고분자용액에 의한 유체수송관벽의 저항감소 -III. 저항감소유체의 입구흐름 영역에 대한 고찰-

Drag Reducton of Pipe Wall For Fluid Flow due to Injected Polymer Solution - III. Consideration of Entrance Region Flow of Drag Reducing Fluids-

As a part of studies of drag reduction phenomenon, at the entrance flow region of abrupt contraction tube flowing water, dilute and concentrated drag reducing polymer solutions contraction losses are estimated experimentally. Futher more, entrance lengths are considered theoretically and are measured experimentally. In the present experiment, fluid temperature is fixed l<TEX>$0^{\circ}C$</TEX> and flow rates are 3,000<Re<20,000. The data for concentrated drag reducing polymer solutions in turbulent flow show that drag reduction is increased as increasing flow rates at the fully developed flow region, but it is decreased as increasing flow rates at the entrance flow region, and that entrance lengths and contraction losses are significantly larger than those of Newtonian fluids. Dilute polymer solutions show that contraction losses and entry lengths for these materials are indistinguishable from the values for Newtonian Fluids. From the theoretical consideration the entrance lengths are somewhat insensitive to Deborah Number. Some experimental measurements on entrance lengths using drag reducing polymer solutions made in this work show a good agreement with the theoretical predictions.