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Hydrodynamics of circular free-surface long water jets in industrial metal cooling Seraj, Mohammad Mohsen


Control cooling in run-out table (ROT) is crucial in managing the properties of steel strip. However, industries still rely on experience and empirical methods due to the complexity and transient nature of cooling process. The associated flow features of ROT cooling received little attention in the literature. The main purpose of this research is to investigate systematically the hydrodynamics of long circular water jets impinging on fixed and moving plate with industrial scale. The fixed plate experiments showed that the impingement film and circular hydraulic jump were disturbed with surface waves and splattering. The experiments on moving plate with single impinging jet demonstrated the effect of jet flow rate and plate speed on wetting zone. For a given plate velocity, the size of wetting area increased according to jet Reynolds number. The moving impingement surface interferes with radial spreading film and the wetting front became noncircular. A new correlation for the radius of wetting front has been proposed. The effect of plate motion on liquid jets interactions were studied experimentally using multiple jets. Nonsplashing thick interaction film or thin upwash splashing fountain at the interaction zone were observed depending on process parameters. If the effect of plate motion was not promoted then the interaction flow structure was preserved similar to stationary plate. However, the moving plate could change the strong splashing fountain interaction flow to nonsplashing thick film depending on the velocity ratio of plate to jet for a given nozzle space. Higher plate speeds and/or lower jet flow rates are more likely to decrease splashing and change the fountain type interaction. Numerical simulations on stationary surface demonstrated that suggested velocity and pressure variation for short laminar jets may be adapted for long turbulent liquid jets if the gravity is considered. Generally, shear-stress transport k-ω model showed better performance after impingement. The moving plate simulations of single jet proved the distortion of the impingement zone. The shifted stagnation point produces noncircular impingement region and unsymmetrical spreading of impingement water film over the surface. Longitudinal negative velocity was occurred at higher plate velocity simulations which represent the backwash flow.

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