towing force of self propulsion test

mehdinakisa1358 · April 28, 2015, 10:04

Hi Dear All,
I'm doing self propulsion test using CFX simulation. How can i calculate the towing force on ship model in Cfx? when propeller rpm changed how measure the towing force changing?

ghorrocks · April 28, 2015, 20:15

You can measure the force on a body using CEL expressions.

You change the rpm and then measure the force - simple.

mehdinakisa1358 · April 28, 2015, 23:59

yes, but i got more force of hull body after increasing the rpm. I need to measure the towing force not Resistance due to ship hull movement.
many thanks

ghorrocks · April 29, 2015, 01:19

Can you post an image of what you are modelling, what you have taken the force from and what you expect the force to be.

mehdinakisa1358 · April 29, 2015, 10:23

pls, imagine, the propeller behind the ship.
rpm is 200rpm. we have the thrust and ship hull resistance. I want to know how can determine the towing force in compare of propulsion test which is get the towing force towed by carriage.

Thanks

ghorrocks · April 29, 2015, 18:17

At a particular speed, if you have the hull resistance force and the propeller thrust force the towing force must be the force required to get these forces to balance.

mehdinakisa1358 · April 29, 2015, 23:59

Yes, very good. many thanks and appreciated.
Mehdi

Ngaru · January 24, 2021, 22:03

I am carrying out self-propulsion for ship model with a rotating propeller using OpenFOAM.
My propeller rotation motions are modelled using AMI.
My problem is that sometimes my propeller behind the hull is rotating however when I use fine mesh my propeller fails to rotate and the case appears like MRF.
I have tried different clearance between the propeller hub and ship bulb but I have not yielded very promising results.

If there is some with AMI knowledge kindly help me.

Best regards
Ngaru

ghorrocks · January 25, 2021, 01:15

Posting your question on the OpenFOAM forum would be a good start. This is the CFX forum.

April 28, 2015, 10:04	towing force of self propulsion test	#1
mehdinakisa1358 New Member mnfbhn Join Date: Mar 2013 Posts: 5 Rep Power: 13	Hi Dear All, I'm doing self propulsion test using CFX simulation. How can i calculate the towing force on ship model in Cfx? when propeller rpm changed how measure the towing force changing?

April 28, 2015, 23:59	towing force	#3
mehdinakisa1358 New Member mnfbhn Join Date: Mar 2013 Posts: 5 Rep Power: 13	yes, but i got more force of hull body after increasing the rpm. I need to measure the towing force not Resistance due to ship hull movement. many thanks

January 24, 2021, 22:03	Self-propulsion	#8
Ngaru New Member jaym Join Date: Aug 2019 Posts: 9 Rep Power: 7	I am carrying out self-propulsion for ship model with a rotating propeller using OpenFOAM. My propeller rotation motions are modelled using AMI. My problem is that sometimes my propeller behind the hull is rotating however when I use fine mesh my propeller fails to rotate and the case appears like MRF. I have tried different clearance between the propeller hub and ship bulb but I have not yielded very promising results. If there is some with AMI knowledge kindly help me. Best regards Ngaru

January 25, 2021, 01:15		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,848 Rep Power: 144	Posting your question on the OpenFOAM forum would be a good start. This is the CFX forum. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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April 28, 2015, 20:15		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,848 Rep Power: 144	You can measure the force on a body using CEL expressions. You change the rpm and then measure the force - simple.

April 29, 2015, 01:19		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,848 Rep Power: 144	Can you post an image of what you are modelling, what you have taken the force from and what you expect the force to be.

April 29, 2015, 10:23		#5
mehdinakisa1358 New Member mnfbhn Join Date: Mar 2013 Posts: 5 Rep Power: 13	pls, imagine, the propeller behind the ship. rpm is 200rpm. we have the thrust and ship hull resistance. I want to know how can determine the towing force in compare of propulsion test which is get the towing force towed by carriage. Thanks

April 29, 2015, 18:17		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,848 Rep Power: 144	At a particular speed, if you have the hull resistance force and the propeller thrust force the towing force must be the force required to get these forces to balance.

April 29, 2015, 23:59		#7
mehdinakisa1358 New Member mnfbhn Join Date: Mar 2013 Posts: 5 Rep Power: 13	Yes, very good. many thanks and appreciated. Mehdi