Method for retrofitting vortex generators on a wind turbine blade

1. A method of retrofitting vortex generators on a wind turbine blade, the wind turbine blade being mounted on a wind turbine hub and extending in a longitudinal direction and having a tip end and a root end, the wind turbine blade further comprising a profiled contour including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending there between, the profiled contour, when being impacted by an incident airflow, generating a lift, the method comprising

feeding a suction side flow with particles and depositing the particles on a surface of the suction side of the wind turbine blade creating a particle deposit on the surface of the suction side of the wind turbine blade,

determining a distribution of the particle deposit on at least a section of the suction side of the wind turbine blade and identifying a separation line based on the distribution of the particle deposit on the suction side of the wind turbine blade, and

mounting one or more vortex panels, including a first vortex panel comprising at least one vortex generator, on the suction side of the wind turbine blade between the separation line and the leading edge of the wind turbine blade, wherein the distribution of deposit is measured by determining at least one parameter indicative of an amount of deposit in a plurality of measurement points or zones on a suction side of a wind turbine.

2. The method according to claim 1 , wherein a first parameter indicative of the amount of deposit is the thickness of deposit in the measurement points or zones.

3. The method according to claim 1 , wherein a second parameter indicative of the amount of deposit is the color of the measurement points or zones.

4. The method according to claim 1 , wherein mounting one or more vortex panels comprises mounting one or more vortex panels at a distance from the separation line in the range from 0.1 meter to 1.5 meters.

5. The method according to claim 4 , wherein the distance from the separation line is in a range from 0.2 meter to 1 meter.

6. The method according to claim 5 , wherein the distance from the separation line is in a range from 0.25 meter to 0.75 meter.

7. The method according to claim 6 , wherein the distance from the separation line is about 0.5 meter.

8. The method according to claim 1 , wherein a length of the wind turbine blade is at least 40 meters.

9. The method according to claim 8 , wherein the length of the wind turbine blade is at least 50 meters.

10. The method according to claim 1 , wherein identifying the separation line on the suction side of the wind turbine blade is at least 40 meters.

11. The method according to claim 1 , wherein the method comprises

applying a separation line indicator to the suction side of the wind turbine,

operating the wind turbine for a period of time, and

wherein identifying the separation line on the suction side of the wind turbine blade is based on the separation line indicator during or after the operation of the wind turbine.

12. The method according to claim 11 , wherein the separation line indicator is a coating facilitating deposit of material on or removal of the coating during operation.

13. The method according to claim 11 , wherein the separation line indicator comprises pressure sensitive paint.

14. The method according to claim 11 , wherein the separation line indicator comprises powder.

15. The method according to claim 11 , wherein the separation line indicator comprises one or more tufts.

16. The method according to claim 1 , wherein identifying the separation line on the suction side of the wind turbine blade comprises identifying the separation line at a distance from the root end in a range from 0.1 L to 0.4 L, where L is a length of the wind turbine blade.

17. The method according to claim 1 , wherein identifying the separation line comprises determining a direction of wind flow in a plurality of measurement points or zones on the suction side of the wind turbine during operation and identifying the separation line based on the wind flow direction at the plurality of measurement points or zones.