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本文用激光多普勒测速法研究了一种硅油(牛顿流体,S)和一种硅橡胶的硅油溶液(非牛顿流体,P)在入口角是180°,60°,30°和15°的矩形隙缝收缩流中心线上的速度分布.流体(P)在切速率 γ>20s~(-1)时符合幂律到流体τ=Kγ~n,n=0.76,K=44.3 dyne·cm~(-2)·s~n,τ是切应力.测定的速度值均以隙缝中充分发展的中心线速度。v_0值归一.矩形隙缝高 0.83 mm,入口前后的收缩比是12,隙缝长/高比18.1,宽/高比14.3,入口前宽/高比1.19.流动实验在室温进行,缝壁切速率(1.7—11)×10~3 S~(-1),广义雷诺数 Re’0.21—2.2,流体(P)在收缩流入口前也没有出现涡流,在180°入口角的流动池观察到两种新现象:(1)入口前有减速区,体积流速愈大,减速愈甚,在入口前4个半缝高处出现速度极小,到入口前2个半缝高处急剧加速,造成极大的拉伸流场,到入口面收缩流的速度调整已基本完成.(2)在隙缝出口处有显著的速度上升,约为v_0值的5%.出口处发散流的速度调整在出口前1.5个半缝高处已开始,中心线速度急剧下降.入口角较小时可以显著地减小入口前的拉伸速度梯度。 相似文献
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我们建立了一套自准直的氦氖激光多卜勒测速装置(LDA)。其光束夹角为8.10°,光斑直径为0.1mm,测定范围为0.5—500cm/s。 作者用此装置研究了聚合物流体的收敛流动。选用的流体是3％硅橡胶(重均分子量约为90万)的硅油(重均分子量为1.5万)溶液(NNS_2)。流变特性测定表明NNS_2是一个有弹性的流体。对比的牛顿流体是标号为500cSt的硅油(NS_1)。 相似文献
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The center line velocity distributions in the convergent flow of a silicone oil as a Newtonian fluid and a solution of silicone rubber ia silicone oil as a non-Newtonian fluid into a rectangular slit of various entrance angles have been measured by means of laser Doppler velocimetry. The non-Newtonian fluid used conformed to the behavior of a power-law fluid at shear rates greater than 20 s~(-1) with a non-Newtonian index n=0.76. The convergent flow studied had a contraction ratio of 12, with slit height of 0.83mm, slit length to height ratio of 18.1, slit width to height ratio of 14.3 and the width to height ratio before entering the slit of 1.19. Flow experiments were done at room temperature with shear rates at the slit wall of (1.7—11)·10~3s~(-1) and generalized Reynolds number 0.21—2.2. No elastic turbulence was observed in front of the slit entrance. The center line velocity gradient along the flow direction was appreciably reduced in the flow cells of small entrance angles. Two new phenomena h 相似文献
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