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Responder a: Quiz avançado – PNA resistência

#4528
fabio
Mestre

Segue o feedback da questao, podemos continuar o topico discutindo em cima deste texto. Para mim ele esclarece o item II que vc esta em dúvida, observe que merchant ships são low speed ships para o PNA, sempre.

I – In the average merchant-ship form, additional trim by the stern in the at-rest condition usually results in an increase in resistance at low speeds and a decrease at high speeds. At low speeds the increased draft aft makes the stern virtually fuller, with a consequent increase in form and separation resistance, whereas at high speeds this is more than offset by the reduction in wave-making due to the finer entrance in the trimmed condition. pg 41

II – In general, except in high-speed ships, the total resistance per unit of displacement will be greater … In ballast condition it is usually necessary to carry considerable trim by the stern in order to ensure adequate immersion of the propeller, and this will have similar effects to those stated in the foregoing—higher resistance at low speeds, less at high speeds. pg 42

III – In ballast condition, at level trim, the wetted surface per unit of displacement is much increased, so that the frictional resistance is increased also, but because of the finer form at the reduced draft, the residuary resistance is decreased. pg 42

IV – In ballast condition, at level trim, the wetted surface per unit of displacement is much increased, so that the frictional resistance is increased also, pg 42

  • Esta resposta foi modificada 4 anos, 5 meses atrás por fabio.