for advanced riser analysis. Deep water oil recovery have forced a change in thesystems used to tension risers, the traditional wire-pulley systems are replacedwith direct acting hydraulic-pneumatic systems. In order to design these systemsto obtain the desired operability, analysis tools including the heave compensationsystem is necessary. As a result a pipe in pipe RIFLEX model have been developed.In this masters thesis the pipe in pipe model will be used to investigate drive-offand weak link fracture. Both subjects investigated exposes the riser to large forces,and will push the model to its limits. Another part of the thesis is focused aroundbatch execution of analyses with the use of MATLAB.The focus of the drive-off study lies mainly in investigating the dynamic behaviourof a deep water riser (3000[m] water depth) compared to a shallow water riser(300[m] water depth). Results are presented for upstream and downstream driveoff scenarios. The maximum offset is 100[m] obtained during a 50[s] period. Driveoffscenarios include cases where the vessel remains at the 100[m] offset, and caseswhere the vessel returns to its original position.Drive-off simulations revealed large differences in dynamic behaviour of the deepwater versus the shallow water system. When observing the lower riser anglefor shallow water simulations, the angle were closely related to the vessel offsetposition. Deep water simulations showed a delay of almost one minute before thelower angle responded with a rotation in the vessels movement direction. Duringthe first minute an initial effect that caused the riser to rotate away from the vesselposition was observed. Current had a limiting effect on the lower angle whendriving upstream, and increased the angle for downstream drive-off. By includinga return motion the riser angle increased more rapidly to large values. Variation inreturn motion had little effect on the maximum amplitude. The results show thatit might be difficult to take advantage of the dynamic delay in the riser response.Bear in mind that offsets of only 100[m] was investigated, the picture might changefor simulations including larger vessel offset.Weak link fracture is of concern since it will release large amounts of stored energythat is potentially harmful for personnel and equipment. Establishing analysismethods for weak link fracture can help to better understand the dynamics ofthe problem. In the present work a suitable analysis model was selected and aparametric study on the effect of drag on response was performed.A weak link fracture was simulated with 460 tonnes over pull. Weak link fracturesis a highly complex problem since the high pressure content of the riser is releasedinto the water, causing a rocket effect. The presented results are only accountingfor potential energy stored as strain in the riser and heave compensation system.A parametric study of the tangential drag versus the maximum vertical amplitudeof the riser is presented. The results are meant to be used as a starting point inan investigation of measures to limit the weak link fracture response.The weak link simulations showed that large accelerations are involved during theweak link fracture, and therefore added mass and mass can be of importance tothe response. Due to the rapid movement after fracture, it was found that specialcare needs to be taken when selecting the time incrementation for the simulations.

MARINTEK's ship motion simulation program SIMAN (ShipX manoeuvring module) is used to develop a ship motion model for NTNU's research vessel R/V Gunnerus. SIMAN uses a 3-DOF linear mathematical model to describe the vessel's motions. In order to verify the SIMAN model of R/V Gunnerus, full-scale trials of R/V Gunnerus were performed in deep water in Trondheimsfjorden. Turning circles, zig-zag- and stopping tests were carried out and analysed. Data was recorded using Seapath and the DP-system installed on R/V Gunnerus. Seapath registered data at 200 Hz, while the DP-system registered data at 1 Hz. Data registration at 1 Hz turned out to be too seldom, especially for the zig-zag manoeuvres.Full-scale trials are simulated in SIMAN. Measured full-scale results are compared with simulated results, and differences between measured and simulated results are identified. It was expected that differences would occur as SIMAN is developed for conventional vessels and offshore vessels, while R/V Gunnerus is an unconventional vessel (L=28.9 m, B=9.6m). The deviations may be due to inaccurate field test results or errors in the modelling in SIMAN. SIMAN underestimated tactical diameter, transfer and advance in the turning circle manoeuvres. The difference increased with increasing rudder angle (and consequently drift angle), which may indicate errors in modelling of the non-linear damping forces. The damping forces are then modified using Oltmann's polynomial for the cross-flow drag coefficient for a tanker. This improved the results, all with the exception of transfer and advance at rudder angles of 20 degrees. It is also shown that the results are sensitive to rudder angle, so incorrect full-scale measurement will affect the results. The difference between measured and simulated zig-zag trials are significant. However, only a few seconds or degrees difference between the simulated and the measured zig-zag results cause a large percentage difference. Possible reasons for the differences are inadequate data registration of the full-scale trials, or errors in modelling in SIMAN. Overestimated results in SIMAN may indicate an unstable model. Increasing the models stability index by reducing Nv had a negligible effect on the simulated results. Decreasing rudder angle in the simulations improved the results. Track reach in the stopping manoeuvres are overestimated by SIMAN. This may be due to modelling issues as R/V Gunnerus is much smaller and responds faster than the vessels that SIMAN is developed for.In the literature there exists several empirical methods to calculate the hydrodynamic coefficients used in manoeuvring equations. The hydrodynamic coefficients of R/V Gunnerus were calculated using approaches given by Wagner Smitt, Norrbin, Inoue, Clarke, Lee and Kijima, as well as using strip theory for a flat plate. Using these coefficients did not improve the simulated results.In order to create a complete motion model for R/V Gunnerus further investigation is necessary. It is recommended that PMM tests are performed to determine the hydrodynamic coefficients. It can also be useful to investigate the non-linear damping forces. In addition, new full-scale zig-zag tests should be performed in a way that 10/10 and 20/20 tests are obtained. Performing several reruns could be used to determine the precision errors of the full-scale trials. In the literature there is a need for vessels to be used for validation of simulation tools. R/V Gunnerus can be used as a case vessel to investigate how the simulation tools predict the manoeuvring performance of an unconventional vessel. The 26th ITTC stated that there is a particular need for mathematical models for low speed manoeuvring, and vessels also used for validation of CFD-methods. R/V Gunnerus can be used as a case vessel for this research. It is then necessary to carry out tests intended for these purposes.

This Master thesis details the development of a mathematical model of ROV SF30k, and its implementation into a DP control system developed by Espen Tolpinrud.The project was performed as a part of the Applied Underwater Robotics atNTNU.A 6DOF model of the ROV was developed. The parameters of the model werefound using both the 3D model of the ROV provided by Sperre AS, and based onthe parameters found previously for ROV Minerva. Both ROVs were developedby Sperre AS and share many similarities. Thrust configuration was developed forthe ROV based on the geometric positions and orientations of its thrusters, whilethrust coefficients were found using propeller data provided by Sperre AS. The DPcontrol system was configured to operate SF 30k by using a configuration file basedon the found parameters.A number of modules were ported from the old DP system, which was tailormadefor ROV Minerva, to the new one. This includes the Kalman Filter, controllersand thrust allocation. An adaptive passive nonlinear observer was developedand implemented.The existing simulator model for ROV Minerva was modified to be able tosimulate ROV SF 30k. This was done by changing the parameters of the processplant model and thrust dynamics.The parameters in the configuration file for the new control system were verifiedduring sea trials onboard R/V Gunnerus on May 29-30th 2012. The thrust allocationparameters were found to be satisfactory during ROV operation, however, themathematical model of the ROV could not be verified due to the small window ofoperation during the sea trials.

In the past, testing of lifeboat design has been carried out solely by experimental means. However, due to the large number of factors which influence the loads on the lifeboat structure and its occupants, optimization studies by experimental means have become both time-consuming and expensive. In addition, many effects cannot be studied at laboratory scale due to the inability to match all similarity requirements.Recent advances in computational fuid dynamics (CFD) have made it possible toanalyze the lifeboats performance under realistic conditions. By not being dependenton a physical model, investigation of a larger range of hull shapes at a variety of launch conditions can be done more easily and cost-ecient.This thesis explores the possibility of using the CD-adapco's CFD-software STARCCM+(STAR) to predict the performance of free-fall lifeboats during the impact phase.The thesis focuses on verification and validation of the software by studying water impact of different two and three-dimensional rigid and elastic wedges.For the two-dimensional case, 2-D rigid wedges with constant vertical velocity andvarying deadrise angles (4 to 81 degrees) are studied with respect to various slammingparameters presented by Zhao and Faltinsen (1992). In the study, good agreementis found between the solution predicted in STAR and the presented numerical andanalytical solutions. It is found that the slamming pressures are strongly dependent onthe deadrise angle; from 300 Pa for the 81 deg. wedge, to 275 000 Pa for the 4 deg. wedge. It is seen that as the deadrise angle is decreased, better resolution in grid size and time step is required to capture the peak pressures.The three-dimensional case includes both rigid and elastic wedges. For the rigid case, a3-D wedge is modeled so to represent an experimental study conducted by Yettou et al.(2006). It is found that STAR predicts a lower impact velocity than what is found inthe experimental study. Following, the pressures predicted are too low. The differenceis however moderate, and STAR is able to predict the displacement and velocity-timehistories of the wedge in a satisfactory manner. It is noted that the reason for thediscrepancy lies in the prediction of motion through air - and not in the simulation ofimpact and motion in water. It is also noted that refinements in grid size and time stepare not of great importance if only displacements and velocities are to be studied.For the elastic wedge case, four different elastic wedges are studied to exploreSTAR's possibilities and limitations related to fuid-structure interaction (FSI). Noverification or validation with existing theory or experimental data is performed. Aqualitative assessment of the results is however carried out and it is found that STARpredicts displacements, velocities, accelerations, pressures, deflections and stresses in a satisfactory manner.

Traditionally ships have been optimized for minimizing the fuel consumption in calm water. For slow, large ships like tankers and bulk carriers this has resulted in very blunt bows with high added resistance due to waves. The objective of this thesis has been to investigate if the optimal bow shape, when realistic wave conditions are taken into account, should be more slender than the current blunt bows. The added resistance is also highly dependent on the actual wave conditions the vessel experiences. Thus a question has been if the optimal bow changes with the operational area, or route, of the vessel.Five designs have been investigated representing a range of waterlines from blunt to sharp. They are based on the MOERI Tanker KVLCC2. KVLCC2A is the original design of the MOERI Tanker with no flare. KVLCC2B has the same water line curve as KVLCC2A, but with straight sides and small bilge radius in the bow. KVLCC2C has a more slender bow by moving volume from the shoulders to above the bulb. KVLCC2D is a blunter design than KVLCC2A and KVLCC2E has been elongated by 8 m compared to KVLCC2C to get a more slender bow.Four routes have been chosen to represent trades and ocean areas. The routes are; Arabian Gulf (AG) to the Gulf of Mexico (GM), AG to Japan, Brazil to China and Norway to the East Coast of US.Calm water resistance has been calculated and verified against experimental data. The wave resistance was calculated numerically using Shipflow. These calculations were not satisfying and should be taken a closer look at. Modification of the results had to be done. The results show that KVLCC2A, KVLCC2C and KVLCC2E have very similar calm water resistance. They have slightly lower values than KVLCC2D. KVLCC2B has the greatest calm water resistance. The added resistance was calculated by ShipX. The sharper bow designs have significantly lower resistance in the diffraction regime, as intended. KVLCC2E has slightly a slightly lower added resistance coefficient in the short wave regime than KVLCC2C.The speed-loss calculations were performed by combining wave statistics for the routes, calm water resistance, added resistance and engine and propulsion characteristics in ShipX. The result is an attainable speed at a given power input, 27 000 kW.The results show that KVLCC2C and KVLCC2E have the lowest speed-loss. The attainable speed is highest for KVLCC2C and it can thus be concluded that a sharper design is more optimal when realistic wave conditions are taken into account. The relative speed loss on different routes between KVLCC2C and KVLCC2A shows that the speed loss of KVLCC2C is 14.2% lower for the AG to GM, 13.8%, 16.2 % and14.9 % for respectively AG to Chiba, Mongstad to East coast of US and Brazil to China. Thus, a small difference can be seen, but not enough to change the best design in this case. A review of innovative bow shapes dealing with added resistance was performed and an evaluation based on working principles and applicability to a large, slow vessel was discussed. The designs reviewed were X-bow (Ulstein Design), a new bow from STX OSV and Beak-bow, Ax-bow and LEADGE-bow designed in Japan especially for larger ships. The two first bows are designed primarily with offshore service vessels in mind and focus more on the long waves. The LEADGE-bow, which is based more or less on the same principles as KVLCC2C, shows that a simple sharpening of the bow is an easy and effective measure. This seems like the most promising bow for large, slow ships of those evaluated.

The importance of offshore renewable energy from wind is expected to increase in the future. Most offshore wind turbines are currently installed in shallow water up to 50 meter water depth on bottom mounted substructures. To harvest more wind energy at deeper waters, offshore floating support structures are needed. Semi-submersible floating wind turbine is one of the proposed floating concepts. Under simultaneous wind and wave loads, fatigue might be an important design consideration. Study of fatigue for such structures is thought to contribute to a better understanding of offshore wind turbines.A local part of a semi-submersible wind turbine was studied. The column-brace connection, or joint, connected a wind turbine tower to a triangular semi-submersible floater. Design, stress concentration factors and fatigue damage of the part were the main topics. To calculate stress concentration factors and fatigue damage, dynamic response analyses and finite element modelling were performed. Only the fatigue limit state was considered.Three different column-brace connection designs were analysed. For the initial design, the stress concentration factors generally were way too large - especially for out-of-plane action. For the third design a horizontal bulkhead at the brace centreline was added. This modification decreased the stress concentrations by a maximum of over 90% for out-of-plane action. The modification was only carried out for brace 1.A long-term fatigue approximation with distribution of mean wind speed in the northern North Sea was considered, while the expected significant wave height and spectral peak period for a given mean wind speed were used, to reduce the simulation effort. The critical fatigue damage was observed for brace 2, with a life time of less than a year. For brace 1 the lowest life time was several hundred years, meaning a conservative design. By reducing and optimizing the brace thickness, one could reduce such conservatism. The critical hot-spot-stresses were found at the crown toe and heel for both brace 1 and brace 2. All fatigue calculations included a design fatigue factor of 3.The modification of brace 1 with horizontal bulkheads as additional stiffening reduced the stress concentrations significantly, and increased the fatigue life considerably. Brace 2 still needs to be modified to decrease the stress concentrations, and thus increase the fatigue life.

In this thesis, the effects on regular waves when propagating from deep to shallow water have been investigated, assuming linear wave theory. The effects of shoaling, refraction, reflection and diffraction have been studied. The process and types of breaking waves has also been reviewed.Linear wave theory, second and higher order Stokes theory, Stream function theory, Solitary wave theory and Cnoidal theory have been reviewed. The relative validity of the different wave theories was also assessed.The effects on the wave spectrum as a sea state travels from deep to shallow water, described by the energy balance equation, has also been addressed. The effects addressed were wind, nonlinear wave-wave interactions, white-capping, bottom friction and surf-breaking. Two computer models for numerically solving the energy balance equation was mentioned, being SWAN and STWAVE where SWAN was chosen for use in the analyses.The NORA10 hindcast was believed not to properly take the change in water depth into account at the Dogger Bank Zone. At a point north of the location of interest, the water depth was of such a magnitude (81m) that the NORA10 hindcast was believed to yield credible data for the significant wave height and spectral peak period. A long term estimate of the 50 year significant wave height was performed from the NORA10 data at the point north of the Dogger Bank Zone, by the environmental contour method. This resulted in an estimated 50 year significant wave height of 11.74m and spectral peak period of 15.68s.The SWAN model was used on a test case from Svangstu (2011) to get familiar with the program, and investigate how the different physical effects influence the solution. With the knowledge acquired from the test case, the Dogger Bank case was analyzed in SWAN, to obtain the 50 year sea state parameters at the location of interest. The 50 year sea state north of the Dogger Bank Zone, the Dogger Bank bathymetry, as well as a constant wind of 23.3 m/s was used as input. The 50 year sea state at the location of interest was found to be characterized by a significant wave height of 7.34m and a spectral peak period of 15.56s. SWAN was found to result in a significant wave height of some 15-27% lower than what was found in NORA10.By performing a short term analysis on the 50-year sea state at the location of interest, the 50-year design wave height was found to be 12.5m, assuming the individual wave heights to be modeled by the Gluhovski distribution. The 90% confidence interval of the design wave period was found to be 9.6s <T< 16.3s. This was estimated from studying the ratio between the period of the three largest waves in a time series, and the spectral peak period of the sea state in 95 time series from Svangstu (2011) By evaluating only the limiting values of the period range, the longest and shortest design wave was found to be 80% and 97.4% of the breaking wave height respectively, assuming linear theory.The wind turbine structure geometry was simplified to be modeled by a cylinder with a diameter of 6m. By computing the kinematics from the Stream Function theory, the maximum base shear and overturning moment using Morison’s equation was found to be 3.67MN and 65.93MN respectively. The effects of the rate of change of added mass momentum was also assessed.From a simplified and conservative approach, the impact loads from a breaking wave was estimated. This resulted in a base shear and overturning moment of such a magnitude that en extensive analysis is recommended on this topic in the future.

The conventional way of transporting personnel from shore to offshore platforms is done by helicopter. For large distances of transportation this results in high costs due to the limitations in the maximum number of persons each helicopter can transport per trip and due to the high prices on helicopter fuel. In this thesis is an alternative solution to this conventional transportation proposed by the utilization of a logistical HUB. The concept is based ferries doing the transportation of personnel from shore to the HUB and helicopters doing the remaining, relatively short, transfer from the HUB to the respective platforms. The HUB evaluated is based on the characteristic Sevan 650 design, having a cylindrical shape with diameter D=78m in the waterline.The models that have been analyzed in this thesis were modeled in GeniE, the hydrodynamic analyses were done in Wadam and the post processing was performed using Postresp.Models of a platform with a single tunnel cut out with varying tunnel length L have been evaluated, and the motions of these models as well as the surface elevation inside the tunnel were studied in detail. It was recorded a two peaked response in heave for the models with tunnel lengths ranging from 30m<L<40m. This unexpected behavior was found to be due to diverging values for the added mass in heave for increasing tunnel lengths for models with intact tunnel bottoms. This was adjusted for by removing the bottom of the tunnel to add damping to the system, resulting in the usual one peaked response in heave being retrieved. The reason the two peaked response in heave occurred was concluded to be due to Wadam neglecting viscous effects including the viscous damping. This leads to the system having little or no damping and the added mass to diverge towards negative infinity giving unphysical motion representations.Since critical situations for the platform-ferry interaction will occur during loading and unloading of personnel from the ferry to the platform and during entry of a ferry into a tunnel, the wave pattern inside and on the immediate outside of this tunnel have been studied and evaluated. A total of 4 different designs for the layout of the tunnels have been proposed and evaluated to find the design that results in the least surface elevation inside the tunnel and at the tunnel entrance. A window of acceptance for the incoming wave headings were established with the intention of minimizing the surface elevation. The designs were also evaluated regarding their ability to resist large motion for a variety of incoming wave periods. It was concluded that a three tunnel solution with the tunnels being shifted 120 degrees relative each other would result in the smallest platform motions for wave periods smaller than 18s. A design consisting of 4 tunnels, where three of the tunnels are shifted 30 degrees relative each other and the last tunnel being located opposite of these three would result in the smallest surface elevations. An operability study was done for all 4 designs proposed based on the elevations inside and at the tunnel entrance. It was found that the 4 tunnel design described above would result in the largest operability for the platform. It was also found that this 4 tunnel solution would be unstable in roll due to an unsatisfactory low transverse metacentric height. This low metacentric height could be adjusted for by installing a vertical wall in the waterline in the transverse direction of the tunnels orientation.

This thesis considers a foil propulsion system on a supply vessel. In analysing the potential of a foil propulsion system, it is imperative to establish a rigid mathematical model. In that respect, modelling of the dynamic system is emphasised, and a comprehensive study is presented on the matter. The equations of motion for an oscillating foil and a vessel are derived, separately. The two systems are then combined, to form the coupled vessel-foil structure. For the vessel, a time-domain model based on Cummins' equation is proposed. Cummins' equation has proven efficient in assessing a unified seakeeping and manoeuvring problem (Fossen [2011]). In line, the vessel-foil system will be exposed to both vessel oscillatory motion due to waves and forward speed effects, i.e seakeeping and manoeuvring. Moreover, the efficiency of the foil is directly dependent on the two.Additionally, aspects of foil control is looked into. In theory, active control could maximise thrust while preventing stall, which would be ideal. The validity of simulations with active control, however, is highly dependent on the accuracy of the emph{basic} vessel-foil model. Consequently, effort has been focused on presenting a rigid mathematical foundation.

When a ship-owner orders a vessel from a shipyard, a contract is written to confirm and guarantee the agreement for both parts. An important requirement of the contract is the vessel's speed at a given engine power, RPM and draught, in "ideal" conditions (i.e. calm, infinitely deep and current free water, with smooth hull and propeller surfaces at with no wind and zero drift and rudder angle). The speed capacity of the recently built ship is measured carrying out a speed trial. It is rarely possible to perform the trial under ideal, contractual conditions, and the speed will normally be reduced by environmental factors. Whenever the test is carried out in conditions deviating from those contractually specified, the speed must be corrected for, to best coincide with the contractual stipulations. These corrections can be of significant magnitude and are of great economic importance. Penalties of considerable size are given to shipyards that fail to deliver in accordance with the contract. There are various standards published providing guidelines regarding the execution of speed trials, the measurements that are to be performed during the trials and corrections for environmental factors that are to be made in retrospect. ISO (2002), Perdon (2002), Bose (2005) and B. Henk (2006) were chosen for evaluation and comparison in this thesis. The recommendations of the standards are occasionally disagreeing.The main resistance contribution is claimed to be wind and wave (Bose (2005) and B. Henk (2006)). B. Henk (2006)) states; "these corrections (small displacement deviations, shallow water, and salinity deviations) are relatively small compared to wind and wave directions". Reinertsen (2011) suspects that the added wave resistances calculated by the Hyundai shipyard are too large. This assumption is based on Haugan (2011)'s (employee of KGJS) mean wave load calculations that generally gave results 30 % lower than those found by Hyundai. An unrealistically large correction factor for wave resistance is most definitely advantageous for the shipyard. This will give a higher calculated contractual speed, and the shipyard is consequently more likely to meet the contractual requirements. The Hyundai shipyard's correction procedures were evaluated based on the relevant standards. The shipyard neglects all resistance components, but the added resistance due to wind and waves (they also correct for large discrepancies between the trim/draught obtained at speed trial and that contractually stipulated. This is however not relevant for tankers, as these generally are capable of achieving design draught at the sea trial). This is consistent with the recommendations of Perdon (2002) and B. Henk (2006). The shipyard does not have the speed trials conducted in head - or following waves, nor head - or following wind. B. Henk (2006) and Perdon (2002) underline the importance of executing the speed trials in head - or following waves. Perdon (2002) argues; "in the case when the waves do not come from the bow or the stern the correction methods are not sufficiently reliable and the effects of steering and drift on the ship's performance may be underestimated". ISO (2002) recommends performing the trials in head and following wind (note that there usually is a correlation between true wind - and wave direction).The Hyundai shipyard assumes that the wave direction with respect to the ship's centerline equals the relative wind angle. This conflicts with the recommendations of the standards. They advise to obtain the wave direction by visual observations or instruments such as buoys or sea wave analysis radars. Furthermore, Hyundai's assumption is highly illogical from a scientific standpoint. In this thesis, the added wave resistance (due to diffraction) was computed by a handful of methods proposed in the literature. The computed values obtained in this report were all substantially larger than those found by Hyundai. This denies Reinertsen (2011)'s suspicion of Hyundai's correction factors for wave resistance being unrealistically high. B. Henk (2006) emphasizes the importance of accounting for the location of the anemometer in the computations of added resistance due to wind. This is not done by the shipyard. B. Henk (2006) proposes a formula for correction of improper placements of the anemometer. In this thesis, the added wind resistance was calculated, including this correction. The added resistance found was 28 % smaller than the value obtained by Hyundai. This is relevant as the wind tends to be a key resistance contribution.Finally, the Energy Efficiency Design Index (EEDI) has been described. The EEDI estimates a ship's CO2 emission per ton-mile of goods transported; put differently, the vessel's impact on the environment in relation to its benefit for society. The EEDI is to be implemented for all new ships, 1st of January 2013. The value of this index will be determined based on results from speed trials.