  We study the two-dimensional flow of foams around a circular obstacle within
a long channel. In experiments, we confine the foam between liquid and glass
surfaces. In simulations, we use a deterministic software, the Surface Evolver,
for bubble details and a stochastic one, the extended Potts model, for
statistics. We adopt a coherent definition of liquid fraction for all studied
systems. We vary it in both experiments and simulations, and determine the
yield drag of the foam, that is, the force exerted on the obstacle by the foam
flowing at very low velocity. We find that the yield drag is linear over a
large range of the ratio of obstacle to bubble size, and is independent of the
channel width over a large range. Decreasing the liquid fraction, however,
strongly increases the yield drag; we discuss and interpret this dependence.
