Propeller nominal wake: KVLCC2

Seervan · November 27, 2017, 14:50

Hi all
I am trying to asses nominal wake fraction of a ship model: KVLCC2
I have determined the velocity contours at propeller disc. So my question is how to determine nominal wake fraction, w ?
The relation is w=1-Va/U which U is the ship or flow velocity.
My guess is that I extract the x-velocity values at propeller disc which are the Va values at every cell, then extract them as a XYZ table as .csv, then use the above formula to asses w at every cell, then take an average on them. Is this approach correct? Any ideas?
Tnx

wester · December 6, 2017, 11:58

After extracting the velocity components, you need to do some post-processing. Please have a look at the following document. There is a description about the post-processing.

https://ittc.info/media/4202/75-03-03-02.pdf

Seervan · December 10, 2017, 11:44

Thanks for the answer

By the way I also found a simple approach that can be useful and it satisfies the ITTC conditions. after forming the propeller disc and converged results, you can define a field function defining the wake. Then create an Surface Average Report within the pertaining node on the related disc. The Surface Average complies the wake integral formula suggested in the references such as "Marine propellers and propulsion" by Carlton, pp.67. Thus you don't need to tabulate the data on the disc and post process them in the hard way.
I validated the data with the MOERI experiment and there is good agreement.

Cheers

November 27, 2017, 14:50	Propeller nominal wake: KVLCC2	#1
Seervan Member Soroush Kargar Join Date: Apr 2017 Posts: 45 Rep Power: 9	Hi all I am trying to asses nominal wake fraction of a ship model: KVLCC2 I have determined the velocity contours at propeller disc. So my question is how to determine nominal wake fraction, w ? The relation is w=1-Va/U which U is the ship or flow velocity. My guess is that I extract the x-velocity values at propeller disc which are the Va values at every cell, then extract them as a XYZ table as .csv, then use the above formula to asses w at every cell, then take an average on them. Is this approach correct? Any ideas? Tnx

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December 6, 2017, 11:58		#2
wester New Member Dong Seo Join Date: Aug 2010 Posts: 4 Rep Power: 15	After extracting the velocity components, you need to do some post-processing. Please have a look at the following document. There is a description about the post-processing. https://ittc.info/media/4202/75-03-03-02.pdf

December 10, 2017, 11:44		#3
Seervan Member Soroush Kargar Join Date: Apr 2017 Posts: 45 Rep Power: 9	Thanks for the answer By the way I also found a simple approach that can be useful and it satisfies the ITTC conditions. after forming the propeller disc and converged results, you can define a field function defining the wake. Then create an Surface Average Report within the pertaining node on the related disc. The Surface Average complies the wake integral formula suggested in the references such as "Marine propellers and propulsion" by Carlton, pp.67. Thus you don't need to tabulate the data on the disc and post process them in the hard way. I validated the data with the MOERI experiment and there is good agreement. Cheers