High Lateral- and Temporal-Resolution Current Sampling: Measurement Set-Up and Some Findings Available to Purchase

This paper presents two high temporal resolution current measurement campaigns where the current is sampled and stored at a frequency of 1Hz. One of the campaigns also included high lateral resolution measurements. The measurements were part of the current measurement program conducted by the Ormen Lange project. The measurements are rather unique and the first successful campaigns of its kind on the Norwegian Continental Shelf. The main objective of these measurements was to measure the turbulence characteristics of the current flow. This was regarded as important input to the design of the numerous free pipeline spans in the Ormen Lange development resulting from the very uneven seabed in the area. The frequencies of particular importance were the frequencies of the first eigenmodes of the free pipeline spans being in the range 0.1–1 Hz. The measurements confirm the shape of the turbulence following the Kolmogorov –5/3 decay law in this frequency range. Measurements along the pipeline route did not reveal any significant differences in the near seabed turbulence intensity along the route. Extrapolating the measurements into a near seabed record mean current speed of 0.5m/s gives a turbulence intensity of approximately 0.1. The high lateral resolution measurements demonstrate local topographic influence on record mean current. This concerns topographic steering, damping and amplification of current speed.