Heave damping characteristics of a buoy form Spar by CFD simulation and experimental studies

Spar hulls with standard configuration such as classic Spar with or without heave damping plates have been in use for several decades. Spar buoy, a deviation from vertical cylinder has been proposed as a support system for oil and gas exploration. A study to establish the heave damping characteristics of such system has been carried out using both CFD simulation and experimental studies in a laboratory wave flume. A classic Spar of 31 m diameter and two buoy form Spars of 20 m and 25 m diameter were considered for investigation. All the Spars have an equal moonpool diameter of 12.5 m. The Spar hulls have been designed for a topside load of 10000 tonnes with a total displacement of 65000 tonnes. The displacement and metacentric height were same for all the Spars. The experimental and the numerical investigation were conducted on a 1:100 Froude scale model of the spar. The free decay test was conducted in the wave flume. Numerical investigation of the heave damping was carried out using STAR-CCM+ software. Three dimensional, shear stress transport (SST) K-omega turbulent viscous regime domain (of size 2m×2m×3m) with multiphase material mixture (sea water and air), with water depth of 2 m is considered. Volume of fluid (VOF) method was used to solve the Reynolds Averaged Navier-Stokes (RANS) equation.