| Research shows that nearly 90%of the fish content through net fishing fishing gear,and the mesh is the most important part of the net fishing gear,effect on the mesh of water power is the main source of resistance net fishing gear,in order to reduce energy consumption,needs analysis and study the factors influencing resistance,sure way to reduce resistance,so the hydrodynamic characteristics of the mesh,for rich fishing gear design theory,optimization of the fishing gear design and enhance the fishing tackle fishing efficiency,improve safety performance such as fishing gear has important academic value and application significance.In addition,because the ultra-high molecular weight polyethylene fiber has high strength,low density,fatigue resistance,low temperature resistance,chemical resistance,resistant to sunlight and other radiation,and a series of advantages,and in be used actually don’t need any protection measures,make the ultra-high molecular weight polyethylene fiber becomes one of the most excellent fishing with material,and the ocean middle-level trawl,tuna longline fishing,and the development of the large-scale deep water anti-wave culture,ultra-high molecular weight polyethylene are now widely used in the fishing fishing gear.The study of the mesh made of UHMWPE has important academic value and application significance for enriching the design theory of fishing gear and optimizing the design of fishing gear.The results of this paper can be used to improve the structure and optimal design of UHMWPE mesh.In this study,in 2019,a series of experimental studies were conducted on five kinds of UHMWPE mesh plates fixed on a square frame by using the static water tank of ocean fisheries research institute,and simulation analysis and research were conducted on the mesh plates fixed on a square frame by using MATLAB software.The results are as follows:(1)This paper analyzes the wake effect of the frame,and finds that the wake effect range increases with the increase of the frame distance,and the wake effect has little effect on the velocity of the mesh.(2)In this paper,when UHMWPE mesh is perpendicular to the incoming flow,the resistance coefficient formula is as follows:Cd90=3.20Re-0.1276(Sk2-0.3926Sk+0.1570)S-0.9830(R2=0.987);when UHMWPE mesh is parallel to the incoming flow,the resistance coefficient formula is as follows:Cd0=0.05Re0.1855(Sk2-0.7054Sk+0.1729)S-0.7627(R2=0.756),the ultra-high molecular weight polyethylene net tilt to flow,drag coefficient and lift coefficient formula respectively:Cdθ=0.83 sin a(Cd90+Cd0)(R2=0.925)and Clθ=0.20 sin(2a)Cd90Sk-0.2948(R2=0.890).This paper studies the formula of the normal drag coefficient of the mesh and finds that the normal drag coefficient is inversely proportional to the Reynolds number,that is,the drag coefficient decreases with the increase of the Reynolds number.In this study,the normal and tangential drag coefficients are functions of Reynolds number,duty cycle and line area.This paper studies the drag coefficient and lift coefficient of UHMWPE mesh,and finds that the drag coefficient tends to increase with the increase of impact Angle,and the lift coefficient reaches its maximum value at about 450 of impact Angle,and the duty cycle has a dual effect on the mesh at different impact angles.This study will be of ultra-high molecular weight polyethylene net drag coefficient and lift coefficient and the polyethylene net drag coefficient and lift coefficient comparison analysis,the results show that the two materials of mesh resistance coefficient is increase with the increase of Angle of attack and trend,and the resistance coefficient of growing fast,with the increase of Angle of attack,the drag coefficient change gradually smooth,in peaked at about 90°Angle of attack;The lift coefficient increases gradually with the increase of the impulse Angle,and reaches the maximum value around 45°.After reaching the maximum value,the lift coefficient decreases gradually,and the impulse Angle of 0°and 900 are the minimum values of the lift coefficient.By comparing the drag coefficient and lift coefficient of the two materials,it is found that the hydrodynamic coefficient of the UHMWPE mesh is slightly higher than that of the polyethylene mesh.(3)In this paper,when UHMWPE mesh is perpendicular to the flow,the resistance formula is:Rd90=1322.92V2(d/a)0.1661 S(R2=0.972);when UHMWPE mesh is parallel to the flow,the resistance formula is:Rd0=17.29V2(d/a)-0.6669S(R2=0.888);when UHMWPE mesh is inclined to the flow,the resistance and lift formula are as follows:theta equals Rdθ=R90+0.896(Rd90-Rd0)sin a(R2=0.939)and Rlθ=24.41 sin(2 α)V2(R2=0.889).This article will be perpendicular to the mesh of the coming flow resistance formula and resistance formula of cotton,ramie mesh and resistance formula of the polyethylene net,this paper compares and analyzes the results showed that the ultra-high molecular weight polyethylene net,polyethylene,ramie and cotton net mesh perpendicular to the flow,mesh resistance have made three kinds of materials with the increase of flow velocity and trend,but the three kinds of materials,ultra-high molecular weight polyethylene net most resistance,followed by cotton,ramie material mesh,mesh of least resistance is polyethylene materials;In this paper,by studying the lifting formula of UHMWPE mesh,it is found that the lifting force of the mesh reaches the maximum at about 45°,and the lifting force increases with the increase of the impact Angle,and gradually decreases after reaching the maximum.It is also found that the lifting force of this experiment is higher than that of the polyethylene mesh.(4)In this paper,we study the ultra-high molecular weight polyethylene net to maximum displacement and flow impact time relationship:y=0.3711t-0.0082(R2=0.999),the ultra-high molecular weight polyethylene net biggest relationship between displacement and added mass coefficient:y=0.003χ-1.5403+0.5472(R2=0.998)and ultra-high molecular weight polyethylene net biggest relationship between displacement and cable diameter:,y=0.003d-1.0682+0.5409(R2=0.999).In this paper,based on the theory of limit yuan,and using the UHMWPE physical modeling,mesh using Newton’s second law for all quality points listed a series of dynamic equations of motion,for the convenience of operation,this article on the complex formula for calculating second order differential equation of first order ordinary differential equation,the amount of calculation is greatly reduced.Finally,in order to use the six levels of runge kutta formula for each quality movement equation.Because this kind of algorithm to step the demand is higher,therefore this article on the step value is 0.00001,the results a higher accuracy and stability.Impact the results show that the flow time and the maximum mesh displacement inverse proportion,which impact the longer,the greater the maximum displacement,but the biggest displacement reached maximum value,even if the increase of ultra-high molecular weight polyethylene net impact time,basic stable and does not increase,the maximum displacement experiment found in mesh to flow impact time was 2.5 s largest mesh displacement tends to be stable;Ultra-high molecular weight polyethylene mesh deformation is related to the cable diameter,the study found that the cable diameter,the greater the net body deformation,the greater the degree of the mesh also the largest amount of displacement;The study also found that the added mass coefficient ratio and net related to deformation degree,with the increase of added mass coefficient ratio,mesh gradually decreases,and the biggest displacement showed a negative correlation between the two. |
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