In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the...In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.展开更多
In this paper, we tested the hydrodynamic characteristics of a new, double-winged otter board that consists of a forewing, a leading edge slat and a trailing edge flap. Flume experiments were conducted in a circulatin...In this paper, we tested the hydrodynamic characteristics of a new, double-winged otter board that consists of a forewing, a leading edge slat and a trailing edge flap. Flume experiments were conducted in a circulating flume tank by using a model with an aspect ratio(AR) of 0.85 and a horizontal planform area( S) of 0.09 m^2. The results indicated that the critical angle( α_(cr)) of the model was 44°, whereas the maximum lift coefficient( C_(Lmax)) was up to 1.715, and the door efficiency( K) was 1.122. The attack angle( α) ranged from 30° to 48° and from 10° to 46° when the lift coefficient( C_L) and door efficiency( K) were greater than 1.2 and 1.0, respectively. To compare the difference between double-winged otter board and traditional Morgere Polyvalent Ovale, same model of Morgere Polyvalent Ovale was also tested under the same experimental conditions. The critical angle( α_(cr)) and maximum of lift coefficient( C_(Lmax)) of the doublewinged otter board were 37.5% and 14.6% larger than those of the Morgere Polyvalent Ovale. Therefore, we concluded that the novel, double-winged otter board was more suitable for bottom trawling fisheries in the deep water of the Mauretania Sea due to its better hydrodynamic characteristics and stability.展开更多
Vertical cambered V-type otter boards are widely used in large and medium-sized trawlers for their good stability and adaptability to various water layers.However,limited numerical studies on the hydrodynamic performa...Vertical cambered V-type otter boards are widely used in large and medium-sized trawlers for their good stability and adaptability to various water layers.However,limited numerical studies on the hydrodynamic performance and structural strength of this type of otter board have been published.In this study,we established the three-dimensional numerical model of the double-slotted vertical cambered V-type otter board according to its special structure and stress feature.We compare the hydrodynamic performance results of our model with those of previous experiments.Using this model,we analyzed the influence of parameters such as attack angle,aspect ratio,dihedral,and deflector angles on its hydrodynamic performance.Moreover,the structural response characteristics of the otter board under typical working conditions were studied.We believe our results will provide theoretical reference for the structural design and optimization of the vertical cambered V-type otter board.展开更多
Numerical simulation is an important method for calculating the hydrodynamic performance of otter boards used in sea floor trawling.Although such simulations have been explored in prior studies,the effects of the prox...Numerical simulation is an important method for calculating the hydrodynamic performance of otter boards used in sea floor trawling.Although such simulations have been explored in prior studies,the effects of the proximity of the otter boards to the seafloor and the plume of upward-drawn sediment during bottom trawling have largely been ignored.In this study,we assessed these factors.The results show that within the angles of attack used during normal operations,the effect of the seafloor bottom boundary of the flow field on the hydrodynamic performance of an otter board is obvious.We found that when the ratio of the distance between the bottom of an otter board and the surface boundary of the flow field to the chord length of the board exceeds 0.4,the influence of the bottom boundary of the flow field on the hydrodynamic performance of the board is negligible.For values of less than 0.4,the seafloor bottom boundary has an increasingly obvious impact on the hydrodynamic performance as this ratio decreases.We also found that the turbid plume of ocean floor sediment raised during bottom trawling has an obvious effect on the lift and resistance coefficients of an otter board at high angles of attack.At low angles,this effect on the lift-to-drag ratio is reversed and less obvious.The simulation results show that the optimal lift-to-drag ratio decreases with an increase in the sediment concentration;however,beyond a certain threshold,an increasing concentration of sediments was not found to have an obvious impact on the lift-to-drag ratio.展开更多
In order to study the influence mechanism of structural type and size on the hydrodynamic performance of vertical curved V-type otter board,this paper based on the computational fluid dynamics method,a three-dimension...In order to study the influence mechanism of structural type and size on the hydrodynamic performance of vertical curved V-type otter board,this paper based on the computational fluid dynamics method,a three-dimensional numerical model of vertical curved V-type otter board is established to calculate and analyze its hydrodynamic performance,and the validity of the numerical simulation results is verified by designing and constructing a scaled model for dynamic flume experiments.On this basis,the effects of different structural parameters,such as the deflector angle,camber,and spacing,on the hydrodynamic performance of the vertical curved V-Type otter board are investigated and the optimal structural design scheme is determined.The results demonstrate that single or synchronous changes of the angle,camber,and spacing of the two deflectors have varying degrees of impact on the hydrodynamic performance of the vertical curved V-Type otter board.To improve the expansion effect of the otter board,setting the angle of the deflector A to 40◦and that of the deflector B to 30◦,or setting the camber of deflectors A and B to 18%,or setting the spacing between deflectors A and B to 380 mm and that between the deflector and the main panel to 670 mm can increase the lift coefficient of the vertical curved V-Type otter board to its maximum value.Considering the overall performance of the otter board,when the angle of the deflector A is set to 25◦and that of the deflector B is set to 30◦,or the camber of the deflector A is set to 6% and that of the deflector B is set to 9%,or the spacing between deflectors A and B is set to 340 mm and that between the deflector and the main panel is set to 610 mm,the lift-to-drag ratio of the otter board can be increased to its maximum value.展开更多
基金supported by the National Key Technology R&D Program(No.2013BAD13B03)the Key R&D Project from Science and Technology Department of Zhejiang Province(Nos.2018C02026,2018C02040)+1 种基金the National Natural Science Foundation of China(No.31072246)the Fundamental Research Funds for the Central Universities(No.201564020)
文摘In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.
基金Supported by the Technological Research on Reforming Otter Boards of Bottom Trawl in Mauretania and Guinea(China National Fisheries Corporation,CNFC)Technological Research on Transformation and Upgrading of Shrimp Trawl in Sierra Leone(CNFC)Far Sea Fisheries Resources Monitoring and Assessment of South China Sea(No.2013050212)
文摘In this paper, we tested the hydrodynamic characteristics of a new, double-winged otter board that consists of a forewing, a leading edge slat and a trailing edge flap. Flume experiments were conducted in a circulating flume tank by using a model with an aspect ratio(AR) of 0.85 and a horizontal planform area( S) of 0.09 m^2. The results indicated that the critical angle( α_(cr)) of the model was 44°, whereas the maximum lift coefficient( C_(Lmax)) was up to 1.715, and the door efficiency( K) was 1.122. The attack angle( α) ranged from 30° to 48° and from 10° to 46° when the lift coefficient( C_L) and door efficiency( K) were greater than 1.2 and 1.0, respectively. To compare the difference between double-winged otter board and traditional Morgere Polyvalent Ovale, same model of Morgere Polyvalent Ovale was also tested under the same experimental conditions. The critical angle( α_(cr)) and maximum of lift coefficient( C_(Lmax)) of the doublewinged otter board were 37.5% and 14.6% larger than those of the Morgere Polyvalent Ovale. Therefore, we concluded that the novel, double-winged otter board was more suitable for bottom trawling fisheries in the deep water of the Mauretania Sea due to its better hydrodynamic characteristics and stability.
基金This research was supported by the National Natural Science Foundation of China(31972845)the Open Fund of National Engineering Research Center for Oceanic Fisheries(A1-2801-18-100401-7).
文摘Vertical cambered V-type otter boards are widely used in large and medium-sized trawlers for their good stability and adaptability to various water layers.However,limited numerical studies on the hydrodynamic performance and structural strength of this type of otter board have been published.In this study,we established the three-dimensional numerical model of the double-slotted vertical cambered V-type otter board according to its special structure and stress feature.We compare the hydrodynamic performance results of our model with those of previous experiments.Using this model,we analyzed the influence of parameters such as attack angle,aspect ratio,dihedral,and deflector angles on its hydrodynamic performance.Moreover,the structural response characteristics of the otter board under typical working conditions were studied.We believe our results will provide theoretical reference for the structural design and optimization of the vertical cambered V-type otter board.
基金the National Natural Science Foundation of China(Grant No.31972845).
文摘Numerical simulation is an important method for calculating the hydrodynamic performance of otter boards used in sea floor trawling.Although such simulations have been explored in prior studies,the effects of the proximity of the otter boards to the seafloor and the plume of upward-drawn sediment during bottom trawling have largely been ignored.In this study,we assessed these factors.The results show that within the angles of attack used during normal operations,the effect of the seafloor bottom boundary of the flow field on the hydrodynamic performance of an otter board is obvious.We found that when the ratio of the distance between the bottom of an otter board and the surface boundary of the flow field to the chord length of the board exceeds 0.4,the influence of the bottom boundary of the flow field on the hydrodynamic performance of the board is negligible.For values of less than 0.4,the seafloor bottom boundary has an increasingly obvious impact on the hydrodynamic performance as this ratio decreases.We also found that the turbid plume of ocean floor sediment raised during bottom trawling has an obvious effect on the lift and resistance coefficients of an otter board at high angles of attack.At low angles,this effect on the lift-to-drag ratio is reversed and less obvious.The simulation results show that the optimal lift-to-drag ratio decreases with an increase in the sediment concentration;however,beyond a certain threshold,an increasing concentration of sediments was not found to have an obvious impact on the lift-to-drag ratio.
基金supported by the National Natural Science Foundation of China(Grant No.31972845)the Open Fund of National Ocean Fisheries Engineering and Technology Research Center(Grant No.A1-2006-21-200208).
文摘In order to study the influence mechanism of structural type and size on the hydrodynamic performance of vertical curved V-type otter board,this paper based on the computational fluid dynamics method,a three-dimensional numerical model of vertical curved V-type otter board is established to calculate and analyze its hydrodynamic performance,and the validity of the numerical simulation results is verified by designing and constructing a scaled model for dynamic flume experiments.On this basis,the effects of different structural parameters,such as the deflector angle,camber,and spacing,on the hydrodynamic performance of the vertical curved V-Type otter board are investigated and the optimal structural design scheme is determined.The results demonstrate that single or synchronous changes of the angle,camber,and spacing of the two deflectors have varying degrees of impact on the hydrodynamic performance of the vertical curved V-Type otter board.To improve the expansion effect of the otter board,setting the angle of the deflector A to 40◦and that of the deflector B to 30◦,or setting the camber of deflectors A and B to 18%,or setting the spacing between deflectors A and B to 380 mm and that between the deflector and the main panel to 670 mm can increase the lift coefficient of the vertical curved V-Type otter board to its maximum value.Considering the overall performance of the otter board,when the angle of the deflector A is set to 25◦and that of the deflector B is set to 30◦,or the camber of the deflector A is set to 6% and that of the deflector B is set to 9%,or the spacing between deflectors A and B is set to 340 mm and that between the deflector and the main panel is set to 610 mm,the lift-to-drag ratio of the otter board can be increased to its maximum value.
