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
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
The effect of the main-panel angle of a single-slotted cambered otter-board was investigated using engineering models in a wind tunnel.Three different angles(0,6,and 12)were evaluated at a wind speed of 28 m/s.Para...The effect of the main-panel angle of a single-slotted cambered otter-board was investigated using engineering models in a wind tunnel.Three different angles(0,6,and 12)were evaluated at a wind speed of 28 m/s.Parameters measured included:drag coefficient Cx,lift coefficient Cy,pitch moment coefficient Cm,center of pressure coefficient Cp,and the liftedrag ratio Cy/Cx,over a range of angle of attack(0e70).These coefficients were used in analyzing the differences in the performance among the three otter-board models.Results showed that the maximum lift coefficient Cy of the otter-board model with a main-panel angle of 0was highest(1.875 at a¼25).However,when the angle of attack was smaller(0<a<22.5),the lift coefficient of the otter-board increased as the angle of the main-panel increased.The maximum Cy/Cx of the otter-board with a main-panel angle of 12was highest(7.417 at a¼2.5),and the liftedrag ratio increased when the angle of the main-panel increased within the angle of attack at small angles(0<a<12.5).A comparative analysis of Cm and Cp showed that the stability of the otter-board with a main-panel angle of 0is better than those of the other models.Therefore,the comparative analysis of Cm and Cp,shows that a larger angle of the main-panel can reduce the stability of single-slotted otter-board.The findings of this study offer useful reference data for the structural optimization of otter-boards for trawling。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 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
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This work is financially supported by the National Key Technology R&D Program(Grant No.2013BAD13B03).
文摘The effect of the main-panel angle of a single-slotted cambered otter-board was investigated using engineering models in a wind tunnel.Three different angles(0,6,and 12)were evaluated at a wind speed of 28 m/s.Parameters measured included:drag coefficient Cx,lift coefficient Cy,pitch moment coefficient Cm,center of pressure coefficient Cp,and the liftedrag ratio Cy/Cx,over a range of angle of attack(0e70).These coefficients were used in analyzing the differences in the performance among the three otter-board models.Results showed that the maximum lift coefficient Cy of the otter-board model with a main-panel angle of 0was highest(1.875 at a¼25).However,when the angle of attack was smaller(0<a<22.5),the lift coefficient of the otter-board increased as the angle of the main-panel increased.The maximum Cy/Cx of the otter-board with a main-panel angle of 12was highest(7.417 at a¼2.5),and the liftedrag ratio increased when the angle of the main-panel increased within the angle of attack at small angles(0<a<12.5).A comparative analysis of Cm and Cp showed that the stability of the otter-board with a main-panel angle of 0is better than those of the other models.Therefore,the comparative analysis of Cm and Cp,shows that a larger angle of the main-panel can reduce the stability of single-slotted otter-board.The findings of this study offer useful reference data for the structural optimization of otter-boards for trawling。
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 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.
