發(fā)布時間：2018-04-28 15:43

  本文選題：網具水動力 + 占空率　； 參考：《上海海洋大學》2017年博士論文

【摘要】：金槍魚圍網是圍捕類漁具中最為先進的一種作業(yè)方式,其作業(yè)原理是利用中上層魚類的表層集群行為,采用圈捕的方式,通過收絞底綱完成包圍魚群,達到捕魚目的。這種圍捕的基本技術最初應用于鮐魚、沙丁魚和溊魚等小型魚種,后來擴展到表層金槍魚漁業(yè)中。目前,金槍魚圍網的目標魚種包括鰹魚Katsuwonus pelamis、黃鰭金槍魚Thunnus albacares等。由于以前的捕撈技術是建立在漁業(yè)資源相對比較豐富、能源成本較低以及捕撈對環(huán)境影響較小的基礎上,但隨著漁業(yè)資源不斷被開發(fā)利用,現在的漁具漁法更關注于生態(tài)環(huán)境的保護,以及能源成本的節(jié)約,從而引發(fā)了漁具設計理念的轉變。圍網網具發(fā)展步入到了網具性能優(yōu)化的階段,這主要是漁業(yè)管理的驅動,使人們不僅僅只關注高效的圍網網具,更多地去關注生態(tài)保護及節(jié)能的優(yōu)化網具。圍網研究的主要內容有網具沉降特性、水動力特性及網具形態(tài)三方面,為了實現網具性能的優(yōu)化適應現如今的捕撈策略,本研究立足于圍網沉降特性和水動力特性研究,對網具本身屬性和捕撈參數進行優(yōu)化,以期提高網具的作業(yè)性能。網具優(yōu)化的參數可包括:網具結構、網具本身屬性、捕撈操作參數、放網模式等。但在網具性能優(yōu)化過程中,1)圍網網具的主要作業(yè)指標及影響因素有哪些?2)不同材料的網片水動力特性的變化規(guī)律?3)對于圍網和拖網漁具,在水中運動均與水流呈小沖角運動,網具的水動力特性如何表現?4)優(yōu)化參數對網具特性的影響效果評估?5)如何評價優(yōu)化網具的漁具性能?這些問題是造成我國金槍魚圍網網具性能優(yōu)化的方向不明確的一些主要原因。為此,本研究通過海上實測調查的結果,得到了網具的作業(yè)性能的影響因素,在實測的基礎上開展新興材料的網具水動力特性研究,了解不同材料和不同結節(jié)類型的網片水動力特性,量化分析下綱配重、放網速度對網具性能的影響,以及不同材料的網具沉降特性的差異,最終提出我國金槍魚圍網的優(yōu)化方案,并通過動水槽試驗評估優(yōu)化后網具性能效果。主要研究結果如下:(1)漁船的放網速度及網具的沉降速度為決定捕撈成功與否的關鍵因素;魚群的運動速度越快,捕撈的可能范圍將急劇下降。當魚群移動速度(下潛速度)超過1.5 m/s時,除非極具表層洄游性魚類之外,稍具有一定深度的魚群,則無捕獲的可能;投網位置的選擇不能忽視,投網位置與魚群中心的距離越近,易導致魚群的反應,從而增加逃逸概率;網具規(guī)模較大時,必須配合操作條件及魚群的動態(tài)性能的判斷作業(yè),從而增加捕獲成功率。(2)海洋環(huán)境和捕撈參數對圍網沉降特性影響:應用廣義可加模型(GAMs)對88網次的海上實測自由魚群捕撈數據進行分析得到:120 m水層的海流速度是環(huán)境因素當中對圍網沉降深度影響最大的因素;長高比較小的圍網具有較好的沉降性能;長高比、放網時間和括綱長度對沉降深度影響顯著;而長高比、放網時間、60 m水層流速、括綱長度和跑綱長度對沉降速度影響顯著;建立的沉降深度和沉降速度最佳模型可用于預測在不同漁法操作和環(huán)境條件下的網具沉降性能,這對于成功捕撈自由魚群是十分必要的。(3)動水槽試驗結果顯示,無結節(jié)聚乙烯(PE)網片的水動力系數與網目占空率有關;當網片平行于來流方向時,占空率與阻力系數存在負相關關系,而當網片垂直于來流時兩者關系為正相關;網片傾斜于水流放置時,阻力系數隨著沖角的增加而增大,升力系數在沖角為50°(臨界沖角)時達到最大;當沖角小于該臨界沖角時和大于臨界沖角時,阻力系數和占空率的關系正好相反,即在小沖角下升、阻力系數與占空率均呈負相關關系,而在大沖角時呈現完全相反的結果。通過非線性擬合得到了聚乙烯網片的水動力系數公式:C_(D90)=5.568α~(0.292)Re~(-0.125)(500 Re 5300)C_(D0)=0.127α~(-0.534)Re~(-0.040)(500 Re 5300)C_(Dθ)=C_(D90)sinθ+（C_(D0)-1.775αsinθ）cos~2θC_(Lθ)=0.251α~(-0.481)C_(D90)sinθcosθ(4)對尼龍(PA)網片,雷諾數和占空率對其水動力系數的影響較為顯著,隨著雷諾數的增大,阻力系數減小并逐漸趨于平穩(wěn);占空率與平行阻力系數存在負相關關系,而與法向阻力系數呈正相關關系;網片傾斜于水流時,升力系數在沖角為50°(臨界沖角)時達到最大;當沖角小于該臨界沖角時和大于臨界沖角時,阻力系數和占空率的關系正好相反,即當沖角趨于0°時占空率越小阻力系數越大,而當沖角趨于90°占空率越大阻力系數越大;在相同條件下,有結網片的阻力系數是無結網片阻力系數的1.23~1.35倍;當雷諾數低于2200,PE網片的阻力系數較PA網片大;但當雷諾數大于2200,PA網片阻力系數反而小于PE網片。根據試驗結果擬合了尼龍網片的水動力系數經驗公式:C_(D90)=1.691α~(0.114)Re~(-0.011)(400 Re 3600)；C_(D90)=19.371R_h~(-0.643)+1.139C_(D0)=0.172α~(-0.407)Re~(-0.031)(500 Re 5500)C_(Dθ)=C_(D90)sinθ+（C_(D0)-0.889αsinθ）cos~2θC_(Lθ)=0.38α~(-0.162)C_(D90)sinθcosθ(5)小沖角是圍網和拖網漁具在水中作業(yè)時較普遍的情況,通過自主設計的試驗裝置,進行了網片水動力的小沖角試驗。發(fā)現試驗框架在0-20°范圍內表現穩(wěn)定,即框架阻力低于總阻力的20%,滿足試驗的基本要求;小沖角條件下,網片阻力系數與雷諾數、占空率和沖角有關;阻力系數隨著沖角的增大而增大,但與占空率和沖角呈負相關關系;相同占空率的無結節(jié)尼龍網片的阻力系數約占有結節(jié)網片的77.9%。根據試驗結果推導出了小沖角條件下的網片阻力系數公式:C_D=0.172α~(-0.407)Re~(-0.031)（1+sinθ~(0.905)~(1.822)上式可應用在漁具(圍網、拖網等)與水流呈小沖角作業(yè)時,網具理論計算及數值模擬方面,同時也可利于此公式對圍網模型準則進行修正。(6)聚乙烯、尼龍和滌綸3種網片的沉降性能動水槽試驗結果表明:網片的沉降深度隨著沉降時間的增加而增加,直至達到最大沉降深度;下綱配重的增加使網片的沉降特性有著顯著性的提高,其中聚乙烯網片的提升幅度最大,其次是尼龍和滌綸網片;占空率與網片的平均沉降速度呈負相關關系;不同材料的網片沉降特性存在顯著性差異,滌綸網片的沉降特性最佳,依次是尼龍網片和聚乙烯網片;試驗結果證明結節(jié)網片的沉降特性劣于無結網片。(7)下綱配重和放網速度對沉降特性影響:利用天然水域中的金槍魚圍網模型網試驗結果與海上實測結果進行了對比。結果發(fā)現,下綱重量的增加和放網速度的增大,有利于模型網的沉降性能提升;下綱配重是影響網具沉降性能最重要的因素;對比網具中部和取魚部的沉降速度,圍網翼端位置的沉降速度最大;模型網的沉降速度達到實物網的97.2%左右,可近似認為模型網的沉降速度能夠客觀反應實物網的沉降速度。這表明了我們的模型試驗可作為一種重要的補充方法去評估原型網的實測性能。(8)在基礎試驗的結果上,利用小沖角阻力系數公式對圍網模型網準則進行修正,然后制作模型網和設計模型網動水槽試驗。本研究采用兩種優(yōu)化的模型網進行動水槽試驗:模型網主網衣部位的網目由原來的25 mm更換為30 mm;模型網主網衣1/3部位(靠近下緣網附近)網衣由30 mm更換為45 mm。通過試驗結果發(fā)現:1)側流放網是較為理想的放網模式,相比于其它放網模式可使優(yōu)化網具在沉降特性、包圍面積方面有著顯著的提高;2)從括綱張力角度來說,順流放網為較佳放網模型,因其產生較小的括綱張力。取魚部的張力較網翼部的張力大,兩個部位的張力均在絞綱完成時達到最大;3)網目增大使網具沉降性能提升和括綱絞收時間減小。對下緣網附近的網目進一步增大,使網具阻力減小9.26%;4)順流放網時,網船移動距離和漂移距離均最小,網目增大網具阻力減小使網船的漂流距離減小�？烧J為上述網具優(yōu)化方案是切實可行的,在網具節(jié)能、網具形態(tài)和沉降特性方面均有顯著性作用,可作為我國大型圍網網具性能優(yōu)化的主要方向。
[Abstract]:Tuna is one of the most advanced mode of operation in hunting fishing gear, its working principle is the use of the surface cluster behavior of pelagic fish, the captured the way through to twist the bottom line complete surrounded by fish, fishing to reach. The basic technologies should be initially used for the hunting fish Xia chub mackerel, sardines and small fish, later Extended to the surface tuna fisheries. Currently, the target species of the tuna Seine include the bonito Katsuwonus pelamis, the yellow fin tuna Thunnus albacares and so on. The fishing technology is based on relatively rich fishery resources, low energy costs and less impact on the environment, but with the continuous fishing resources With the exploitation and utilization, the fishing gear and fishing method now pays more attention to the protection of the ecological environment and the saving of the energy cost, which leads to the change of the design concept of fishing gear. The development of the Seine net has stepped into the stage of the optimization of the performance of the net gear, which is mainly driven by the fishery management, which makes people not only pay attention to the efficient Seine net, and go more to the customs. The main content of the study on the ecological protection and energy saving. The main contents of the study are the settlement characteristics of the nets, the hydrodynamic characteristics and the shape of the net gear in three aspects. In order to optimize the performance of the nets to adapt to the current fishing strategy, this study is based on the study of the settlement characteristics and hydrodynamic characteristics of the Seine, and the properties of the nets and the fishing parameters are optimized. In order to improve the performance of the net, the parameters of the optimization can include the structure of the net, the property of the net, the fishing operation parameters, the mode of the net, and so on. But in the process of optimizing the performance of the net, 1) what are the main operating indexes and the influencing factors of the Seine net? 2) the change law of the hydrodynamic characteristics of the mesh of the material? 3) for the Seine net And trawl fishing gear, moving in water with small punching angle in water, how to perform the hydrodynamic characteristics of the nets? 4) optimizing the effect of parameters on the property of the net gear? 5) how to evaluate the performance of the fishing gear for the optimization of the net gear? These problems are the main reasons for the uncertain direction of the performance optimization of the tuna Seine nets in China. In this study, the influence factors of the performance of the net gear are obtained by the results of the survey on the sea. On the basis of the measurement, the hydrodynamic characteristics of the new materials are studied. The hydrodynamic characteristics of the mesh of different materials and different types of nodules are understood, the weight of the next class is quantified, the effect of the net speed on the performance of the net is different, and the difference of the net speed is different. In the end, the optimization of tuna Seine in China is put forward, and the performance effect of the optimized net is evaluated through the flume test. The main results are as follows: (1) the speed of the fishing boat and the speed of the net gear settlement are the key factors to determine whether the fishing is successful or not; the faster the speed of the fish is, the fishing The possible range will decline sharply. When the fish group moves faster than 1.5 m/s, the fish group with a certain depth is not possible except for the highly migratory fish. The selection of the net position can not be ignored and the location of the net is closer to the distance from the center of the fish, which can lead to the response of the fish, thus increasing the escape probability. When the size of the net is large, it is necessary to match the operating conditions and the dynamic performance of the fish group to increase the capture success rate. (2) the influence of the marine environment and the fishing parameters on the settlement characteristics of the Seine net: using the generalized additive model (GAMs) to analyze the fishing data of the measured free fish group at sea at the 88 net times: the current velocity of the 120 m water layer It is the most important factor affecting the settlement depth of the enclosing network among the environmental factors; the relatively small long height of the fence has better settlement performance; the length and height ratio, the length of the length of the 60 m water layer, the length of the outline and the length of the running program have significant influence on the settlement velocity, and the depth of the settlement. The optimum model of degree and settlement velocity can be used to predict the settling property of the nets under different fishing operation and environmental conditions, which is necessary for the successful fishing of free fish. (3) the results of the flume test show that the hydrodynamic coefficient of the nodular polyethylene (PE) mesh is related to the net occupancy rate; when the net is parallel to the direction of the flow, it occupies the direction of the net. There is a negative correlation between the void fraction and the drag coefficient, while the relationship between the mesh and the flow is positive. The drag coefficient increases with the increase of the angle of impact when the net is inclined to the flow, and the lift coefficient reaches the maximum when the punching angle is 50 degrees (critical angle); when the punching angle is smaller than the critical angle and the critical angle is larger than the critical angle, the drag coefficient is the resistance system. The relationship between the number and the occupancy rate is the opposite, that is, the drag coefficient is negatively correlated with the occupying ratio at the small punching angle, and the result is completely opposite at the big punching angle. The hydrodynamic coefficient formula of the polyethylene mesh is obtained by nonlinear fitting. C_ (D90) =5.568 alpha ~ (0.292) Re~ (-0.125) (500 Re 5300) C_ (D0) =0.127 a (-0.534) Re~ (-0.0) 40) (500 Re 5300) C_ (D theta) =C_ (D90) sin theta + (C_ (D0) -1.775 alpha sin theta) cos~2 theta (theta) C_ (theta), theta theta (4), the Reynolds number and the occupying ratio have a significant influence on the hydrodynamic coefficients. With the increase of Reynolds number, the drag coefficient decreases and tends to be stable, and the occupying ratio and the parallel drag coefficient are negative. There is a positive correlation between the coefficient of resistance and the coefficient of resistance. When the net is inclined to the flow, the lift coefficient reaches the maximum when the impact angle is 50 degrees (critical angle). When the impact angle is less than the critical angle and the critical angle of impact, the relation between the drag coefficient and the duty ratio is exactly opposite, that is, the smaller the space ratio is, the smaller the drag coefficient is, the more the drag coefficient is. In the same condition, the resistance coefficient is 1.23~1.35 times of the resistance coefficient of no net plate, and when the Reynolds number is lower than 2200, the resistance coefficient of the PE mesh is larger than that of the PA mesh, but when the Reynolds number is greater than 2200, the resistance coefficient of the PA mesh is smaller than that of the PE mesh. According to the experimental results, the results are in accordance with the test results. C_ (D90) =1.691 alpha ~ (0.114) Re~ (-0.011) (400 Re 3600); C_ (D90) =19.371R_h~ (-0.643) +1.139C_ (D0). The small punching angle test of the net sheet hydrodynamic force is carried out by the self designed test device. It is found that the test frame is stable in the range of 0-20 degrees, that is, the frame resistance is lower than 20% of the total resistance, which satisfies the basic requirements of the test; the resistance coefficient of the mesh and the Reynolds number, the occupying ratio and the impact under the small punching angle condition. The resistance coefficient increases with the increase of the punching angle, but has a negative correlation with the occupying ratio and the punching angle; the resistance coefficient of the nodular nylon mesh with the same occupancy rate is about 77.9%. of the nodular mesh. The formula of the resistance coefficient of the mesh under the condition of small punching angle is derived: C_D=0.172 alpha ~ (-0.407) Re~ (-0.031) (1+sin theta ~ (0.)) 905) ~ (1.822) can be applied to the theoretical calculation and numerical simulation of the net gear when the fishing gear (Seine, trawl, etc.) and the water present a small punching angle. At the same time, this formula can also help to correct the mesh model criterion. (6) the settlement dynamic flume test results of 3 kinds of net sheet of polyethylene, nylon and polyester show that the subsidence depth of the mesh is with the sink. The increase of the drop time increases until the maximum settlement depth is reached. The increase of the lower class weight makes the settlement characteristics of the mesh significantly improved, among which the polyethylene mesh is the largest, followed by nylon and polyester mesh; the occupying ratio has a negative correlation with the average settlement velocity of the mesh; the net sheet settlement characteristics of different materials exist. In the significant difference, the settlement characteristics of the polyester mesh were the best, followed by nylon mesh and polyethylene mesh. The experimental results proved that the settlement characteristics of the nodular mesh were inferior to that of the non net plates. (7) the influence of the lower class weight and the net speed on the settlement characteristics: the results of the tuna Seine model net test in the natural waters were carried out with the measured results from the sea. The result shows that the increase of the weight of the lower class and the increase of the speed of the net, which is beneficial to the settlement performance of the model net, is the most important factor affecting the settlement performance of the net, and the settlement velocity of the wing end of the fence is the largest, and the settlement speed of the model net reaches 97.2% of the physical network. The settlement velocity of the model net can objectively reflect the settlement velocity of the physical network. It shows that our model test can be used as an important supplementary method to evaluate the measured performance of the prototype network. (8) in the result of the basic test, the formula of the small punching angle resistance system is used to correct the net model net criterion. This study uses two optimized model net moving flume tests: the mesh mesh of the main mesh of the model net is replaced by the original 25 mm to 30 mm; the network coat 1/3 part of the model net (near the lower edge net) is replaced by 30 mm to 45 mm. and is found by the test results: 1) the side flow network is compared. Compared with the other mode, the optimal net mode can improve the settlement characteristics and the area of the surrounding area. 2) from the point of view of the outline tension, the smooth discharge network is a better net model, because it produces smaller outline tension. The tension of the fish section is larger than the net wing, and the tension of the two parts is all hanging. When the program is completed, it reaches the maximum; 3) the net mesh device subsidence performance enhancement and the outline hoisting time decrease. To further increase the net mesh near the lower edge network, the net gear resistance is reduced by 9.26%; 4) the net ship moving distance and drift distance are the least, the net mesh resistance decreases and the drift distance of the net ship decreases. The optimization scheme of the net gear is practicable. It has a significant effect on the energy saving of the net, the shape of the net and the characteristics of the settlement. It can be used as the main direction of the performance optimization of the large Seine nets in our country.

【學位授予單位】：上海海洋大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：S972.21
，

本文編號：1815898