The pressure to drive a Boger fluid through a long converging channel was measured as a function of flow rate. The channel geometry and flow rates were designed to avoid an upstream vortex and to maximize extensional effects, specifically, to achieve Deborah numbers up to 3 along with a minimum strain of 3. The first measurements of pressure drop were made with two Newtonian fluids, and predictions were made by analysis and Fluent. The latter two agreed to within 1%, and the measurements deviated from these by 5% at most. Four Boger fluids were prepared – three PIB/PB solutions and a solution of PAA in corn syrup. Only one produced reliable pressure-drop measurements, and the data exactly matched that for an equivalent Newtonian fluid, in contrast to the literature where non-Newtonian pressure drops were up to several times higher. Although elasticity apparently had no effect, significant die swell was observed at the channel exit. The explanation for the matching data appears to lie with the radial presssure distribution, which caused migration of the fluid inward, thus lowering shear rates and shear stresses at the wall. Measurements of die swell were made and used to calculate N₁, from which the axial stress due to shearing on the exit plane was estimated. The extensional stress at the centreline was also estimated, and found to be only a small fraction of the shearing axial stress.

测量驱动Boger流体通过一个长的会聚通道的压力与流量的关系。通道的几何形状和流速旨在避免上游涡流并最大程度地发挥延伸作用，特别是要使Deborah数达到3，最小应变为3。首先对两种牛顿流体进行了压降测量，并且通过分析和Fluent进行预测。后两者同意在1％以内，并且测量值最多偏离5％。准备了四种Boger流体–三种PIB / PB溶液和PAA玉米糖浆溶液。与非牛顿压降高出几倍的文献相比，只有一个能产生可靠的压降测量值，并且数据与等效牛顿流体的数据完全匹配。尽管弹性显然没有影响，但在通道出口处观察到明显的模头膨胀。匹配数据的解释似乎与径向压力分布有关，径向压力分布导致流体向内迁移，从而降低了壁处的剪切速率和剪切应力。进行模头膨胀的测量，并用于计算N参照图₁，由此估计了由于在出口平面上的剪切而引起的轴向应力。还估计了中心线处的拉伸应力，发现该应力仅是剪切轴向应力的一小部分。