content_image/362836.jpg content_image/362835.jpg content_image/362834.jpg content_image/362833.jpg
To determine the fluid velocity v and external-potential intensity V$_{0}$ we examine the effective external potential, defined as 

<img src='content_image/362836.jpg'>

i.e., the sum of external periodic potential and a fictitious potential representing the constant friction force acting on particles (see Fig. 1(b)). If bvd$_{0}$ ≫ V$_{0}$ , particles do not feel the periodic potential, while if bvd$_{0}$ ≪ V$_{0}$ particle hopping is essentially unbiased. Let Δ E$_{G}$ (Δ E$_{P}$ ) denote the difference between a given maximum of V$_{eff}$ and the first minimum to the right (left) of this maximum. In this way, Δ E$_{G}$ (Δ E$_{P}$ ) is the potential barrier separating a given potential minimum from its left (right) neighbor. A simple calculation shows that 

with 

such that the potential minima occur at x$_{j}$ = 2 jd$_{0}$ + x$_{0}$ , and maxima at y$_{j}$ = 2 jd$_{0}$ + 1 − x$_{0}$ for j an integer. Given Δ E$_{G}$ and Δ E$_{P}$ , we can determine x$_{0}$ , v and V$_{0}$ . We take Δ E$_{P}$ ∼ k$_{B}$T , and Δ E$_{G}$ ≫ k$_{B}$T , so that a particle has a finite rate of jumping to the well on the right, and virtually no chance of jumping in the opposite direction. A good correspondence with lattice TASEP is obtained using Δ E$_{G}$ = 20 k$_{B}$T and Δ E$_{P}$ = 2 k$_{B}$T . For these values we have, 

<img src='content_image/362835.jpg'>

<img src='content_image/362834.jpg'>

<img src='content_image/362833.jpg'>

To maintain the interparticle repulsion in the presence of the external potential, we must take U$_{0}$ substantially greater than V$_{0}$ . On the other hand, very large values 

