The Research And Development On Biplane Type Hyper Lift Trawl Door

This paper mainly reports the research and development of Biplane type Hyper Lift Trawl Door(biplane type HLTD and slotted biplane type HLTD), which combines the advantage of Single type Hyper Lift Trawl Door(HLTD,λ=1.0) with strong points of old biplane type otter board together. We made use of modeling experiment to analyze the hydrodynamic characteristic of otter board.The main body of this article consists of two parts,on the one hand,in order to the wing of biplane type hyper lift trawl door, slotted HLTD is designed.By adjusting slot range of 0c、0.1c、0.2c、0.3c and effective aspect ratio of 1.4、1.6、1.8、2.0 to investigate the hydrodynamic characteristic of slotted HLTD; On the other hand, slotted HLTD is used as the rear wing of biplane type otter board to design slotted biplane type HLTD. By adjusting slot range of 0c、0.1c、0.2c、0.3c and effective aspect ratio of 1.4、1.6、1.8、2.0 to investigate the hydrodynamic characteristic of slotted biplane type HLTD.The results: ①slotted HLTD, the maximum lift coefficient of HLTD will decrease when aspect ratio exceeds 1.0. On the contrary, the maximum lift coefficient of slotted HLTD will increase. With slot increasing, the maximum lift coefficient of single type HLTD will become larger. In addition to it, when aspect ratio becomes larger, stall angle will decrease. Considering that objective reality, we select the optimum slot and aspect ratio that slot is 0.2c and aspect ratio is 2.0. The maximum lift coefficient of this kind of type is 2.28 at the angle 32°of attack. ②Biplane type Hyper Lift Trawl Door, biplane type HLTD is similar to HLTD. With aspect ratio becoming bigger, the maximum lift coefficient of biplane type HLTD will decrease as well. But the maximum lift coefficient of slotted biplane type HLTD will increase. Particularly, when aspect ratio is 2.2, the maximum lift coefficient is bigger than the maximum lift coefficient of biplane type HLTD, and when attack angle exceeds stall angle, lift coefficient does not fell sharply.In addiction to it, the maximum lift coefficient is 2.19 at angle 30°of attack when the aspect ratio reaches 3.1. For slotted biplane type HLTD of aspect ratio 2.2, the maximum lift coefficient will decrease with gap chord ratio becoming larger. But lift –drag ratio has a trend growth. Besides stagger angle 0°,stagger angle has noting influence on the lift coefficient and lift-drag ratio. The maximum lift coefficient reaches 2.18 at stagger angle 30°, gap chord ratio 0.9. The hydrodynamic characteristic of biplane type HLTD added slot is as good as single type HLTD, and it also has higher stability when it is working. Biplane type HLTD is worth researching and working in our ocean countries.