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Turning circle

saji vf

Hello ,

We are doing a turning circle simulation by giving radius and angular velocity in Rz motion (unsteady case) !

my doubt is:

1. how much time it will take to complete the  simulation if my body is an appended model with mesh size of 11M?

2. i ran the simulation for around 200 sec with time step size of 0.023 .

3. can you guide me how to proceed further to get the convergence and complete the simulation.

Thank you .

  • 0

    Hi,

    If you need to run 200 seconds of physical time, this means you need 8695 time steps to complete the simulation (since you are using a time step of 0.023s).

    So this will depends on the machine and the number of cores you are using, but if you imagine that each time step takes 30 seconds, you will need 72 hours.

    You can always activate the rotating frame method as well to get a more stable convergence (Mesh Management > Domain Mesh Management > Rotating frame method) since the rotation is here imposed.

    Best regards,

    Benoit

  • 0 in reply to Benoit Mallol

    Hello sir,

    in Z-axis gyration which velocity should be specified ,

    1. ship advancing velocity or angular velocity of the vessel in final velocity.

    2. my radius of the circle is 56.627, how to specify it.

    3. is it a single simulation or we should run resistance and restart from it. some best practices can you advice.

    Thank you.

  • 0 in reply to saji vf

    Hi,

    1. Since it is Rz and expressed in rad/s, it has to be the angular velocity.

    2. it corresponds to the gyration center. Only putting the "radius" would not be enough since it could be located anywhere in space. In the documentation, it is true that the picture shows [rad] but it is an old picture that should be updated. Gyration is expressed in meters in the GUI (see below).

    3. You can do it in 1 simulation or 2. For 1 simulation, you just need to prescribe "Initial time (t0)" to the time where the gyration will start. With 2 simulations it will be easier to avoid user mistakes: you perform a first convergence and when ok, you stop the simulation and make a restart from here, prescribing the gyration center from this position.

  • 0 in reply to Benoit Mallol

    Hello,

    When we do 2 simulations, first simulation we reach our convergence after that restarting my case from that and give the gyration center my doubt is, do we need to specify angular velocity too in z gyration or gyration center is enough.

    Thank you.

  • +1 in reply to saji vf

    Hi,

    Yes, you must specificy the angular velocity too, otherwise the ship will not turn. However, in the restart you might want to deactivate the Tx DOF since the rotation and its speed will be handled by Rz? Unless you want to combine both effects.

    Best regards,

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