1980 年 28 巻 312 号 p. 11-18
In the previous our paper the accuracy of numerical method for steady two dimensional lifting surfaces in an incompressible inviscid flow was investigated. In this paper the work is extended to unsteady cases, where the kernel function includes the logarithmic singularity.
The difficulty becomes severe as the reduced frequency increases. It is found that careless treatments of this singularity make numerical calculation impractical even for low values of the reduced frequency, say larger than two or three. Through appropriate manipulation of this singularity, drastic improvement of the accuracy of numerical solutions is established.