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Model Requirements for the Holtrop Analysis |
  
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Model Requirements for the Holtrop Analysis |
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It is critical to satisfy various requirements for the model when running the Displacement Hull Holtrop Prediction. These are:
| - | MUST ONLY select external hull surfaces that are “wet” at the static waterline for which the analysis is being performed. Do not include appendages such as rudders. |
| - | MUST ONLY represent half of the hull |
| - | MUST have a transverse coordinate of 0 on the centerline |
| - | Integrated skegs may be included as part of the hull |
As a general statement, there is not a lot of difference between adding a skeg's volume and wetted surface as part of the "hull", versus independently treating it as an appendage. The viscous component of the skeg's drag is larger when evaluated as an independent appendage due to a shorter viscous length and Reynolds number, and corresponding higher frictional drag coefficient (plus a small form drag). On the other hand, there will be an increase in the predicted bare-hull wave-making drag when adding the skeg's displacement into the "hull". (The increase in wave-making drag is often proportionally many times greater than the increase in displacement.) So, what you gain in one, you lose in the other. The magnitude of the viscous and wave-making differences will depend on hull geometry and speed, but fortunately, the overall difference between the two approaches is rarely more than a few percent.
| - | MUST have a surface normal direction pointing outward into the water. The surface normal direction can be verified by selecting the surface, then selecting Direction from the Rhino Analyze menu. |
