Calculating FRAM’s Dead Water
The internal wave (dead water) resistance on the Polar ship FRAM is obtained by two methods. The first is empirical, based on the original observations (Nansen, F.: Farthest North, Westminster: Archibald Constable and Company, 2 Whitehall Gardens, 1897. Vol. 1). The second is a strongly nonlinear interfacial method in three dimensions. The intersection between the empirical and theoretical resistances determines accurately the ship speed which is investigated varying the depth of the pycnocline, a quantity that was not measured by Nansen. A reduction to a fifth of the usual speed of the FRAM because of the dead water, as observed by Nansen, corresponds to a mid-depth of the pycnocline of slightly less than 4 m while FRAM’s draught was 5 m. The wave wake at Froude number slightly above 0.5 is calculated by the nonlinear method. The linear ship wake and dead water resistance are found to be invalid.
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