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- Andersson, Robin, et al.
(author)
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Experimental Study of Head Loss over Laser Scanned Rock Tunnel
- 2016
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In: Experimental Study of Head Loss over Laser Scanned Rock Tunnel. - Portland : Utah State University. - 9781884575754 ; , s. 22-29
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Conference paper (peer-reviewed)abstract
- 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.
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| 3. |
- Hedberg, P. A. Mikael, 1989-, et al.
(author)
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Numerical modelling of flow in parallel spillways
- 2020
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In: Proceedings of the 8th IAHR International Symposium on Hydraulic Structures ISHS2020. - : The University of Queensland.
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Conference paper (peer-reviewed)abstract
- Mathematical modelling of single spillways is well documented in literature. For parallel spillways however, there is a lack of documented, verified, and validated cases. Here, in this article, ANSYS-CFX is used to simulate the flow over three parallel ogee-crested spillways. For mesh size verification, a grid convergence study is performed by Richardson extrapolation. The turbulence model chosen for this simulation is the k-ε model and the volume of fluid method is used to simulate the water-air interface. This article details the models ability to accurately predict flow distribution at the spillways, and the water levels. The mesh is kept relatively coarse at the channel inlet with increased mesh density at the spillways. The results are validated against experimental data from Vattenfall AB, R&Ds laboratories. The geometry and boundary conditions of the experiment are tailored for CFD. The flow rate of each spillway is measured separately with high accuracy, and for several different inlet volumetric flows. The simulation results lie within the error estimates of the measuring tools used in the experiments, within ±1%. The volume flow rate differences between the three outlets is very small, within ±1%.
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| 7. |
- Ahrens, Jens, 1978, et al.
(author)
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Tutorial on scaling of the discrete fourier transform and the implied physical units of the spectra of time-discrete signals
- 2020
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In: 148th Audio Engineering Society International Convention.
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Conference paper (peer-reviewed)abstract
- The combination of the time-discrete property of digital signals together with the commonly employed definition of the discrete Fourier transform (DFT) can cause ambiguity when interpreting magnitude spectra with respect to the physical unit of the signal under consideration. Standardized scaling of spectra increases the comparability of frequency-domain data that are published in scientific articles or data sheets of commercial products. We present and discuss in this tutorial a collection of the most relevant scaling options for DFT spectra to yield amplitude spectra, power spectra, and power density spectra, and we illustrate how an implied physical unit of the underlying signal is reflected by the magnitude of the spectrum. The tutorial is accompanied by Matlab/Octave scripts that demonstrate the different cases.
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| 8. |
- Almefelt, Lars, 1968, et al.
(author)
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Exploring Requirements Management in the Automotive Industry
- 2003
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In: 14th International Conference on Engineering Design Research for Practice - innovative products, processes and organisations.
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Conference paper (peer-reviewed)abstract
- This paper presents an empirical study carried out in the automotive industry, with the aim to bring forward new experiences and knowledge on management of requirements in practice. Adopting a qualitative systems approach, and using multiple information sources, the requirements management process during the development of a passenger car cockpit has been mapped out. The logical reconstruction of the requirements management process is complemented with descriptions of associated phenomena, such as important events and attitudes. Findings are presented, analysed and discussed considering also factors underlying observed phenomena.
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| 9. |
- Andersson, Anders G., et al.
(author)
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A numerical study of the location and function of the entrance of a fishway in a regulated river
- 2010
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In: 8th International Symposium on ECOHYDRAULICS. ; , s. 277-284
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Conference paper (peer-reviewed)abstract
- Simulation driven design with Computational Fluid Dynamics has been used to evaluate the flow downstream a hydropower plant with regards to upstream migrating fish. Field measurements with an Acoustic Doppler Current Profiler were performed and the measurements were used to validate the simulations. The measurements indicate a more unstable flow than the simulations and the tailrace jet from the turbines is stronger in the simulations. The simulations are however considered to capture the important features of the flow in a way that makes them viable for attraction water simulations. A fishway entrance was included in the simulations and the subsequent attraction water was evaluated for two positions and two angles of the entrance at different turbine discharges. Results show that both positions are viable and that a position where the flow from the fishway does not have to compete with the flow from the power plant will generate superior attraction water. Simulations were also performed further downstream where the flow from the turbines meets the old river bed which is the current fish passage for upstream migrating fish. A modification of the old river bed was made in the model as one scenario to generate better attraction water. This considerably increases the attraction water although it cannot compete with the flow from the tailrace tunnel.
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