  A dynamic wetting problem is studied for a moving thin fiber inserted in
fluid and with a chemically inhomogeneous surface. A reduced model is derived
for contact angle hysteresis by using the Onsager principle as an approximation
tool. The model is simple and captures the essential dynamics of the contact
angle. From this model we derive an upper bound of the advancing contact angle
and a lower bound of the receding angle, which are verified by numerical
simulations. The results are consistent with the quasi-static results. The
model can also be used to understand the asymmetric dependence of the advancing
and receding contact angles on the fiber velocity, which is observed recently
in physical experiments reported in Guan et al Phys. Rev. Lett. 2016.
