A method for cleaning a gas turbine unit. The invention further relates to a nozzle for use in washing the gas turbine unit. The nozzle is arranged to atomize a wash liquid in the air stream in an air intake of the gas turbine unit and comprises a nozzle body comprising an intake end for intake of said wash liquid and outlet end for exit of said wash liquid. The nozzle further comprises a number of orifices that are connected to the outlet end and respective orifice is arranged at a suitable distance from a center axis of said nozzle body, whereby the local density of the injected wash liquid in a desired area can be increased with preserved droplet size and thereby the efficiency of the cleaning process can be significantly improved at the same time as the risk for damaging the components in the gas turbine unit is significantly reduced.