Ratchet effect (net transport without any obvious bias) has been obtained in a periodic potential system. In the present work, in contrast, the net transport of particles is obtained numerically in a potential-free system with friction coefficient in the form of a traveling wave and driven by a zero-mean sinusoidal force. The nature of particle trajectories and hence the direction and magnitude of the particle current strongly depend on the ratio ($r$) of the frequencies of the friction coefficient and the periodic drive. The effect of the amplitude of the two periodic functions on the net current is also investigated.

中文翻译：

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定期驱动的无电势系统中的净运输

在周期性电势系统中已获得棘轮效应（无明显偏差的净传输）。相反，在当前的工作中，在无电势的系统中以运动波的形式并由零均值正弦力驱动的无电势系统在数值上获得了粒子的净传输。粒子轨迹的性质以及粒子电流的方向和大小在很大程度上取决于该比率（$\mathrm{[R}$）的摩擦系数和周期性驱动的频率。还研究了两个周期函数的幅度对净电流的影响。