静水中扭波推进水动力的数值模拟

摘要

The Gymnarchus Niloticus Fish (GNF) with long dorsal-fin generally cruises with high efficiency and extra-ordinal maneuverability while it can keep its body for the straight line. The un-steady flow field of torsinal wave propulsion is calculated using the dynamic grid technique includ-ing spring-based smoothing model and local grid remeshing, which is adaptable to the fin surface de-forming significantly for torsional wave propulsion at stationary water. In the present numerical sim-ulation, the maximum swing amplitude of fin ray reaches 85°. The numerical simulation result is compared with hydrodynamics experiments result. The pressure distribution on the fin surface and its variation with fin ray phase, and the relationship with thrust force production, the force fluctuation with wave frequency are analyzed. The results indicate that the thrust force coefficients do not vary with fin wave frequency. The frequency of surge force and heave force are both 2 times of wave fre-quency while the sway force frequency is the same as the wave frequency.%尼罗河魔鬼鱼（GNF)采用长背鳍扭波推进，具有较高的推进效率和机动性，而鱼体主体可以保持直线不变形。为适应扭波推进过程中鳍面的大摆角变形，文中采用动网格技术求解了静水中扭波推进非定常流场，鳍面最大计算摆角达到85°，并通过与水动力实验结果比较验证了数值计算方法的可靠性。文中还分析了鳍面压力分布随相位的变化及其与推力产生的关系，以及水动力随扭波频率的脉动规律。研究表明，推力系数不随扭波频率而变化，轴向、垂向力波动频率是扭波频率的2倍，而侧向力脉动频率与扭波频率一致。