A bench-marking activity of numerical methods for analysis of Wave Energy Converters (WEC) was proposed under the Ocean Energy Systems (OES) International Energy Agency (IEA) Task 10 in 2015. The purpose of the benchmark is to do a code-2-code comparison of the predicted motions and power take out for a WEC. A heaving sphere was used as a first simple test case. The participants sim- ulated heave decay and regular and irregular wave cases. The numerical methods ranged from linear methods to viscous methods solving the Navier-Stokes equa- tions (CFD). An overview of the results from the first phase of the benchmark was reported in [1]. The present paper focus on the simulations of the sphere using one fully nonlinear time-domain BEM one transient RANS method and one transient Direct FE method with no turbulence model. The theory of the three methods as well as the modeling of the sphere are described. Heave decay and heave motions for steep regular waves were selected as test cases in order to study and compare the capability to handle nonlinear effects. Computational efficiency and applicability of the three methods are also discussed
