Marine Resistance prediction


#1

Hlw guys,
I am using A model of armored personnel carrier to predict its resistance in water at a speed of 6 knot. Now during laminer flow simulatoin i have had no problem but in case of turbulent flow simulation it is giving a problem saying - Inconsistent boundary condition types. Possibly the empty boundary conditions were not correctly assigned for a 2D mesh. Please check the boundary conditions.

As i am a newbie i am not understanding what is the mistake i have done in boundary condition. This is being used in my thesis project. So i require an expert advice from this forum. I would be grateful if anybody could find out what is the mistake i have done.

Thank you
Regards
Taufiq


#2

Hey @dungree!

Nice to see you so motivated using our platform for your projects :slight_smile: Could you share the project with us please so that we can have a closer look at it?

Cheers!

Jousef


#3

Hlw @jousefm,
Extremely sorry that i forgot to share the link. Link to the project is -

https://www.simscale.com/projects/dungree/resistance_prediction_of_armored_personnel_carrier_1/


#4

I followed the steps that was done by @dheiny in hull resistance analysis… Also i am expecting some expert advice from @sjoshi . I have last few days left to collect my result so i m kinda out of track if i cant figure it now. :frowning: .

Regards
Taufiq


#5

@PowerUsers_CFD, what is your opinion on that one? Will also try another simulation by myself later on.

Cheers!

Jousef


#6

I have a project here:

https://www.simscale.com/projects/1318980/resistance_prediction_of_armored_personnel_carrier/

produces no errors about boundary conditions, seems to be identical setup to David Heiny’s but is producing numerical instabilities. I’ll keep looking if you would like.

Kind regards,
Darren


#7

Mine is currently at 25% but as you said some instabilities are produced as well as time step continuity errors which might be fixed later on (maybe no need at single precision roundoff error…).

Will post my results later on. Cheers!

Jousef


#8

Hi @dungree!

I have performed two simulations. One with a “normal mesh” meaning that there is no refinement between both phases and another one called “refined mesh” where I have refined the phase boundary. You can have a look at both results. Please note that there are quite some oscillations that have been damped during the process by adapting some numerical settings (can also be seen inside the simulation of course). Let me know if you are satisfied with the results and give us some feedback.

Project link: 6DOF Simulation - Armored personnel carrier

All the best!

Jousef


#9

Hi @jousefm,
Many Many thanks for the help guys. This forum and as well as the platform itself is awesome. Too bad i came to know about it at end of my project. However i’ll talk to my professor about the result and let u guys update about this project. Force was said to be equalized at the end but for a mysterious reason it is not becoming so. i have used star ccm plus previously and maxsurf resistance module to validate the result. Even if i dont get the desired result it was only you guys who helped me promptly and took your valuable time to look after it. Keep the good works going. I ll be in touch always.

N.B;- Can u guide me about the Filter to generate a screenshot like yours in the online post processor. That would be very much helpful for me.

Regards
Taufiq


#10

Hi @1318980,
Thanks a lot or the help bro. I have had a look at the project. I ll show talk to my professor about the instability. Thanks a lot for kind gesture to look after my project and helping me. I ll update you about the project afterwards. Best of luck buddy.

Regards,
Taufiq


#11

Hi @dungree and thanks a lot for your kind words! We really do appreciate that and hope that we can help you with other projects as well :slight_smile: May I know which turbulence model you were using when using Star CCM or any other program (besides SimScale)?

Regarding the resources for post-processing I can recommend two links that may help you:

Please let us know if you like them and if you found what you were looking for. Wish you all the best!

Jousef


#12

Hlw @jousefm,
Welcome brother :slight_smile: . Following models i have used for physical model setup in star CCM plus-

Implicit Unsteady time group
Eulerian Multiphase Material group
Volume of Fluid (VOF) Multiphase Modelgroup
Turbulent viscous regime
and k-epsilon turbulence model
optional models were Gravity,Cell Quality Remediation, and VOF Waves

I have followed the step by step tutorial provided with the software and previously i messed up with dynamic fluid body interaction for calculating sink and trim. This time i have excluded the sink and trim calculation and rather opting for only resistance calculation.

Regards
Taufiq