| 1. |
- Sarmast, Sasan, et al.
(författare)
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Validation of the actuator line and disc techniques using the New Mexico measurements
- 2016
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Ingår i: Journal of Physics, Conference Series. - : Institute of Physics (IOP). - 1742-6588 .- 1742-6596. ; 753:3
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Tidskriftsartikel (refereegranskat)abstract
- Actuator line and disc techniques are employed to analyse the wake obtained in the New Mexico wind turbine experiment. The New Mexico measurement campaign done in 2014 is a follow-up to the MEXICO campaign, which was completed in 2006. Three flow configurations in axial flow condition are simulated and both computed loads and velocity fields around the rotor are compared with detailed PIV measurements. The comparisons show that the computed loadings are generally in agreement with the measurements under the rotor's design condition. Both actuator approaches under-predicted the loading in the inboard part of blade in stall condition as only 2D airfoil data were used in the simulations. The predicted wake velocities generally agree well with the PIV measurements. In the experiment, PIV measurements are also provided close to the hub and nacelle. To study the effect of hub and nacelle, numerical simulations are performed both in the presence and absence of the hub geometry. This study shows that the large hub used in the experiment has only small effects on overall wake behaviour.
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| 2. |
- Forghani, Kamran, et al.
(författare)
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Maximizing value yield in wood industry through flexible sawing and product grading based on wane and log shape
- 2024
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Ingår i: Computers and Electronics in Agriculture. - : Elsevier. - 0168-1699 .- 1872-7107. ; 216
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Tidskriftsartikel (refereegranskat)abstract
- The optimization of sawing processes in the wood industry is critical for maximizing efficiency and profitability. The introduction of computerized tomography scanners provides sawmill operators with three-dimensional internal models of logs, which can be used to assess value and yield more accurately. We present a methodology for solving the sawing optimization problem employing a flexible sawing scheme that allows greater flexibility in cutting logs into products while considering product quality classes influenced by wane defects. The methodology has two phases: preprocessing and optimization. In the preprocessing phase, two alternative algorithms are given that generate and evaluate the potential sawing positions of products by considering the 3D surface of the log, product size requirements, and product quality classes. In the optimization phase, a maximum set-packing problem is solved for the preprocessed data using mixed-integer programming (MIP), aiming to obtain a feasible cut pattern that maximizes value yield. This is implemented in a system named FlexSaw, which takes advantage of parallel computation during the preprocessing phase and utilizes a MIP solver during the optimization phase. The proposed sawing methods are evaluated on the Swedish Pine Stem Bank. Additionally, FlexSaw is compared with an existing tool that utilizes cant sawing. Results demonstrate the superiority of flexible sawing. While the practical feasibility of implementing a flexible way of sawing logs is constrained by the limitations of current sawmill machinery, the potential increase in yield promotes the exploration of alternative machinery in the wood industry.
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| 3. |
- Lindström, John, et al.
(författare)
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Use of cloud services in functional products : availability implications
- 2014
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Ingår i: Product Services Systems and Value Creation. - : Elsevier. ; 16, s. 368-372
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Konferensbidrag (refereegranskat)abstract
- The paper addresses the potential use of cloud services in Functional Products (FP) and its possible implications for availability. Further, how the implications for availability can be understood via modelling and simulation is addressed. The paper adds further specificity to literature by indicating the FP constituents for which cloud services are applicable and adequate.
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| 4. |
- Reed, Sean, 1982-, et al.
(författare)
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Service support system modelling language for simulation-driven development of functional products
- 2013
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Ingår i: 2nd International Through-life Engineering Services Conference. - : Elsevier. ; 11, s. 420-424
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Konferensbidrag (refereegranskat)abstract
- A functional product (FP) comprises of an integrated package of hardware and support services sold under a performance-based contract. A barrier to the adoption of FP is the lack of tools for obtaining predictions of availability and support costs during product development. A previous paper by the authors described a simulation-driven development strategy for designing FP that are optimised for functional availability and support costs. This iterative strategy involves representing the FP design in a modelling language; using a software code to automatically generate and analyse a simulation model from this representation to produce detailed performance predictions; and using these predictions as feedback to improve the design. The use of a modelling language facilitates the representation of the design details within the hardware and support system that influence availability and support costs. This includes the maintenance process design, maintenance strategy design and maintenance resource availability design. In this paper, an overview of a modelling language the authors have developed for this purpose is described.
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| 5. |
- Xu, Cheng, et al.
(författare)
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Scalable Validation of Industrial Equipment using a Functional DSMS
- 2017
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Ingår i: Journal of Intelligent Information Systems. - : Springer. - 0925-9902 .- 1573-7675. ; 48:3, s. 553-577
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Tidskriftsartikel (refereegranskat)abstract
- A stream validation system called SVALI is developed in order to continuouslyvalidate data streams from industrial equipment. The functional data model of SVALI allows the user to dene meta-data and queries about the equipment in terms of types and functions. The two system functions model-andvalidate and learn-and-validate provide such validation functionality. The experiments show that parallel stream processing enables SVALI to scale very well with respect to response time and system throughput. The paper is based on a real world application for wheel loader slippage detection at Volvo Construction Equipment.
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| 6. |
- Rezaeiravesh, Saleh, et al.
(författare)
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Assessment of uncertainties in hot-wire anemometry and oil-film interferometry measurements for wall-bounded turbulent flows
- 2018
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Ingår i: European journal of mechanics. B, Fluids. - : Elsevier. - 0997-7546 .- 1873-7390. ; 72, s. 57-73
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the sources of uncertainty of hot-wire anemometry (HWA) and oil-film interferometry (OFI) measurements are assessed. Both statistical and classical methods are used for the forward and inverse problems, so that the contributions to the overall uncertainty of the measured quantities can be evaluated. The correlations between the parameters are taken into account through the Bayesian inference with error-in-variable (EiV) model. In the forward problem, very small differences were found when using Monte Carlo (MC), Polynomial Chaos Expansion (PCE) and linear perturbation methods. In flow velocity measurements with HWA, the results indicate that the estimated uncertainty is lower when the correlations among parameters are considered, than when they are not taken into account. Moreover, global sensitivity analyses with Sobol indices showed that the HWA measurements are most sensitive to the wire voltage, and in the case of OFI the most sensitive factor is the calculation of fringe velocity. The relative errors in wall-shear stress, friction velocity and viscous length are 0.44%, 0.23% and0.22%, respectively. Note that these values are lower than the ones reported in other wall-bounded turbulence studies. Note that in most studies of wall-bounded turbulence the correlations among parameters are not considered, and the uncertainties from the various parameters are directly added when determining the overall uncertainty of the measured quantity. In the present analysis we account for these correlations, which may lead to a lower overall uncertainty estimate due to error cancellation Furthermore, our results also indicate that the crucial aspect when obtaining accurate inner-scaled velocity measurements is the wind-tunnel flow quality, which is more critical than the accuracy in wall-shear stress measurements.
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| 7. |
- Göteman, Malin, 1980-, et al.
(författare)
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Methods of reducing power fluctuations in wave energy parks
- 2014
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Ingår i: Journal of Renewable and Sustainable Energy. - : AIP Publishing. - 1941-7012. ; 6, s. 043103-
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Tidskriftsartikel (refereegranskat)abstract
- One of the major challenges in constructing effective and economically viable wave energy parks is to reduce the large fluctuations in power output. In this paper, we study different methods of reducing the fluctuations and improve the output power quality. The parameters studied include the number of devices, the separating distance between units, the global and local geometries of the array, sea state and incoming wave direction, and the impact of including buoys of different radii in an array. Our results show that, e. g., the fluctuations as well as power per device decrease strictly with the number of interacting units, when the separating distance is kept constant. However, including more devices in a park with fixed area will not necessarily result in lowered power fluctuations. We also show that varying the distance between units affects the power fluctuations to a much larger extent than it affects the magnitude of the absorbed power. The fluctuations are slightly lower in more realistic, randomized geometries where the buoys tend to drift slightly off their mean positions, and significantly lower in semi-circular geometries as opposed to rectangular geometries.
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| 8. |
- Aidanpää, Jan-Olov, et al.
(författare)
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Developments in rotor dynamical modeling of hydropower units
- 2009
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Ingår i: Proceedings of the IUTAM Symposium on Emerging Trends in Rotor Dynamics. - Dordrecht : Encyclopedia of Global Archaeology/Springer Verlag. - 9789400700192
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Konferensbidrag (refereegranskat)
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| 9. |
- Karlsson, Martin, et al.
(författare)
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Rotor Dynamic Analysis of an Eccentric Hydropower Generator With Damper Winding for Reactive Load
- 2007
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Ingår i: Journal of applied mechanics. - : ASME International. - 0021-8936 .- 1528-9036. ; 74:6, s. 1178-1186
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Tidskriftsartikel (refereegranskat)abstract
- Asymmetry in the magnetic circuit, around the air gap circumference, in a hydroelectric generator will give rise to a unbalanced magnetic pull. In this paper a hydropower rotor system is modeled and the influence of electro-mechanical forces due to overexcitation is analyzed The active power has been kept constant and the rotor excitation has been changed in order to vary the output of reactive power The electromagnetic field is solved with the finite element method Two electromagnetic models are compared: one with and one without damper winding. The mechanical model of the generator consists of a four id disk connected to an elastic shaft su orted b two bearin s de rees of freedom ri pp y g g g with linear properties. It has been found that the unbalanced magnetic pull slightly increasesfor reactive loads resulting in a decrease of natural frequencies and an increase of unbalance response. When the damper winding is included, the magnetic pull will decrease compared to the model without damper winding, and the pull force has two components: one radial and one tangential. The tangential component can influence the stability of the mechanical system for a range of design parameters.
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| 10. |
- Lundström, Ludvig, et al.
(författare)
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Influence on the stability of generator rotors due to radial and tangential magnetic pull force
- 2007
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Ingår i: IET Electric Power Applications. - : Institution of Engineering and Technology (IET). - 1751-8660 .- 1751-8679. ; 1:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Forces due to nonuniform airgaps in rotating electrical machines have been a researchtopic for over 100 years. However, most research in the area of rotating electrical machines hasbeen performed on motors. Large forces in hydropower generators can lead to expensive damageand failures. Therefore, it is of interest to calculate the forces that arise in a large synchronousgenerator with an eccentric rotor and study the influence these forces have on the stability of thegenerator rotor. A 74 MVA synchronous hydropower generator was simulated with an eccentricrotor, using a time-stepping finite-element technique. The forces were calculated using Coulomb’svirtual-work method and simulations were performed for no-load and load cases. The resultingforce was found to be reduced significantly when a damper winding was taken into account. Aninteresting effect of the rotor damper winding was that it reduced the eccentricity force andintroduced a force component perpendicular to the direction of eccentricity. The results from thefinite-element simulations were used to determine how the forces affect the stability of the generatorrotor. Damped natural eigenfrequencies and damping ratio for load and no-load conditions arepresented. When applying the forces computed in the time-dependent model, the damped naturaleigenfrequencies were found to increase and the stability of the generator rotor was found to bereduced compared with when the forces were computed in a stationary model.
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