基于导流板形状变化的双开缝曲面网板水动力性能研究

摘要

开展风洞试验研究导流板形状变化对双开缝曲面网板水动力性能的影响,以优化网板导流板结构,提高双开缝曲面网板的水动力性能.试验设计4种导流板形状的网板模型,分别为矩形、扇形、凸梯形和凹梯形,4块网板模型的基本结构参数相同,展弦比2.5,叶板的曲率12％,双层导流板的预设角度30°和25°,主面板角度12°,试验风速28 m·s-1,冲角(α)范围0°～ 70°,模型安装于塔式六分量机械-应变天平的立柱上,分别对网板所受到的阻力、升力和力矩进行测量.结果显示:在网板升力系数方面,4块网板模型的最大升力系数为Cy(凸梯形)＞Cy(矩形)＞Cv(扇形)＞Cv(凹梯形),具有凸梯形结构的网板模型的最大升力系数较高,为1.946(α =47.5°);在网板阻力系数方面,在冲角为30°时,Cx(扇形)＞Cx(矩形)＞Cx(凹梯形)＞Cx(凸梯形),具有凸梯形结构的网板模型阻力系数较低;4块网板模型的最大升阻比关系为Cy/Cx(凸梯形)＞Cy/Cx(矩形)＞Cy/Cx(扇形)＞Cy/Cx(凹梯形),具有凸梯形结构的网板模型最大升阻比较高,为7.486(α=30°);在稳性对比方面,扇形导流板结构网板模型稳性较好,Cm绝对值与Cp变异系数分别为0.061和5.43％.试验表明,具有凸梯形导流板的双开缝曲面网板可以产生较大的升力,且阻力较小,具有良好的工作效果;具有扇形导流板的双开缝曲面网板稳性较高.试验结果可为拖网网板的结构优化设计提供参考.%In order to improve the hydrodynamic performance of double-slotted cambered otter board by optimizing the deflector structure,the effect of the deflector shape of double-slotted cambered otter board on hydrodynamic performances was investigated by model wind tunnel test.Four deflector shapes were designed in otter-board models:rectangle,fan shape,convex trapezoid and concave trapezoid.The basic structural parameters of four otter-board models were the same,the aspect ratio was 2.5,the camber ratio was 12％,the angle of double-layer deflector was 30° and 25°,and the angle of main-panel was 12°.The otter-boards models were installed on the six-component mechanical tower-balance separately,and the test was conducted in wind tunnel with the flow velocity at 28 m · s-1 and the angle of attack α measured from 0° to 70° to obtain drag coefficients Cx,lift coefficient Cy,pressure-center coefficient Cp,calculated lift to drag ratio Cy/Cx and to give the relation curve of these values and angle of attack α.For comparison in the lift coefficient of four otter-board models,the results showed that the relationship of the maximum lift coefficient Cy between four otter-board models was Cy (convex trapezoid) ＞ Cy (rectangle) ＞ Cy (fan shape) ＞ Cy (concave trapezoid),the maximum lift coefficient Cy of the otter-board model with convex trapezoid structure was higher,it was 1.946 (α =47.5 °).For comparison in the drag coefficient of four otter-board models,the results showed that the relationship of the drag coefficient Cx between four otter-board models at the attack angel of 30°was Cx (fan shape) ＞ Cx (rectangle) ＞ Cx (concave trapezoid) ＞ Cx (convex trapezoid),the drag coefficient Cx of the otter-board model with convex trapezoid structure was lower.For comparison in the lift to drag ratio of four otter-board models,the results showed that the relationship of the maximum lift to drag ratio Cy/Cx between four otter-board models was C,/Cx (convex trapezoid) ＞ Cy/Cx (rectangle) ＞ Cy/Cx (fan shape) ＞ Cy/Cx (concave trapezoid),the maximum lift to drag ratio Cy/Cx of the otter-board model with convex trapezoid structure was higher,it was 7.486 (α =30°).In comparison of stability,the stability of otter board model with double fan deflector structure was better,and its lower absolute value of Cm and variable coefficient Cp were 0.061 and 5.43％ respectively.Therefore,the double-slotted cambered otter-board with convex trapezoidal deflector could provide larger lift and have good working effect,the double-slotted cambered otter-board with fan shaped deflector had the higher stability.The results would offer the reference for the structural optimization design of trawl otter board.