|Modelprojekt, 1. modul, 2002, id:271|
|Findes på RUb:||Ja|
When a vertical jet hits a leveled surface, an equilibrium will arise. Within a radius r of the jet, the level of the liquid will be low. At a distance r from the jet this level will increase abruptly. This ring discontinuity is called the hydraulic jump. While preparing a thesis at the University og Copenhagen  in 1995, two students observed that the hydraulic jump could assume a polygonal form. In 1997, this peculiar discovery gave rise to a model, which had the purpose of describing which physical mechanisms are the governing of the existence of the polygonshaped jump. The basis of the model is an asserted linetension combined with a balance of forces extered on the exterior of the jump. The development of this model is not documented in detail in any publication. In this report the existing model is deployed and analysed. This is done to clarify if the mechanisms of the model gives sufficient conditions to verify the existence of the polygonal jumps. The report concludes that the model is capable of reflecting a numberof qualitative characteristics of the jump. The linetension, however, is not substantiated in any physical principle. Because of this a new model, which is better theoretically founded, is desirable. In this report the controlling equations of a new model is deduced from the physical principle of mass preservation (among others). The two models will be briefly compared and discussed.