Examensarbeten för masterexamen

Browse

Senast publicerade

Visar 1 - 5 av 1224
  • Post
    Aerodynamic Analysis of the Bi-Radial MKII Sail for the Olympic Sailing Class Dinghy ILCA 7
    (2022) Magnander, Gustaf; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Bensow, Rickard; Larsson, Lars
    The most widely used model for sail force coefficients is probably Hazen’s model. The model, which is presented in [18], offers great flexibility and can be used for a wide range of different sail plans. However, even if it has been extensively used since Hazen presented the model in 1980 and is still used today 4 decades later, it has shown not to be fully satisfying for downwind analysis of sails. To properly analyze the Olympic sailing class dinghy ILCA 7 sailing downwind, the aerodynamic sail coefficients of the new bi-radial MKII sail first has to be retrieved from experimental wind tunnel tests. The sail coefficients can then be used in a Velocity Prediction Program (VPP), where they are balanced against the corresponding hydrodynamic coefficients, obtained from experimental towing-tank tests of a full-scale ILCA dinghy in 2014 at SSPA, a Swedish Maritime Consulting Company, situated at the main campus of Chalmers University of Technology in Gothenburg Sweden. With the output from the VPP, in the form of a polar plot, the optimal way to sail the ILCA 7 dinghy can be established, which is of great value for the Swedish elite ILCA 7 dinghy sailor, who will have the honor of representing Sweden at the Summer Olympics 2024. A 1:7 scale model of the new bi-radial MKII sail, released in 2016, was manufactured by North Sails and tested for downwind sailing in flat water conditions, in the low turbulence subsonic wind tunnel, at Chalmers University of Technology. The sail model was tested for two different apparent wind speeds that represented light and strong wind conditions. The Reynolds numbers for these two conditions were 1.8×105 and 3.0×105, respectively. Even though the flow at these Reynolds numbers presumably is turbulent, a grid, that induced turbulence with an intensity of 2% was used and the sail model was therefore with certainty tested in turbulent flow. For the light wind condition, the sail model was tested for five different headings, three different heel angles (upright condition included), seven different sheet angles and for each configuration of these, three different settings with the kicker were tested. For the strong wind condition, only the heading corresponding to when the ILCA 7 dinghy is sailed dead downwind in a planing mode was of interest; for that heading, the sail model was tested for the upright sailing condition, i.e. with a heel angle of 0°, for four different sheet angles and three different settings with the kicker. For each configuration of these variables, for both wind conditions, the other two trim controls, the outhaul and the cunningham were continuously trimmed. Altogether 327 different configurations of the above mentioned variables were tested. This Master’s Thesis describes how the aerodynamic sail coefficients were retrieved from experimental tests in Chalmers low-turbulence subsonic wind tunnel and how the measurements were corrected for blockage effects, after performing a numerical analysis with Reynolds Averaged Navier-Stokes (RANS) simulations, using the commercial CFD-code STAR-CCM+. The final results is a full set of sail coefficients needed for optimizing downwind sailing of the ILCA 7 dinghy, using a VPP.
  • Post
    Evaluating the effect of live-streamed video from accident sites in maritime SAR using UAV_Analysis of control using the Contextual Control Model (COCOM)
    (2022) Granholm, Leo; Grote, Benjamin; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Forsman, Fredrik; Forsman, Fredrik
    Maritime search and rescue is an important part in the maritime industry that is regulated partly under the International Maritime Organization (IMO). In Sweden, maritime search and rescue is mainly organized by the Swedish Sea Rescue Society. Together with RISE, Chalmers Maritime Human Factors, Airpelago, Smartplanes, and Infotiv, the Swedish Sea Rescue Society have initiated the project Eyes-On-Scene (E-O-S) which is an Unmanned Aerial Vehicle (UAV) based support system that aims to support the responders in their search and rescue operations. The project is to be fully operational in 2023. To test whether a video from a maritime accident scene has an effect on the control of the responders, exercises have been conducted at three rescue stations in the Gothenburg area with a total number of 23 participants. Further, the study aimed to get the subject matters’ opinions and suggestions for improvements on the system. At each station, two exercises were conducted, one with a video from the accident site and one without. The responders’ actions and conversations in the rescue operations were recorded. Afterwards, the responders participated in a focus group discussion. The results were then analyzed based on the Contextual Control Model (COCOM) in order to determine whether a video from a maritime accident site has an effect on the level of control of the responders. The analysis shows that a video from an accident scene can increase the level of control among search and rescue responders. Finally, several suggestions have been given by the participants to aid the future work of the E-O-S project.
  • Post
    Finite Element Modelling of Knee Joint and Femur for Future Injury Assessment
    (2022) Svensson, Gustav; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Iraeus, Johan; Pipkorn, Bengt; Iraeus, Johan
    The purpose of this thesis was to develop and validate a FE model of the femur and knee with associated ligaments, tendons and cartilage. In the future, the model will be integrated into the SAFER HBM representing a 50th percentile male and used to develop the capability of the SAFER HBM to assess femur and knee injury risk. In total, eleven parts, including the femur, patella, anterior cruciate ligament, poste rior cruciate ligament, medial collateral ligament, lateral collateral ligament, patellar tendon, quadriceps tendon and cartilage on the distal end of the femur, posterior side of the patella and on the tibial plateau, were modelled using eight node solid el ements. The femur and the patella models are based on geometry models from a CT scan of a 50th percentile female, and the soft tissue models are based on geometry descriptions found in the literature. The cortical and trabecular bone tissues of the femur and the patella were modelled with isotropic material properties. All models were meshed in accordance to the requirements and quality criteria of SAFER HBM standards. The femur was validated against previously published three-point-bending and com bined loading tests. 23 tests were replicated using explicit LS-DYNA simulations. Two methods were used to evaluate the correlation between the tests and the simula tions. The response of the simulations, reaction force of the actuator versus actuator displacement, were plotted together with statistically evaluated corridors, ±2 stan dard deviations of the mean reaction, from the tests. To assess the correlation in an objective sense, a CORA evaluation was made on the time-history results. The results showed that the average time-force CORA score were 0.720 and 0.752 for the three-point-bending set and the combined load set. This CORA score corresponds to good biofidelity.
  • Post
    INTERMODAL TRANSPORT OF GOODS AND PASSENGERS IN RURAL COASTAL AREAS
    (2022) Kaktavicius, Tomas; Huus, Ayrton; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Ringsberg , Henrik; Ringsberg , Henrik
    Within last two decades of research regarding intermodal transportation of goods and passengers in rural areas was done separately. Statistics and research methods of two subjects has to be combined as intermodal transportation of goods as well as passengers and subject of rural areas are becoming more intertwined due to increased growth of rural areas and their need of almost constant flow of goods (Jones et al., 2000). The purpose of this thesis is to explore options to combine goods transportation with passenger transportation in rural coastal areas of Sweden. The following research takes into consideration the rural areas inhabitant´s and passenger´s opinions, needs and points of view regarding combined transportation, handling of goods and passengers in rural coastal areas. The project was conducted by collecting quantitative and qualitative data of travellers’ and inhabitants’ opinions and attitudes about combined transport of people and goods on passenger ferries in the Swedish archipelago. This was conducted by analysing the results and by constructing a recommendation. The research is limited to maritime transportation in the archipelago of the Swedish west coast and municipalities of Orust, Lysekil and city of Gothenburg. The information was gathered from relevant academic literature sources as well as interviews and questionnaires. Flow of goods is limited to parcels, goods aimed for construction, hazardous goods, palletized goods and recyclable waste. Logistical transport mode – boats/ferries.
  • Post
    Driver subjective feedback study during crosswind gusts on driving simulator for high speed straight line driving
    (2022) Garje Mohankumar, Anup; Sawanth, Sai Kishan; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Jacobson, Bengt; Brandt, Adam
    The passenger vehicle industry develops aerodynamic designs that have low drag to improve vehicle efficiency at high speeds. The low drag aerodynamic design affects crosswind stability during straight line driving, this is crucial for passengers and other road user safety. The thesis work subjectively evaluates vehicle high-speed stability under crosswind gusts on VI grade DIM 250 moving platform 6 DOF driving simulator. The simulator allowed testing the high speed response of a high-fidelity vehicle model with groups of drivers in a controlled virtual environment. Initial CAE work focuses on the complexity of SUV vehicle models and the implementation of crosswind gusts in the desktop CAE simulation and driving simulator, coupling between aerodynamics and vehicle dynamics. Stochastic crosswind gust tests were designed on Matlab & Simulink and implemented on CarRealTime vehicle dynamics model on the driving simulator that simulated the change in aerodynamic flow conditions and resulting vehicle aerodynamic forces and moments. Driving clinic is conducted to find the correlation between driver subjective feedback and vehicle’s objective metric response. The vehicle crosswind sensitivity is evaluated using a developed proxy measure. Finally, through statistical tests the study found that the subjective instability feeling is triggered by the vehicle change in lateral and centripetal accelerations response amongst the experienced driver and steering torque demand for common drivers during straight line driving at high speeds under aerodynamic crosswind gusts. The implementation of crosswind gusts on driving simulator is evaluated subjectively.