Instability of jets, threads, and sheets of viscous fluid
1969; Multidisciplinary Digital Publishing Institute; Linguagem: Inglês
10.1007/978-3-642-85640-2_30
ISSN2673-3161
Autores Tópico(s)Sports Dynamics and Biomechanics
ResumoThe instability which I propose to discuss is well-known in the form it assumes when a very viscous fluid like thick oil or honey falls in a stream onto a plate. A short distance above the plate the stream begins to wave or rotate in spiral form. It is possible to calculate the diameter at points in a steady falling stream of viscous fluid, and it is found that it thickens up very rapidly a short distance above the plate which stops the motion. The reason for the instability is clear. If the stream is very thin the longitudinal compression acts in the same way as end compression in a thin elastic rod. The rod becomes unstable at a certain load, and less force is needed to move the ends towards one another when the rod is bent than when it is straight. This is called the Euler instability. If however the stream is thick it may be that the work required to produce a given amount of longitudinal compressive strain is less if it remains straight than if it bends. Figures 1 and 2 show thin and thick streams of glycerine falling onto a plate. In Fig. 2 the stream spreads out so steadily that a reflection of the upper part of the stream can be seen in the fluid spreading on the plate.
Referência(s)