RU2147540C1 - Method of check of ship seaworthiness - Google Patents

Abstract

FIELD: shipbuilding; technology of checking of ship seaworthiness during her service. SUBSTANCE: method is based on measurement of rolling period and determination of metacentric height through calculations. In calculating the metacentric height, drafts fore and aft, apparent period, relative bearing and ship's speed at irregular waves are additionally measured. Besides that, the following magnitudes are measured; angular displacement relative to transversal and vertical axes, linear and angular acceleration relative to longitudinal, transversal and vertical central axes. Depth of water under keel at ship'' midship section is additionally measured to determine the factor of shallow waters. According to this factor, the actual metacentric height and speed are determined to ensure safe navigation of ship. EFFECT: enhanced reliability of estimation of safe operation of ship in shallow waters. 1 dwg

Description

 The invention relates to shipbuilding, in particular to methods for monitoring the seaworthiness of a vessel under operating conditions, and can be used to create expert navigation safety systems.

 A known method of monitoring seaworthiness [1], based on measuring the rolling period and determining the calculation of the methancentric height, when calculating which additionally measure the bow and stern, the apparent wave period, course angle and speed of the vessel on irregular waves, as well as angular movements relative to the transverse and vertical axes and linear and angular accelerations relative to the longitudinal, transverse and vertical central axes.

 The invention is aimed at improving the reliability of assessing the safety of operation of a vessel in shallow water by controlling stability and adverse events that occur when the vessel moves on a limited fairway.

 The technical result is achieved by additionally measuring the depth of the water under the keel in the midship of the vessel, establishing a factor characterizing the presence of shallow water, and depending on this factor, determining the actual methancentric altitude and speed mode, ensuring the safe operation of the vessel.

 The drawing shows a structural-functional diagram of a device that implements the proposed method.

 The method of monitoring the seaworthiness of the vessel is as follows.

 The heading angle of the wave, the speed of the vessel, the apparent period of the wave, the bow draft are measured, the angular displacements relative to the longitudinal, transverse and vertical central axes, the linear and angular accelerations of all types of oscillatory motion of the ship on the wave as a dynamic system with six degrees of freedom and simultaneously record the depth H water under the keel in the middle of the ship.

характеризующий наличие влияния мелководья, где T_Н - средняя осадка, замеренная в условиях мелководья по способу [1];

- средняя длина волны, м;

- средний период волны, с; h_3% - 5,28

- высота волны 3%-ной, обеспеченности; D_ζ - дисперсия волновых ординат, определенная по способу [1].According to the measurements, the displacement, metacentric height and the appropriate CT are applied, the stability and other seaworthiness of the vessel are estimated, for which the spectral density and parameters of sea waves, dispersion of displacements, speeds and the average frequency of oscillations of the wave profile relative to the hull, dispersion and average frequency are calculated oscillations of the minimum immersion of the axis of the propeller, the yaw dispersion, the dispersion of the projections of the acceleration vector during the oscillatory motion of the vessel on a wave, as well as factor

characterizing the presence of the influence of shallow water, where T _N is the average sediment measured in shallow water according to the method [1];

- average wavelength, m;

- the average period of the wave, s; h _3% - 5.28

- wave height of 3% security; D _ζ is the dispersion of the wave ordinates, determined by the method [1].

F(H_W/T_H)=0,013[3,5-(H_W/T_H)]+0,0076 [3,5-(H_W/T_H)]²,
2. Характерных явлений, возникающих при движении судна на ограниченном фарватере:
- увеличения средней осадки
T_н> T_∞ при Fr_Н > 0,3;
- наличия ходового дифферента
ψ_н> ψ_∞ при Fr_Н > 0,6;
- возможности удара днища судна о ложе фарватера
H_w< 1,3T_н,
где

- число фруда по глубине; V_Н - скорость судна на мелководье, замеренная по способу [1], м/с; G - ускорение силы тяжести, м/с²; T_∞, ψ_∞ - значения средней осадки и дифферента на глубокой воде, замеренные по способу [1]; ψ_н - величина дифферента на мелководье.Based on these data, an assessment is made of:
1. Actual metacentric height
h _n = h _∞ (C _n / C _∞ ) ² ,
where h _∞ is the metacentric height in deep water calculated by the method [1]; C _n / C _∞ - the relative value of the inertial coefficient in deep water and shallow water, determined by the formula:

F (H _W / T _H ) = 0.013 [3.5- (H _W / T _H )] + 0.0076 [3.5- (H _W / T _H )] ² ,
2. The characteristic phenomena that occur when the vessel moves on a limited channel:
- increase in average precipitation
T _n > T _∞ for Fr _H >0.3;
- presence of running trim
ψ _n > ψ _∞ for Fr _H >0.6;
- the possibility of hitting the bottom of the vessel on the bed of the channel
H _w <1.3T _n
Where

- the number of fruits in depth; V _N - ship speed in shallow water, measured by the method [1], m / s; G - acceleration of gravity, m / s ² ; T _∞ , ψ _∞ - mean rainfall and trim in deep water, measured by the method [1]; ψ _n - the value of the trim in shallow water.

 The described procedures for processing measurement data are carried out using special processors and a high-speed personal computer and are implemented in an expert system that allows you to evaluate the seaworthiness of the vessel and make informed decisions to eliminate adverse events when the vessel moves on a limited fairway and ensure operational safety.

 The device (see drawing) contains sensors for heading angle 1 and vessel speed 2, the values of which are entered into the computer using display 22, sediment sensors with bow 3 and stern 4, angular displacement sensors during oscillatory motion of the vessel relative to longitudinal 5, transverse 6 and vertical 7 axes, acceleration sensors 8-13 of all types of motion of the vessel on a wave, the depth gauge of the water under the keel on the midship of the vessel 14, the signals from which through the switching and preprocessing unit 15 are sent to specialized processors for further processing: a quarrel-classifier 16, which allows to analyze the measured signals in order to establish their statistical characteristics, check the stationarity property, identify their distributions and estimate the spectral densities, a processor editor 17, which performs editing of emissions and scaling of the measured signals, and a metrological processor 18, which performs periodic self-checking, self-calibration and correction of measurements. The database 20 and the knowledge base 21 of the expert system are controlled by an intelligent processor of a high-speed computer 19, which also provides an interface with the user through a color graphic display 22, printing the results 23 and interaction between specialized processors 16 and 17.

Literature
1. Patent of the Russian Federation N 2040429, IPC B 63 B 39/04, published. 07/27/95.

Claims (1)

 A method of monitoring the seaworthiness of a vessel based on measuring the rolling period and calculating a metacentric height, the calculation of which further measures precipitation by the bow and stern, the apparent wave period, course angle and speed of the vessel on irregular waves, as well as angular movements relative to the transverse and vertical axes, linear and angular accelerations relative to the longitudinal, transverse and vertical central axes, characterized in that they additionally measure the depth of the water under the keel in the middle of the vessel, tanavlivayut factor characterizing the presence of shallow water, and depending on this factor determines the actual metacentric height and speed mode that provides operation safety of the ship.