| 1. |
- Nilsson, August Håkan, et al.
(författare)
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The Cantril Ladder elicits thoughts about power and wealth
- 2024
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Ingår i: Scientific Reports. - 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- The Cantril Ladder is among the most widely administered subjective well-being measures; every year, it is collected in 140+ countries in the Gallup World Poll and reported in the World Happiness Report. The measure asks respondents to evaluate their lives on a ladder from worst (bottom) to best (top). Prior work found Cantril Ladder scores sensitive to social comparison and to reflect one’s relative position in the income distribution. To understand this, we explored how respondents interpret the Cantril Ladder. We analyzed word responses from 1581 UK adults and tested the impact of the (a) ladder imagery, (b) scale anchors of worst to best possible life, and c) bottom to top. Using three language analysis techniques (dictionary, topic, and word embeddings), we found that the Cantril Ladder framing emphasizes power and wealth over broader well-being and relationship concepts in comparison to the other study conditions. Further, altering the framings increased preferred scale levels from 8.4 to 8.9 (Cohen’s d = 0.36). Introducing harmony as an anchor yielded the strongest divergence from the Cantril Ladder, reducing mentions of power and wealth topics the most (Cohen’s d = −0.76). Our findings refine the understanding of historical Cantril Ladder data and may help guide the future evolution of well-being metrics and guidelines.
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| 2. |
- Nilsson, Håkan, 1962-
(författare)
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Upplevelsen av existentiella hot : ett hot mot folkhälsan!?
- 2024
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Ingår i: Socialmedicinsk Tidskrift. - 0037-833X .- 2000-4192. ; 101:1, s. 21-38
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Existentiellt hot är ett begrepp som allt oftare nämns i samband med medias rapportering av kriget i Ukraina, Israel och Hamas-frågan och den pågående klimatkrisen. Vi hör även begreppet nämnas i samband med AI forskningens eventuella utveckling av en superintelligent varelse av det mer hotfulla slaget. Av dessa nämnda skäl finns det anledning att se närmare på hur detta begrepp kan förstås utifrån olika kontexter. Med detta sagt har syftet med denna artikel varit att introducera och utreda begreppet existentiellt hot. Till min kännedom har ingen definition av begreppet existentiellt hot presenterats i en svensk kontext.
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| 3. |
- Odebrant, Joel
(författare)
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Spår, kropp, tid : En undersökning av den måleriska gestens materialitet 1952–1965
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I Spår, kropp, tid undersöks den måleriska gestens materialitet i måleri som förknippas med abstrakt expressionism och informell konst. Ett återkommande drag i beskrivningarna av denna konst är att den sägs peka mot, eller handla om, individen eller individualitet; antingen som ett uttryck förkonstnärens inre liv genom fria, improviserade stråk på duken, eller i relation till sociala och historiska sammanhang där individualiteten har uppfattats som undertryckt av industrialismens effekter eller av kollektivistisk statligpolitik. I den här undersökningen är perspektivet istället riktat mot den måleriska gesten och dess materialitet. Stilbeteckningar och historiska förklaringsmodeller sätts inom parentes och fokus ligger istället på den måleriska gesten som sådan. Den måleriska gesten är det övergripande analytiska begrepp utifrån vilket konstverken analyseras, och som i avhandlingens analyskapitel utvecklas och fördjupas i en ackumulerande process. Syftet medavhandlingen är att utveckla begrepp och metoder för att beskriva och tolka den måleriska gesten ur ett materialitetsperspektiv. Detta görs genom nära analyser av femton målningar från sent 1950-tal och tidigt 1960-tal av niokonstnärer från Sverige, Polen och forna Tjeckoslovakien. Studien bygger på nära analyser av målningarna med fokus på konstverkens materialitet. Analyserna etablerar och diskuterar begrepp och perspektiv på målningarna, som representerar olika materiella, formella och teoretiska aspekter av den måleriska gesten. De aspekter av den måleriska gesten som behandlas i undersökningens tre analyskapitel är: den måleriska gesten som ett abduktivt index; den måleriska gesten som ett uttryck för kroppslighet; den måleriska gesten som en visualisering av heterokroni, dvs. en uppfattning av tiden som mångfaldig. Undersökningen visar att den måleriska gesten kan förstås som en materiell nod, dvs. en förgreningspunkt, som sammanflätar frånvarande och närvarande kroppar, rum och temporaliteter. Den måleriska gestens meningsstruktur är polysemisk och beror på hur materialiteten inkluderas i relationer både inom och utanför måleriets materiella struktur.
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| 4. |
- Salehi, Saeed, 1987, et al.
(författare)
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Modal analysis of vortex rope using dynamic mode decomposition
- 2024
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Ingår i: Physics of Fluids. - 1070-6631 .- 1089-7666. ; 36:2
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Tidskriftsartikel (refereegranskat)abstract
- The decelerating swirling flow in the draft tube of hydraulic turbines at part load conditions often results in a self-induced instability known as vortex rope. This phenomenon is associated with detrimental pressure pulsations in the hydropower system that need to be mitigated. A deep understanding of such instability is essential for developing effective mitigation and control strategies. The current article exploits the dynamic mode decomposition (DMD) algorithm to perform an in-depth modal analysis of the physical aspects of the vortex rope. DMD can efficiently identify distinct coherent structures with isolated frequencies. The sparsity-promoting variant of DMD is exploited to extract the most influential modes. The computational fluid dynamics (CFD) data is generated via a resolved improved delayed detached eddy simulation using OpenFOAM. Frequency analysis of the CFD data uncovered peaks at the normalized frequencies of f/fn=0.56 and 0.63, whose origins seemed initially unclear. Nevertheless, the DMD modal analysis elucidates that these excitations are associated with the rotation of the reunited vortex and fluctuations of the separated boundary layer, respectively. The non-linear dynamics of the flow field are unveiled through a modal decomposition revealing distinctive coherent structures with isolated frequencies. These include rotational and plunging modes of the vortex rope, traveling wakes of the blades, boundary layer separation due to strong adverse pressure gradient, and a reunited vortex core. The flow field reconstruction through time dynamics of DMD modes highlights while it is possible to achieve a perfect flow field reconstruction considering all recovered modes, the model typically fails to predict future behavior with an acceptable level of accuracy. The chaotic nature of the resolved turbulent flow field presents a substantial challenge for predicting the future through a model built based on prior events. The current modal analysis not only provides a more comprehensive understanding of the physics underlying the vortex rope phenomenon but also lays the groundwork for potential future applications in controlling mechanisms.
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| 5. |
- Truijen, Daan, et al.
(författare)
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Impact of Dual Variable Speed and Inlet Valve Control on the Efficiency and Operating Range of Low-Head Contra-Rotating Pump-Turbines
- 2024
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Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 12, s. 86854-86868
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to make pumped hydropower storage (PHS) technology feasible for regions with a flat topography, recent research shows promising results using a contra-rotating reversible pump-turbine at low-head. In this study, the impact of dual variable speed and inlet valve control is analyzed to evaluate the effect of these three degrees of freedom (DOFs) on the system efficiency and operating range. To this end, analytical models are described to assess pump-turbine performance, conduit losses and electromechanical losses. Methodologically, optimal efficiency maps are computed for every combination of the three DOFs to evaluate individual and combined effects on the overall efficiency. Furthermore, three energy storage cycles are analyzed to further study the performance in realistic use-cases. Key conclusions include an increase in round-trip efficiency by combining variable speed ratio and inlet valve control of 5.6% and 2.0% compared with only variable speed ratio control and variable inlet valve control, respectively. Furthermore, it is shown that using only 1 DOF significantly limits the operating range, with the addition of a variable inlet valve granting a higher impact than a variable speed ratio. Combining inlet valve and speed ratio control leads not only to the highest efficiency, but also the largest operating range, with a maximum round-trip efficiency of 67.5% and an energy storage capacity of 58.6 Wh/m2. The results confirm that exploiting both dual variable speed operation and inlet valve control yields the maximum efficiency and operating range, and is thus the preferred topology for contra-rotating reversible pump-turbines in low-head operation.
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| 6. |
- Truijen, D. P. K., et al.
(författare)
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Hardware-in-the-loop emulator test-setup for a dual-rotor contra-rotating pump-turbine
- 2024
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Ingår i: IET Conference Proceedings. - 2732-4494. ; , s. 81-88
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Konferensbidrag (refereegranskat)abstract
- Recently, contra-rotating reversible pump-turbines (CR RPTs) have been proposed to increase the efficiency of low-head pumped hydropower storage applications, which are promising to provide energy storage for non-mountainous regions. To study the control architectures for these systems, a dual-rotor hardware-in-the-loop (HIL) emulator test-setup is developed. The HIL test-setup employs two induction machines controlled by separate regenerative variable frequency drives to emulate the torques on the two runners. A quasi-steady-state RPT model is developed based on 380 steady-state computational fluid dynamics (CFD) simulations and compared to three transient CFD simulations to analyse the dynamics. Furthermore, the runner torques are adapted to account for the lower friction and higher inertia of the HIL test-setup compared to the prototype CR RPT, ensuring accurate emulation. Finally, it is shown how precise calibration of the drive torque response averts torque errors related to the machine model estimator used in direct torque control. The developed emulator setup offers a cost-effective and controlled environment to optimise and validate control architectures for the novel CR RPT, providing a higher fidelity than theoretical simulation by including the physical effects of the drivetrain, electrical machines and converters that are not entirely captured in mathematical models.
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| 7. |
- Arabnejad Khanouki, Mohammad Hossein, 1988, et al.
(författare)
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A novel single-fluid cavitation model with gas content and slip velocity, applied to cavitating tip leakage vortex
- 2023
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Ingår i: International Journal of Multiphase Flow. - 0301-9322. ; 169
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we develop a new model based on the single-fluid approach which consider the effects of gas content and slip velocity between the gas/vapor phase and the liquid phase in cavitation modeling. The derivation of the mathematical formulation of the model is presented in the context of Large Eddy Simulation (LES), although a similar derivation can be developed for a Reynolds-averaged Navier–Stokes (RANS) framework. To validate the model and to study the effect of including this physics, a cavitating Tip Leakage Vortex (TLV) formed around the NACA0009 foil is simulated. The results of the simulation are compared with the available experimental data and the results obtained from a conventional single-fluid approach. This comparison shows that the new model predicts cavitation regions in significantly better agreement with the experimental data, compared to the conventional single-fluid approach. This better agreement is observed for both the cavitation regions in the TLV and the cavitation regions at the leading edge. Analyzing the results, the reason for this significant improvement is shown to be the accumulation of non-dissolved gas due to the consideration of the slip velocity, and the effect of this accumulation in the cavitation formation. Furthermore, the effects of gas content and the size of nuclei in the incoming flow to the TLV are investigated, and these effects are discussed in detail.
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| 8. |
- Arabnejad Khanouki, Mohammad Hossein, 1988, et al.
(författare)
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Investigation of Flow-Induced Instabilities in a Francis Turbine Operating in Non-Cavitating and Cavitating Part-Load Conditions
- 2023
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Ingår i: Fluids. - : MDPI AG. - 2311-5521. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- The integration of intermittent renewable energy resources to the grid system requires that hydro turbines regularly operate at part-load conditions. Reliable operation of hydro turbines at these conditions is typically limited by the formation of a Rotating Vortex Rope (RVR) in the draft tube. In this paper, we investigate the formation of this vortex using the scale-resolving methods SST-SAS, wall-modeled LES (WMLES), and zonal WMLES. The numerical results are first validated against the available experimental data, and then analyzed to explain the effect of using different scale-resolving methods in detail. It is revealed that although all methods can capture the main features of the RVRs, the WMLES method provides the best quantitative agreement between the simulation results and experiment. Furthermore, cavitating simulations are performed using WMLES method to study the effect of cavitation on the flow in the turbine. These effects of cavitation are shown to be highly dependent on the amount of vapor in the RVR. If the amount of vapor is small, cavitation induces broadband high-frequency fluctuations in the pressure and forces exerted on the turbine. As the amount of cavitation increases, these fluctuations tend to have a distinct dominant frequency which is different from the frequency of the RVR.
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| 9. |
- Fahlbeck, Jonathan, 1992, et al.
(författare)
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Cavitation Simulations of a Low Head Contra-rotating Pump-turbine
- 2023
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Ingår i: OpenFOAM Workshop (OFW18) Book of abstracts. ; , s. 348-349
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To meet the demands of a larger share of the electrical energy produced by intermittent renewable energy sources, an increasing amount of plannable energy sources is needed. One solution to handle this is to increase the amount of energy storage in the electrical grids. The most widespread energy storage technology today is by far pumped hydro storage (PHS). In an attempt to enable PHS at low-head sites, the ALPHEUS (augmenting grid stability through low head pumped hydro energy utilization and storage) EU Horizon 2020 research project was formed. In ALPHEUS, new axial flow, low-head, contra-rotating pump-turbine (CRPT) designs are investigated. A CRPT has two individual runners rotating in opposite directions. CRPTs developed within the ALPHEUS project have already been thoroughly analysed at stationary and transient operating conditions by the authors. However, the effects on the CPRT's performance due to potential cavitation on the runner blade surfaces have previously not been investigated. For that reason, the current study focuses on running cavitation simulations on a model scale CRPT using the OpenFOAM computational fluid dynamics (CFD) software. In the CFD simulations, cavitation is modelled as a two-phase liquid-vapour mixture using the interPhaseChangeDyMFoam solver. The two runner domains have a prescribed solid body rotation. Condensation and evaporation processes are handled with the Schnerr-Sauer model. Turbulence is managed with the k-omega shear stress transport-scale adaptive simulation (kOmegaSSTSAS) model. Flow-driving pressure differences over the computational domain are achieved with the headLossPressure boundary condition to emulate a larger experimental test facility of which the CRPT is part. Figure 1 shows a snapshot in time of an iso-surface (light blue) of cavitating cloud with alpha_liquid=0.9 in turbine mode. At this operating point, a small amount of cavitating flow is found by the suction side of the leading edges of the left runner, which is facing a lower reservoir. In Figure 2, the same type of iso-surface is shown, however now in pump mode. It is seen that the pump mode operating condition is much worse than the turbine mode. The cavitating cloud covers most of the suction side of the left runner, additionally, the tip-clearance region is also exposed to cavitation. Furthermore, traces of cavitation are found on the leading edges of the right runner as well as on the left small-support struts. It is thus important to, at least, analyse the pump mode to determine if and how much cavitation affects the CRPS's operating performance.
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| 10. |
- Fahlbeck, Jonathan, 1992, et al.
(författare)
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Surrogate based optimisation of a pump mode startup sequence for a contra-rotating pump-turbine using a genetic algorithm and computational fluid dynamics
- 2023
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Ingår i: Journal of Energy Storage. - : Elsevier BV. - 2352-152X. ; 62
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Tidskriftsartikel (refereegranskat)abstract
- Contra-rotating pump-turbines (CRPT) have been proposed as a new solution for pumped hydro storage (PHS) at low-head sites. The two individually operated runners give both flexibility and complexity during transient operation, such as startup. This paper presents an optimisation approach for the pump mode startup sequence of a CRPT. The aim is to minimise the loads during fast startups and thus extend the lifetime and increase the flexibility of the CRPT. The startup sequence is decomposed into five design variables which determine a valve opening and the speedup of each runner rotational speed. The optimisation procedure includes transient computational fluid dynamics (CFD) simulations and global surrogate-based optimisation (SBO). An objective function, based on an integration of the time derivative of the axial force, is derived and transformed into a Gaussian-process surrogate model. The results show that the SBO can predict an optimal combination of the five variables that limits unfavourable load variations during the pump mode startup sequence. For an optimal startup sequence, the valve should be opened up during 73% of the sequence, the upstream runner should speed up during most of the sequence, and the downstream runner should speed up during the final third of the sequence. The outcome of this work is beneficial for a safe startup operation of possible future PHS with CRPTs.
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