Variational 1-D Two-Fluid Model For Vertical Adiabatic Slug Flows

Numerical simulation of vertical adiabatic slug flows is performed using a variational one-dimensional (1-D) Two-Fluid Model (TFM), that incorporates the wake entrainment instability to make the model dynamic. Use of the variational TFM requires formulation of the inertial coupling coefficient to define the kinetic coupling between the phases. Using a lumped parameter model for flow over two cylindrical bubbles, the inertial coupling coefficient for slug flow wake entrainment phenomena is obtained. A variational 1-D TFM linear stability analyses comprising the characteristics and the dispersion relation and non-linear numerical simulations are performed, to demonstrate the wake entrainment instability leading to formation of long Taylor bubbles. Finally, the wavelengths, amplitudes and propagation velocities of the void waves from non-linear simulations are validated with two sets of experimental data.