Study of air compressibility effects on the aerodynamic performance of the IEA-15 MW offshore wind turbine

•• Compressibility effects of the IEA-15 MW wind turbine are examined.•• Compressibility effects have a significant effect on aerodynamic of the large wind turbine.•• A detailed analysis the compressible results for the tip airfoil and the rotor is presented.•• The compressibility effects on the wake of the IEA-15 MW turbine are discussed.•• Validations of the numerical method against experimental data are performed.