EXPERIMENTAL INVESTIGATION OF TURBULENCE NEAR CYLINDERS

Model tests with locally generated turbulence near horizontal and vertical cylinders are reported. Turbulence is measured with newly developed ultra-sonic probes, and spectral density functions and auto-correlation functions are given. Tests are carried out in uniform currents, in sinusoidal waves, and in combinations of current and waves. Results are given for a viscous laminar boundary layer corresponding to a very fine sediment, and for a turbulent boundary layer corresponding to a hydraulically rough bottom. In Norway recent scour research, initiated by the North Sea oil operations, has been guided in three directions: 1) Scour around big gravity structures 2) Distribution of pore pressures in the ground under wave loads. 3) Local scour near unburied pipelines.