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The computational results demonstrate that the present lift force model for prolate spheroidal particles is applicable in flow cases with streamwise and non-streamwise flow shear, even if some (reasonably small) accuracy for the case of the streamwise-only shear is lost.Įn utilisant la simulation numérique directe (DNS), la dynamique de particules non sphériques inertielles dans un écoulement turbulent de canal a été étudiée numériquement. In order to validate the ability of the present method for capturing the lift component arising from non-streamwise flow shear, the lift force model is compared with established generalised Saffman-type lift models by simulating the motion of a particle in lid-driven cavity flow. The accuracy of the novel shear lift force model for prolate spheroidal particles is verified by comparing it with the lift force model proposed in Part I via simulating the axial migration of a prolate spheroidal particle in the Poiseuille flow. The novelty in the presented method is the computation of the shear lift force model for prolate spheroidal particles taking into account also non-streamwise flow shear. The present method assumes that the particle slip velocity is parallel to the fluid velocity along the particle trajectory.
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In Part II the influence of the non-streamwise flow shear on the lift force is also taken into account. The method proposed in the Part I calculates the lift force arising from the dominant streamwise flow shear. The method can be applied to the computation of lift forces exerted on prolate spheroidal particles (or fibres) in arbitrary non-uniform flows. The present contribution is the second part of a two-part research work presenting a generic method to extend lift force models that were originally devised for single linear shear flow to arbitrary flow conditions. , with a significantly decreased computational cost, rendering it as suitable for the implementation in large scale Lagrangian particle tracking.
#ULTRASONIC ILIFT FULL#
The implementation of the simplified lift model leads to computational results with reasonably small difference to the results of the full lift model of Cui et al. The computational results demonstrate that the present lift force model for prolate spheroidal particles is applicable in flow cases with streamwise and non-streamwise flow shear. The simplified shear-induced lift model for prolate spheroidal particles is verified by comparing it with several established lift force models via simulation of a prolate spheroidal particle moving in the Poiseuille and lid-driven cavity flows. This unified model is successfully simplified into a shear-induced lift model for prolate spheroidal particles moving in arbitrary flow conditions via analogy arguments. The paper proposes a unified shear-induced lift force model which divides the lift force into four lift components arising from the spin tensor, the volumetric and the deviatoric parts of the rate of deformation tensor, and the inertia effect of the Stokes drag. The computational results confirm the correctness of the proposed shear lift force models. The new generalised Saffman-type lift model is compared with an established generalised Saffman-type lift model by simulating the axial migration of a spherical particle in Poiseuille flow. In order to verify the proposed shear lift force for prolate spheroidal particles, numerical simulations of a particle moving in Poiseuille flow at four different initial positions and two aspect ratios are perfomed. The derived numerical algorithm is applied to the computation of a dedicated shear lift force model for prolate spheroidal particles (or axisymmetric ellipsoidal particles) and a novel generalised Saffman-type lift force model for spherical particles in a general shear flow.
#ULTRASONIC ILIFT SERIES#
The method computes the lift force due to the dominant streamwise flow shear in the Stokes flow regime by implementing a series of coordinate transformations, facilitating the computation of the lift force from dominant streamwise flow shear. The paper proposes a generic method to extend lift force models that were originally devised for single linear shear flow, to arbitrary flow conditions.