The Measurement of the Frictional Force Exerted on a Sphere by a Viscous Fluid, when the Center of the Sphere Performs Small Periodic Oscillations Along a Straight Line

Abstract

BY GEORGE F. MCEWEN. 'HP V HE purpose of the following investigation was to devise a method '-*• by which Stokes's law of the frictional resistance of a fluid to the motion of a sphere whose center performs small periodic oscillations could be applied to the measurement of the coefficient of viscosity of fluids. The two main objects were: first, to obtain as close an agreement as possible between the actual working conditions and those demanded by theory; second, to devise a process of measuring the force acting on the sphere, even for fluids having a very large coefficient of viscosity. The contents of this paper fall under the following five heads; I. The effect of the internal friction of fluids on the motion of pendulums, from Sir G. G. Stokes's Math, and Phys. Papers, Cambridge, 1880 and 1901, Vols. I. and III. II. An account of the method adopted in the present investigation to overcome the difficulties mentioned by Stokes, and to more nearly realize in the experimental work the ideal condition assumed in the theory from which Stokes's law was deduced. III. Experimental tests of the present method. IV. Suggestions for future research. V. Summary of the paper. I. THE EFFECT OF THE INTERNAL FRICTION OF FLUIDS ON THE MOTION OF PENDULUMS. I. Observations on the Motion of Pendulums, An account of the experiments made by Bessel, Baily, Dubuat, and Sabine, and the theoretical results obtained by Poisson, Challis and Plana is given in Stokes's Math, and Phys. Papers, Vol. III., pp. 1-7. The effect of the surrounding fluid on the time of vibration of a pendulum was computed by Poisson, Challis, Green, and Plana from the hydrodynamical theory of a frictionless fluid. A fair agreement with the observations was found in some cases, but in many cases, especially No. 6.] MEASUREMENTS OF FRICTIONAL FORCE. 493 MEASUREMENTS OF FRICTIONAL FORCE.

Modulation of water surface waves with a coiling-up-space metasurface

“…The energy from WSWs is considered as one kind of clean renewable energies to defuse the incoming energy crisis, and its energy density is at least four times larger than that from wind or solar. [1][2][3] In the past years, many works have been made to clarify the interaction between WSWs and the engineering structures such as rippled bottom, 4,5 floating disk arrays, 6 and Helmholtz arrays, 7 etc. Many interesting phenomena such as water-wave shifter, negative gravity and complete band gaps have been observed for modulation of WSWs.…”

Wavefront modulation of water surface wave by a metasurface

“…As an important type of classic waves, the water surface wave (WSW) has received great attention because rich energy is stored in the WSW of oceans, which is considered as one kind of clean renewable energy to defuse the incoming energy crisis. [1][2][3] Its energy density is much larger than that of wind power and solar power, while it is almost immune to weather. [4] In the past few years, many researches have already been made to study the interactions between WSW and engineering structures such as rippled bottom, [5][6][7] floating disk arrays, [8] Helmholtz arrays, [9] etc.…”