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General HydroStatics
Ship Stability Software |
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Command of the Week
(New or interesting aspects of GHS that you may not know about) |
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GROUND /FLOOR (review)
(Requires GHS version 15.88 or later with Condition Graphics) |
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GROUND /FLOOR allows the user to define the "seafloor" using one of two methods: 1) a data file containing real-world bathymetry data of the area around the vessel, or 2) a constant depth.
When using the file option, points on the seafloor are specified with a location and a depth sounding. The location of each point may be in standard length units, such as feet or meters, and referenced from a seafloor datum, or latitude and longitude coordinates using the degrees-minutes-seconds format, e.g. 48d8'39.03", -122d45'17.0136". When using the constant depth option, the seafloor is oriented parallel to the waterplane at the specified depth and extended in all directions. Part of the power of GROUND /FLOOR is realized when it is used iteratively. If the attitude or condition of a vessel changes, a new call to GROUND /FLOOR will update the ground points to reflect the new condition. Take, for example, the following scenario: The LCG and TCG of the fishing vessel are initially set off-center to induce heel and trim. Using the constant depth option, the floor is then decreased to simulate an outgoing tide. Once the vessel is out of the water, the LCG and TCG are shifted back to normal, and the vessel is re-floated. |
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In this simulation, one may see how the ground points attempt to "follow" the most critical grounding locations on the vessel as the floor decreases. The ground points also reflect the shift in LCG and TCG. As the floor increases, the zero heel condition results in a symmetrical pattern.
The run file used to create this example may be downloaded here. |
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Questions, comments, or requests?
Contact Creative Systems, Inc. USA phone: 360-385-6212 Fax: 360-385-6213 Office hours: 7:00 am - 4:00 pm Pacific Time, Monday - Friday Mailing address: PO Box 1910 Port Townsend, WA 98368 USA Click here for an index to this and previous COWs |