Russell J. Donnelly

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As part of a long-range study of vortex rings, their dynamics, interactions with boundaries and with each other, we present the results of experiments on thin core rings generated by a piston gun in water. We characterize the dynamics of these rings by means of the traditional equations for such rings in an inviscid fluid suitably modifying them to be(More)
www.physicstoday.org Many experiments seem daunting at first glance, owing to the sheer number of physical variables they involve. To design an apparatus that circulates fluid, for instance, one must know how the flow is affected by pressure, by the apparatus’s dimensions, and by the fluid’s density and viscosity. Complicating matters, those parameters may(More)
Attenuation of second sound in helium II has been used to observe up to 6 orders of magnitude of decaying vorticity displaying four distinctly different regimes of decaying grid turbulence in a finite channel. A purely classical spectral model for homogeneous and isotropic turbulence describes most of the decay of helium II vorticity in the temperature(More)
We study experimentally the slowing of viscous vortex rings. In particular we do so using the concept of drag coefficient, which is a bulk coefficient which aims to capture the various mechanisms of slowing that can occur. At early times of flight the ring slows at a certain rate. After some time, instabilities (which we refer to as Kelvin waves) begin to(More)
In an investigation on vortex rings suggested to me by Prof. Tomaschek, we succeeded in observing a novel 18 phenomenon, namely the appearance of waves on the core of the vortex ring and unstable regions within the 19 rings. The success was mainly attributed to novel coloring method we applied. The present paper presents 20 a thorough description of the(More)
Passing a fluid through a grid is a well-known mechanism used to study the properties of turbulence. Oscillating a horizontal grid vertically in a tank has also been used extensively and is considered to be a source of almost homogenous isotropic turbulence. When the oscillating grid is turned on a turbulent flow is induced. A front translates into the(More)