Spatiotemporal signatures of elastoinertial turbulence in viscoelastic planar jets
Spatiotemporal signatures of elastoinertial turbulence in viscoelastic planar jets
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DOI：
10.1103/physrevfluids.8.064610
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发表时间：
2022-07
影响因子：
2.7
通讯作者：
Sami Yamani;Yashasvi Raj;T. Zaki;G. McKinley;Irmgard Bischofberger
中科院分区：
文献类型：
--
作者：
Sami Yamani;Yashasvi Raj;T. Zaki;G. McKinley;Irmgard Bischofberger
在高变形速率下，聚合物稀溶液中粘弹性和惯性之间的相互作用可导致惯性弹性不稳定性。这些不稳定性的非线性演化产生的湍流状态与显着不同的时空特征相比，牛顿湍流，称为弹性惯性湍流（EIT）。我们探讨EIT通过研究的动态淹没平面射流的稀聚合物水溶液注入到一个静态的水箱的水使用纹影成像和激光多普勒测速仪（LDV）的组合。我们展示了流体弹性如何对射流稳定性产生非单调效应，这取决于其大小，从而产生两种不同的制度，其中弹性效应可以使射流不稳定或稳定。与粘弹性射流的线性稳定性分析一致，惯性弹性剪切层不稳定性出现在射流边缘附近的小弹性水平，独立于流体柱中的大规模波动。这种扰动模式的增长使流动不稳定，导致与牛顿射流中向湍流过渡所需的条件相比，在较低雷诺数和更靠近喷嘴处发生湍流过渡。流体弹性的增加将剪切层不稳定性合并为射流柱的整体不稳定性。在这种情况下，剪切层中产生的弹性拉伸应力起到部分稳定流动的“弹性膜”的作用，延迟向湍流的转变，以达到更高的惯性水平和距喷嘴更大的距离。在远离喷嘴的完全湍流状态下，平面粘弹性射流表现出与EIT相关的独特时空特征。
The interplay between viscoelasticity and inertia in dilute polymer solutions at high deformation rates can result in inertio-elastic instabilities. The nonlinear evolution of these instabilities generates a state of turbulence with significantly different spatio-temporal features compared to Newtonian turbulence, termed elasto-inertial turbulence (EIT). We explore EIT by studying the dynamics of a submerged planar jet of a dilute aqueous polymer solution injected into a quiescent tank of water using a combination of schlieren imaging and laser Doppler velocimetry (LDV). We show how fluid elasticity has a nonmonotonic effect on the jet stability depending on its magnitude, creating two distinct regimes in which elastic effects can either destabilize or stabilize the jet. In agreement with linear stability analyses of viscoelastic jets, an inertio-elastic shear-layer instability emerges near the edge of the jet for small levels of elasticity, independent of bulk undulations in the fluid column. The growth of this disturbance mode destabilizes the flow, resulting in a turbulence transition at lower Reynolds numbers and closer to the nozzle compared to the conditions required for the transition to turbulence in a Newtonian jet. Increasing the fluid elasticity merges the shear-layer instability into a bulk instability of the jet column. In this regime, elastic tensile stresses generated in the shear layer act as an ``elastic membrane'' that partially stabilizes the flow, retarding the transition to turbulence to higher levels of inertia and greater distances from the nozzle. In the fully turbulent state far from the nozzle, planar viscoelastic jets exhibit unique spatio-temporal features associated with EIT.