Boundary conditions

Henry Arrigo · July 23, 2010, 11:18

hi all
I want to run a boat with a thrust force in a domain. I suppose there shouldn 't be any inlet or outlet. so my problem is how to define the boundaries. remember the domain is a cubic which has 6 faces as boundaries. Now I m confused how to assign boundaries. can you please help me fellas? I would be so thankful

regards.
henry

sail · July 26, 2010, 05:47

Hi Henry. I belive it depends on what are you looking for.

i would suggest to calculate an approximate speed your boat will reach with a given thrust, set inlet velocity at that speed, take care that the boat have some margin to move foward or aft a bit and than wait and see what happen.

btw, may i ask why are you using this approach instead the simpler given speed ---> which resistance i go?

Henry Arrigo · July 26, 2010, 18:03

Hi sail
Thanks for your reply
The reason I want to do so is that I want to study the sea-keeping and maneuverability of the boat.
The only way I can do this is to push the boat with a thrust force in a 6DOF manner.
Do yo have any idea how to run this simulation

sail · July 27, 2010, 05:48

i'm afraid i don't know how to help you with the maneuvrability analysis, but for the seakeeping i still let the flow have some speed. this will avoid running the simulation in the whole accelleration time and just concentrate on the speed you are looking after.

than the trust applied to the boat will give oscillation in speed as she encounters the waves.

i take you have already looked at the tutorial on the 6dof.

if you want do have a real 6dof with maneuverabilty and all, i don't know. i've heard from a cd adaptco representative in turin that he did it using a macro file to remesh everything but i might as well have misunderstood the procidings.

please let me know if you make some advancements.

Henry Arrigo · July 27, 2010, 06:33

for the sea-keeping you are right. but for the maneuverability i suppose there is no need to remesh the domain. because star-CCM+ uses the moving domain approach, and move the whole domain with the mesh. fore example in the tut 6DOF that you mentioned,if you take a look at the domain in various time steps, you ll see the domain is rotating with the mesh. this is a well known approach in 6 DOF CFD analysis.
i ll keep you posted if i get any new info.
can you please put your email over here to be in contact.
tnx

July 23, 2010, 11:18	Boundary conditions	#1
Henry Arrigo Senior Member Henry Arrigo Join Date: Jun 2010 Location: Italy Posts: 100 Rep Power: 15	hi all I want to run a boat with a thrust force in a domain. I suppose there shouldn 't be any inlet or outlet. so my problem is how to define the boundaries. remember the domain is a cubic which has 6 faces as boundaries. Now I m confused how to assign boundaries. can you please help me fellas? I would be so thankful regards. henry

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July 26, 2010, 05:47		#2
sail Senior Member Vieri Abolaffio Join Date: Jul 2010 Location: Always on the move. Posts: 308 Rep Power: 16	Hi Henry. I belive it depends on what are you looking for. i would suggest to calculate an approximate speed your boat will reach with a given thrust, set inlet velocity at that speed, take care that the boat have some margin to move foward or aft a bit and than wait and see what happen. btw, may i ask why are you using this approach instead the simpler given speed ---> which resistance i go?

July 26, 2010, 18:03		#3
Henry Arrigo Senior Member Henry Arrigo Join Date: Jun 2010 Location: Italy Posts: 100 Rep Power: 15	Hi sail Thanks for your reply The reason I want to do so is that I want to study the sea-keeping and maneuverability of the boat. The only way I can do this is to push the boat with a thrust force in a 6DOF manner. Do yo have any idea how to run this simulation

July 27, 2010, 05:48		#4
sail Senior Member Vieri Abolaffio Join Date: Jul 2010 Location: Always on the move. Posts: 308 Rep Power: 16	i'm afraid i don't know how to help you with the maneuvrability analysis, but for the seakeeping i still let the flow have some speed. this will avoid running the simulation in the whole accelleration time and just concentrate on the speed you are looking after. than the trust applied to the boat will give oscillation in speed as she encounters the waves. i take you have already looked at the tutorial on the 6dof. if you want do have a real 6dof with maneuverabilty and all, i don't know. i've heard from a cd adaptco representative in turin that he did it using a macro file to remesh everything but i might as well have misunderstood the procidings. please let me know if you make some advancements.

July 27, 2010, 06:33		#5
Henry Arrigo Senior Member Henry Arrigo Join Date: Jun 2010 Location: Italy Posts: 100 Rep Power: 15	for the sea-keeping you are right. but for the maneuverability i suppose there is no need to remesh the domain. because star-CCM+ uses the moving domain approach, and move the whole domain with the mesh. fore example in the tut 6DOF that you mentioned,if you take a look at the domain in various time steps, you ll see the domain is rotating with the mesh. this is a well known approach in 6 DOF CFD analysis. i ll keep you posted if i get any new info. can you please put your email over here to be in contact. tnx