure chalk of the Upper Cretaceous Tor Formation have been studied on core material from the Dan and South Arne fields, Danish North Sea. Detailed investigations were carried out on 56 vertical plug samples with porosities ranging from 14% to 45%, i.e. measurement of P-and S-wave velocities of dry and water-wet samples and microtextural image analysis on backscatter micrographs. Porosity is the primary control on sonic velocities and elastic moduli of chalk with identical pore fluids. For chalk samples dominated by fine carbonate particles (mud) we obtain a well-defined relation between elastic moduli and porosity, which can be modeled using a modified upper Hashin-Shtrikman bound. The trend is defined by a bulk and shear modulus at zero porosity of 54 and 22 GPa, and by a high-porosity end-member at 47%. We find that compaction, grain size distribution, and possibly mineralogy, rather than pore-filling cementation, control the variation of porosity for the samples. Variations in chalk particle size distribution and the content of non-carbonates influence the relation between elastic properties and porosity for the samples investigated even though the carbonate content is &gt;95%. South Arne samples are found to be stiffer than Dan/Gorm samples for identical porosities e.g. a porosity of 30% corresponds on average to a bulk modulus of 17 GPa and 14 GPa, respectively, for the saturated samples. Conversely, a bulk modulus of 15 GP