A few days ago, Associate Professor Liu Nansheng and collaborators in the Computational Fluid Mechanics Laboratory, School of Engineering Science, University of Science and Technology of China made significant progress in the study of complex turbulent flow of non-Newtonian fluids. The turbulent drag increase caused by macromolecular additives was first discovered through numerical simulation of Taylor-Couette Phenomenon, and proposed that the driving mechanism of this phenomenon stems from the inertial-elastic G? Tler instability induced by the elastic effect of macromolecules. The research results were published in Phys. Rev. Lett. On September 13th, and the relevant mechanism can be used to guide the turbulent flow control of complex engineering of non-Newtonian fluids.
Taylor-Couette turbulent large-scale Taylor vortex breakup and drag increase caused by macromolecular additives
Research by Associate Professor Liu Nansheng and collaborators shows that macromolecular additives can cause a drastic increase in resistance of more than 60% in curved wall turbulence, which is the same as macromolecules in turbulent flow on flat walls (channels or round tubes) that have been previously concerned The induced drag reduction effect of up to 70% is diametrically opposed. The analysis indicates that there is a highly nonlinear interaction between macromolecular stretching and fluid shear, which causes the large-scale Taylor vortex structure in the flow field to break into two small-scale vortex structures with completely different formation mechanisms, that is, inertial instability The Taylor vortex and the G? Tler vortex triggered by elastic instability cause a sharp increase in turbulence resistance; the specific root of the G? Tler vortex structure is that macromolecular additives induce local elastic instability near the static outer cylinder, and Further triggered the stronger G? Tler instability.
The scientific explanation of the new flow phenomenon and its mechanism discovered in this work is highly evaluated and affirmed by international scholars. The research results are considered by the reviewers as "very interesting and scientifically sound, provided a plausible mechanism based on elastically modified G? Tler vortices for "Concave walls", and published in the US "Physical Review Letters" [Physical Review Letters]. Associate Professor Liu Nansheng is the first author of the paper. This work was supported by the National Natural Science Foundation of China.
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