A rotor blade for a wind turbine is provided. The rotor blade includes an aerodynamic device for influencing the airflow flowing from the leading-edge section of the rotor blade to the trailing edge section of the rotor blade. The aerodynamic device is mounted at a surface of the rotor blade and includes a pneumatic or hydraulic actuator, such as a hose a cavity, of which the volume depends on the pressure of a fluid being present inside the pneumatic or hydraulic actuator. The rotor blade further includes a control unit for controlling the pressure of the fluid in the hose or the cavity of the aerodynamic device.