Rheology Projects:
Numerical Investigation of Rheological Behavior of Heavy Crude Oil on interfacial Instability of Water-Lubricated Pipe Transport
This study investigates the core-annular flow of two different rheological fluids in which two immiscible fluids meet in parallel streams. The velocity correction scheme and AdamsBashforth algorithm are employed for the pressure-velocity coupling and time integration of momentum equation respectively. Three different benchmarks including NewtonianNewtonian, Thixotropic-Newtonian, and Viscoelastic- Newtonian, are considered for this study. For simulations of Thixotropic and Viscoelastic fluids, Moore and Oldroyd-B models are applied respectively. The governing equations include Incompressible Navier-Stokes, shear dependent-viscosity equation (for Thixotropic fluids), constitutive equation for extra polymeric stress (for viscoelastic fluids) and concentration equation (for evaluation the fluid interfaces). For validation, the numerical results of core-annular flow of two similar viscoelastic fluids in a 2D channel are compared with the analytical solution of Oldroyd-B. Various parameters are studied for each of three mentioned cases. The numerical results show that in the flow of Newtonian-Newtonian fluids or Newtonian-Thixotropic flows, the most dominant factor that affects the pressure gradient in the channel depends on the type of initial fluid in the channel and the type of second fluid that disperses to the initial fluid. In addition, the viscosity of the core fluid and the geometry of the problem are the critical parameters for the instability of the fluids interface. For viscoelastic-Newtonian flows, regarding the sudden jump of polymeric stress from its maximum value in the interfacial boundary of the viscoelastic-Newtonian flow to zero,a stabilization correlation is suggested that dependents on the problem geometry. Numerical results show that the viscoelasticNewtonian flow has different characteristics compared to the two previous ones. Weissenberg and Reynolds number are the most prominent parameters in the behavior of interfacial instability of viscoelastic-Newtonian flows. Figure 1 shows time evolution of concentration field of a concentric core annular flow of a viscoelastic-Newtonian fluid at We=10. Figure 2 presents time evolution of concentration field of a concentric core-annular flow of abthixotropic-Newtonian fluid.
