Anderson E J, DeMont M E
Biology Department, St Francis Xavier University, PO Box 5000, Antigonish, Nova Scotia, Canada B2G 2W5.
J Exp Biol. 2000 Sep;203(Pt 18):2851-63. doi: 10.1242/jeb.203.18.2851.
High-speed, high-resolution digital video recordings of swimming squid (Loligo pealei) were acquired. These recordings were used to determine very accurate swimming kinematics, body deformations and mantle cavity volume. The time-varying squid profile was digitized automatically from the acquired swimming sequences. Mantle cavity volume flow rates were determined under the assumption of axisymmetry and the condition of incompressibility. The data were then used to calculate jet velocity, jet thrust and intramantle pressure, including unsteady effects. Because of the accurate measurements of volume flow rate, the standard use of estimated discharge coefficients was avoided. Equations for jet and whole-cycle propulsive efficiency were developed, including a general equation incorporating unsteady effects. Squid were observed to eject up to 94 % of their intramantle working fluid at relatively high swimming speeds. As a result, the standard use of the so-called large-reservoir approximation in the determination of intramantle pressure by the Bernoulli equation leads to significant errors in calculating intramantle pressure from jet velocity and vice versa. The failure of this approximation in squid locomotion also implies that pressure variation throughout the mantle cannot be ignored. In addition, the unsteady terms of the Bernoulli equation and the momentum equation proved to be significant to the determination of intramantle pressure and jet thrust. Equations of propulsive efficiency derived for squid did not resemble Froude efficiency. Instead, they resembled the equation of rocket motor propulsive efficiency. The Froude equation was found to underestimate the propulsive efficiency of the jet period of the squid locomotory cycle and to overestimate whole-cycle propulsive efficiency when compared with efficiencies calculated from equations derived with the squid locomotory apparatus in mind. The equations for squid propulsive efficiency reveal that the refill period of squid plays a greater role, and the jet period a lesser role, in the low whole-cycle efficiencies predicted in squid and similar jet-propelled organisms. These findings offer new perspectives on locomotory hydrodynamics, intramantle pressure measurements and functional morphology with regard to squid and other jet-propelled organisms.
采集了高速、高分辨率的鱿鱼（莱氏拟乌贼）游泳的数字视频记录。这些记录用于确定非常精确的游泳运动学、身体变形和外套腔体积。从采集的游泳序列中自动将随时间变化的鱿鱼轮廓数字化。在轴对称和不可压缩条件的假设下确定外套腔体积流量。然后使用这些数据计算喷射速度、喷射推力和外套内压力，包括非定常效应。由于对体积流量进行了精确测量，避免了使用估计的流量系数的常规做法。推导了喷射和全周期推进效率的方程，包括一个包含非定常效应的通用方程。观察到鱿鱼在相对较高的游泳速度下会喷出高达94%的外套内工作流体。因此，在通过伯努利方程确定外套内压力时，使用所谓的大水库近似法的常规做法会导致根据喷射速度计算外套内压力时出现重大误差，反之亦然。这种近似法在鱿鱼运动中的失效也意味着整个外套内的压力变化不能被忽略。此外，伯努利方程和动量方程的非定常项被证明对外套内压力和喷射推力的确定具有重要意义。为鱿鱼推导的推进效率方程与弗劳德效率不同。相反，它们类似于火箭发动机推进效率方程。与根据考虑鱿鱼运动装置推导的方程计算出的效率相比，发现弗劳德方程低估了鱿鱼运动周期中喷射期的推进效率，高估了全周期推进效率。鱿鱼推进效率方程表明，在鱿鱼和类似喷射推进生物预测的低全周期效率中，鱿鱼的再填充期起的作用更大，喷射期起的作用更小。这些发现为鱿鱼和其他喷射推进生物的运动流体力学、外套内压力测量和功能形态学提供了新的视角。
