Abstract
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.
Highlights
Hydropower Development in SwedenIn Sweden, an abundance of river streams that connect with more than 100,000 lakes gives the country’s landscape a unique character and beauty
Most of the hydropower dams in Sweden were built before 1980
Perhaps the most significant benefit of the model tests is the identification of unexpected problems that are disregarded in the design process
Summary
In Sweden, an abundance of river streams that connect with more than 100,000 lakes gives the country’s landscape a unique character and beauty. There are approximately 1000 hydropower dams of varying size and age (one power station has two or more dams). The largest river is the Lule älv river with 15 large dams, ten of which are situated north of the Arctic Circle. They account for approximately 10% of the hydroelectric production in the country. The largest power plant is the 945 MW Harsprånget on the Lule älv river, operating at a 107 m head and a 1040 m3 /s turbine flow rate. Vänern on the Göta älv river is the largest hydropower reservoir, with a 9400 Mm3 active storage volume. Can CFD predict reasonably accurate as a design tool without physical model testing? What is the accuracy? Can CFD predict reasonably accurate as a design tool without physical model testing? (3) To explain the sources of errors associated with both the physical and numerical modeling
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