A Numerical Estimation Method for Thrust Deduction Fraction of Ships under Ice Conditions

Abstract

The invention provides a method for estimating the numerical value of the thrust deduction fraction of a ship under ice layer conditions. 1. Carry out numerical simulation of the water resistance of the bare hull based on the target ship, and collect the water resistance of the bare hull at different speeds. 2. Based on the target ship, carry out numerical simulation of self-propulsion behind the ship, and collect water resistance, effective propeller thrust and torque at different speeds and speeds. Through the definition of thrust deduction, the thrust deduction of the ship in water is solved. 3. Carry out self-propulsion simulation after the ship through the self-propulsion model of the target ship with attached ice, and collect water resistance, propeller effective thrust and torque at different speeds and speeds. Thrust derating in ice is performed based on the difference in effective thrust, and the thrust derating fraction in ice water is obtained. This method takes into account the influence of ice on the wake field and the blocking effect of ice on the propeller, and ignores the influence of direct contact between crushed ice and the propeller, which can effectively solve the problem of large errors in the calculation of thrust derating by conventional ships.

Description

technical field [0001] The invention relates to a method for predicting ship performance in ice areas, in particular to a method for estimating thrust derating of ships under ice. Background technique [0002] The ice layer condition is one of the main working conditions of polar ships. Layer ice formed by natural conditions is a common situation in polar navigation. When a polar ship encounters a layer of ice, a large ice load will be generated, which makes the research on the propulsion performance of polar ships different from that of conventional ships. [0003] In a conventional ship towing test, the ship's towing force is balanced against the resistance of the bare hull. In the conventional ship self-propulsion test, the total thrust of the ship is balanced with the resistance of the bare hull and the increase in resistance under the interaction of the propeller. The physical origin of the increase in resistance is due to the accelerated flow of the fluid before and...

AI Technical Summary

Problems solved by technology

The ice-water interaction shows that the crushed ice attached to the bottom of the hull moves forward with the hull and flows to the stern, which causes the wake field in the area not originally affected by the propeller to change, thus affecting the propulsion performance.

[0004] The research on the navigation performance of polar ships in the ice layer mainly relies on model tests and early real ship data, and is limited to numerical methods at the present stage. It is very difficult to use numerical simulation methods to estimate thrust deduction under ice layer conditions. The reason is that the direct realization of the estimation of thrust deduction under the condition of layer ice involves ship-ice-propeller-flow multiphase coupling, and the mechanism of action is very complicated

Some researchers will directly use the thrust deduction calculation method of conventional ships to complete the thrust deduction estimation method of polar ships, and the error is relatively large

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