A group of people sitting together

Avinoam Nir

Nir
Professor Emeritus
Phone:
8292119
avinir@technion.ac.il
Room:
355

Research Fields

Fluid Mechanics and Transport Phenomena in Multiphase Suspensions

Research Topics

Dynamics of hybrid compound drops in viscous fluids
Hybrid drops are composed of several immiscible phases. Their dynamics and deformation in viscous fluids is complex because of the existence of several interfaces. We study such systems using conformal mapping techniques and numerical methods. We are interested in macro and micro gravity environments and the effect of thermocapillarity induced by temperature or concentration fields.
Thermocapillary interaction of drops and bubbles
We study diffusive, convective and deformation effects on the interaction of drops and bubbles. Pattern formation and the effect on coalescence emerge. The effort is grossly directed to two avenues : 1. Spontaneous interaction due to interfacial transport. 2. Interaction induced by external gradients.
Turbulent patterns on free interface of sheared suspensions
This project is in collaboration with Prof. Raphael Semiat. The combined effects of particle shear-induced diffusion and capillary forces lead to a turbulent flow pattern at a free surface of a sheared suspension. It is a curious phenomenon since the high the effective viscosity (particle concentration) the stronger is the observed turbulence.
Deformation patterns of slender drops and bubbles in non-Newtonian systems
This project is in collaboration with dr. Moshe Favelukis of Shenkar College.
Dynamics of drops and bubbles in Newtonian and yield-stress fluids
Dynamics, interaction and deformation of droplets in Newtonian yield-stress materials such as Bingham fluids reveal interesting and unusual phenomena. This research combines analytic and numerical models to be solved using Boundary Integral representations and the use of corroborating calculations via application of available software and codes.

Publications

Prakash, J., Lavrenteva, O.M., and Nir, A., 2014 “Application of Clebsch variables to fluid-body interaction in presence of non-uniform vorticity” Phys. Fluids 26, 077102.

Prakash, J., Lavrenteva, O.M., and Nir, A., 2013 “Interaction of bubbles in inviscid and low-viscosity shear flow”, Phys. Rev. E 88(2), 023021.

Prakash, J., Lavrenteva, O.M., Byk, L. and Nir, A., 2013 “Interaction of equal size bubbles in shear flow”, Phys. Rev. E 87. 043002.

Zabarankin, M., Lavrenteva, O.M., Smagin, I. and Nir, A., 2013 “Viscous Drop in Compressional Stokes Flow” J. Fluid Mech. 720, 169-191.

Holenberg, Yu., Lavrenteva, O.M., Shavit, U., and Nir, A., 2012 “Particle tracking velocimetry and particle image velocimetry study of the slow motion of rough and smooth solid spheres in a yield stress fluid”, Phys. Rev. E 86(6), 066301 [6 pages] (2012).

Holenberg, Yu., Lavrenteva, O.M. Shavit, U., Liberzon, A. and Nir, A., 2012 ” PTV and PIV study of the motion of viscous drops in yield stress material”, J. Non-Newtonian Fluid Mech. 193, 129-143.

Favelukis, M., Lavrenteva, O.M. and Nir, A., 2012 “On the evolution and breakup of slender drops in an extensional flow” Phys. Fluids. 24 (4) 043101, 13 pages.

Lavrenteva, O.M., Smagin, I. and Nir, A., 2011 “Boundary-integral simulations of sedimentation of deformable viscoplastic double-emulsion drops in a Newtonian fluid”, Transactions of Academenergo N 4.

Zabarankin, M. and Nir, A., 2011 “Generalized Analytic Functions in an Extensional Stokes Flow with a Deformable Drop” SIAM J. Appl. Math. 71, No. 4, 925-951.

Lavrenteva, O. M., Rosenfeld, L. and Nir, A., 2011 “Shape change, engulfment, and breakup of partially engulfed compound drops undergoing thermocapillary migration” Phys. Rev. E 84, 056323, 11 pages.