Measurements of wall pressure fluctuations under a turbulent boundary layer were made on the fuselage of a sailplane. This flow offers a noise-free environment with a low free stream turbulence level. The axisymmetric boundary layer undergoes natural transition and develops in a zero pressure gradient region. Spectra of the wall pressure were found to decrease at low frequency in agreement with calculations based upon a turbulence-mean shear interaction mechanism. Velocity fluctuations a t several positions within and outside the boundary layer were measured and correlated with the wall pressure. A special conditional correlation method was also employed to find the contribution of various velocity fluctuations to the wall pressure. A conditioning signal was formed based upon the signs of u and v and the turbulent-non-turbulent nature of the flow. This signal was time lagged and correlated with the wall pressure signal. It was found that in the outer portion of the boundary layer (y/6 > 0.5), irrotational motions were more highly correlated with the wall pressure than vortical motion.

The virtual mass of a long, transversely vibrating tube submerged in a liquid was experimentally determined. The tube was surrounded by rigid tubes in a hexangular array and in square array, at pitch-to-diameter ratios from 1.25 to 1.5. The inertia coefficients observed were considerably larger than for a cylinder in an infinite volume of fluid, but smaller than one would compute assuming an annulus inscribed within the clear space around the vibrating tube. The results show the reduction of natural frequencies in a submerged tube bundle for one particular relative motion of tubes. Experimental results concerning the increase in damping due to the surrounding tubes are briefly indicated.

Eight synthetic casting materials were evaluated with respect to tensile and fatigue strengths, exothermicity (evolution of heat during polymerization), permeability (porosity), radiolucency, and cost. Strength determination for a five‐layer sample included measurement of the ultimate load at which a material failed, the ability to absorb energy, and the stiffness a material possessed after application of a cyclic stress. Results indicated that Vet Cast was superior with respect to tensile and fatigue strengths. The exothermic reaction associated with the “curing” or polymerization process was evaluated and not considered excessive although Ultra Cast attained a temperature of 48.0°C and was uncomfortable to handle during application. Permeability was determined. Delta Lite and Hexcelite NS were the most permeable materials and dried more rapidly and thoroughly after immersion than the other casting materials. Hexcelite NS was considered the least radiolucent material and was the most expensive material studied. Each of the synthetic casting materials demonstrated superiority in one or more of the categories tested. No one product demonstrated consistent superiority in criteria appropriate for clinical application.

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