Hydrodynamic interactions between swimming microorganisms in a linearly density stratified fluid
Hydrodynamic interactions between swimming microorganisms in a linearly density stratified fluid
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DOI：
10.1103/physreve.103.013109
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发表时间：
2021-01-20
影响因子：
2.4
通讯作者：
Ardekani, Arezoo M.
中科院分区：
文献类型：
--
作者：
More, Rishabh, V;Ardekani, Arezoo M.
由于海洋生物的运动，海洋和湖泊维持着强烈的生物活动，对生态和环境产生重大影响。个体生物的运动及其相互作用在游泳生物的集体运动中起着重要作用。然而，无处不在的垂直密度分层在这些水生环境中显着改变了游泳者的相互作用相比，在一个均匀的流体。此外，生物体的大小在很大范围内变化，这导致有限的惯性。为此，我们数值研究了一对模型游泳生物在两种配置之间的相互作用：（1）相互接近和（2）在线性密度分层流体中以有限惯性并排移动。我们使用原型的降阶蠕动模型的数值模拟的游泳生物。我们给出了不同Re（范围为1-50）和Ri（范围为0-10）时相互作用的蠕动（拉动器和推动器）对的轨迹和接触时间。根据蠕动Re和Ri，我们观察到蠕动相互作用可以分类为：（i）在高Re和低Ri下，牵引器被捕获在圆形回路中，（ii）在低Re和高Ri下，牵引器彼此逃逸，分离角随着分层的增加而减小，（iii）在碰撞后，推动器彼此粘附并偏离碰撞平面，无论是低Re还是高Ri，（iv）以其他方式逃逸的顶推者，其分离角随分层而增加。分层也增加了蠕动对的接触时间。所提出的结果可以是有用的，以了解背后的机制，在分层的环境，如海洋和湖泊中的水平层的浮游生物的积累。
Oceans and lakes sustain intense biological activity due to the motion of marine organisms, which has significant ecological and environmental impacts. The motion of individual organisms and their interactions with each other play a significant role in the collective motion of swimming organisms. However, ubiquitous vertical density stratification in these aquatic environments significantly alters the swimmer interactions as compared to in a homogeneous fluid. Furthermore, organisms have sizes varying over a wide range which results in finite inertia. To this end, we numerically investigate the interactions between a pair of model swimming organisms in two configurations: (1) approaching each other and (2) moving side by side with finite inertia in a linearly density stratified fluid. We use the archetypal reduced-order squirmer model to numerically model the swimming organisms. We present trajectories and the contact times of interacting squirmer (puller & pusher) pairs for different Re in the range 1-50 and Ri in the range 0-10. Depending on the squirmer Re and Ri we observe that the squirmer interactions can be categorized as (i) pullers getting trapped in circular loops at high Re and low Ri, (ii) pullers escaping each other with separating angle decreasing with increasing stratification at low Re and high Ri, (iii) pushers sticking to each other after the collision and deflecting away from the collision plane for either low Re or high Ri, (iv) pushers escaping otherwise with an angle of separation increasing with stratification. Stratification also increases the contact time for squirmer pairs. The presented results can be useful to understand the mechanisms behind the accumulation of planktonic organisms in horizontal layers in a stratified environment such as oceans and lakes.