[en] Effect of channel walls on inviscid flow around a circular cylinder placed in the midstream is evaluated by a model with a source in a mapping plane. Comparison is made between the present theory and experimental data of several investigators in subcritical and supercritical regions. The present theory requires empirical values of back pressure coefficient and separation angle for a circular cylinder. In subcritical region, the present theory agrees well with the experimental data for h/d = 0 to h/d = 0.667. In supercritical region, a slight difference was observed in the vicinity of the separation point. Generally, agreement between the present theory and experiments is well. (author)