On modeling of curved jets of viscous fluid hitting a moving surface

A jet of Newtonian fluid can fall from the oriented nozzle onto the moving surface in three regimes. A flow regime depends on the process parameters and is characterized by the dominant effect in themomentumtransfer through the jet crosssection. To model the three jet flow regimes we describe the jet by the effects of inertia, longitudinal viscosity, and gravity. The key issue is to prescribe the boundary conditions for the jet orientation, which follow from the conservation of momentum for the dynamic jet. If the jet is under tension, the principal part of the conservation of momentum equation is of hyperbolic type, and the boundary conditions for the jet shape follow from the directions of characteristics. From this we find that the boundary conditions for the jet orientation are determined by the dominant effect in the momentum transfer through the jet cross-section, which can be due to inertia, or due to viscosity. This choice of boundary conditions allows us to find the solution to the steady jet model for all parameters, and partition the parameter space between the three jet flow regimes.