RU2781020C1 - Broaching prevention system - Google Patents

Abstract

FIELD: shipbuilding.

SUBSTANCE: invention relates to the field of shipbuilding and can be used in building and modernising ships. Broaching prevention system includes a floating anchor containing a shell made of a flexible material, linked with a folding frame attached to a tow bar and to a buoy, as well as a mechanism for folding/unfolding the frame and the shell. The mechanism for folding/unfolding the frame and the shell is equipped with control cables secured on the stern of the ship on both sides of the tow bar and, by means of a coupling, linked with the central control rod of the anchor, linked with the stiffeners of the folding frame by means of slings.

EFFECT: safety of marine navigation is increased.

1 cl, 7 dwg

Description

The invention relates to the field of shipbuilding and relates to means of increasing the directional stability of ships.

A ship hull is known, containing a skin reinforced with a set of elliptical frames, and the areas of the frames equidistant from the midship frame are equal to each other, which made it possible to reduce the wave resistance of the vessel (SU 816859, IPC V63V 1/06, publ. 30.03.1981 g .).

The disadvantage of this ship's hull is that on a tail wave, the occurrence of the phenomenon of broach is possible. Due to a sharp change in the speed of the flow around the ship's hull during the transition from the wave base to the top (Fig. 1, Fig. 2, Fig. 3), due to a decrease in towing resistance, the ship begins to accelerate (Fig. 4), and when descending from the top to the front slope waves, the nasal tip begins to flow around the flow at a higher speed, which leads to its deceleration. In this state, the ship, being on the border of motion stability, receives a random disturbance and sharply turns around with a lag to the wave, which can lead to capsizing (Chizhiumov S.D. Fundamentals of vessel dynamics in waves: textbook. - Komsomolsk-on-Amur: GOU VPO "KnAGTU", 2010. - S. 106-108.).

An anchor device is known (SU 463581, IPC V63V 21/48, publ. 03/15/1975), containing several parachute anchors made of an elastic shell with slings attached to the towing cable, and the parachute anchors are fixed in series at a certain distance one from another on the same cable.

The disadvantages of this anchor device include the fact that it cannot be used to prevent the vessel from turning sideways to the wave and capsizing it in broach conditions, because. installation and opening of the anchor requires considerable time, and the process of an uncontrolled turn of the vessel with a lag to the wave occurs very quickly, as a result of which the navigator will not even have time to make an appropriate decision and issue a command to launch the anchor device into the water.

A system for preventing broaching is known (RU 2620849, IPC V63V 43/02, V63V 39/06, V63N 25/44, publ. 30.05.2017), containing stabilizer wings fixed on the hull of the vessel. The hull is made with recesses on the bow end for the stabilizer wings fixed in the recess on the side of the bow of the vessel with the possibility of rotation about the vertical axis, and each recess is equipped with an elastic element, the rigidity of which is chosen such that it ensures the deflection of the stabilizer wing from the hull, provided that the ship's speed relative to the water flow is less than the specified value.

The disadvantage of this broaching prevention system is that the stabilizer wings are installed in the bow of the vessel, therefore, when the bow of the vessel approaches the wave base, where the particle velocity in the wave can be directed against the direction of the vessel (Fig. 2), the stabilizer wings can not open, as a result of which, in the conditions of a favorable wave, the vessel can be turned sideways to the wave and capsized.

As the closest analogue, a floating anchor is adopted, containing a shell of a flexible material, a folding frame connected at one end to a buoy, and at the other - to a plumb line, while the folding frame is attached with slings to the towing rod, and the mechanism for folding the frame and shell having a brace. In order to expand the operational capabilities by using the anchor as a rudder to control the direction of drift and increase the reliability of the anchor, the shell is made with channels that are interconnected by longitudinal membranes and are made with longitudinal walls fixed on their sides and connected to slings. The anchor is equipped with a traverse with sling attachment points located along it, connected by its ends to the towing rod, and a control unit, and the folding frame is made in the form of a hinged multiple parallelogram, sequentially edging all the inlets of the shell channels with its links (SU 1358295, IPC V63V 21/48 , published on October 27, 2004).

A significant disadvantage of this floating anchor is that it is not included in the work in the event of a turn of the vessel in a horizontal plane with a sharp displacement of the aft end in the lateral direction, which occurs in the case of broach (Chizhiumov S.D. Fundamentals of the dynamics of ships in waves: textbook. allowance - Komsomolsk-on-Amur: GOU VPO "KnAGTU", 2010. - S. 106-108.). As a result of this, a vessel on a favorable sea may become unstable on its course, turn around with a lag to the wave and capsize. The occurrence of this phenomenon is associated with a change in the velocity of the flow around the body when it hits the top of the wave and then passes to its forward slope (Fig. 1 and Fig. 2). At the top of the wave, there is a sharp decrease in the towing resistance of the vessel (Fig. 4), as a result of which it begins to accelerate. After hitting the front slope, the flow velocity changes, the forward motion of the vessel begins to slow down. This process is unsteady, in addition, due to the non-stationarity of the water flow in the propeller disk, its thrust is continuously changing, which is reflected in the dynamics of the ship. Because Since this situation is developing rapidly, the navigator is not able to make the right decision and control a floating anchor of a known design to adjust the vessel's motion mode. As a result, the ship, being on the front slope of the wave, can be turned around relative to the initial direction of movement, while creating the preconditions for the ship to roll over under the action of a capsizing moment, which is formed due to the difference in hydrodynamic pressures on the sides.

The invention solves the problem of improving the safety of navigation, excluding the occurrence of broaching, by providing an automatic response of the system to a sharp displacement of the aft end of the vessel in the lateral direction and creating conditions for the emergence of forces that counteract the displacement and contribute to the return of the vessel to its original position.

To obtain the required technical result in a broach prevention system, including a floating anchor containing a shell made of flexible material, connected to a folding frame attached to a towing rod and a buoy, a frame and shell folding/unfolding mechanism, it is proposed to equip the frame and shell folding/unfolding mechanism with controls ropes, which are fixed at the stern of the vessel on both sides of the towing rod, and connected by means of a coupling to the central control rod of the anchor, which, using slings, is proposed to be connected to the stiffening ribs of the folding frame.

In the proposed technical solution, in the event of the beginning of the turn of the vessel in a horizontal plane on a favorable wave, one of the control cables is tensioned (when the stern is shifted to the right, the right cable is pulled out, when the stern is shifted to the left, the left one), the central control rod of the floating anchor is moved to the ship's hull and the folding frame and shell made of flexible material, due to which a hydrodynamic force is created that acts in the area of the aft end of the vessel in the direction opposite to the initial direction of movement of the vessel, as a result, the stability of the vessel on the course increases and the possibility of its turning lag to the wave and capsizing is excluded.

The attached graphics show:

in fig. 1 - wind wave profile;

in fig. 2 - change in the horizontal component of the velocity of surface particles along the wavelength:

in fig. 3 - trajectory of particles in a wind wave;

in fig. 4 - curve of the vessel's towing resistance;

in fig. 5 - ship with installed broaching prevention system;

in fig. 6 - node I in FIG. 5;

in fig. 7 is section A-A in FIG. 6.

The following designations are used on graphic materials:

1 - control cable;

2 - towing traction;

3 - arc guide;

4 - towing traction support bracket;

5 - slings;

6 - stiffening ribs of a floating anchor;

7 - central control rod of a floating anchor;

8 - coupling for fastening control cables;

9 - shell made of flexible material;

10 - roller;

11 - ship's hull;

12 - buoy;

,

- длина троса управляющего по левому и правому борту соответственно, м;

,

- length of the control cable on the port and starboard sides, respectively, m;

x - horizontal coordinate axis, m;

y - vertical coordinate axis, m;

u _x - horizontal component of particle velocity in the wave, m/s;

υ _c - vessel speed, m/s;

R _with - towing resistance of the vessel, kN.

The design of the broach prevention system consists of a floating anchor containing a folding frame made of stiffening ribs 6 of the floating anchor and a shell 9 made of flexible material. The folding frame is attached to the hull 11 of the vessel with the help of a towing rod 2 and is connected to the buoy 12. The ends of the stiffening ribs 6 of the floating anchor are connected by means of slings 5 to the central control rod 7 of the floating anchor, the other end of the rod 7 is connected by means of a coupling 8 to the control cables 1, attached to the hull 11 of the vessel at the aft end. The towing rod 2 is connected to the bracket 4 of the support of the towing rod 2, equipped with a roller 10 installed in the guide arc 3, attached to the hull 11 of the vessel at the aft end.

The broach prevention system works as follows. When operating the ship in conditions of slight waves and when moving on the oncoming waves, the floating anchor is taken out of the water so as not to create additional water resistance to the movement of the ship.

When the vessel is moving in conditions of fair waves, when there may be a danger of broaching, a floating anchor containing a folding frame of ribs 6 of the stiffness of the floating anchor and a shell 9 of flexible material is launched into the water and held at a predetermined distance from the water surface by means of a buoy 12. At the same time towing rod 2, through which the forces from the floating anchor are transmitted to the hull 11 of the vessel, is connected to the bracket 4 to support the towing rod 2, equipped with a roller 10 installed in the guide arc 3. This design avoids getting the towing rod 2 into the propeller operation area. In this case, the movement of the roller 10 in the guide arc 3 allows the towing rod 2 to rotate freely relative to the hull 11 of the vessel.

To study the emergence of the phenomenon of broach, one should consider the features of a real wind wave. According to (Shuleikin V.V. Physics of the sea. M.: Nauka, 1968. - 1080 p.), the profile of wind waves deviates from the trochoidal one, while the tops of the waves become more pointed, and the soles become flatter. The general equations of the family of curves to which the wind wave profiles belong are written as:

where θ - phase angle, rad;

a, b - semiaxes of some ellipse, m;

R is the radius of the rolling circle, m.

The radius of the rolling circle is determined by the expression:

where λ is the wavelength, m.

Ellipse parameters are determined from the conditions:

where h - wave height, m;

- радиус производящей окружности, м;

- radius of generating circle, m;

- осредненное на протяжении длины волны значение скорости дрейфового течения, м/с;

is the drift current velocity averaged over the wavelength, m/s;

υ=ω⋅r ₀ - speed of particle movement along the circumference, m/s;

ω - circular frequency of the wave, rad/s.

The conducted studies (Shuleikin V.V. Physics of the sea. - M.: Nauka, 1968. - 1080 p.) showed that the trajectory of particles in a wave is quite complex and contains loops. Here, in accordance with the elementary theory of trochoidal waves, the rotational motion of particles is superimposed on translational motion, explained by the Stokes effect (“wave” flow), as well as drift from the action of the wind. In this case, both components of the translational motion are not constant, but continuously change along the wavelength.

According to (Shuleikin V.V. Physics of the sea. - M.: Nauka, 1968. - 1080 p.), the instantaneous value of the horizontal velocity of a particle in a wave u _x can be determined from the expression

It can be seen that the horizontal component of the velocity of particles in the wave varies along its length.

.The calculation results using formulas (1) - (5) are shown in Fig. 1 - fig. 3. The calculation was performed for a wave with a length of λ=30 m and a height of h=3 m at averaged over the wavelength value of the drift current velocity

.

Let us consider the influence of the change in the speed of the flow around the hull on the dynamics of the ship in a tail wave using the example of the Tuntselov-1 type MTF of project 1331, which has a length between perpendiculars of 30 m and a maximum displacement of 367 tons. Let the ship move at a speed of 6 m/s, being on the back slope waves in the region of its base, where the velocity of fluid particles is close to zero (Fig. 2). In this case, according to FIG. 4 the towing resistance of the vessel is about 58 kN. After hitting the top of the wave, the speed of the vessel relative to the aquatic environment will decrease due to the fact that the particles of the liquid have a speed of about 2.5 m/s (Fig. 2), directed in the direction of the vessel. Under such conditions, the towing resistance of the ship will decrease by more than 6 times and will be about 9 kN (Fig. 4), because of this, the speed of the ship will begin to increase.

A sharp decrease in the towing resistance of the vessel will also lead to the fact that the propeller of the vessel will become hydrodynamically light, so the engine speed will begin to increase. As a consequence of everything described, the mode of movement of the vessel in such conditions will be unsteady.

After the vessel is on the front slope of the wave, and its bow approaches its sole, the bow of the vessel will be in a zone where liquid particles move at low speed in the direction of the vessel or even in the opposite direction, while the stern of the vessel will be in conditions of associated flow at a significant speed. As a result, the nasal tip will begin to slow down due to a sharp increase in the resistance forces on it, because. according to fig. 2, the velocity of the liquid particles in the region of the wave base can be directed opposite to the direction of the vessel's motion.

In such conditions, the mode of motion of the ship is unsteady. Therefore, the forces of resistance and drift, as well as the moment acting on the hull, depend not only on the magnitude of the parameters that determine the state of motion at every moment, but also on the nature of the entire process preceding this state (Nebesnov V.I. Engine dynamics in the hull system Vessel - Propellers - Engines - L.: Sudpromgiz, 1961. - 374 p.) The nature of the process during such movements of the vessel is extremely complex. The curvilinearity of the trajectory of the ship's center of gravity, yaw, as well as changes in the conditions of interaction between propellers, rudders and the ship's hull determine the change in time of the angles of attack at various points of the diametrical plane and local velocities of the water flow. In this regard, the vessel can be turned sideways to the wave and capsized.

In the case of the implementation of the proposed system to prevent broaching, if the ship begins to turn lag to the original course, then the tension of one of the control cables 1 weakens, and the other increases (if the stern is shifted to the left, then the left control cable 1 is pulled, if to the right, the right control cable 1 Due to the tension of the control cable 1, connected by means of the coupling 8 for fastening the control cables with the central control rod 7 of the floating anchor, it moves in the direction of the ship hull 11. In this case, the central control rod 7 of the floating anchor acts on the slings 5, which turn the stiffeners 6 floating anchor, forming a folding frame, and open the shell 9 of flexible material.After opening the shell 9 of flexible material on the floating anchor, there is a hydrodynamic force transmitted by means of towing rod 2 to the hull 11 of the vessel at the aft end.

As a result, a force acts on the aft end of the hull 11 of the vessel, directed opposite to the initial course of the vessel. This force ensures the stability of the vessel on the course and eliminates the possibility of a sharp turn of the vessel with a log to the wave and its capsizing. A ship with a traditional design does not have sufficient stability in conditions of tail waves and, due to random disturbances, often turns perpendicular to the original direction of movement and capsizes.

и центральная управляющая тяга 7 плавучего якоря перемещается в направлении от корпуса 11 судна. Это сопровождается уменьшением натяжения строп 5, поворотом ребер 6 жесткости плавучего якоря в первоначальное положение и закрытием оболочки 9 из гибкого материала, что, в свою очередь, ведет к резкому уменьшению гидродинамической силы, действующей на плавучий якорь, в результате чего он не оказывает существенного влияния на буксировочное сопротивление судна.Under the action of a force acting on the aft end of the hull 11 of the vessel, the vessel begins to turn in the opposite direction in the horizontal plane and returns to its original course. In this case, the tension of the control cable 1 weakens, the lengths of the control cables 1 from the left and right sides are aligned

and the central control rod 7 floating anchor moves in the direction from the hull 11 of the vessel. This is accompanied by a decrease in the tension of the lines 5, the rotation of the stiffening ribs 6 of the floating anchor to its original position and the closing of the shell 9 of flexible material, which, in turn, leads to a sharp decrease in the hydrodynamic force acting on the floating anchor, as a result of which it does not have a significant effect on the ship's towing resistance.

It should be noted that an extreme situation associated with the occurrence of broach can develop rapidly in conditions of significant uncertainty. In such conditions, a person is practically not able to make the right decisions on the management of the ship, and his actions can only aggravate the situation. In particular, the helmsman, seeing the turn of the ship to the side (for example, to the right) and not knowing that the flow around the ship's hull is coming from the stern, seeks to return the ship to its previous course by turning the rudder to the left, which turns the ship even faster with a lag to the wave and creates prerequisites for the ship to capsize under the action of a capsizing moment, which is formed due to the difference in hydrodynamic pressures on the sides. Therefore, the use in such a situation of the design of the closest analogue, as well as other known designs of floating anchors, the operation of which is carried out by the crew, will not ensure the safety of the vessel.

Thus, the proposed design increases the directional stability of the vessel on a fair wave, prevents the vessel from turning sideways to the wave, which makes it possible to avoid capsizing the vessel, and, consequently, increase the safety of navigation.

Claims (1)

Broaching prevention system, including a buoyant anchor containing a shell of flexible material connected to a folding frame attached to the towing rod and buoy, a frame and shell folding/unfolding mechanism, characterized in that the frame and shell folding/unfolding mechanism is equipped with control cables fixed at the stern of the vessel on both sides of the towing rod and by means of a coupling connected to the central control rod of the anchor, which is connected by means of slings to the stiffening ribs of the folding frame.

Images