New velocity file set for measurements of water-air flows

For the primary time, researchers at D-BAUG have measured air-water flows with velocities exceeding 40 m/s. To this finish, two difficult measurement campaigns have been carried out within the tunnel spillway of a 225 m excessive dam, for which particular probes first needed to be developed. With the brand new knowledge, current design tips will be validated, and so-called scale results will be assessed extra precisely. This is related for the secure operation of hydraulic buildings.

High-velocity air-water flows typically happen in hydraulic buildings similar to spillways or low-level shops at dams. Air entrainment impacts the movement properties of the air-water combination and should subsequently be thought-about within the design of such buildings. Existing design tips are based on small-scale mannequin assessments. However, since sure related processes can’t be scaled arbitrarily, so-called scale results might happen when upscaling from the lab to prototypes. Validation knowledge from prototypes are subsequently all of the extra essential for the secure design of dams and hydropower buildings.

However, because of the excessive effort concerned, such in-situ measurements of air-water flows are fairly uncommon. The final comparable measurements date again to the Nineteen Seventies, the place movement velocities of round 20m/s have been achieved—a spread that may now even be investigated in small-scale fashions. During a three-year examine, researchers from the Laboratory of Hydraulics, Hydrology and Glaciology developed particular measuring devices along with companions from the Water Research Laboratory on the University of New South Wales, Australia. The two measurement campaigns passed off in 2019 and 2020 within the tunnel spillway of the Luzzone Dam in Switzerland.

The examine is a crucial step towards a greater understanding of scale results for air-water flows. It confirms settlement with current empirical design equations for some bulk air-water movement properties similar to imply air focus, whereas extra detailed properties similar to droplet measurement are considerably influenced by scale results. Thereby, the examine helps to improves design suggestions of safety-relevant hydraulic buildings similar to spillways and low-level shops at dams.

The analysis was revealed within the Journal of Hydraulic Engineering.