KR102121833B1 - System and method for calculating frictional resistance of floating ice based on hull shape information - Google Patents

Abstract

The present invention distinguishes the modeled hull surface into a plurality of linear grids, and considers the dynamic fluid force according to the increase in the ship's ship speed, based on the normal vector values for each linear grid and the results of calculating the area and buoyancy for each linear grid. The present invention relates to a system and method for calculating frictional resistance of floating ice based on linear information capable of accurately calculating normal force and frictional resistance acting on the hull surface.

Description

System and method for calculating frictional resistance of floating ice based on linear information{SYSTEM AND METHOD FOR CALCULATING FRICTIONAL RESISTANCE OF FLOATING ICE BASED ON HULL SHAPE INFORMATION}

The present invention relates to a system for calculating frictional resistance of floating ice based on linear information and a calculation method, more specifically, to distinguish a modeled hull surface into a plurality of linear grids, normal vector values for each linear grid, and each linear grid Based on the result of calculating the area and buoyancy of each star, the frictional resistance calculation system of floating ice based on linear information that can accurately calculate the normal force and frictional resistance acting on the surface of the hull considering the dynamic fluid force according to the increase in the ship's ship speed, and It is about the calculation method.

In general, the frictional resistance is basically determined by the vertical force and friction coefficient generated in the vertical direction to the hull surface by the buoyancy of the floating ice in contact with the hull. However, as shown in FIG. 1, the fluid force acting on the floating ice can be assumed to be a static pressure when the ship's speed is very small, but additional dynamic pressure should be considered as the ship's speed increases, but the current estimation method does not take this into account. .

When the bow angle is defined as shown in FIG. 2, the vertical force F _n acting on the bow is determined by the buoyancy force and the dynamic fluid force. In addition, the tangential force F _t can be estimated by F _t =μF _n by the friction coefficient and the vertical force.

Therefore, the resistance F _H acting in the opposite direction to the progress of the hull and F _V acting in the vertical direction are as follows.

(1) F _H =F _n cosβ+F _t sinβ=F _n (cosβ+μsinβ)

(2) Fv=F _n sinβ-F _t cosβ=F _n (sinβ-μcosβ)

According to equations (1) and (2), it can be seen that the friction force plays a role of reducing the vertical force F _V. Therefore, when the dynamic fluid force is generated according to the increase in the speed of the ship, it can be seen that the vertical force F _n changes, and thus, the buoyancy resistance as well as the frictional resistance change, and the resistance directly appears.

On the other hand, the surface of the hull is a three-dimensional curved surface, and geometric information of the hull surface is essentially required to calculate the buoyancy and frictional forces acting on the hull surface.

For example, a process of gridding the hull surface into a plurality of parts as shown in FIG. 3 and calculating the buoyancy resistance and frictional resistance in each grid is required. In this process, a normal vector perpendicular to the surface in each grid is required.

In general, the vertical normal vector on the surface defines one of two directions perpendicular to the surface as a positive (+) direction as shown in FIG. 4. At this time, the lattice and the node of the hull surface discretized with triangular elements often do not have a uniform alignment system as shown in FIG. 4, resulting in a problem that the direction of the surface normal vector is inconsistent.

When the dynamic fluid force acting on the floating ice is generated according to the increase in the speed of the ship, the vertical force change, the buoyancy resistance change, and the frictional resistance also change, whereas at present, the fluid force acting on the floating ice without considering the dynamic fluid force has a very high linear velocity. Since it is assumed to be a static pressure when it is small, there is a limit in evaluating accurate frictional resistance.

Korean Patent Publication No. 10-1999-0071792

The present invention is derived to solve the above-mentioned problems, and distinguishes the modeled hull surface into a plurality of linear grids, based on the result of calculating the normal vector values for each linear grid and the area and buoyancy for each linear grid. , We intend to provide a method for evaluating frictional resistance of floating ice based on linear information that can accurately calculate the normal force and frictional resistance acting on the hull surface in consideration of the dynamic fluid force according to the increase in the ship's ship speed.

The frictional resistance calculation system for floating ice based on linear information according to an embodiment of the present invention uses a node information obtaining unit to obtain node information for one or more linear grids constituting the hull surface of the modeled hull model data, using the node information The one or more linear grids by using the grid node setting unit for aligning and setting the linear grid nodes for each of the one or more linear grids, the normal vector calculation unit for calculating the normal vectors for the one or more linear grids, and the calculated normal vector. It may include a friction resistance calculating unit for selecting a linear grid in which buoyancy occurs, and calculating frictional resistance acting on the hull model data using buoyancy acting on the selected area of each linear grid.

In one embodiment, the node information acquiring unit may be characterized in that the hull model data modeled from a CAD file is loaded.

In one embodiment, the node information may be characterized in that lattice planes and panel points of the one or more linear lattices implemented in hexadecimal numbers are implemented by converting to ASCII codes.

In one embodiment, the grid node setting unit sets a direction toward a fluid region as a reference normal vector direction among two directions perpendicular to a surface of the one or more linear grids, and among the one or more linear grids, a first linear grid and If there is a second linear lattice that is adjacent and shares one side, the node of the second linear lattice is changed so that the reference normal vector direction of the second linear lattice matches the reference normal vector direction of the first linear lattice. It can be characterized by rearranging.

In one embodiment, the frictional resistance calculator selects one or more linear lattices that generate buoyancy among the one or more linear lattices using the dynamic pressure distribution of the hull surface estimated through computational fluid analysis (CFD) technique, and selects The area and buoyancy for each of the one or more linear grids are calculated, and normal force and frictional resistance acting on the hull model data may be calculated using the calculated area and buoyancy values.

A method of calculating frictional resistance of floating ice based on linear information according to another embodiment of the present invention comprises obtaining node information for one or more linear grids constituting the hull surface of the modeled hull model data, and using the node information Reordering and setting the linear grid nodes for each of the linear grids, calculating the normal vectors for the one or more linear grids, and using the calculated normal vectors, selecting a linear grid generating buoyancy among the one or more linear grids Then, using the buoyancy acting on the selected area of each linear grid may include calculating the frictional resistance acting on the hull model data.

In one embodiment, acquiring node information for the one or more linear grids may include loading the modeled hull model data from a CAD file.

In one embodiment, the node information may be characterized in that lattice planes and panel points of the one or more linear lattices implemented in hexadecimal numbers are implemented by converting to ASCII codes.

In an embodiment, the step of aligning and setting a normal vector perpendicular to the surface of the one or more linear grids may set a direction toward a fluid region as a reference normal vector direction among two directions perpendicular to the surface of the one or more linear grids. And a second linear lattice adjacent to the first linear lattice and sharing one side among the one or more linear lattices, a reference normal vector direction of the second linear lattice and a reference normal of the first linear lattice And reordering the nodes of the second linear grid to match the vector directions.

In one embodiment, the step of calculating the frictional resistance acting on the hull model data is one in which buoyancy is generated among the one or more linear grids using the dynamic pressure distribution of the hull surface estimated through CFD technique. Selecting the linear gratings above, calculating the area and buoyancy for each of the selected one or more linear gratings, and calculating the normal force and frictional resistance acting on the hull model data using the calculated area values and buoyancy values. It may include.

According to an aspect of the present invention, since it is possible to calculate a constant normal vector in consideration of the adjacency of adjacent hull lattices, the normal force and frictional resistance acting on the surface of the hull are accurately calculated in consideration of the dynamic fluid force according to the increase in the speed of the hull. It has the advantage of being able to.

1 is a view showing the vertical force and friction coefficient due to the buoyancy of the floating ice generated in the vertical direction on the surface of the hull.
2 is a view showing the bow angle and the action force of the hull surface.
3 is a view showing a vertical unit vector for the hull grid of the hull surface represented by the curved surface.
4 is a diagram showing an example of a normal vector that is inconsistent with the direction in which the nodes of the linear lattice on the CAD file are directed.
5 is a view showing the configuration of the frictional resistance calculation system 100 of floating ice based on linear information according to an embodiment of the present invention.
6 is a view showing the hydrodynamic pressure values generated on the hull surface of the modeled hull model data.
FIG. 7 is a view showing nodes and directions in which the nodes of the linear grating are directed and directions in which the nodes of the linear grating are directed on the CAD file.
8 is a diagram illustrating a table for rearranging nodes using adjacent sides of a linear grid and a process of rearranging nodes of the linear grid using these tables.
9 is a view showing a state in which the normal vectors are aligned on the surface of the hull.
10 is a view showing a process of calculating a normal vector in a linear grid.
11 is a view showing a process of calculating the frictional resistance of the floating ice through the system for calculating the frictional resistance of the floating ice based on the linear information shown in FIG. 5 in a sequence.

Hereinafter, preferred embodiments are provided to help understanding of the present invention. However, the following examples are only provided to more easily understand the present invention, and the contents of the present invention are not limited by the examples.

5 is a view showing the configuration of the frictional resistance calculation system 100 of floating ice based on linear information according to an embodiment of the present invention, and FIG. 6 is a hydrodynamic pressure value generated on the hull surface of modeled hull model data FIG. 11 is a view showing a process of calculating the frictional resistance of the floating ice through a system for calculating the frictional resistance of the floating ice based on the linear information shown in FIG. 5 in a sequence.

5, 6 and 11, the frictional resistance calculation system 100 of floating ice based on linear information according to an embodiment of the present invention is largely obtained from the node information acquisition unit 110, the grid node setting unit 120, It may be configured to include a normal vector calculation unit 130 and the friction resistance calculation unit 140.

Here, each part may refer to an intangible software configuration for implementing each function, not a typed physical configuration, and the frictional resistance calculation system 100 for floating ice based on linear information in the present invention is a computer. It may be implemented in the form of software or programs executable on the device.

First, before explaining the present invention, the relationship between the motion of floating ice and the flow around the hull will be examined.

Referring to Figure 6, the basic concept is to assume that the motion of floating ice past the bow is correlated with the flow around the hull. That is, the floating ice moves to the bottom of the ship, makes contact with the hull, and the area that generates resistance and friction by buoyancy is affected by the distribution of dynamic pressure generated by the flow around the hull. As shown in FIG. 6, the dynamic pressure distribution around the moving hull is actually applied to the hull by the static pressure, and the dynamic fluid force acts in the direction toward the hull, and the dynamic pressure decreases past the bow.

On the other hand, in order to analyze the flow around the hull and calculate the normal force and frictional resistance acting on the hull through this, the computational fluid analysis (CFD) technique is used in the present invention, which will be described again.

Returning to FIG. 5 again, the node information acquisition unit 110 serves to acquire node information for one or more linear grids forming the hull surface of the modeled hull model data.

At this time, the node information acquisition unit 110 loads the CAD file modeled and stored in the hull model data from a separate database (3D CAD File database) in which the CAD file is stored, and receives the node information from the imported hull model data. To acquire. In this case, the hull model data may be data as shown in FIG. 3.

Here, the node information may mean a file format implemented by converting lattice plane information and panel point information of one or more linear lattices implemented in hexadecimal numbers into ASCII codes. , Examples of grid surface information and node information on the hull surface are shown in [Table 1] (examples of grid surface information on the hull surface) and [Table 2] (examples of node information on the hull surface).

3 2ea 298 2e9 0 0
3 83 2ea 2e9 0 0
3 2e8 83 2e9 0 0
3 2eb 83 2e8 0 0
3 d5 83 2eb 0 0
3 2e7 2eb 2e8 0 0
3 299 c 1 0 0
3 2ee d5 2eb 0 0

1.2254999250e+000 1.9927295404e-002 0.0000000000e+000
1.1287499500e+000 2.0000000000e-002 1.1736475000e-002
1.2013124313e+000 1.9945471553e-002 2.9341187500e-003
1.1771249375e+000 1.9963647702e-002 5.8682375000e-003
1.1529374438e+000 1.9981823851e-002 8.8023562500e-003
1.1272287400e+000 1.9935816296e-002 0.0000000000e+000
1.1517965362e+000 1.9933686073e-002 0.0000000000e+000
1.1763643325e+000 1.9931555850e-002 0.0000000000e+000
1.2009321287e+000 1.9929425627e-002 0.0000000000e+000
1.1279893450e+000 1.9967908148e-002 5.8682375000e-003
1.1272287500e+000 0.0000000000e+000 0.0000000000e+000
1.2254999250e+000 0.0000000000e+000 0.0000000000e+000
1.1517965438e+000 0.0000000000e+000 0.0000000000e+000

The grid node setting unit 120 rearranges and sets one or more grid nodes for each linear grid using the node information.

More specifically, the grid node setting unit 120 sets a direction toward the fluid region as a reference normal vector direction among two directions perpendicular to a surface of at least one linear grid.

For example, the normal vector on the surface of the linear grating sets one direction of two directions perpendicular to the surface in a positive direction. In the present invention, the direction toward the fluid region is set in a positive direction. do.

To do this, the nodes of each linear grid discretized with triangular elements must be aligned counterclockwise (CCW) when viewed from the fluid domain. Since the grid and the nodes do not have a uniform alignment system on the CAD file, the grid node setting section At 120, the grid nodes are rearranged. This will be described in more detail with reference to FIGS. 7 and 8.

FIG. 7 is a diagram showing nodes and directions in which the nodes of the linear grid are directed, and directions in which the nodes of the linear grid are directed on the CAD file, and FIG. 8 is a table for rearranging nodes using adjacent sides of the linear grid, A diagram showing a process of rearranging nodes of a linear grid using such a table.

Referring first to Fig. 7(a), nodes in a linear lattice discretized with triangular elements are aligned in a direction toward the counterclockwise direction (CCW) when viewed from the fluid region. In FIG. 7(a), 1, 2, and 3 denote nodes of a linear lattice, and <1>, <2>, and <3> denote sides constituting a linear lattice.

In FIG. 7(a), as the current fluid region is positioned on the top of the linear grid, the upward direction is the direction that the vertical normal vector of the linear grid faces.

However, as shown in Fig. 7(b), the linear lattice and nodes by the CAD file do not have a constant alignment system, and in the adjacent linear lattice, the direction of the vertical normal vector is reversed.

For example, in the linear lattice in FIG. 7(a), the transitions of nodes 1, 2, and 3 appear as (1, 2), (2, 3), and (3, 1), respectively, but in FIG. 7(b) In a linear grid, (1, 2), (2, 3), and (3, 1) become (2, 1), (1, 3), and (3, 2) inverted.

Therefore, it is necessary to change the position of these nodes to match the vertical normal vector directions of linear grids adjacent to each other.

Referring to FIG. 8, the grid node setting unit 120 of the present invention rearranges nodes using one side (for example, a side <1> formed by nodes 1 and 2 in FIG. 7 ).

More specifically, when the linear grating shown in FIG. 7(a) is assumed to be the first linear grating and the linear grating shown in FIG. 7(b) is assumed to be the second linear grating, node 1 forming a side <1> , 2 is shared by the first and second linear grids.

Therefore, the grid node setting unit 120 changes the position of the node as shown in the table for (1, 2), (2, 3), and (3, 1), which are the positions of each node of the first linear grid.

In FIG. 8(a), the reference grid refers to the first linear grid (the linear grid in FIG. 7(a)), and the adjacent grid refers to the second linear grid (the linear grid in FIG. 7(b)).

If the nodes of the first linear grid are 1 and 2, the node direction is counterclockwise (CCW), but in the case of the second linear grid, the node direction is clockwise (CW), so the grid node setting unit 120 In, the positions of nodes 2 and 3 are changed.

In addition, since the node directions in the nodes 2 and 3 are clockwise (CW), the positions of the nodes 1 and 3 are changed in the grid node setting unit 120.

In addition, since the node direction at the nodes 3 and 1 is clockwise (CW), the positions of the nodes 1 and 2 are changed in the grid node setting unit 120.

Accordingly, as shown in FIG. 8(b), the directions of the vertical normal vectors of the second linear grid adjacent to the first linear grid are all aligned in an upward direction.

Through the node rearrangement process of the grid node setting unit 130, a normal vector on the hull surface may be aligned as illustrated in FIG. 8.

Returning to FIG. 5 again, the normal vector calculation unit 130 uses a vector product of vectors consisting of two sides of the linear grid (eg, sides <1> and <3> in FIG. 7(a)). Thus, the normal vector V _n is calculated. This will be described in more detail with reference to FIG. 10.

10 is a view showing a process of calculating a normal vector in a linear grid.

Referring to FIG. 10, the normal vector V _n calculated by the normal vector calculating unit 130 may be represented as follows.

In addition, the unit normal vector n can be expressed as follows.

Returning to FIG. 5 again, the frictional resistance calculator 140 selects a linear grid in which buoyancy occurs among one or more linear grids using the calculated normal vector, and then uses buoyancy acting on the selected area of each linear grid. The normal force and frictional resistance acting on the hull model data are calculated.

To this end, the frictional resistance calculator 140 selects one or more linear lattices generating buoyancy from one or more linear lattices using the dynamic pressure distribution of the hull surface estimated through Computational Fluid Dynamics (CFD) technique. do. In one embodiment, the frictional resistance calculator 140 uses a computational fluid analysis technique based on the incompressibility, continuous equation for steady flow, and momentum equation to obtain a dynamic distribution of pressure on the surface of the hull. The equation for this is as follows.

난류 모델이 적용된 난류 운동에너지 k 방정식이 적용된다. standard k-

난류모델은 난류 운동 에너지 k 및 난류 운동 에너지 소실률

을 기본으로 하여 난류량을 예측하는 반경험(semi-empirical)모델이다. 이러한 난류 운동에너지 k 방정식은 운동량 방정식에서 유도할 수 있는 반면에 난류운동에너지 소실률

방정식은 물리적 타당성 및 수학적 개념의 유사성을 이용하여 얻어진 방정식이다. 이에 대한 수학식은 다음과 같다.In addition, the friction resistance calculating unit 140 is the most widely used standard k- for various turbulent flows in computational fluid analysis.

The turbulent kinetic energy k equation with the turbulence model is applied. standard k-

In the turbulence model, turbulent kinetic energy k and turbulent kinetic energy loss rate

It is a semi-empirical model that predicts turbulent flows based on. The turbulent kinetic energy k equation can be derived from the momentum equation, while the turbulent kinetic energy loss rate

The equation is an equation obtained using physical validity and similarity of mathematical concepts. The equation for this is as follows.

After selecting the linear grid where buoyancy occurs, the frictional resistance calculator 140 calculates the buoyancy F _B acting on each linear grid when the area of the selected grid is'A'.

Here, ρ _w is the density of seawater, ρ _i is the density of ice, h is the thickness of ice, and g is the gravitational acceleration. In addition, the buoyancy F _B is a vector in the vertical direction, and plays a role of generating resistance and frictional resistance according to changes in potential energy due to hull motion. If the resistance due to the change in potential energy is R _B , the following equation is applied.

Here, z is the depth of the center of gravity of the floating ice, and l is the horizontal distance between the hull's bow and the center of gravity of the floating ice.

Next, when the buoyancy F _B acting on each linear lattice is calculated through the above equation, the frictional resistance calculating unit 140 applies normal force F _n and frictional resistance F acting on the hull surface through the following equation. _f is calculated as follows.

Where ρ is the dynamic pressure and μ is the friction coefficient. In addition, the normal force means a force acting in the opposite direction of the vertical unit vector in the linear grid, and may be determined by the combined force of buoyancy and dynamic pressure.

Next, the process of calculating the frictional resistance of the floating ice based on the linear information through FIG. 11 will be described in order.

11 is a view showing a process of calculating the frictional resistance of the floating ice through the system for calculating the frictional resistance of the floating ice based on the linear information shown in FIG. 5 in a sequence.

Referring to FIG. 11, first, the node information for one or more linear grids constituting the hull surface of the modeled hull model data is obtained (S101), and the node information is used to reorder and set the grid node position for each linear grid. It is done (S102).

Then, after calculating the normal vector for each linear grid (S103), a linear grid generating buoyancy is selected using the calculated normal vector (S104). Then, after calculating the buoyancy acting on the area of each selected linear grid (S105), the normal force and frictional resistance acting on the hull surface are calculated (S106).

Although described above with reference to the preferred embodiments of the present invention, those skilled in the art may variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that you can.

100: system for calculating frictional resistance of floating ice based on linear information
110: node information acquisition unit
120: grid node setting unit
130: normal vector calculator
140: friction resistance calculator

Claims (10)

A node information acquiring unit that acquires node information for one or more linear grids constituting the hull surface of the modeled hull model data;
Using the node information, among two directions perpendicular to the surface of the one or more linear grids, a direction toward the fluid region is set as a reference normal vector direction, and among the one or more linear grids, one side adjacent to the first linear grid If there is a second linear grid that shares, the first and second linear grids share each other so that the reference normal vector direction of the second linear grid coincides with the reference normal vector direction of the first linear grid. A grid node setting unit for reordering by changing positions of nodes of the second linear grid based on sides;
A normal vector calculating unit for calculating the normal vectors for the one or more linear grids; And
Using the calculated normal vector, after selecting a linear lattice generating buoyancy among the one or more linear lattices, calculating frictional resistance acting on the hull model data using buoyancy acting on the area of each selected linear lattice. Friction resistance calculation unit, characterized in that it comprises, the frictional resistance calculation system of floating ice based on linear information.
According to claim 1,
The node information acquisition unit,
A system for calculating frictional resistance of floating ice based on linear information, characterized in that the hull model data modeled from a CAD file is loaded.
According to claim 1,
The node information,
A system for calculating the frictional resistance of floating ice based on linear information, characterized in that the lattice planes and panel points of the at least one linear grid implemented in hexadecimal are converted to ASCII codes.
delete According to claim 1,
The friction resistance calculation unit,
Using the dynamic pressure distribution of the hull surface estimated through computational fluid analysis (CFD), one or more linear lattices generating buoyancy are selected from the one or more linear lattices, and area and buoyancy for each selected one or more linear lattices are calculated. And, using the calculated area value and buoyancy value, characterized in that to calculate the normal force and frictional resistance acting on the hull model data, frictional resistance calculation system of floating ice based on linear information.
Obtaining node information for at least one linear grid constituting the hull surface of the modeled hull model data through the node information acquisition unit;
Through the grid node setting unit, among the two directions perpendicular to the surface of the one or more linear grids using the node information, a direction toward a fluid region is set as a reference normal vector direction, and a first linear grid among the one or more linear grids If there is a second linear lattice adjacent to and sharing one side, the first and second linear lattices are such that the reference normal vector direction of the second linear lattice matches the reference normal vector direction of the first linear lattice. Rearranging by changing positions of nodes of the second linear grid based on one side shared by each other;
Calculating a normal vector for each of the one or more linear grids through a normal vector calculating unit; And
After selecting the linear lattice generating buoyancy among the one or more linear lattices using the calculated normal vector through the frictional resistance calculating unit, and acting on the hull model data using buoyancy acting on the selected area of each linear lattice. Comprising the step of calculating the frictional resistance, characterized in that it comprises, the frictional resistance calculation method of floating ice based on linear information.
The method of claim 6,
The step of obtaining node information for the one or more linear grids is:
And loading the modeled hull model data from a CAD file through the node information acquiring unit, wherein the frictional resistance of floating ice is calculated based on linear information.
The method of claim 6,
The node information,
A method of calculating frictional resistance of floating ice based on linear information, characterized in that the lattice planes and panel points of the at least one linear grid implemented in hexadecimal are converted to ASCII codes.
delete The method of claim 6,
The step of calculating the frictional resistance acting on the hull model data is
Selecting one or more linear lattices generating buoyancy from the one or more linear lattices by using the dynamic pressure distribution of the hull surface estimated by a CFD technique in the frictional resistance calculator;
Calculating the area and buoyancy of each of the at least one linear grid selected by the frictional resistance calculator; And
And calculating the normal force and the frictional resistance acting on the hull model data using the calculated area value and the buoyancy value through the frictional resistance calculation unit. Resistance calculation method.

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