Numerical investigation of the aerodynamic and wake characteristics of a floating twin-rotor wind turbine under surge motion

•Aerodynamics and wake of a twin-rotor floating wind turbine are carefully studied.•Effect of surge motion on power and wake of twin-rotor floating turbine is evaluated.•A comparison of aerodynamic and wake of single and twin rotors is implemented.•Wake model for a twin-rotor floating wind turbine is firstly proposed.•Maximum power gain reaches 13% for the twin-rotor floating wind turbine.