Helical propulsion in shear-thinning fluids
Helical propulsion in shear-thinning fluids
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DOI：
10.1017/jfm.2016.807
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发表时间：
2017-02-10
影响因子：
3.7
通讯作者：
Zenit, Roberto
中科院分区：
文献类型：
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作者：
Gomez, Saul;Godinez, Francisco A.;Zenit, Roberto
游动的微生物通常必须在复杂的非牛顿流体中推动自己。我们进行了实验与自我推进的螺旋游泳者驱动的外部旋转磁场中的剪切稀化非弹性流体。类似于在牛顿流体中游泳，我们获得每种流体的运动速度，该运动速度与游泳者的旋转频率成线性比例，但是具有取决于流体的功率指数的前因子。流体被认为总是增加螺旋的游泳速度，最多快50，因此是迄今为止报道的最强的这种类型。最大的相对增加是对于大约0.6的流体动力指数。使用简单的缩放，我们认为，速度的增加是不是直接由于螺旋丝周围的流动粘度的局部降低，而是假设，它起源于由于粘度分层周围的游泳者的约束效应。
Swimming micro-organisms often have to propel themselves in complex non-Newtonian fluids. We carry out experiments with self-propelling helical swimmers driven by an externally rotating magnetic field in shear-thinning inelastic fluids. Similarly to swimming in a Newtonian fluid, we obtain for each fluid a locomotion speed that scales linearly with the rotation frequency of the swimmer, but with a prefactor that depends on the power index of the fluid. The fluid is seen to always increase the swimming speed of the helix, up to 50 faster, and thus the strongest of such type reported to date. The maximum relative increase is for a fluid power index of approximately 0.6. Using simple scalings, we argue that the speed increase is not due directly to the local decrease of the flow viscosity around the helical filament, but hypothesise instead that it originates from confinement-like effect due to viscosity stratification around the swimmer.