減速時における粘性抵抗について (その1) : 平板,一様減速中

抄録

Many researchers have presented various theories of boundary layer in unsteady flow. However they seem to have been confined to problems of laminar boundary layer. It is interesting to know how a turbulent boundary layer responds to the process of deceleration of the body. This paper is concerned with an experimental investigation in the phenomenon of decelerating a flat plate uniformly in towing condition, as one of the most simple case. The following remarks. become known from this experiment. (1) A secondary boundary layer is formed from the back edge of the flat plate in the field of the initial boundary layer. (2) Momentum thickness of the initia boundary layer is increased by the growth of the secondary boundary layer, while the shape factor (ratio of displacement thickness and momentum thickness) is not changed. (3) During the process of constant deceleration, the viscous drag has just smaller value than that of steady case at any instantanous velocity, but the difference of them is too small to make a clear distinction.