| 1. |
- Andersson, L. Robin, et al.
(författare)
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Localized roughness effects in non-uniform hydraulic waterways
- 2021
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Ingår i: Journal of Hydraulic Research. - : Taylor & Francis. - 0022-1686 .- 1814-2079. ; 59:1, s. 100-108
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Tidskriftsartikel (refereegranskat)abstract
- Hydropower tunnels are generally subject to a degree of rock falls. Studies explaining this are scarce and the current industrial standards offer little insight. To simulate tunnel conditions, high Reynolds number flow inside a channel with a rectangular cross-section is investigated using Particle Image Velocimetry and pressure measurements. For validation, the flow is modelled using LES and a RANS approach with k - ε turbulence model. One wall of the channel has been replaced with a rough surface captured using laser scanning. The results indicate flow-roughness effects deviating from the standard non-asymmetric channel flow and hence, can not be properly predicted using spatially averaged relations. These effects manifest as localized bursts of velocity connected to individual roughness elements. The bursts are large enough to affect both temporally and spatially averaged quantities. Both turbulence models show satisfactory agreement for the overall flow behaviour, where LES also provided information for in-depth analysis.
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| 2. |
- Burman, Anton J., et al.
(författare)
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Case Study of Transient Dynamics in a Bypass Reach
- 2020
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Ingår i: Water. - : MDPI. - 2073-4441. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- The operating conditions of Nordic hydropower plants are expected to change in the coming years to work more in conjunction with intermittent power production, causing more frequent hydropeaking events. Hydropeaking has been shown to be detrimental to wildlife in the river reaches downstream of hydropower plants. In this work, we investigate how different possible future hydropeaking scenarios affect the water surface elevation dynamics in a bypass reach in the Ume River in northern Sweden. The river dynamics has been modeled using the open-source solver Delft3D. The numerical model was validated and calibrated with water-surface-elevation measurements. A hysteresis effect on the water surface elevation, varying with the downstream distance from the spillways, was seen in both the simulated and the measured data. Increasing the hydropeaking rate is shown to dampen the variation in water surface elevation and wetted area in the most downstream parts of the reach, which could have positive effects on habitat and bed stability compared to slower rates in that region.
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| 3. |
- Burman, Anton J., 1992-, et al.
(författare)
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Hydraulic classification of hydropeaking stages in a river reach
- 2023
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Ingår i: Rivers Research and Applications. - : John Wiley & Sons. - 1535-1459 .- 1535-1467. ; 39:4, s. 692-702
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Tidskriftsartikel (refereegranskat)abstract
- Hydropower is an important tool in the struggle for low-emission power production. In the Nordic countries, hydropower operating conditions are expected to change and work more in conjunction with intermittent power production. This in turn might increase the amount of hydropeaking events in the reaches downstream of hydropower plants. The current work investigates the influence of highly flexible, high-frequency hydropeaking on the hydrodynamics in the downstream reach. By quantifying four different dynamic stages in the study reach, the influence of the hydropeaking frequencies was investigated in the bypass reach of the Stornorrfors hydropower plant in the river Umeälven in northern Sweden. The hydrodynamics in the study reach were numerically modelled using the open source solver Delft3D. Eight different highly flexible future hydropeaking scenarios, varying from 12 to 60 flow changes per day, were considered. A method for identifying four hydropeaking stages—dewatering, dynamic, alternating and uniform —was introduced. The hydropeaking frequency directly decided the stage in most of the study reach. Furthermore, a Fourier analysis showed a significant difference between the stages and their corresponding power spectra. The classification of stages put forward in this work provides a novel, simple method to investigate the hydrodynamics due to hydropeaking in a river reach.
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| 4. |
- Burman, Anton J., 1992-, et al.
(författare)
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Investigating damping properties in a bypass river
- 2020
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Ingår i: River Flow 2020. - London : Taylor & Francis Group. ; , s. 2361-2366
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Konferensbidrag (refereegranskat)abstract
- The operating conditions of hydropower plants in Sweden are expected to change in the coming decades with potentially many hydropeaking events every day. It is therefor important to understand how inherent damping properties in rivers can be used to mitigate potential negative influences on fluvial ecosystems. The effect of the upstream dam closing time and the Manning number distribution in the reach on the transient behavior of the downstream water level and wetted area is investigated. In the study reach the shallow-water equations are solved using the open-source solver Delft3D. The simulations show that the transient change in water level is mainly dependent on the upstream dam closing time. The dynamics of the wetted area is considerably affected by the closing time of the dam. The Manning number has a negligible effect on the transient behavior for the wetted area and the waterlevel. The results in this study can be used for future ecohydraulical applications such as identifying potential stranding zones.
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| 5. |
- Burman, Anton J., 1992-, et al.
(författare)
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Modelling the downstream longitudinal effects of frequent hydropeaking on the spawning potential and stranding susceptibility of salmonids
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 796
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Tidskriftsartikel (refereegranskat)abstract
- Hydropower plant operating conditions are expected to change to be more in tandem with intermittent power production so as to meet the requirements of the Paris Agreement, which in turn may negatively impact ecological conditions downstream of the hydropower plants. The current study investigates how highly flexible hydropower operating conditions may impact several salmonid species (European grayling, Atlantic salmon and brown trout) in the River Umeälven, a major river in northern Sweden; specifically, how changes in hydropeaking frequency may affect the area of the downstream watercourse that is hydraulically suitable for spawning (potential spawning area) and how changes in spill gate closing time may affect the propensity to stranding. River hydrodynamics were modeled using the open-source solver Delft3D, with a range of hydropeaking frequencies (from 10 to 60 starts and stops per day) and a range of spill gate closing times from (1–30 min). Increasing the hydropeaking frequency caused a reduction in potential spawning area, but also a reduction in dewatering of potential spawning area at low flows. Increasing spill gate closing time caused a decrease in propensity to stranding. Effects were dependent on both species and life-stage, and declined longitudinally with distance downstream from the spillway outlet. The modelling approach used here provides an effective method for predicting likely outcomes of flexible hydropower operating conditions, taking into account fish species and life-stages present and watercourse characteristics.
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| 6. |
- Forslund, Tobias O. M., 1992-, et al.
(författare)
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A dual-lattice hydrodynamic-thermal MRT-LBM model implemented on GPU for DNS calculations of turbulent thermal flows
- 2022
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Ingår i: International journal of numerical methods for heat & fluid flow. - : Emerald Group Publishing Limited. - 0961-5539 .- 1758-6585. ; 35:5, s. 1703-1725
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Tidskriftsartikel (refereegranskat)abstract
- PurposeThe purpose of this paper is to present a fast and bare bones implementation of a numerical method for quickly simulating turbulent thermal flows on GPUs. The work also validates earlier research showing that the lattice Boltzmann method (LBM) method is suitable for complex thermal flows.Design/methodology/approachA dual lattice hydrodynamic (D3Q27) thermal (D3Q7) multiple-relaxation time LBM model capable of thermal DNS calculations is implemented in CUDA.FindingsThe model has the same computational performance compared to earlier publications of similar LBM solvers. The solver is validated against three benchmark cases for turbulent thermal flow with available data and is shown to be in excellent agreement.Originality/valueThe combination of a D3Q27 and D3Q7 stencil for a multiple relaxation time -LBM has, to the authors’ knowledge, not been used for simulations of thermal flows. The code is made available in a public repository under a free license.
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| 7. |
- Forslund, Tobias O. M., 1992-, et al.
(författare)
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Non-Stokesian flow through ordered thin porous media imaged by tomographic-PIV
- 2021
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Ingår i: Experiments in Fluids. - : Springer. - 0723-4864 .- 1432-1114. ; 62:3
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Tidskriftsartikel (refereegranskat)abstract
- The 3D flow-fields in a staggered and cubic arrangement of mono-radii cylinders are investigated using tomographic-PIV. The cylinder Reynolds-number is in the range of ≈10 to ≈800 giving an almost complete overview of the transition region. Two pore-scale effects are discovered. The first, visible in the cubic packing, is a spatially alternating lateral velocity field, which has a significant impact on the pressure drop and transversal dispersion. The second effect, present in the staggered array, is an example of a disturbance propagation effect that takes place in the laminar steady region; this manifests as a peculiar and complex flow-pattern. In accordance with other studies, it is shown that Darcy’s law can, from an engineering point of view be valid far beyond the limit for Stokesian flow.
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| 8. |
- Forslund, Tobias O.M. 1992-, et al.
(författare)
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Steady-State Transitions in Ordered Porous Media
- 2023
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Ingår i: Transport in Porous Media. - : Springer Nature. - 0169-3913 .- 1573-1634. ; 149:2, s. 551-577
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Tidskriftsartikel (refereegranskat)abstract
- Previously performed experiments on flow through an ordered porous media cell with tomographic particle image velocimetry reveal a complex three-dimensional steady-state flow pattern. This flow pattern emerge in the region where inertial structures have been previously reported for a wide range of packings. The onset of these steady-state inertial flow structures is here scrutinized for three different types of packing using a finite difference method. It is concluded that the onset of the flow structure coincides with a symmetry break in the flow field and discontinuities in the pressure drop, volume averaged body forces and heat transfer. A quantity for identifying the transition is proposed, namely the pressure integral across the solid surfaces. It is also shown that the transition can both increase and decrease the heat transfer dependent on the actual geometry of the porous medium.
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| 9. |
- Forslund, Tobias O. M., 1992-, et al.
(författare)
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The Effects of Periodicity Assumptions in Porous Media Modelling
- 2021
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Ingår i: Transport in Porous Media. - : Springer. - 0169-3913 .- 1573-1634. ; 137:3, s. 769-797
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Tidskriftsartikel (refereegranskat)abstract
- The effects of periodicity assumptions on the macroscopic properties of packed porous beds are evaluated using a cascaded Lattice-Boltzmann method model. The porous bed is modelled as cubic and staggered packings of mono-radii circular obstructions where the bed porosity is varied by altering the circle radii. The results for the macroscopic properties are validated using previously published results. For unsteady flows, it is found that one unit cell is not enough to represent all structures of the fluid flow which substantially impacts the permeability and dispersive properties of the porous bed. In the steady region, a single unit cell is shown to accurately represent the fluid flow across all cases studied
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| 10. |
- Höller, J. Bastian, et al.
(författare)
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Integrating Downstream Ecological, Social and Economic Effects of Hydropower to Hydraulic Modeling: A Review
- 2023
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Ingår i: World Journal of Mechanics. - 2160-049X .- 2160-0503. ; 13:8, s. 149-172
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Forskningsöversikt (refereegranskat)abstract
- Hydropower gains increasing importance as a steerable and controllable power source in a renewable energy mix and deregulated markets. Although hydropower produces fossil-free energy, it has a significant impact on the local environment. This review investigates the effects of flow alterations by hydropower on the downstream river system and the possibilities to integrate these effects into hydraulic modeling. The results show that various effects of flow regulation on the ecosystem, but also social and economic effects on related communities were observed in the last decades. The application of hydraulic models for investigations of ecological effects is common. Especially hydraulic effects and effects on fish were extensively modeled with the help of hydraulic 1D- and 2D-simulations. Current applications to investigate social and economic effects integrated into hydraulic modeling are meanwhile limited. Approaches to realizing this integration are presented. Further research on the economic valuation of ecosystems and integration of social and economic effects to hydraulic models is necessary to develop holistic tools to support decision-making on sustainable hydropower.
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