The goal of the present work is to study the driven flow field in a circular tube at front of a long bubble. That results show that the radius of curvature R SinӨ=constant which is assumed by Pitts 【1】 . Using unsteady flow and source flow and line source flow can verify R SinӨ=constant by panel method. The number is 3.538. Image method can simulate the wall of circular tube. Finally, the fractional converge ratio can be used to describe driven flow field of a long bubble in the circular tube.