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planing hull

saji vf

Hello , we are doing a case on planing hull which contains a single step and interceptor, and when it comes to my issue is

1.when we keep the interceptor at the back of the transom trim will increase or decrease?

2. how to run a unsteady case of planing hull because i want to see the heave and pitch motion and how much time it will take for the simulation.

3. can we do a planing hull simulation without using savitsky method when we dont know our final trim .

thank you

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  • +1

    Hi,

    - For 1, I guess this is a question of naval architecture, not about CFD here. :-)

    - 2. As soon as you activate a multi fluid model (air and water), you are in a Steady mode where time matters. This is mandatory for VOF models with a 6 DOF solver where motions are solved. Moving on to Unsteady will still solve the exact same equations but will be more accurate in time taking into account what happened 2 time steps ago instead of just 1. In other words, the Steady mode for multi fluid corresponds to the mode where you expect a "steady"/"stabilized" result.

    - 3 solutions here: a) you use Savitsky and it will estimate the final trim for you (you do not have to do it yourself), b) you can indeed impose an expected final trim angle but it does not have to be accurate or c), you forget about the Savitsky mode and start the simulation from flat condition (0 speed). Here, you might have to activate the overset feature to accept large mesh deformation since planing hulls usually have large trim angles. However, with overset, simulation time increases by a factor 2.

    Best regards,

    Benoit

Reply
  • +1

    Hi,

    - For 1, I guess this is a question of naval architecture, not about CFD here. :-)

    - 2. As soon as you activate a multi fluid model (air and water), you are in a Steady mode where time matters. This is mandatory for VOF models with a 6 DOF solver where motions are solved. Moving on to Unsteady will still solve the exact same equations but will be more accurate in time taking into account what happened 2 time steps ago instead of just 1. In other words, the Steady mode for multi fluid corresponds to the mode where you expect a "steady"/"stabilized" result.

    - 3 solutions here: a) you use Savitsky and it will estimate the final trim for you (you do not have to do it yourself), b) you can indeed impose an expected final trim angle but it does not have to be accurate or c), you forget about the Savitsky mode and start the simulation from flat condition (0 speed). Here, you might have to activate the overset feature to accept large mesh deformation since planing hulls usually have large trim angles. However, with overset, simulation time increases by a factor 2.

    Best regards,

    Benoit

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