Gas wiping is a decisive operation in hot-dip galvanizing process. In special, it has a crucial influence on thethickness and uniformity in coating film, but may be subsequently responsible for the problem of splashing. Theprogress of industry demands continuously the reduction of production costs which may relate directly with theincrease of coating speed, and the speed up of coating results in the increase of stagnation pressure in gas wipingsystem in final. It is known that the increase of stagnation pressure may accompany a harmful problem of splashingin general. Together with these, also, from the view point of energy consumption, it is necessary to design anozzle optimally. And there is known that the downward tilting of nozzle using in air knife system is effective toprevent in somewhat the harmful problem of splashing. In these connections, first, we design a nozzle with constantexpansion rate. Next, for the case of actual coating conditions in field, the effects of tilting of the constantexpansion rate nozzle are investigated by numerical analysis. Under the present numerical conditions, it wasturned out that the nozzle of constant expansion rate of p=having a downward jet angle of 5° is the most effectiveto diminish the onset of splashing, while the influence of small tilting of the nozzle on impinging wall pressureitself is not so large.
