Andersen Anders, Wadhwa Navish, Kiørboe Thomas
Department of Physics and Centre for Ocean Life, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
National Institute for Aquatic Resources and Centre for Ocean Life, Technical University of Denmark, DK-2920 Charlottenlund, Denmark.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Apr;91(4):042712. doi: 10.1103/PhysRevE.91.042712. Epub 2015 Apr 24.
The stresslet provides a simple model of the flow created by a small, freely swimming and neutrally buoyant aquatic organism and shows that the far field fluid disturbance created by such an organism in general decays as one over distance squared. Here we discuss a quieter swimming mode that eliminates the stresslet component of the flow and leads to a faster spatial decay of the fluid disturbance described by a force quadrupole that decays as one over distance cubed. Motivated by recent experimental results on fluid disturbances due to small aquatic organisms, we demonstrate that a three-Stokeslet model of a swimming organism which uses breast stroke type kinematics is an example of such a quiet swimmer. We show that the fluid disturbance in both the near field and the far field is significantly reduced by appropriately arranging the propulsion apparatus, and we find that the far field power laws are valid surprisingly close to the organism. Finally, we discuss point force models as a general framework for hypothesis generation and experimental exploration of fluid mediated predator-prey interactions in the planktonic world.
应力子提供了一个由小型、自由游动且中性浮力的水生生物所产生流动的简单模型，并表明这种生物在远场产生的流体扰动通常以距离平方分之一的形式衰减。在此，我们讨论一种更安静的游动模式，它消除了流动中的应力子分量，并导致由力四极子描述的流体扰动以距离立方分之一的形式更快地在空间中衰减。受近期关于小型水生生物引起的流体扰动的实验结果启发，我们证明了采用蛙泳式运动学的游动生物的三斯托克斯子模型就是这样一种安静游动者的例子。我们表明，通过适当地布置推进装置，近场和远场中的流体扰动都能显著降低，并且我们发现远场功率定律在令人惊讶地接近生物的地方仍然有效。最后，我们讨论点力模型，将其作为浮游生物世界中流体介导的捕食者 - 猎物相互作用的假设生成和实验探索的一般框架。
