Abstract
It is known that the velocity fluctuation appears in the laminar boundary layer near the point of separation or the transition region from laminar to turbulent flow in the boundary layer and the percentage fluctuation may be maximum at those points. From these points of view, the pressure fluctuation must occur there due to thus fluctuating velocity and it can be recognized by following expressions, that is for the isotropic turbulent flow from Taylor's statical theory of turbulence as the fluctuating prassure gradient is
then
where u'=√uu2 is mean square deviation of the wind from the mean, A and B constants and M, the mesh length which the turbulence is produced, and for the smooth surface of body, in Pohlhausen's method concerned with Kármáns momentum integral equation for the laminar boundary layer a following relation which may be considered to contain a fluctuating quantity must hold in his solution near above points.
where λ' is a fluctuating quantity and function of Uδ/ν or Ux/ν. p, the steady and p', the variable pressure.
Considering the maximum points of the pressure fluctuation are in general corresponding to above points, therefore these points can be then indicated by observing the maximum position of pressure fluctuation. The author investigated an experimental method of measuring and observed the maximum points of pressure fluctuations on the surface of an aerofoil by means of an appartus with piezo-electric Rocelle-salt. In order to clear that such points obtained are the transition region, the profile drag was measured in other side and discussed on the experimental results. This paper is the report of the experimental result and the theorit cal discussion on the maximum points of pressure fluctuations and an accurate measurement, concerned with the relation between the pressure fluctuating velocity near those points is now progress.
