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- Persistent gliding waterframe: the waterframe conceptual projectPublication . Morgado, João Paulo Salgueiro; Silvestre, Miguel Ângelo RodriguesUnderwater gliders are autonomous vehicles that profile vertically by controlling buoyancy and move horizontally due to its wings.[14,17] At the top of a bounce, the glider decreases its buoyancy, which causes it to begin to sink. As the glider sinks, the hydrodynamic shape of the exterior (waterframe design) produces horizontal motion. The gilder uses a method of control to adjust pitch and roll as it continues forward. At the bottom of a bounce, the glider becomes more buoyant, which causes it to begin an upward path. Again, horizontal motion is produced by the shape of the waterframe and mainly by wings. When the glider reaches the surface, it will communicate with a ground station, sending out the data it collected during the dive and receiving instructions for its next trajectory.[5] This type of vehicles can operate over long ranges and are relatively low cost [2] ocean research vehicles, making them the ideal choice for locate potential areas in the ocean that would be suitable for sea farming. The PGW will be equipped with sensors that will monitoring the underwater environment. The data collected from the PGW will help researchers monitor the fish population and even implement sea farming. The driving customer requirements for the PGW include a four-month continuous operational runtime, the ability to produce a lower cost system than the current competitors, a two-year useful life before refitting, the ability to launch and recover the PGW from a boat or a dock, the ability to reach a maximum depth of 300 meters, the ability to navigate within 1000 meters of the PGW’s intended course, and all fluids contained in the PGW must be biodegradable. This thesis presents the development of the waterframe for small (75 Kg, 2,00m long) autonomous underwater vehicle with operating speeds about and ranges up to 3000 Km . A half scale prototype was built and performance tests need to be done to evaluate waterframe's performance.
- Development of an open source software tool for propeller design in the MAAT projectPublication . Morgado, João Paulo Salgueiro; Silvestre, Miguel Ângelo Rodrigues; Marques, José Carlos PáscoaThis thesis presents the development of a new propeller design and analysis software capable of adequately predicting the low Reynolds number performance. JBLADE software was developed from QBLADE and XFLR5 and it uses an improved version of Blade Element Momentum (BEM) theory that embeds a new model for the three-dimensional flow equilibrium. The software allows the introduction of the blade geometry as an arbitrary number of sections characterized by their radial position, chord, twist, length, airfoil and associated complete 360º angle of attack range airfoil polar. The code provides a 3D graphical view of the blade, helping the user to detect inconsistencies. JBLADE also allows a direct visualization of simulation results through a graphical user interface making the software accessible and easy to understand. In addition, the coupling between different JBLADE modules avoids time consuming operations of importing/exporting data, decreasing possible mistakes created by the user. The software is developed as an open-source tool for the simulation of propellers and it has the capability of estimating the performance of a given propeller geometry in design and off-design operating conditions. The current development work was focused in the design of airship propellers. The software was validated against different propeller types proving that it can be used to design and optimize propellers for distinct applications. The derivation and validation of the new 3D flow equilibrium formulation are presented. This 3D flow equilibrium model accounts for the possible radial movement of the flow across the propeller disk, improving the performance prediction of the software. The development of a new method for the prediction of the airfoil drag coefficient at a 90 degrees angle of attack for a better post-stall modelling is also presented. Different post-stall methods available in the literature, originally developed for wind turbine industry, were extended for propeller analysis and implemented in JBLADE. The preliminary analysis of the results shows that the propeller performance prediction can be improved using these implemented post-stall methods. An inverse design methodology, based on minimum induced losses was implemented in JBLADE software in order to obtain optimized geometries for a given operating point. In addition a structural sub-module was also integrated in the software allowing the estimation of blade weight as well as tip displacement and twist angle changes due to the thrust generation and airfoil pitching moments. To validate the performance estimation of JBLADE software, the propellers from NACA Technical Report 530 and NACA Technical Report 594 were simulated and the results were checked against the experimental data and against those of other available codes. The inverse design and structural sub-module were also validated against other numerical results. To verify the reliability of XFOIL, the XFOIL Code, the Shear Stress Transport k-ω turbulence model and a refurbished version of k-kl-ω transition model were used to estimate the airfoil aerodynamic performance. It has been shown that the XFOIL code gives the closest prediction when compared with experimental data, providing that it is suitable to be used in JBLADE Software as airfoil’s performance estimation tool. Two different propellers to use on the MAAT high altitude cruiser airship were designed and analysed. In addition, the design procedure and the optimization steps of the new propellers to use at such high altitudes are also presented. The propellers designed with JBLADE are then analysed and the results are compared with conventional CFD results since there is no experimental data for these particular geometries. Two different approaches were used to obtain the final geometries of the propellers, since, instead of using the traditional lift coefficient prescription along the blade, the airfoil’s best L3/2/D and best L/D were used to produce different geometries. It was shown that this new first design approach allows the minimization of the chord along the blade, while the thrust and propulsive efficiency are maximized. A new test rig was developed and used to adequately develop and validate numerical design tools for the low Reynolds numbers propellers. The development of an experimental setup for wind tunnel propeller testing is described and the measurements with the new test rig were validated against reference data. Additionally, performance data for propellers that are not characterized in the existing literature were obtained. An APC 10”x7” SF replica propeller was built and tested, providing complementary data for JBLADE validation. The CAD design process as well as moulds and propeller manufacture are also described. The results show good agreement between JBLADE and experimental performance measurements. Thus it was concluded that JBLADE can be used to design and calculate the performance of the MAAT project high altitude cruiser airship propellers.