|کد مقاله||کد نشریه||سال انتشار||مقاله انگلیسی||ترجمه فارسی||نسخه تمام متن|
|4994848||1368189||2018||11 صفحه PDF||ندارد||دانلود کنید|
â¢Wall-normal segregation of inertial spherical particles in a specific asymmetric turbulent Couette-Poiseuille flow with vanishing wall shear was demonstrated and explained.â¢The particle wall-normal segregation may appear near shear-free walls, depending on particle inertia. The near-wall coherent turbulent structures are strong and local in the flow, and are not a prerequisite for the particles to segregate near the wall region. They do, however, perform an inertial selection and determine the actual segregation ability of the particles.â¢The LSSs are weak but global in the flow, which play an important role in the wall-normal particle segregation.
Inertial particles dispersed in wall-bounded flows in pipes and channels are known to accumulate close to the walls. The segregation ability depends greatly on the inertia-selection effects of the near-wall quasi-coherent turbulent structures, which are formed near both walls where shear stresses are high. Here, however, we investigated if and how particles segregate in the vicinity of walls in absence of mean shear. A tailor-made turbulent CouetteâPoiseuille flow was designed such that the mean shear vanished at the moving wall, thereby resulting in an asymmetric flow with conventional near-wall turbulent structures only at one wall. In addition, Large-Scale Structures (LSSs) were observed in the flow, which greatly influenced the distribution of the inertial particles. Particles of five different inertia groups were embedded in the directly simulated turbulence field and examined. It was found that particles of high inertia segregated near the stationary wall where mean shear prevailed, but also near the moving wall where mean shear was absent. However, due to the qualitatively distinct near-wall flow structures, the inertia effects on the actual segregation were different at the two walls. Mechanisms causing the asymmetric wall-normal segregation were explored with the focus on the moving-wall region, where the quasi-coherent turbulent structures were absent, and the local fluid structures were dominated by imprints of the LSSs.
Journal: International Journal of Multiphase Flow - Volume 98, January 2018, Pages 45-55