Abstract: For prediction of flood-induced low-frequency noises under the joint discharge from multi-tunnels, turbulent flows are numerically simulated to analyze velocity distributions and vorticity fluctuation characteristics and identify vortex structures, and noise intensities are predicted based on the vortex sound theory. The results show the vortex structures are concentrated around the jet nappe plunging location and its downstream region where flow shear is intense. And large-scale vortex structures can be observed such as hairpin vortices and horseshoe vortices in the plunge pool. Data analysis reveals that several dominant frequencies of vorticity pulsation are in the range of 0-2 Hz, and the predicted sound pressure level (SPL) can reach up to 140 dB. However, it is reduced to 122 dB at a distance of 1 km from the pool under the dissipation effects of water-air interfaces and atomized droplets.

Key words: low-frequency noise, spillway tunnel, numerical simulation, vorticity fluctuation, vortex sound theory