Signature 1000 - Reynolds stresses, Noise

Up to Current profilers and current meters

Signature 1000 - Reynolds stresses, Noise

Posted by Jan Tiede at August 02. 2017

Hi,

 

I'm setting up a Nortek Signature 1000 for Reynolds stress estimations in a tidal channel. I was wondering which of the burst modes provided by the device is preferable for that. As far as I can tell both the 4 beam burst and the 5 beam burst modes allow rapid measurements. Furthermore I was wondering about the noise level of both modes and how to determine the level.

 

Thanks!

 

Best Regards

 

Jan

Re: Signature 1000 - Reynolds stresses, Noise

Posted by Steven Figueroa at September 19. 2017

Hi Jan,

 

I have experienced calculating Reynolds stresses in tidal channels with the signature.  In the deployment wizard, it will tell on the right the horizontal and vertical velocity precisions.  To reduce noise, I think you have to keep those low (~ 1 cm/s?).  It can be done by using large bin sizes, less sampling frequency, and a smaller velocity range (i.e. more precision at cost of less spatiotemporal resolution).  When I calculated TKE and Reynolds stress before knowing this, they were overestimated by two orders of magnitude (see a post of mine in the forum) compared to a simultaneously deployed vector.

 

I would like to know how to reduce the velocity range, as I am testing signature turbulence measurements on an intertidal flat.  But, my feeling now is that the Signature is better suited for turbulence measurements in deeper (~10 m) sites, as velocity precision seems to fall quickly with decreasing cell size.

 

 Not sure about 4 and 5 beam bursts, I wonder, too.

Re: Signature 1000 - Reynolds stresses, Noise

Posted by Steven Figueroa at September 19. 2017
Previously Steven Figueroa wrote:

Hi Jan,

 

I have experienced calculating Reynolds stresses in tidal channels with the signature.  In the deployment wizard, it will tell on the right the horizontal and vertical velocity precisions.  To reduce noise, I think you have to keep those low (~ 1 cm/s?).  It can be done by using large bin sizes, less sampling frequency, and a smaller velocity range (i.e. more precision at cost of less spatiotemporal resolution).  When I calculated TKE and Reynolds stress before knowing this, they were overestimated by two orders of magnitude (see a post of mine in the forum) compared to a simultaneously deployed vector.

 

I would like to know how to reduce the velocity range, as I am testing signature turbulence measurements on an intertidal flat.  But, my feeling now is that the Signature is better suited for turbulence measurements in deeper (~10 m) sites, as velocity precision seems to fall quickly with decreasing cell size.

 

 Not sure about 4 and 5 beam bursts, I wonder, too.

 

EDIT: information about configuring the velocity range (VR) is in another post.  There is also the getprecision command in the terminal emulator.

Re: Signature 1000 - Reynolds stresses, Noise

Posted by Jan Tiede at October 06. 2017
Previously Steven Figueroa wrote:
Previously Steven Figueroa wrote:

Hi Jan,

 

I have experienced calculating Reynolds stresses in tidal channels with the signature.  In the deployment wizard, it will tell on the right the horizontal and vertical velocity precisions.  To reduce noise, I think you have to keep those low (~ 1 cm/s?).  It can be done by using large bin sizes, less sampling frequency, and a smaller velocity range (i.e. more precision at cost of less spatiotemporal resolution).  When I calculated TKE and Reynolds stress before knowing this, they were overestimated by two orders of magnitude (see a post of mine in the forum) compared to a simultaneously deployed vector.

 

I would like to know how to reduce the velocity range, as I am testing signature turbulence measurements on an intertidal flat.  But, my feeling now is that the Signature is better suited for turbulence measurements in deeper (~10 m) sites, as velocity precision seems to fall quickly with decreasing cell size.

 

 Not sure about 4 and 5 beam bursts, I wonder, too.

 

EDIT: information about configuring the velocity range (VR) is in another post.  There is also the getprecision command in the terminal emulator.
Hi Steven,
 
thanks for your insights they are very helpful.
 
I could not find the post about configuring the velocity Range. Could you point me to it?
 
Cheers
 
Jan
Powered by Ploneboard
Log in


Forgot your password?
New user?