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Andreasson, Patrik
Publications (10 of 25) Show all publications
Andersson, R., Hellström, J. G., Andreasson, P. & Lundström, S. (2019). Numerical investigation of a hydropower tunnel: Estimating localised head-loss using the manning equation. Water, 11(8), Article ID 1562.
Open this publication in new window or tab >>Numerical investigation of a hydropower tunnel: Estimating localised head-loss using the manning equation
2019 (English)In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 11, no 8, article id 1562Article in journal (Refereed) Published
Abstract [en]

The fluid dynamics within a water tunnel is investigated numerically using a RANS approach with the k-ε turbulence model. The computational model is based on a laser scan of a hydropower tunnel located in Gävunda, Sweden. The tunnel has a typical height of 6.9 m and a width of 7.2 m. While the average cross-sectional shape of the tunnel is smooth the local deviations are significant, where some roughness elements may be in the size of 5 m implying a large variation of the hydraulic radius. The results indicate that the Manning equation can successfully be used to study the localised pressure variations by taking into account the varying hydraulic radius and cross-sectional area of the tunnel. This indicates a dominant effect of the tunnel roughness in connection with the flow, which has the potential to be used in the future evaluation of tunnel durability. ANSYS-CFX was used for the simulations along with ICEM-CFD for building the mesh. 

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
ANSYS-CFX, Case-study, Head-loss, Hydropower, Rock tunnel, Surface roughness
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-75622 (URN)10.3390/w11081562 (DOI)000484561500036 ()2-s2.0-85070288117 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-08-21 (svasva)

Available from: 2019-08-21 Created: 2019-08-21 Last updated: 2019-10-08Bibliographically approved
Andreasson, P. (2019). Teori om strålar - för vägledning vid utformning av lockvatten. Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Teori om strålar - för vägledning vid utformning av lockvatten
2019 (Swedish)Report (Other academic)
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2019. p. 13
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-77104 (URN)978-91-7790-512-7 (ISBN)
Available from: 2019-12-09 Created: 2019-12-09 Last updated: 2019-12-09Bibliographically approved
Yang, J., Andreasson, P., Teng, P. & Xie, Q. (2019). The Past and Present of Discharge Capacity Modeling for Spillways: A Swedish Perspective. Fluids, 4(10), Article ID 4010010.
Open this publication in new window or tab >>The Past and Present of Discharge Capacity Modeling for Spillways: A Swedish Perspective
2019 (English)In: Fluids, ISSN 2311-5521, Vol. 4, no 10, article id 4010010Article in journal (Refereed) Published
Abstract [en]

Most of the hydropower dams in Sweden were built before 1980. The present dam-safety guidelines have resulted in higher design floods than their spillway discharge capacity and the need for structural upgrades. This has led to renewed laboratory model tests. For some dams, even computational fluid dynamics (CFD) simulations are performed. This provides the possibility to compare the spillway discharge data between the model tests performed a few decades apart. The paper presents the hydropower development, the needs for the ongoing dam rehabilitations and the history of physical hydraulic modeling in Sweden. More than 20 spillways, both surface and bottom types, are analyzed to evaluate their discharge modeling accuracy. The past and present model tests are compared with each other and with the CFD results if available. Discrepancies do exist in the discharges between the model tests made a few decades apart. The differences fall within the range −8.3%–+11.2%. The reasons for the discrepancies are sought from several aspects. The primary source of the errors is seemingly the model construction quality and flow measurement method. The machine milling technique and 3D printing reduce the source of construction errors and improve the model quality. Results of the CFD simulations differ, at the maximum, by 3.8% from the physical tests. They are conducted without knowledge of the physical model results in advance. Following the best practice guidelines, CFD should generate results of decent accuracy for discharge prediction.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
spillway, bottom outlet, design flood, discharge capacity, model tests, computational fluid dynamics (CFD)
National Category
Water Engineering Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-72663 (URN)10.3390/fluids4010010 (DOI)000464468000001 ()2-s2.0-85063403125 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-02-28 (marisr)

Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-04-30Bibliographically approved
Andersson, L. R., Larsson, S., Hellström, J. G., Andreasson, P., Andersson, A. G. & Lundström, S. (2018). Characterization of Flow Structures Induced by Highly Rough Surface Using Particle Image Velocimetry, Proper Orthogonal Decomposition and Velocity Correlations. Engineering, 10, 399-416
Open this publication in new window or tab >>Characterization of Flow Structures Induced by Highly Rough Surface Using Particle Image Velocimetry, Proper Orthogonal Decomposition and Velocity Correlations
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2018 (English)In: Engineering, ISSN 1947-3931, Vol. 10, p. 399-416Article in journal (Refereed) Published
Abstract [en]

High Reynolds number flow inside a channel of rectangular cross section is examined using Particle Image Velocimetry. One wall of the channel has been replaced with a surface of a roughness representative to that of real hydropower tunnels, i.e. a random terrain with roughness dimensions typically in the range of ≈10% - 20% of the channels hydraulic radius. The rest of the channel walls can be considered smooth. The rough surface was captured from an existing blasted rock tunnel using high resolution laser scanning and scaled to 1:10. For quantification of the size of the largest flow structures, integral length scales are derived from the auto-correlation functions of the temporally averaged velocity. Additionally, Proper Orthogonal Decomposition (POD) and higher-order statistics are applied to the instantaneous snapshots of the velocity fluctuations. The results show a high spatial heterogeneity of the velocity and other flow characteristics in vicinity of the rough surface, putting outer similarity treatment into jeopardy. Roughness effects are not confined to the vicinity of the rough surface but can be seen in the outer flow throughout the channel, indicating a different behavior than postulated by Townsend’s similarity hypothesis. The effects on the flow structures vary depending on the shape and size of the roughness elements leading to a high spatial dependence of the flow above the rough surface. Hence, any spatial averaging, e.g. assuming a characteristic sand grain roughness factor, for determining local flow parameters becomes less applicable in this case.

Place, publisher, year, edition, pages
Scientific Research Publishing, 2018
Keywords
CFD, Validation, Hydraulic Roughness, PIV, Hydropower
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71097 (URN)10.4236/eng.2018.107028 (DOI)
Available from: 2018-10-04 Created: 2018-10-04 Last updated: 2019-08-12Bibliographically approved
Andersson, R., Burman, A., Hellström, J. G. & Andreasson, P. (2018). Inlet Blockage Effects in a Free Surface Channel With Artificially Generated Rough Walls. In: Daniel Bung ; Blake Tullis (Ed.), Proceedings of the 7th IAHR International Symposium on Hydraulic Structures: . Paper presented at 7th International Symposium on Hydraulic Structures, Aachen, Germany, 15-18 May 2018 (pp. 723-732).
Open this publication in new window or tab >>Inlet Blockage Effects in a Free Surface Channel With Artificially Generated Rough Walls
2018 (English)In: Proceedings of the 7th IAHR International Symposium on Hydraulic Structures / [ed] Daniel Bung ; Blake Tullis, 2018, p. 723-732Conference paper, Published paper (Refereed)
Abstract [en]

When considering free surface flow in channels, it is essential to have in-depth knowledge about the inlet flow conditions and the effect of surface roughness on the overall flow field. Hence, we hereby investigate flow inside an 18m long channel by using Particle Tracking Velocimetry (PTV) and Acoustic Doppler Velocimetry (ADV). The roughness of the channel walls is generated using a diamond-square fractal algorithm and is designed to resemble the actual geometry of hydropower tunnels. Four different water levels ranging from 20 to 50cm are investigated. For each depth, the inlet is blocked by 25 and 50% at three positions each, at the centre, to the right and to the left in the flow-direction. The flow is altered for each depth to keep the flow velocity even throughout the measurements. PTV is applied to measure the velocity of the free water surface; four cameras are placed above the setup to capture the entirety of the channel. The results show a clear correlation between roughness-height and velocity distribution at depths 20-30 cm. The surface roughness proved effective in dispersing the subsequent perturbations following the inlet blockage. At 50cm, perturbations from the 50% blockage could be observed throughout the channel. However, at 20cm, most perturbations had subsided by a third of the channel length. The ADV was used to capture the velocity in a total of 375 points throughout the channel, at a depth of 50 cm with no inlet perturbations.

Keywords
Hydraulic roughness, PTV, diamond-square algorithm, free-surface flows
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-71096 (URN)10.15142/T3P644 (DOI)2-s2.0-85054178430 (Scopus ID)9780692132777 (ISBN)
Conference
7th International Symposium on Hydraulic Structures, Aachen, Germany, 15-18 May 2018
Available from: 2018-10-04 Created: 2018-10-04 Last updated: 2018-10-12Bibliographically approved
Yang, J., Andreasson, P., Högström, C.-M. & Teng, P. (2018). The tale of an intake vortex and its mitigation countermeasure: A case study from akkats hydropower station. Water, 10(7), Article ID 881.
Open this publication in new window or tab >>The tale of an intake vortex and its mitigation countermeasure: A case study from akkats hydropower station
2018 (English)In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 10, no 7, article id 881Article in journal (Refereed) Published
Abstract [en]

The upgrade of Akkats power station in Sweden included a new, separate waterway for the addition of a 75 MW generating unit. The vertical intake of its headrace was formed by means of lake tapping. A physical model was used to help understand the blasting process involving fragmented rock, water, air, and gas. Upon commissioning of the unit, swirling flows occurred unexpectedly at the intake, which gave rise to negative consequences including limitations in power output. Echo-sounding showed that the blasted piercing resulted in an irregular intake. A hydraulic model, as part of the design process, was built to examine potential countermeasures for vortex suppression. The final solution was a segmented barrier between the intake and the dam. It effectively suppressed the intake flow circulations; only minor intermittent vortices were left. The fabricated steel segments were anchored into the bedrock, stretching to 1.0 m below the lowest legal reservoir level. The local intake headloss was also reduced. The implemented solution was tested under full turbine loading and the result was satisfactory. Even during winter seasons with ice cover above the wall, the power station ran normally. The case study is expected to provide guidance for solving similar problems with vortex formation.

Place, publisher, year, edition, pages
Basel: MDPI, 2018
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-70324 (URN)10.3390/w10070881 (DOI)2-s2.0-85049645374 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-10 (andbra)

Available from: 2018-08-10 Created: 2018-08-10 Last updated: 2018-11-26Bibliographically approved
Yang, J. & Andreasson, P. (2016). Bending the spillway flow for safety upgrades. International Water Power and Dam Construction, 68(11), 36-43
Open this publication in new window or tab >>Bending the spillway flow for safety upgrades
2016 (English)In: International Water Power and Dam Construction, ISSN 0306-400X, E-ISSN 1538-6414, Vol. 68, no 11, p. 36-43Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Progressive Media Group, 2016
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-66652 (URN)2-s2.0-85033576873 (Scopus ID)
Available from: 2017-11-20 Created: 2017-11-20 Last updated: 2017-11-24Bibliographically approved
Andersson, R., Larsson, S., Hellström, G., Andreasson, P. & Andersson, A. (2016). Experimental Study of Head Loss over Laser Scanned Rock Tunnel (ed.). In: (Ed.), Experimental Study of Head Loss over Laser Scanned Rock Tunnel: Hydraulic Structures and Water System Management, ISHS 2016, Portland, United States, 27 - 30 June 2016. Paper presented at International Symposium on Hydraulic Structures : 27/06/2016 - 30/06/2016 (pp. 22-29). Portland: Utah State University
Open this publication in new window or tab >>Experimental Study of Head Loss over Laser Scanned Rock Tunnel
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2016 (English)In: Experimental Study of Head Loss over Laser Scanned Rock Tunnel: Hydraulic Structures and Water System Management, ISHS 2016, Portland, United States, 27 - 30 June 2016, Portland: Utah State University , 2016, p. 22-29Conference paper, Published paper (Refereed)
Abstract [en]

Flow in hydropower tunnels is characterized by a high Reynolds number and often very rough rock walls. Due to the roughness of the walls, the flow in the tunnel is highly disturbed, resulting in large fluctuations of velocity and pressure in both time and space. Erosion problems and even partial collapse of tunnel walls are in some cases believed to be caused by hydraulic jacking from large flow induced pressure fluctuations. The objective of this work is to investigate the effects of the rough walls on the pressure variations in time and space over the rock surfaces. Pressure measurement experiments were performed in a 10 m long Plexiglas tunnel where one of the smooth walls was replaced with a rough surface. The rough surface was created from a down-scaled (1:10) laser scanned wall of a hydraulic tunnel. The differential pressure was measured at the smooth surface between points placed at the start and end of the first four 2 m sections of the channel. 10 gauge pressure sensors where flush mounted on the rough surface; these sensors measure the magnitude and the fluctuations of the pressure on the rough surface. The measurements showed significant spatial variation of the pressure on the surface. For example, sensors placed on protruding roughness elements showed low gauge pressure but high fluctuations. The differential pressure indicated a head loss through the tunnel that was almost four times higher than a theoretical smooth channel.

Place, publisher, year, edition, pages
Portland: Utah State University, 2016
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-40310 (URN)10.15142/T360628160853 (DOI)2-s2.0-84988981565 (Scopus ID)f63f31d3-d2db-4351-8149-87a65d10ced0 (Local ID)978-1-884575-75-4 (ISBN)f63f31d3-d2db-4351-8149-87a65d10ced0 (Archive number)f63f31d3-d2db-4351-8149-87a65d10ced0 (OAI)
Conference
International Symposium on Hydraulic Structures : 27/06/2016 - 30/06/2016
Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-10-04Bibliographically approved
Jonsson, P., Andreasson, P., Hellström, G., Jonsén, P. & Lundström, S. (2016). Smoothed Particle Hydrodynamic Simulation of Hydraulic Jump using Periodic Open Boundaries (ed.). Applied Mathematical Modelling, 40(19-20), 8391-8405
Open this publication in new window or tab >>Smoothed Particle Hydrodynamic Simulation of Hydraulic Jump using Periodic Open Boundaries
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2016 (English)In: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 40, no 19-20, p. 8391-8405Article in journal (Refereed) Published
Abstract [en]

The natural phenomena hydraulic jump that is commonly used in spillways as an energy dissipater coupled to hydropower applications has been investigated with Smoothed Particle Hydrodynamics. A new approach was applied based on a periodic open boundary condition. The model consisted of a tank, a gate, a stilling basin and periodic open boundaries at each end of the computational domain. The tank provided a hydraulic head and in turn a specific flow through the gate, and a downstream condition in terms of a depth for the jump. The gate elevation had a major impact and was calibrated to ensure a correct and stable flow rate, when compared to experiments. With the proper flow rate, the position of the jump toe was significantly improved. The jump toe oscillated with a frequency in good agreement with experimental findings found in the literature and the oscillation amplitude increased with Froude number. However, for high Froude number cases the position was still too close to the gate but could be improved by including a correction based on the length of the jump. The depths in both the super- and subcritical zones was in good agreement with experiments and previous numerical studies. Furthermore, the Froude number was in-line with the definition of super- and subcritical flows.

National Category
Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Fluid Mechanics; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-6399 (URN)10.1016/j.apm.2016.04.028 (DOI)000383309700017 ()2-s2.0-84969548789 (Scopus ID)4a090de8-59cc-42e0-9d45-ab12699f7a57 (Local ID)4a090de8-59cc-42e0-9d45-ab12699f7a57 (Archive number)4a090de8-59cc-42e0-9d45-ab12699f7a57 (OAI)
Note

Validerad; 2016; Nivå 2; 2016-11-21(andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Jonsson, P., Jonsén, P., Andreasson, P., Lundström, S. & Hellström, G. (2015). Modelling Dam Break Evolution over a Wet Bed with Smoothed Particle Hydrodynamics: A Parameter Study (ed.). Engineering, 7(5), 248-260
Open this publication in new window or tab >>Modelling Dam Break Evolution over a Wet Bed with Smoothed Particle Hydrodynamics: A Parameter Study
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2015 (English)In: Engineering, ISSN 1947-3931, E-ISSN 1947-394X, Vol. 7, no 5, p. 248-260Article in journal (Refereed) Published
National Category
Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Fluid Mechanics; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-5032 (URN)10.4236/eng.2015.75022 (DOI)30d2b155-537b-4413-a041-bb19c11171e8 (Local ID)30d2b155-537b-4413-a041-bb19c11171e8 (Archive number)30d2b155-537b-4413-a041-bb19c11171e8 (OAI)
Note

Validerad; 2015; Nivå 1; 20150522 (stlu)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
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