We conduct experiments with force-free magnetically driven rigid helical swimmers in Newtonian and viscoelastic (Boger) fluids. By varying the sizes of the swimmer body and its helical tail, we show that the impact of viscoelasticity strongly depends on the swimmer geometry: it can lead to a significant increase of the swimming speed (up to a factor of 5), a similar decrease (also up to a factor of 5), or it can have approximately no impact. Using an analysis of our data along with theoretical modeling we suggest that the influence of viscoelasticity on helical propulsion is controlled by an asymmetry effect, previously reported for dumbbell swimmers, wherein the front-back size mismatch leads to a non-Newtonian elastic force that can either enhance or hinder locomotion.

中文翻译：

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前后不对称控制粘弹性对螺旋泳的影响

我们使用牛顿和粘弹性（Boger）流体中的无力磁力驱动的刚性螺旋游丝进行实验。通过改变游泳者身体及其螺旋状尾巴的大小，我们表明粘弹性的影响在很大程度上取决于游泳者的几何形状：它可以导致游泳速度的显着提高（最高达5倍），类似的下降（最多5倍），否则可能几乎没有影响。使用我们对数据的分析以及理论模型，我们认为粘弹性对螺旋推进力的影响是由非对称效应控制的，这种效应先前曾报道过哑铃游泳者，其中前后尺寸失配会导致非牛顿弹性力。增强或阻碍运动。