Sampling volume location using Vectrino

Hi,

How do I know the exact distance of the sampling volume to the bottom using Vectrino? In your manual you say that the distance between the centre transducer and the sampling volume is approximately 5 cm; on the other hand he Vectrino gives me the distance from the centre transducer to the bottom. Since the first distance is approximated, how can I have the real distance of the sampling volume to the bottom?
This is very important for me since I have to calculate the wall shear stress based on the mean velocity gradient in the viscous sublayer (I can't apply the law of the wall because I have a recirculation)
Thanks.

Amy

Dear Amy

Don't you do the wall stress relative to the bottom? Maybe we are missing something but we have assumed that the critical number is the distance from the wall to the mid-point of the sampling volume?

Best regards, Atle Lohrmann

Moved to velocimeters