Potential theory of the pressure distribution on a wing section shall always give the values bigger than the ones obtained from the experiments in a viscous flow. It comes from the viscous effect due to the boundary layer around a wing section. The boundary layer on the suction side of a wing section grows thicker than the one on the pressure side, when the wing section has some angle of attack against a viscous flow. Such unequality in the boundary layer thickness hydrodynamically brings the virtual reduction of the attack angle as well as the camber ratio of a wing section due to the decline of the nose-tail line, or effectively distorts the section shape so that the trailing edge should be slightly raised up from the original. The author proposes a practical method to form the distorted wing section, in which the experimental slope of lift curve is utilized, and by which the pressure distribution can be computed for a wing section in a real flow. The pressure distribution thus computed for an exemplified wing section is in rather good agreement with the experimental result.

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Large scale structures in outer layer of wall-bounded shear flows, that is, a zero-pressure-gradient boundary layer and plane wall jet above flat plates, were investigated experimentally. Our objective is to clarify mean properties of the large scale structures in the intermittent region. Measurements were made by using I-type and X-type hot-wire probes, and an I-type rake probe with 16 hot wires along the spanwise direction. Turbulent/non-turbulent intermittency factor was calculated, and then from these distributions, a center position and width of the intermittent region were estimated. And also, RMS values of the streamwise velocity fluctuation at the center position were defined as a velocity scale. Wavenumber spectra were transformed from the measured velocity data by the rake probe, and spanwise length scales were estimated from these spectra. Reynolds number dependencies of scales of length and velocity were examined.

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We previously reported that the experimental crack velocity in a center-cracked specimen of unsaturated polyester resin is well expressed by one of the three different velocity equations of a constant stress, a mixed condition and a constant strain due to the central crack length C₀₁ under tension. Here, we show that the three different velocity equations are well fitted to express the velocity of fast fracture in PMMA sheet specimens having different crack lengths. The experimental crack velocity generally decreases as the crack length increases, and its change with the relative crack length C₁/C₀₁. The velocity expressions, combined with the existing relation between crack velocity and a dynamic stress-intensity factor, give the variations of the dynamic stress-intensity factor and a dynamic strain-energy release rate with C₁/C₀₁ for the specimens, both of which are in qualitative agreement with the experimental variations of the number of fracture surface marks and their density in the specimens.

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