Method for determining the flow of a fluid close to a surface of an object immersed in the fluid

Method for determining the flow of water, in particular seawater or freshwater or brackwater, close to a surface of a boat immersed in the water by analyzing at least one confocal measurement volume in the water, comprising the steps of:

• focusing light into the at least one confocal volume within the water;
• detecting and determining the luminescence of at least one particle comprised in the confocal volume, which is measured by Fluorescence Correlation Spectroscopy FCS;
• and
• determining the flow velocity of the water along the object immersed in water, preferably along parts of a boat, in particular its hull, keel or rudder, based on the determination of the luminescence using a correlation function, in particular an auto correlation function or a cross correlation function.

Method for determining the flow of water, in particular seawater or freshwater or brackwater, close to a surface of an object immersed in the water by analyzing at least one confocal measurement volume in the water, comprising the steps of:

• focusing light into the at least one confocal volume within the water;
• detecting and determining the reflexion of at least one particle in the confocal volume, wherein the following steps are comprised:
• irradiating the at least one particle in the at least one confocal volume, imaging the confocal volume on detecting means for detecting the reflexion intensity of reflected light from of the particle, recording of the reflexion intensity by the detecting means,
• determining the flow velocity of the water along the object immersed in water, preferably along parts of a boat, in particular its hull, keel or rudder, based on a correlation function, in particular an auto correlation function or a cross correlation function, depending from the recorded reflexion intensity.