| 1. |
- Andersson, Niklas, et al.
(author)
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Methodology for fast development of digital solutions in integrated continuous downstream processing
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In: Biotechnology and Bioengineering. - 0006-3592.
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Journal article (peer-reviewed)abstract
- The methodology for production of biologics is going through a paradigm shift from batch-wise operation to continuous production. Lot of efforts are focused on integration, intensification, and continuous operation for decreased foot-print, material, equipment, and increased productivity and product quality. These integrated continuous processes with on-line analytics become complex processes, which requires automation, monitoring, and control of the operation, even unmanned or remote, which means bioprocesses with high level of automation or even autonomous capabilities. The development of these digital solutions becomes an important part of the process development and needs to be assessed early in the development chain. This work discusses a platform that allows fast development, advanced studies, and validation of digital solutions for integrated continuous downstream processes. It uses an open, flexible, and extendable real-time supervisory controller, called Orbit, developed in Python. Orbit makes it possible to communicate with a set of different physical setups and on the same time perform real-time execution. Integrated continuous processing often implies parallel operation of several setups and network of Orbit controllers makes it possible to synchronize complex process system. Data handling, storage, and analysis are important properties for handling heterogeneous and asynchronous data generated in complex downstream systems. Digital twin applications, such as advanced model-based and plant-wide monitoring and control, are exemplified using computational extensions in Orbit, exploiting data and models. Examples of novel digital solutions in integrated downstream processes are automatic operation parameter optimization, Kalman filter monitoring, and model-based batch-to-batch control.
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| 2. |
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| 3. |
- Engström, Jens, et al.
(author)
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Buoy geometry and its influence on survivability for apoint absorbing wave energy converter : Scaleexperiment and CFD simulations
- 2017
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Conference paper (peer-reviewed)abstract
- For wave energy to be an economically viable energysource, the technology has to withstand power levelsduring storms that can be close to 50 times higher thanduring normal operating conditions, and withstandmany years of wear. The impact of high wave loads isstudied not only within the field of wave energy, buthas long been a subject of study for ships, platformsand other offshore structures.To model the force on the device under extreme and/orovertopping waves is a difficult task. Experiments areexpensive and difficult to implement, and numerical meth-ods are either very computationally demanding CFD-methods, or less accurate approximative methods. Inaddition, the performance and experienced forces during extreme waves are model dependent, and differentoffshore structures must be studied independently.Here, a 1:20 scale model of the Uppsala Universitypoint-absorber type wave energy converter (WEC) has been tested in extreme wave conditions at the COASTLaboratory Ocean Basin at Plymouth University. The WEC consists of a linear generator connected to a buoyat the sea surface, and performance of two differentbuoys is studied: a cylinder and cylinder with moon-pool. Two types of wave sets have been used: focusedwaves embedded into regular waves, and irregular waves. The focus of this paperis on comparing the performance of the two buoys, and on analysing the experimental data using a numerical model. A fully non-linear computational fluid dynamics(CFD) model based on OpenFOAM is presented and validated.
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| 4. |
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| 5. |
- Frost, Anna E., et al.
(author)
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Partial Stator Overlap in a Linear Generator for Wave Power : An Experimental Study
- 2017
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In: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 5:4
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Journal article (peer-reviewed)abstract
- This paper presents a study on how the power absorption and damping in a linear generator for wave energy conversion are affected by partial overlap between stator and translator. The theoretical study shows that the electrical power as well as the damping coefficient change quadratically with partial stator overlap, if inductance, friction and iron losses are assumed independent of partial stator overlap or can be neglected. Results from onshore experiments on a linear generator for wave energy conversion cannot reject the quadratic relationship. Measurements were done on the inductance of the linear generator and no dependence on partial stator overlap could be found. Simulations of the wave energy converter's operation in high waves show that entirely neglecting partial stator overlap will overestimate the energy yield and underestimate the peak forces in the line between the buoy and the generator. The difference between assuming a linear relationship instead of a quadratic relationship is visible but small in the energy yield in the simulation. Since the theoretical deduction suggests a quadratic relationship, this is advisable to use during modeling. However, a linear assumption could be seen as an acceptable simplification when modeling since other relationships can be computationally costly.
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| 6. |
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| 7. |
- Sjökvist, Linnea, et al.
(author)
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Calculating Buoy Response for a Wave Energy Converter - a Comparsion Between Two Computational Methods and Experimental Results
- 2017
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In: Theoretical and Applied Mechanics Letters. - : Elsevier BV. - 2095-0349. ; 7:3, s. 164-168
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Journal article (peer-reviewed)abstract
- When designing a wave power plant, reliable and fast simulation tools are required. Computational fluid dynamics (CFD) software provides high accuracy but with a very high computational cost, and in operational, moderate sea states, linear potential flow theories may be sufficient to model the hydrodynamics. In this paper, a model is built in COMSOL Multiphysics to solve for the hydrodynamic parameters of a point-absorbing wave energy device. The results are compared with a linear model where the hydrodynamical parameters are computed using WAMIT, and to experimental results from the Lysekil research site. The agreement with experimental data is good for both numerical models.
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| 8. |
- Sjökvist, Linnea
(author)
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Hydromechanical simulations of wave energy conversion : Linear aspects
- 2014
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Licentiate thesis (other academic/artistic)abstract
- Hydrodynamic simulations of buoy movement is crucial when designing a point absorbing wave power plant. The wave energy converter (WEC) that is developed in the Lysekil project by Uppsala University is studied in this thesis. The buoy motion in response to an incoming wave can be simulated using potential linear wave theory by deriving a transfer function from the Fourier transformed equation of motion and solve it. The buoy response is found from the convolution between the incoming wave and the transfer function in time domain. It have been found that this approach shows good agreement with experimental results for normal operating conditions.The hydromechanical parameters exciting force, added mass and radiation damping have been simulated in WAMIT, using BIEM, and in COMSOL, using FEM. This was done to compare the simulation model built in COMSOL with the commercial software WAMIT. The results were comparable. The hydromechanical parameters were used to calculate buoy movement and line force in response to a 30 minutes sea state measured at the Lysekil research site. The simulated buoy movement and line force was compared to experimental results, and showed good agreement.A WEC is a complicated dynamical system. The buoy motion, and thereby the translator velocity, depends on the buoy geometry and dimensions, the mass of the moving parts of the system and on the damping force from the generator. The damping force from the generator is dependent on the translator velocity. The above mentioned approach for motion simulation can be used if the damping force from the generator is linear and described by the velocity multiplied with a constant damping coefficient. In this thesis have it been studied how the buoy draft and radius of cylinder buoys are influencing the performance of a WEC, assuming a constant generator damping coefficient. The results were compared to the experimental power from the WECs L2 and L3, two identical generators with cylinder buoys of different dimensions. It was concluded that the experimental difference in power absorption between L2 and L3 could be derived from the difference in draft and buoy mass, rather than buoy radius. The largest part of the difference have however been concluded to derive from the incorrect line lengths.
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| 9. |
- Sjökvist, Linnea, et al.
(author)
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Numerical models for the motion and forces of point-absorbing wave energy converters in extreme waves
- 2017
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In: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 145, s. 1-14
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Journal article (peer-reviewed)abstract
- Reliable simulation tools are necessary to study the performance and survivability of wave energy devices, since experiments are both expensive and difficult to implement. In particular, survivability in nonlinear, high waves is one of the largest challenges for wave energy, and since the wave loads and dynamics are largely model dependent, each device must be studied separately with validated tools. In this paper, two numerical methods based on fully nonlinear computational fluid dynamics (CFD) are presented and compared with a simpler linear method. All three methods are compared and validated against experimental data for a point-absorbing wave energy converter in nonlinear, high waves. The wave energy converter consists of a floating buoy attached to a linear generator situated on the seabed. The line forces and motion of the buoy are studied, and computational cost and accuracy are compared and discussed. Whereas the simpler linear method is very fast, its accuracy is not sufficient in high and extreme waves, where instead the computationally costly CFD methods are required. The OpenFOAM model showed the highest accuracy, but also a higher computational cost than the ANSYS Fluent model.
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