Numerical simulations using a boundary integral method are used to model three inviscid fluid flows with surface tension. The problems considered are the motions of a free drop, the self-similarity in the shape of inviscid pinchoff, and the evolution of a finite jet. Various shapes of drops are studied, and their frequencies of oscillation are compared to result in the literature. Non-linear shapes are evolved, simulating a drop after ejection from a finite jet, which determines whether the drop holds together or forms satellites. Special numerical techniques are added to the code for free drops in order to model the pinchoff process. Evidence is found for a similarity solution for inviscid pinchoff which adopts a double-cone shape with one cone angle greater than 90°. A novel result is that the two cone angles are always about 18.1° and 112.8° independent of the initial conditions. The potential far from the pinchoff region in the numerical simulations is shown to match with certain scalings expected from a similarity solution. A model of a finite axisymmetric jet evolving from a fixed nozzle is used to simulate various conditions of drop ejection. Driven by a time-dependent backpressure, the jet forms a neck due to surface tension and pinches off. Various backpressure functions are imposed which cause different shapes of jets to emerge. The model is intended to simulate a drop-on-demand ink-jet printing process for which the optimum result is a fast, satellite-free drop that can be ejected repeatably.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:598431 |
| Date | January 1997 |
| Creators | Day, R. F. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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