Drag Coefficient of Single Spherical Particle in Drag Reducing Polymer Fluids.

Document Type : Research Studies

Authors

1 Mechanical Engineering Department., Faculty of Engineering., Mansoura University., Mansoura., 35516., Egypt.

2 Mechanical Engineering Department., Faculty of Engineering., Cairo University., Cairo., Egypt.

Abstract

An experimental study for the drag of solid spheres in drag reducing Fluids is presented. Polyacrylamide solutions of different concentrations are considered. The drag coefficient is measured by tie terminal velocity of the spherical particle falling in stagnant fluid using high speed camera, Compared to Newtonian Fluid results, the drag of solid particle in polymer solutions exhibit reduced values. However, a drag increase Is exhibited at low Reynolds number. Analysis of the data show the presence of a critical Reynolds number that distinguish between the drag increase and drag reduction regions. It has been postulated that the measured drag is a result of two opposing effects of polymer additives. One is flow resistance increase due to increased extensional viscosity. The other, is the reduction in the form drag due to the influence of these additives on vortex shedding and boundary layer separation. It has been found that the experimental data of drag coefficient is best correlated with the polymer -particle parameter ᴓ or Weissenberg number Ws as well as Reynolds number. 

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