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Numerical simulations of hydrodynamics of multiple water jets impinging over a horizontal moving plate

University of British Columbia

The use and control of water jet impingement in the run-out table (ROT) are crucial in the steel plate cooling phase. Because of the complexity of the involved heat transfer process, the industries still mostly rely on a trial-and-error method for controlling the ROT cooling process. Although there are some experimental and numerical studies of the jet impingement cooling on ROT, the process is not fully understood. The analysis of hydrodynamics of water jet impingement is a key to understanding the process better. This aspect has received little attention in literature and it is the objective of this research. At first, Computational Fluid Dynamics (CFD) axisymmetric simulation of water jet was considered to explore wetting front propagation on stationary surface. In the case of a moving plate, there are different zones over the plate surface and appropriate three-dimensional geometry and model must be built in order to have a complete analysis and realistic outcomes. Nine cases (namely three distinct jet flow rates of 15, 22, and 30 L/min impinging on different plate speeds of 0.6, 1.0, and 1.5 m/s) were numerically investigated. Two main regions were carefully inspected; the propagations of water fronts in wetting zones and the interactions of wall jets in interaction zones. The realizable k-ε turbulent model (RKE) was utilized with the aid of a non-equilibrium wall function treatment and it showed good performance. The numerical results were validated with the experimental data obtained by other members of the UBC ROT group and showed reasonable agreement in terms of wetting front spreading and wall jets interaction type. Higher plate speeds and/or lower jet flow rates require dense mesh near the target surface to avoid water flow intermittency and capture the wetting front propagation as well as the hydraulic jump configuration. A huge air backflow was depicted when the plate was at the highest speed. Due to the plate movement, the symmetric wetting zone was distorted and became noncircular. According to the flow rate amount and the plate speed, different water wall jet interaction type and a corresponding bulge of water ahead of interaction zone (Int-Z) were captured.

Text

2015-10-24

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/54783

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/