239 research outputs found
Particle tracking study in the Mersey Estuary
No full textA nested modeling system has been applied to Liverpool Bay to accurately simulate the circulation during the three month period January to March 2008. The model has been applied for a particle tracking study investigating the movement of 2 sediment mixes (70:30 silt to medium sand and 50:50 fine sand to medium sand) for 3 different deposit tonnages (10, 500 and 1500 Tonnes). The disposal sites are those already used for maintenance dredging within the Mersey Estuary: IS120 (close to the mouth), IS128 and IS110 (with increasing distance into the inner estuary). Following the release of sediment at the start of all the scenario simulations the majority (83% or more) of the deposited sediment remains within the Mersey Estuary after the 3 month simulation. A small percentage of fine particles (<12%) are able to drift north along the English coast with a few leaving the Liverpool Bay coastal cell (11 a and b). When deposited in larger quantities a small percentage of coarse sediment is also found to leave the estuary (<17%) in a westward pathway towards the Welsh coast. Initially the sediment follows a pathway out of the estuary via the main navigation channel, where it is then influenced by the residual flow within the bay. This typically moves sediment back onshore before diverging at Formby Point. The simulated fine particles follow the path of the northerly drift interacting with the Ribble Estuary before continuing north. The coarse fraction continues to move west from the end of the main channel. The particles remaining within the estuary accumulate close to the shorelines in the inner region, potentially increasing the required maintenance dredging within the docks. The deposits close to the Mersey Narrows have greater tendency to become transported offshore than those from the disposal sites situated with greater distance into the inner estuary
Fine particle retention and deposition in regions of cyclonic tidal current rotation
No full textBenthic sediments in continental shelf seas control a variety of biogeochemical processes, yet their composition, especially that of fine sediment, remains difficult to predict. Mechanisms for mud or fine sediment deposition and retention are not fully understood. Using sediment data and a hydrodynamic model of the Northwest European shelf seas, a relationship is shown to exist between fine benthic sediment composition and regions of cyclonic tidal current rotation. The reduced thickness of cyclonic tidal benthic boundary layers compared with the anticyclonic case promotes deposition of fine sediment and trapping of resuspended material. Adding the effects of the benthic boundary layer thickness, as influenced by ellipticity or not, sheds some light on the limitations of approaches only focusing on bed shear stress and sediment pathways to predict the location of mud deposits. A tidal boundary layer predictor that includes ellipticity alongside tidal current magnitude and depth was shown to spatially agree with maps of mud deposits
“Intelligent” Cinematography in Pre-Revolutionary Kazan: Role of Professor L.O. Darkshevich in Educational Film Development
No full textThe paper analyzes the development of educational cinematography in Kazan during the period of 1908–1916. The author draws attention to the review written by L.O. Darkshevich (1858–1925), the worldwide famous neuropathologist and professor of the Kazan University, of “Drinking and
Its Consequences” (1913), a scientific and popular film. It is assumed that the critical attitude of the neurosurgeon to the first steps of educational cinematography reflects the desire of this person to use his authority to influence the development of “intelligent cinematography”. Furthermore, the paper provides examples of active use of this type of art for educational purposes. Notably, there was a special scientific and popular cinema theatre in Kazan. The Kazan Society of Public Universities actively used cinematography during lectures. During the First Word War, films were screened for free in hospitals for wounded soldiers of the Kazan region. Scientific cinematography was also supported by the state: film demonstrators were exempt from taxes if charity events were held
Two-dimensional, two-phase granular sediment transport model with applications to scouring downstream of an apron
No full textWe present a two-dimensional, two-phase model for non-cohesive sediment transport. This model solves concentration-weighted averaged equations of motion for both fluid and sediment phases. The model accounts for the interphase momentum transfer by considering drag forces. A collisional theory is used to compute the sediment stresses, while a two-equation (k–ε) fluid turbulence closure is implemented. A benchmark sediment transport problem concerning the scouring downstream of an apron is carried out as an example and numerical results agree with existing experimental data
Stille oogenblikken. Gedenkboek van het verzet der Delftsche studenten en docenten gedurende de jaren 1940-1945.
No full textVerzetsboek van Delftse studenten gedurende de 2e Wereldoorlog. Bevat geannoteerde voorblad (2006). Op voorblad gedenkplaat naar een ontwerp van prof. L.O. Wenkebach door Paul Huf.Delft University of Technolog
Acceptance-by-Design Elicitation of Social Requirements for Intelligent Infrastructures
No full textEngineering Systems and ServicesTechnology, Policy and Managemen
Algal blooms and Membrane Based Desalination Technology
No full textSeawater desalination is rapidly growing in terms of installed capacity (~80 million m3/day in 2013), plant size and global application. An emerging threat to this technology is the seasonal proliferation of microscopic algae in seawater known as algal blooms. Such blooms have caused operational problems in seawater reverse osmosis (SWRO) plants due to clogging and poor effluent quality of the pre-treatment system which eventually forced the shutdown of the plant to avoid irreversible fouling of downstream SWRO membranes. As more extra large SWRO plants (>500,000 m3/day) are expected to be constructed in the coming years, frequent chemical cleaning (>1/year) of SWRO installations will not be feasible, and more reliable pre-treatment system will be required. To maintain stable operation in SWRO plants during algal bloom periods, pre-treatment using ultrafiltration (UF) membranes has been proposed. This thesis addresses the effect of algal blooms on the operation of UF pre-treatment and SWRO. Experimental investigations demonstrated that marine algal blooms can impact the backwashability of UF and can accelerate biological fouling in RO. However, it is unlikely that algae themselves are the main causes of fouling but rather the transparent exopolymer particles (TEPs) that they produce. To better monitor TEPs, a new method capable of measuring TEP as small as 10 kDa was developed and showed that TEPs can be effectively removed by UF pre-treatment prior to SWRO. This work also demonstrated that although TEPs and other algal-derived material (AOM) are very sticky and can adhere to UF and RO membranes, adhesion can be much stronger on membranes already fouled with AOM. Moreover, a model was developed to predict the accumulation of algal cells in capillary UF membranes which further demonstrated that the role of algal cells in UF fouling is not as significant as that of AOM and TEPs. Overall, this study demonstrates that better analytical methods and tools are essential in elucidating the adverse impacts of algal blooms in seawater on the operation of membrane-based desalination plants (UF-RO). It also highlighted the importance of developing effective pre-treatment processes to remove AOM from the raw water and reduce the membrane fouling potential of the feed water for downstream SWRO membranes.Water ManagementCivil Engineering and Geoscience
Smart Wind Turbine: Analysis and Autonomous Flap
No full textWind turbines convert kinetic energy of the wind into electrical energy. Unfortunately, this process is everything but constant, as the wind source shows large fluctuations with high and low frequencies. This turbulence, together with the wind shear and yawed inflow, excites the turbine structure, thereby driving the loads and the design of turbines in general and blades in particular. In response to this, several control mechanisms have been applied to wind turbines since the generation of stall controlled machines in the 1980s. While collective pitch control was applied first, the control mechanisms have become more localised and act on individual turbine blades, rather than on the rotor as a whole. An advanced control scheme is termed 'smart wind turbine'. These type of wind turbine actively measures vibrations of its blades through a set of distributed sensors throughout the blades and then aims to counteract the vibrations using aerodynamic modifications around the blades' trailing edges close to the tips by means of control surface deflections. This thesis investigates two aspects of the smart rotor concept: the analysis of smart rotors and the design of an autonomous flap concept. For the analysis, a wind turbine analysis tool with special focus on smart rotors and controller implementation has been developed. This code, the Delft University Smart Wind turbine Analysis Tool (DU-SWAT), has been benchmarked not only against conventional wind turbine codes, but a comparison study with the first utility-scale smart rotor experiment, the Sandia National Laboratories Smart Rotor, was performed. The experimentally obtained eigenfrequencies of the test turbine matched closely those of the numerical study. The difference in the first eigenfrequency is 2.7% or 0.1 Hz (4.4 Hz experimentally, 4.5 Hz numerically). A second comparison step was a time domain analysis of the wind turbine response to a step deflection input of the flaps. For the tower response, the frequencies and the amplitudes of the numerical and experimental responses agree very well. For blade vibrations, an increase in damping in the numerical simulations is observed. While for low flap deflection amplitudes, up to 5 degrees, the response amplitude is predicted well. When high step deflections are modelled, the numerical simulations increasingly fail to accurately capture the dynamics of the turbine. In combination with the differences in damping, this leads to the conclusion that vortices, shed from the flap tips, interact with the larger tip vortices, possibly due to the proximity of the flaps to the blade tips. This inaccuracy of high flap deflection angles is however of limited importance, as it was demonstrated that the periodic (1P) load, the most dominant contributor to fatigue damage, could be alleviated effectively even with deflection angles up to 5 degrees. The individual flap controller has been tuned to the NREL 5MW reference turbine and has been used to study both fatigue and extreme loads according to the certification regulations. Failure-free cases were included in the analysis, and loads have been monitored throughout the turbine. The fatigue load reduction of the blade root bending moment of 24\% corresponds well with the findings of previous researchers. Besides this verification, it was also shown that the structural loads increase nowhere in the turbine, with the exception of the blade root torsional moment. Several other loads decrease, for example the tower torsion moments and the bending moments in the turbine shaft. The extreme load reduction is smaller than the fatigue load reduction. Still, the ultimate tip deflection and the ultimate blade root bending moment could be reduced by 7\% and 8\%, respectively. The moments in the tower are also reduced. Besides load alleviation, an additional functionality of the smart rotor was established. The flaps can be used to increase the power production of the turbine by responding to fluctuations in the wind speed and the delays in the adjustment of the rotor speed due to the rotor inertia. An intermediate step of the wind turbine analysis was the development of a suitable structural model. The developed structural dynamics model, which is based on modal equations of motion, is not limited to wind turbine structures, but rather applicable to a broad range of engineering problems concerning structural vibrations. The model closes the gap between modal reductions, which are typically used in linear vibration analysis, and non-linear geometry. For that purpose the structure is segmented and the segments are joined by rigid-body displacements in a co-rotational framework, which introduces geometric non-linearities. This allows modelling of the structural dynamics for large deformations, while maintaining linear stress information of the finite element model of all segments. The basic assumption underlying this approach is that the structural displacement is large, but the strains remain small, which is typically the case for slender structures such as wind turbine blades. The second major topic, which has been addressed in this dissertation, is the physical implementation of a flap system. The described flap system is fully autonomous and is mounted as a free-floating flap, which means that the flap can freely rotate around a hinge axis. The flap is controlled by a trailing edge tab and driven by servo actuators. The flap is mass underbalanced and aeroelastically unstable in interaction with one of the main structural modes. This renders the flap system highly responsive to control inputs, but also to external excitations. When vibrating, the kinetic energy of the flap is converted by electromagnetic harvesters into electric energy. This energy is either stored in a battery or used to power the sensors and the actuators. It was demonstrated that the instability of the flap dramatically increases the amount of harvested energy by, in case of the experiment, a factor of 225 for wind speeds just below and above the flutter speed. The flap system measures the vibrations through accelerometers. When unstable, the vibration amplitude is either limited by structural delimiters or can be actively controlled by the control system. It was shown, that the flap system can be self-sufficient during the controlled limit cycle oscillation. Id est the power produced during limit cycle oscillation is greater than the power consumed to keep the oscillation amplitude constant. The main advantage of the autonomous flap is its improved replaceability compared with non-autonomous ones. As it neither needs a connection to a central control unit and a power system, nor is an integral part of the wind turbine blades like seamless solutions, it can be exchanged easily in case of failure. In conclusion, smart wind turbines have a great potential to improve the cost efficiency by reducing loads for most turbine components as has been shown in this dissertation. This can be achieved using the novel flap concept, which helps, due to its plug-and-play nature, to reduce maintenance costs.Wind Energy/Aerospace Structures and Computational MechanicsAerospace Engineerin
Residual circulation modelled at national UK scale to identify sediment pathways to inform coastal evolution models
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