This is a forum for discussion of topics relating to the Dreadnought era, prior to the ascendency of naval aviation. We will be discussing history, ship design, and naval wargaming.
Wednesday, August 25, 2004
Residual resistance tables
I have been working the issue of programmatically calculating power curves for ships for slightly more than two years. My previous approach had enough problems, that I set the problem down for about a year. I have picked it back up, and have taken a new tact. Instead of using sparse matrices, I am using complete matrices with all values populated.
As The Speed and Power of Ships has graphs that do not cover the space for all ships, I have assumed that they can be extended. The underlying assumption is that residual resistance is a continuous function and has no discontinuities. Given that, it is possible to extend the graphs, by plotting resistance, given the prismatic coefficient and the speed-length ratio, in one direction. The other necessity is to extend the graphs for greater displacement-length ratios, so that we can calculate power for 1860's ironclads. That requires displacement length ratios up to 420. The higher speed-length ratios are needed for fast destroyers that are fairly short. I am only computing for speed-length ratios up to 2.5, but I expect to have to go above 3.0, eventually.
I had done enough experiments that it seemed to be possible to get reasonable approximate figures, so I am going forward with the project. A useful aid has been the ability to look at data with line charts, using Excel spreadsheets. That speeds up the process, so I don't have to use paper and end up having to estimate numbers from pencil-drawn graphs.
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