Rohr Jim J, Fish Frank E
SSC San Diego, 53560 Hull Street, 211, San Diego, CA 92152, USA.
J Exp Biol. 2004 Apr;207(Pt 10):1633-42. doi: 10.1242/jeb.00948.
Swimming efficiencies of fish and cetaceans have been related to a certain synchrony between stroke cycle frequency, peak-to-peak tail/fluke amplitude and mean swimming speed. These kinematic parameters form a non-dimensional wake parameter, referred to as a Strouhal number, which for the range between 0.20 and 0.40 has been associated with enhanced swimming efficiency for fish and cetaceans. Yet to date there has been no direct experimental substantiation of what Strouhal numbers are preferred by swimming cetaceans. To address this lack of data, a total of 248 Strouhal numbers were calculated for the captive odontocete cetaceans Tursiops truncatus, Pseudorca crassidens, Orcinus orca, Globicephala melaena, Lagenorhynchus obliquidens and Stenella frontalis. Although the average Strouhal number calculated for each species is within the accepted range, considerable scatter is found in the data both within species and among individuals. A greater proportion of Strouhal values occur between 0.20 and 0.30 (74%) than the 0.25-0.35 (55%) range predicted for maximum swimming efficiency. Within 0.05 Strouhal increments, the greatest number of Strouhal values was found between 0.225 and 0.275 (44%). Where propulsive efficiency data were available (Tursiops truncatus, Pseudorca crassidens, Orcinus orca), peak swimming efficiency corresponded to this same Strouhal range. The odontocete cetacean data show that, besides being generally limited to a range of Strouhal numbers between 0.20 and 0.40, the kinematic parameters comprising the Strouhal number provide additional constraints. Fluke-beat frequency normalized by the ratio of swimming speed to body length was generally restricted from 1 to 2, whereas peak-to-peak fluke amplitude normalized by body length occurred predominantly between 0.15 and 0.25. The results indicate that the kinematics of the propulsive flukes of odontocete cetaceans are not solely dependent on Strouhal number, and the Strouhal number range for odontocete cetaceans occurs at slightly ( approximately 20%) lower values than previously predicted for maximum swimming efficiency.
鱼类和鲸类的游泳效率与划水周期频率、尾鳍/鲸尾叶峰峰值幅度和平均游速之间的某种同步性有关。这些运动学参数形成了一个无量纲的尾流参数，称为斯特劳哈尔数，在0.20至0.40的范围内，该参数与鱼类和鲸类提高的游泳效率相关。然而，迄今为止，尚未有直接的实验证据表明游泳鲸类偏好何种斯特劳哈尔数。为了解决这一数据缺失的问题，对圈养的齿鲸类动物宽吻海豚、伪虎鲸、虎鲸、黑圆头鲸、斜纹原海豚和热带点斑原海豚计算了总共248个斯特劳哈尔数。尽管为每个物种计算的平均斯特劳哈尔数在公认范围内，但在物种内部和个体之间的数据中都发现了相当大的离散度。与预测的最大游泳效率的0.25 - 0.35（55%）范围相比，更多比例的斯特劳哈尔值出现在0.20至0.30之间（74%）。在0.05的斯特劳哈尔增量范围内，最大数量的斯特劳哈尔值出现在0.225至0.275之间（44%）。在有推进效率数据的情况下（宽吻海豚、伪虎鲸、虎鲸），峰值游泳效率对应于相同的斯特劳哈尔范围。齿鲸类动物的数据表明，除了通常局限于0.20至0.40的斯特劳哈尔数范围外，构成斯特劳哈尔数的运动学参数还提供了额外的限制。通过游速与体长之比归一化的鲸尾叶拍频通常限制在1至2之间，而通过体长归一化的鲸尾叶峰峰值幅度主要出现在0.15至0.25之间。结果表明，齿鲸类动物推进性鲸尾叶的运动学并不 solely 依赖于斯特劳哈尔数，并且齿鲸类动物的斯特劳哈尔数范围出现在比先前预测的最大游泳效率略低（约20%）的值处。
