Interactions between a pair of equal-size viscous drops in shear are numerically investigated at finite Reynolds number ͑Re= 0.1-10͒. At low Reynolds number the simulation compares well with a previous experimental observation. Apart from the usual pairwise motion where drops driven by shear pass over each other ͑type I trajectory͒, finite inertia introduces a new type ͑type II͒ of reversed trajectory where drops approaching each other reverse their initial trajectories. The new trajectory is explained by a reversed streamline pattern observed around a single drop in an imposed shear, and is similar to what is also observed for rigid spheres at finite inertia. However, drop deformability introduces a nonuniform transition from one to the other type of trajectory-drops display type I trajectory for high and low capillary numbers and type II for intermediate capillary numbers. The phenomenon is explained by noting that increasing capillary number gives rise to competing effects-while it increases drop deformation and therefore increases resistance to sliding motion, it also increases drop flexibility, decreases inclination angle, and overall effect of the drop's presence is reduced, all helping them to slide by. The nonuniform behavior-type II trajectory for an intermediate range of capillary numbers-occurs only at Reynolds number above a critical value. Further increase in Reynolds number increases the range of capillary numbers for type II trajectory. For type I trajectory, terminal cross-stream separation increases linearly with increasing inertia indicating an enhanced shear induced diffusion. Increasing initial streamwise separation aids in reversed ͑type II͒ trajectory due to increased overlap with the reversed streamline zone. Increasing cross-stream distance expectedly facilitates ͑type I͒ sliding motion. For passing drops ͑type I trajectory͒, terminal cross-stream separation is not appreciably affected by capillary number and initial drop separation.

We numerically investigated the film flow down an inclined plate using the volume of a fluid (VOF) method. The flow simulations have been systematically carried out for a wide range of parameters, such as inlet size, inclination angle, contact angle, flow rates and solvent properties (viscosity and surface tension). Based on the simulation results, scaling theory is being proposed for both interfacial area and for film thickness in terms of the Kapitza number (Ka).The Kapitza number is advantageous because it depends only on solvent properties. The Kapitza number decreases with increased solvent viscosity and is fixed for a given fluid. To investigate the effects of solvent properties on interfacial area a small inlet cross-section was used. The interfacial area decreases with increased value of Ka and scaling for interfacial area in terms of Ka is proposed. The time to reach pseudo-steady state of rivulet is also observed to increase with decreasing Ka. For a fixed flow rate, the inlet cross-section has marginal effect on the interfacial area; however, the developed width of the rivulet remains unchanged. In addition to inlet size, flow rate and solvent properties, the impact of contact angle on film thickness and interfacial area was also investigated. The contact angle has negligible effect for a fully wetted plate, but it significantly affects the interfacial area of the rivulet. A scaling theory for interfacial area in terms of the contact angle and Ka is presented.

The expansion dynamics and spectral behaviour of plasma produced by a Nd:YAG laser (λ = 1.064 μm, pulse width: 8 ns) from barium target and expanding in 0.45 T transverse magnetic field in vacuum (10−5 Torr pressure) are investigated using time-of-flight optical emission spectroscopy. The experiments are carried out at various laser fluences from 12 to 31 J/cm2. The temporal profiles of neutral (Ba I 553.5 and 577.7 nm) lines are temporally broadened, while that of ionic (Ba II 413.0 and 455.4 nm) lines show strong confinement in the presence of a magnetic field. In the absence of magnetic field, the temporal profile of Ba I 553.5 nm is exactly reproduced by fitting with two Shifted Maxwell Boltzmann (SMB) Distribution components, while in the presence of a magnetic field the profile could only be fitted with three components. The field enhanced and field induced SMB components of neutral profile are correlated with populations of ground state, metastable states, and long-lived Rydberg states present in the barium plasma, while SMB components of ionic lines are explained on the basis of the presence of super-elastic collisions among the excited species in the plasma. The spatial variation of electron temperature and temporal variation of electron density are deduced and correlated to the different collisional processes in the barium plasma. The ionic profiles show efficient confinement in the presence of a magnetic field at higher fluences.

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Geodesic acoustic modes (GAMs) can be excited by mode coupling to primary modes such as the drift waves and ion temperature gradient modes in tokamak plasmas. Recent global numerical simulations of ion temperature gradient modes show excitation of GAMs and indicate that the radial wave-number of the excited GAMs scales inversely as the ion Larmor radius. Also the modes are excited dominantly in the edge region of the device. Furthermore there is a nonlinear downshift of the GAM frequency compared with the predicted linear mode frequency. The mode-coupling analysis presented in this paper provides an explanation of the scaling of the radial wave-number, the preferential excitation of GAMs in the outer half of the plasma and the nonlinear downshift of the frequency of GAMs.