CN110750900A - Method for estimating shape of middle layer trawl net in operation process - Google Patents
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Abstract
The invention provides a method for estimating the shape of a middle-layer trawl net in the operation process, which comprises the following steps: and (3) assuming that the middle-layer trawl is an elliptical cone body during operation, establishing an equation and the acquired net mouth height data, and determining the shape of the net mouth during towing. And solving an equation according to the horizontal (long axis) cross section structure of the trawl and the parameters of the netting gear to obtain the horizontal expansion of the net sleeve, and the distance from the long axis at the connection part of the net body and the net mouth central point to the horizontal expansion central point of the net sleeve. Determining the shape of the net mouth, the shape of the net body and the net body connecting part, and the length of the net sleeve and the net body assembling lacing line, and then obtaining the partial shape of the trawl net body. And establishing an equation to obtain the shape of the outline. After the length of the net sac lacing line is determined, the shape of the net sac can be obtained by combining the ellipse of the section of the net sac connection part of the net body. According to the estimation result, the operation condition of the netting gear can be known during operation, accidents are avoided, the fishing operation is adjusted, and the fishing success rate is improved.
Description
Technical Field
The invention relates to the field of research on hydrodynamic performance of fishing gears, in particular to a method for estimating the shape of a middle-layer trawl net in the operation process.
Background
Trawl is the most extensive and efficient fishing technology in marine fishery, and the output of trawl accounts for more than 40% of the total world fishing output. Trawl fishing is a fishing mode in which a fishing boat is adopted to drag a bag-shaped net to force a caught object to enter the net. When the trawl is dragged, the trawl interacts with the water power, so that the net has a shape change. The trawl net shape can reflect the stress state of the trawl net and the selection mechanism of the fishing object, and the research on the related shape has positive promoting effect on improving the fishing efficiency and realizing the balanced fishing.
China begins to carry out ocean trawling fishery in the last 80 th century, and due to the fact that trawling dimensions are huge, an operation water layer extends from the sea surface to thousands of meters underwater, the form of a net tool is difficult to monitor, and a large amount of personnel and financial resources are consumed, the research on the form of the trawling is slow. With the development of fishing instruments and the use of net position instruments, the effective observation of the form of the net opening of the trawl is realized on commercial fishing boats, but the integral form of the trawl is difficult to effectively monitor. At this time, a convenient and reliable method for estimating the shape of the trawl net during operation is urgently needed.
Disclosure of Invention
The invention designs a middle layer trawl shape estimation method aiming at the integral shape research of the middle layer trawl which is not developed in China, and can know the operation condition of the netting gear, adjust the shape of the netting gear and improve the fishing efficiency according to the towing real-time data. The specific scheme is as follows:
a method for estimating the shape of the trawl net in middle layer during operation features that the trawl net in middle layer is an elliptical cone symmetrical up and down, the net bag is an elliptical column, the upper line of the opening of trawl net in middle layer has floats and the lower line has sinkers,
the floaters and the sinkers assembled by the superior line and the inferior line in the dragging process are stressed unevenly but are symmetrical left and right, and the shapes of the floaters and the sinkers can be approximately regarded as an exponential function y which is α xβThe equation is parabolic when β is 2, i.e. y is α x2；
Firstly, an ellipse equation and an ellipse perimeter equation are established:
x2/hi 2+y2/vi 2＝1 (1)
Li＝2πvi+4(hi-vi) (2)；
hi. vi are respectively horizontal direction axes and vertical direction axes of different elliptical sections in the elliptical vertebral body, i is 0, 1 and 2, i is 0 which is the elliptical section of the end point of the mesh sleeve, i is 1 which is the elliptical section of the mesh opening, and i is 2 which is the elliptical section of the connection part of the mesh body and the mesh sac; during the dragging period, the vertical expansion data of the net mouth is measured by a net position meter and is set as a net mouth ellipse minor axis v1Calculating the horizontal expansion width h of the net mouth according to the formula of the perimeter of the ellipse1；
According to the symmetry characteristics of the elliptic cone, the following formula is obtained:
(S03-S02)a0-a2S03＝0 (3)
(S03-S02+S12)a0-a1S03＝0 (4)
(a0-a1)S02-(S02-S12)(a0-a2)＝0 (5)
y＝αx2(8)；
aiis half of the major radius of the i-segment ellipse, i.e. ai＝1/2hi，SiiFrom the end point of the major axis of the i-segment ellipse to the end point of the major axis of the i' segment ellipse, S03The distance from the vertex of the elliptic cone to the end point of the net sleeve (the length is referred to the net lacing length), a01/2 mesh sleeve horizontal expansion; d1Is the distance from the central point of the net opening to the central point of the horizontal expansion of the net sleeve, y0Is the height of the horizontal expansion point of the parabola horizontal plane, and is combined with 1/2 horizontal expansion a of the mesh sleeve0The parabola is solved by substituting equation 8.
According to the estimation result, the operation condition of the netting gear can be known during operation, accidents are avoided, the fishing operation is adjusted, and the fishing success rate is improved. The fishing efficiency can be evaluated after the operation is finished, and the change trend of the trawl shape under different working conditions is determined, so that a foundation is provided for optimizing netting design and ensuring operation safety.
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In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
FIG. 1 is a schematic view of a medial trawl approximating an elliptical vertebral body during towing; the upper right corner is the shape of the trawl which is similar to the sac part of the elliptic cone as a whole, and the lower right corner is the shape of the sac which is similar to the elliptic cylinder. .
FIG. 2 is a schematic diagram of an outline (bottom outline) that may be approximated as an exponential function during towing;
figure 3a is a schematic view of a top view of a middle layer of a trailer,
fig. 3b is a schematic view of the right part of the horizontal cross section of an elliptical cone.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.
In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed.
The invention provides a method for estimating the shape of a middle-layer trawl net in the operation process, which comprises the following steps: according to the trawl design concept, assuming that the middle layer trawl is an elliptical cone during operation, establishing an equation and collected net mouth height data, and determining the shape of the net mouth during towing. And solving an equation according to the horizontal (long axis) cross section structure of the trawl and the parameters of the netting gear to obtain the horizontal expansion of the net sleeve, and the distance from the long axis at the connection part of the net body and the net mouth central point to the horizontal expansion central point of the net sleeve. Determining the shape of the net mouth, the shape of the net body and the net body connecting part, and the length of the net sleeve and the net body assembling lacing line, and then obtaining the partial shape of the trawl net body. And establishing an equation to obtain the shape of the outline. After the length of the net sac lacing line is determined, the shape of the net sac can be obtained by combining the ellipse of the section of the net sac connection part of the net body.
During operation, the morphology of the mid-trawl is estimated with the following assumptions:
according to the design concept of the middle trawl, the middle trawl can be approximately regarded as an elliptic cone which is symmetrical up and down, and the net sac can be approximately regarded as an elliptic cylinder (figure 1). A. A' represents the end points of the net sleeves at two sides, B is the middle point of the upper net line of the net opening, C is the middle point of the upper half part of the net body and the net sac connecting part, D is the middle point of the side part of the net opening, E is the middle point of the side part of the net sac opening, and F is the middle point of the upper half part of the net sac tail end. The different cross sections of the elliptical vertebral bodies are elliptical, OiAt the center point of the different cross-sections, LiThe circumferential lengths of different sections are (i is 0, 1, 2, i is 0, i is an elliptical section where the end point of the mesh sleeve is located, i is 1, i is an elliptical section of the mesh opening, and i is 2, i is an elliptical section where the mesh sac is connected with the mesh body). Wherein, the upper right corner of the drawing 1 is the shape of the net sac part of the trawl, which is similar to the elliptic cone as a whole, and the lower right corner is the shape of the net sac which is similar to the elliptic cylinder.
Because the upper line and the lower line are assembled with the floater and the sinker in the dragging process and are stressed unevenly but are symmetrical left and right, the shapes of the upper line and the lower line can be approximately regarded as an exponential function y which is α xβThe equation is parabolic when β is 2, i.e. y is α x2(FIG. 2).
The elliptical perimeters of the vertical sections during towing are all assumed to be straightened lengths and are fixed.
hi、viA horizontal axis and a vertical axis (i ═ i) which are respectively different elliptical cross sections in the elliptical vertebral body0. 1 and 2. i is 0 and is the elliptical section of the end point of the mesh sleeve, i is 1 and is the elliptical section of the mesh opening, i is 2 and is the elliptical section of the connecting part of the mesh body and the mesh sac), the elliptical equation and the elliptical perimeter equation are as follows:
x2/hi 2+y2/vi 2＝1 (1)
Li＝2πvi+4(hi-vi) (2)
during the dragging period, the vertical expansion data of the net mouth is measured by the net position instrument (assuming that the horizontal expansion of the net mouth is larger than the vertical expansion), and the elliptic minor axis v of the net mouth is set1And calculating the horizontal expansion of the net opening (the major axis hi of the ellipse) according to an ellipse perimeter formula.
From the elliptic cone characteristics (symmetry) and the above assumptions, the following formula is derived:
(S03-S02)a0-a2S03＝0 (3)
(S03-S02+512)a0-a1S03＝0 (4)
(a0-a1)S02-(S02-S12)(a0-a2)＝0 (5)
y＝αx2(8)
as shown in FIGS. 3a and 3b, aiIs half of the major axis of the i-section ellipse section, i.e. ai＝1/2hi，S12The distance from the end point of the elliptic major axis of the net mouth to the end point of the elliptic major axis of the net body and the net sac connection part is S02The distance from the end point of the mesh sleeve to the end point of the long axis of the ellipse at the connection part of the mesh sac of the mesh body is S03Is the distance from the apex of the elliptical cone to the end point of the mesh sleeve, Sii’Is referenced to the length of the lacing line of the side net assembly. d1Horizontally expanding from the central point of the net opening to the net sleeveDistance of the center point. y is0Is the height of A, A' in the horizontal plane of the parabola, in combination with a0Then, the equation (8) is substituted to obtain the result.
The estimation of trawl shape is mainly based on mathematical model and mastering of netting gear specification. Taking the middle layer trawl as an example, the trawl is applied to trawls in different fishing areas, and the styles are similar. And determining the shape of the trawl door through the door opening data acquired by the net position instrument and gradually calculating the shape of the trawl door to the net sac. According to the estimation result, the operation condition of the netting gear can be known during operation, accidents are avoided, the fishing operation is adjusted, and the fishing success rate is improved. The fishing efficiency can be evaluated after the operation is finished, and the change trend of the trawl shape under different working conditions is determined, so that a foundation is provided for optimizing netting design and ensuring operation safety.
The above description is of the preferred embodiment of the invention. It is to be understood that the invention is not limited to the particular embodiments described above, in that devices and structures not described in detail are understood to be implemented in a manner common in the art; those skilled in the art can make many possible variations and modifications to the disclosed embodiments, or modify equivalent embodiments to equivalent variations, without departing from the spirit of the invention, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.
Claims (1)
1. A method for estimating the shape of the trawl net in the middle layer during operation, wherein the trawl net in the middle layer is regarded as an elliptical cone which is symmetrical up and down, the net sac is an elliptical column, the head line of the net mouth of the trawl net in the middle layer is provided with a floater, the foot line is provided with a sinker,
the floaters and the sinkers assembled by the superior line and the inferior line in the dragging process are stressed unevenly but are symmetrical left and right, and the shapes of the floaters and the sinkers are approximately regarded as an exponential function y which is α xβThe equation is parabolic when β is 2, i.e. y is α x2；
Firstly, an ellipse equation and an ellipse perimeter equation are established:
x2/hi 2+y2/vi 2＝1 (1)
Li＝2πvi+4(hi-vi) (2)；
hi. vi are respectively horizontal direction axes and vertical direction axes of different elliptical sections in the elliptical vertebral body, i is 0, 1 and 2, i is 0 which is the elliptical section of the end point of the mesh sleeve, i is 1 which is the elliptical section of the mesh opening, and i is 2 which is the elliptical section of the connection part of the mesh body and the mesh sac; during the dragging period, the vertical expansion data of the net mouth is measured by a net position meter, and the minor axis of the ellipse is set as v1Calculating the horizontal expansion width h of the net mouth according to the formula of the perimeter of the ellipse1；
According to the symmetry characteristics of the elliptic cone, the following formula is obtained:
(S03-S02)a0-a2S03＝0 (3)
(S03-S02+S12)a0-a1S03＝0 (4)
(a0-a1)S02-(S02-S12)(a0-a2)＝0 (5)
y＝αx2(8)；
wherein, aiIs half of the major radius of the i-segment ellipse, i.e. ai＝1/2hi，Sii’From the end point of the major axis of the i-segment ellipse to the end point of the major axis of the i' segment ellipse, S03The distance from the apex of the elliptic cone to the end point of the mesh sleeve, a01/2 mesh sleeve horizontal expansion; d1Horizontally expanding from the central point of the net opening to the net sleeveDistance of sheet center point, y0Is the height of the horizontal expansion point of the parabola horizontal plane, and is combined with 1/2 horizontal expansion a of the mesh sleeve0The parabola is solved by substituting equation 8.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB695361A (en) * | 1948-12-01 | 1953-08-12 | Robert Larsen | Floating trawl |
| NO20071503L (en) * | 2006-10-18 | 2008-04-22 | Aker Biomarine Asa | Method and device by floating drum. |
| WO2008048107A1 (en) * | 2006-10-18 | 2008-04-24 | Aker Biomarine Asa | Floating trawl methods and arrangements |
| CN103039407A (en) * | 2012-12-31 | 2013-04-17 | 河北省海洋与水产科学研究院 | One-boat beam haul-bag single-sac bottom trawl for investigating and sampling marine demersal creatures |
| CN103947617A (en) * | 2014-04-10 | 2014-07-30 | 浙江海洋学院 | Bottom trawl |
| CN103988816A (en) * | 2014-05-13 | 2014-08-20 | 中国水产科学研究院东海水产研究所 | Antarctic krill trawl fishing net |
-
2019
- 2019-10-18 CN CN201910991878.9A patent/CN110750900B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB695361A (en) * | 1948-12-01 | 1953-08-12 | Robert Larsen | Floating trawl |
| NO20071503L (en) * | 2006-10-18 | 2008-04-22 | Aker Biomarine Asa | Method and device by floating drum. |
| WO2008048107A1 (en) * | 2006-10-18 | 2008-04-24 | Aker Biomarine Asa | Floating trawl methods and arrangements |
| CN103039407A (en) * | 2012-12-31 | 2013-04-17 | 河北省海洋与水产科学研究院 | One-boat beam haul-bag single-sac bottom trawl for investigating and sampling marine demersal creatures |
| CN103947617A (en) * | 2014-04-10 | 2014-07-30 | 浙江海洋学院 | Bottom trawl |
| CN103988816A (en) * | 2014-05-13 | 2014-08-20 | 中国水产科学研究院东海水产研究所 | Antarctic krill trawl fishing net |
Non-Patent Citations (1)
| Title |
|---|
| 刘莉莉;胡夫祥;万荣;郑基;高敏;朱媛媛;董舒闯: "捕鱼拖网形状与张力特性的数值模拟与水槽试验", 农业工程学报, vol. 33, no. 9 * |
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