The tidal stream industry has seen large growth in recent years, and the number of pre-commercial scale devices currently being tested reflects this development. However, commercialising this technology whilst showing that their environmental impacts is minimal remains a challenge. The impact on benthic communities is not considered to be a key strategic consenting issue, yet it is anticipated that the benthic habitat will change as a result of the presence of tidal turbines. To date, only single tidal turbine devices have been installed to demonstrate the application of tidal stream technology but despite successful tests there are still uncertainties surrounding the quantitative impacts these turbines have on local benthic communities. Unlike the wind industry, where physical effects of wind turbines have been catalogued through deployment of thousands of turbines, the tidal stream industry lacks these array scale quantitative data. Local impacts are known, but understanding the scale of the impacts and their relative significance of large arrays remains unknown. Tidal turbines (both single and arrays) interact with the hydrodynamics by decreasing the near field current flow directly in its wake through energy extraction and the drag caused by the physical structure. However, turbines may also affect the far field hydrodynamics, altering bed characteristics, sediment transport regimes and suspended sediment concentrations. As benthic habitats are closely linked to the physical seabed composition and the hydrodynamic conditions, the benthic environment is affected by to changes in the current flow. This thesis presents a series of studies investigating the interaction between tidal turbines and the benthic environment. Based on the hydrodynamic modelling software, TELEMAC2D, a numerical model has been developed to investigate the hydrodynamic impact of a single tidal array at Ramsey Sound, Pembrokeshire as well as the cumulative impact of multiple tidal developments in the Irish Sea. Based on the results of the models, the hydrodynamic outputs were used as inputs to drive a species distribution model, based on the software MaxEnt, to investigate how the distribution of benthic species altered in the presence of a 10MW tidal array at Ramsey Sound. Results of the study showed the development would have a minimal negative impact on the benthic environment.

Sediment accretion and elevation change in tidal forests, and the corresponding ability of these wetlands to keep pace with sea-level rise (SLR), represent data gaps in our understanding of wetland sustainability. Surface Elevation Tables and marker horizons were installed in three mature tidal forests and a restored tidal marsh, allowing us to measure elevation change, accretion, and subsidence. Additionally, we measured predictor variables to test for their significance in explaining accretion and elevation change rates. Mean accretion at our sites was 11.67 +/- 3.01 mm yr-1 and mean elevation change was -20.22 +/- 8.10 mm yr-1, suggesting subsidence occurring beneath the sites. Processes contributing to accretion and elevation change at our sites may be driven by hydrologic patterns. Comparing our elevation trends with SLR trends suggests that our study sites may not keep pace with SLR. However, we may be observing short-term oscillations that do not indicate true long-term trends.

Στην παρούσα μεταπτυχιακή διατριβή προσπαθούμε να δώσουμε μια τάξη μεγέθους της παλιρροϊκής ενέργειας που υπάρχει στα παλιρροϊκά ρεύματα του Στενού Ρίου – Αντιρρίου και προτείνουμε την εγκατάσταση υδροστροβίλων “παλίρροιας” με την οποία θα μπορούσαμε να εξάγουμε την ενέργεια αυτή για να την εκμεταλλευτούμε ως ηλεκτρική ενέργεια στα σπίτια μας. Στο Κεφάλαιο 1, γίνεται μία εισαγωγή σχετικά με το φαινόμενο της παλίρροιας εξηγώντας τον τρόπο και τα αίτια που το δημιουργούν. Στο Κεφάλαιο 2, αναπτύσσονται κάποιες βασικές σχέσης υδραυλικής οι οποίες μας βοηθούν στον υπολογισμό της ταχύτητας και της ισχύς του παλιρροϊκού ρεύματος. Επίσης, γίνεται κατηγοριοποίηση των υδροστροβίλων ‘παλίρροιας’, καθώς παρουσιάζονται συγκεκριμένα μοντέλα εταιριών με τα τεχνικά χαρακτηριστικά τους. Στο Κεφάλαιο 3, περιγράφεται ο αλγόριθμος του οργανισμού EPRI, με τον οποίο γίνεται ο υπολογισμός της συνολικής μέσης ετήσιας παλιρροϊκής ενέργειας, η οποία μπορεί να είναι διαθέσιμη και να “εξαχθεί” από έναν υδατικό πόρο. Προτείνεται μια παραλλαγή της μεθόδου αυτής προσαρμοσμένη στα δικά μας δεδομένα και πραγματοποιείται σύγκριση μεταξύ των δύο. Στο Κεφάλαιο 4, παρουσιάζονται τα αριθμητικά και γραφικά αποτελέσματα για την ισχύ των παλιρροϊκών ρευμάτων του Στενού Ρίου – Αντιρρίου. Ορίζεται η περιοχή μελέτης και επικεντρωνόμαστε σε αυτή για την ανάλυση των χρονοσειρών της ταχύτητας των ρευμάτων. Στο Κεφάλαιο 5, παρουσιάζεται η εγκατάσταση τριών μοντέλων υδροστροβίλων στην περιοχή μελέτης. Τέλος, στο Κεφάλαιο 6, παρουσιάζεται μια περιβαλλοντική μελέτη για το έργο της εγκατάστασης υδροστροβίλων ‘παλίρροιας’ στο Στενό Ρίο – Αντιρρίου και παρατίθενται τα γενικά συμπεράσματα που προέκυψαν από τα προηγούμενα κεφαλαία. Παρατηρήσαμε, ότι η ισχύς του ρεύματος που μπορούμε να εξάγουμε από την περιοχή μελέτης που ορίσαμε είναι κατά μέση τιμή περίπου το 60% του μέγιστου επιτρεπτού που μπορούμε να εξάγουμε από τη συνολική διατομή του Στενού Ρίου - Αντιρρίου. Τα συστήματα των υδροστροβίλων, που προτείνονται μετά από την θεωρητική εφαρμογή τους στην περιοχή μελέτης, φαίνεται να μπορούν να καλύψουν με ηλεκτρική ενέργεια μεγάλο μέρος της περιοχής της Πάτρας. Οι δυσκολίες που θα έχουμε να αντιμετωπίσουμε στην περίπτωση της εγκατάστασης υδροστροβίλων “παλίρροιας” θα είναι ο τρόπος με τον οποίο θα τοποθετηθούν οι βάσεις των υδροστροβίλων στον πυθμένα, λόγω της σύστασης του πυθμένα, αλλά και οι αποστάσεις που θα πρέπει να τηρηθούν από τους πυλώνες της γέφυρας Ρίου – Αντιρρίου, το οποίο θα μπορούσε να λιγοστέψει τον αριθμό τον υδροστροβίλων που θα μπορούσαμε να εγκαταστήσουμε στο σύστημα. Τέλος, ένας σημαντικός παράγοντας που θα πρέπει να εξεταστεί είναι ότι ένα τέτοιο έργο μπορεί από περιβαλλοντικής άποψης να είναι θετικό, αλλά από οικονομικής πλευράς θα αύξανε αρκετά τους λογαριασμούς της Δ.Ε.Η, για λόγους συντηρήσεις, αρχικού κόστους εγκατάστασης, περιβαλλοντικών τελών κτλ. / -

Deltastream is an on-going project carried by Tidal Energy Limited since almost twenty years. It is a tidal energy converter with a triangular shape and one turbine on each tower. It has gone through many evolutions of design but a first prototype will be installed in the end of 2014 at Ramsey Sound. The deployment and recovery operations will be carried out with a single lift point through a heavy lift frame. Two issues have to be tackled during the operation: the rate of flooding of the ballasts and the tension on the lift crane cable. The most favourable sea state must be found in order to minimise the crane cable tension as well as the best inlets and outlets configuration for the ballasts system. In order to tackle those issues, preliminary analytical work was conducted on the demonstrator to assess the stability during the flooding process. A scaled model was designed and built in order to be tested in a wave-towing tank. The results from the tests highlight that the deployment and the recovery operations are safe for both the barge and Deltastream for the range of wave conditions tested in the tank. However, the sea state has an important impact on the proceeding of the operations, especially the period of the waves.

Numerical and experimental investigations of tidal current energy extraction have been conducted in this study. A laboratory-scale water flume was simulated using commercial computational fluid dynamics (CFD) code FLUENT. In the numerical model, the tidal current turbine is represented with an actuator disk, which produces a pressure drop associated with energy loss. The free water surface is considered in the model using a volume of fluid method and is allowed to deform freely. Numerical results identified that a localised wake is formed behind the tidal current turbine and there is considerable localised flow acceleration around and most especially, under the energy extraction device. A free water surface drop is visualised in the model results due to the energy extraction and this free surface drop is believed to have an impact on the recovery of turbine wake. The influence of other parameters like water depth, ambient turbulence and flow speed on the tidal current energy extraction are also testified, based on the numerical model. Numerical results demonstrated that, because of the existence of a free water surface, tidal turbine interaction with the flow is a complicated three dimensional problem. Therefore, completely using the theoretical methods of wind turbines for tidal current turbine study would be inappropriate. Two physical tests were deigned for the experimental investigation of energy extraction from tidal currents and were carried out under different testing conditions: one was in moving water using a natural open channel and the other was in still water using a towing tank. Comparing experimental and numerical results of wake velocity profiles, good qualitative agreement has been obtained, which proves that the proposed numerical model can provide essential insight into the mechanism of wake development behind tidal current turbines. Experimental results also confirmed that, although moving water is the real operational condition of tidal turbines, a towing tank is still an ideal facility for the experimental study of tidal turbines, especially at the early stages of understanding of the detailed physical processes governing the performance of rotors and turbine wake behaviour. This study is a comprehensive investigation into tidal current energy extraction at laboratory scale. Environmental impact of tidal current energy extraction is further recognized and an appropriate experimental facility for the model testing of tidal energy extraction devices is recommended.

The Jurassic Tilje Formation located on the Norwegian continental shelf contains many thick (>10 mm) and macroscopically homogenous mudstone layers. These mudstone layers are interpreted to have accumulated rapidly from “fluid-mud,” a highly concentrated aqueous suspension of fine-grained sediment. Fluid muds in the Tilje are recognized in tidal-fluvial channel, mouth-bar and distal delta-front environments. From detailed thin-section work it is clear that these mudstone layers are not homogenous. Three facies are observed: unstratified mudstone (UM), some of which contain “floating” coarse grains, planar-laminated mudstone (PLM) and cross-laminated mudstone (CLM). Each facies represents deposition at differing suspended-sediment concentrations (SSC) (UM−high SSC, PLM−low-moderate SSC and CLM−low SSC). The thickest mudstone layers are always associated with underlying dune-scale cross-bedding, which has led to a proposed model where fluid mud can accumulate and is protected from the over-riding flow in the troughs of large dunes. This model is most relevant to tidal-fluvial channels where large dunes occur in the deepest water and in terminal distributary channels in mouth bars. The vertical stacking of facies within a single mudstone layer allows reconstruction of changes of the near-bed SSC values and current velocities that reflect deceleration and acceleration of the tidal currents over the tidal cycle or waning wave energy following a storm. Based on repeating patters termed “vertical successions” and “succession combinations,” individual tidal cycles can be observed within single mudstone layers and the relative strength of subordinate and dominant currents can be ii inferred. To aide in the understanding of how mud can accumulate over the complete range of SSCs, current velocities and grain sizes, a preliminary three-dimensional bedform phase diagram has been constructed for fine-grained sediment based on recent flumes studies. The phase diagram can be applied to mudrocks beyond the Tilje Formation. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2013-09-15 17:14:19.827

Approved for public release; distribution is unlimited / Langmuir circulations in a coastal environment at an inner shelf site with strong tidal forcing were examined using a 4-month observation of high-resolution velocity profiles during the ONR-sponsored CBLAST-Low air-sea interaction experiment. Because of their potential contributions to mixing processes in the surface boundary layer, Langmuir circulations are important for naval operations such as ASW, MCM and Amphibious operations in littoral waters. A detection algorithm for upwelling / downwelling velocities due to Langmuir circulations was developed. Analyses focused on long-fetch, unstratified water column conditions with locally developed seas. The observations showed that strong Langmuir circulations greatly reduced water column shear arising from the tidally forced bottom boundary layer, while there was no significant effect from the strong tidal boundary layer on the formation of Langmuir cells. Long fetch conditions had the strongest vertical velocities with Langmuir number 0.1-0.4, while short fetch conditions have weaker vertical velocities with Langmuir number greater than 0.5. Cell vertical velocities were correlated with the water friction velocity, but penetration depths did not depend on forcing mechanisms. Spacing and penetration depths were correlated for increasing wind speed and wave heights whereas this correlation was not seen for constant high wind speed and wave heights. / Lieutenant Junior Grade, Turkish Navy

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / Children with prolonged mechanical ventilation after cardiac surgery have a higher risk for poor outcome due to a variety of ventilator‐associated morbidities. It therefore becomes essential to identify these children at higher risk of prolonged mechanical ventilation as well as find methods to identify children ready to be extubated as early as possible to avoid these complications. One physiological variable, the pulmonary dead space fraction (VD/VT), has been suggested as a possible indicator of prolonged mechanical ventilation. VD/VT essentially measures the amount of ventilated air that is unable to participate in gas exchange. Can VD/VT be used successfully in children undergoing cardiac surgery to identify those at risk for prolonged mechanical ventilation and identify those ready for extubation? Retrospective chart review of 461 patients at Phoenix Children’s Hospital in the Pediatric Cardiac Intensive Care Unit since the initiation of standard application of the Philips NM3 monitors in October 2013 through December 2014. From the 461 patients screened, only 99 patients met all the inclusion criteria. These 99 patients consisted of 29 patients with balanced single ventricle physiology and 61 patients with two ventricle physiology. Initial postoperative and pre‐extubation VD/VT values correlated with length of mechanical ventilation for patients with two ventricle physiology but not for patients with single ventricle physiology. Additionally, pre‐extubation VD/VT values of greater than 0.5 indicated higher rates of extubation failure in two ventricle patients. Conclusion: For children with two ventricle physiology undergoing cardiac surgery, VD/VT should be used clinically to estimate the length of mechanical ventilation for these children. VD/VT should also be checked in these patients before attempting to extubate. If VD/VT is found to be higher than 0.5, extubation should not be attempted since the patient is at a much higher risk for extubation failure.

The mesopause region monthly mean winds and semidiurnal tidal amplitudes and phases over Central Europe in the height range between 85-105 km have been measured at Collm Observatory continuously since September 1982. The regular annual cycle of the semidiurnal tidal amplitudes show in all cases maximum values during late August and September. In contrast to that, in autumn 2002 no enhancement of the tidal amplitudes was measured, while the autumn tidal phase transition occurred unusually early. The unexpected behaviour of the semidiurnal tides seems to be connected with a very early autumn transition of the zonal prevailing winds. This suggests that in 2002 the zonal mean winds influence the tidal propagation in a different way than usual. / Die monatlich gemittelten Grundwinde und halbtägigen Gezeiten werden am Collm seit September 1982 im Höhenbereich zwischen 85-105 km gemessen. Der normale Jahresgang der halbtägigen Gezeiten zeigt maximale Amplituden im Winter und vor allem im Spätsommer/Herbst. Dieses Maximum ist im Jahre 2002 nicht zu verzeichnen. Dies ist begleitet von einer ungewöhnlich frühen Phasenänderung von der Sommer- zur Winterposition. Das Verhalten der Gezeiten scheint mit einer sehr frühen Änderung des zonalen Grundwindes vom Sommer- zum Winterregime verbunden zu sein, so dass die Anomalie der mittleren Zirkulation für die Gezeitenanomalie verantwortlich zu sein scheint.

The turbulent properties of flow in rivers are of fundamental importance to aquatic organisms yet are rarely quantified during routine river habitat assessment surveys or the design of restoration schemes due to their complex nature. This thesis uses a detailed review of the literature to highlight the various ways in which plants and animals modify the flow field, how this can deliver beneficial effects; and how turbulence can also generate threats to growth and survival. The thesis then presents the results from detailed field assessments of turbulence properties undertaken on low, intermediate and high gradient rivers to advance scientific understanding of the hydrodynamics of rivers and inform effective habitat assessment and restoration. A reach-scale comparison across sites reveals spatial variations in the relationships between turbulent parameters, emphasising the need for direct measurement of turbulence properties, while a geomorphic unit scale assessment suggests that variations in turbulence at the scale of individual roughness elements, and/or within the same broad groupings of geomorphic units (e.g. different types of pools) can have an important influence on hydraulic habitat. The importance of small-scale flow obstructions is further emphasised through analysis of the temporal dynamics of turbulence properties with changes in flow stage and vegetation growth. The highest magnitude temporal changes in turbulence properties were associated with individual boulders and vegetation patches respectively, indicating flow intensification around these sub-geomorphic unit scale features. Experimental research combining flow measurement with underwater videography reveals that more sophisticated turbulence parameters provide a better explanation of fish behaviour and habitat use under field conditions, further supporting direct measurement of turbulent properties where possible. The new insights into interactions between geomorphology, hydraulics and aquatic organisms generated by this work offer opportunities for refining habitat assessment and restoration design protocols to better integrate the important role of turbulence in generating suitable physical habitat for aquatic organisms.