Drag Reduction of Deepwater Risers by the Use of Helical Grooves

Model tests were carried out in a towing tank to investigate the effects of helical grooves on the drag loading of stationary circular cylinders in uniform and steady currents. A series of models were made and tested, including smooth and rough cylinders with and without grooves. The maximum Reynolds number achieved in the tests was about 4×10⁵. The comparative results between the smooth and grooved cylinders show that the helical grooves reduce the drag loading by between 18 and 25% depending upon the cylinder surface roughness and the Reynolds number. This is a continuation of our work published in OMAE06 in Hamburg on VIV suppression by the use of helical grooves.