Wavy interface

The clad plate is x-rayed perpendicular from the steel side and the film contacts the aluminum. Radiography reveals the wavy interface of explosion-welded, aluminum-clad steel as uniformly spaced, light and dark lines with a frequency of one to three lines per centimeter. The waves characterize a strong and ductile transition joint and represent the acceptable condition. The clad is interpreted to be nonbonded when the x-ray shows complete loss of the wavy interface (see X-ray technology). 

Annular flow, wavy interface (Henry, 1971) Under this condition the virtual mass of gas flowing over a wavy surface can be approximated by flow over a surface made of continuous rows of half-cylinders ... 

Explosive Bonding, Mechanism of. An aero-hydrodynamic analogy is used to construct a description of the formation of wavy interfaces during expl bonding, which is described by J.T. Kowalick D.R. Hay in Metallurgical Transactions, Vol 2, July 1971, pp 1953-58... 

Chum flow or slug flow-annular (dispersed) flow transition. The flow becomes annular when the gas flow rates are enhanced to a certain point. The high gas flow rate causes a wavy interface of the liquid film. As a consequence, parts of the waves will enter the gas core as entrained drops. This results in an upward flow direction of the liquid, due both to interfacial shear and to drag on the waves and drag on the droplets. Annular flow can therefore exist only when the gas velocity is sufficient to lift the droplets in the gas core. The minimum gas velocity required to suspend a drop is determined from the balance between the gravity and drag forces on the drop. 

Wavy flow As stratified but with a wavy interface due to higher velocities <0.3 >5... 

In this mode of flow, the gravitational forces dominate and the gas phase flows in the upper part of the pipe. At relatively low flowrates, the gas-liquid interface is smooth, but becomes ripply or wavy at higher gas rates thereby giving rise to the so-called wavy flow . As the distinction between the smooth and wavy interface is often ill-defined, it is usual to refer to both flow patterns as stratified-wavy flow. 

The purpose of this chapter is to show the role of the model used for the interfacial shear at different stages of stability analyses of the stratified flow configuration and to summarize progress made in formulating a closure law which reflects the dynamics of the interaction involved in turbulent gas flow over a mobile wavy interface. 

Recently, Hanratty presented a comprehensive review of the attempts to account for the interfacial waviness in modelling the interfacial shear stress for the stability analysis of gas-liquid two-phase flows [53]. Basically, the approach taken was to implement the models obtained for the surface stresses in air flow over a solid wavy boundary as a boundary condition for the momentum equation of the liquid layer over its it mobile wavy interface. Craik [98] adopted the interfacial stresses components which evolve from the quasi-laminar model by Benjamin [84]. Jurman and McCready [99], Jurman et al. [100], and Asali and Hanratty [101] used correlated experimental values of shear stress components (phase and amplitude) based on turbulent models which consider relaxation effects in the Van Driest mixing length. Since the characteristics of the predicted surface stresses are dependent on the wave number, Asali and Hanratty picked the phase and amplitude values which correspond to the wave lengths of the capillary ripples observed in their experiments of thin liquid layers sheared by high gas velocities [101]. It was shown that the growth of these ripples is controlled by the interfacial shear stress component in phase with the wave slope. 

Akai, M., Inoue, A., Aoki, S., and Endo, K., A Co-Current Stratified Air-Mercury Flow with Wavy Interface, Int. J. Multiphase Flow, Vol. 6,... 

Other types of instabilities may exist, for example, a problem has been observed in feedblock coextrusion of axis5mimetric sheet (27). A wavy interface is also characteristic of this instability, but the wave pattern is more regular when viewed from the surface. The instability originates in the die, well ahead of the die land, and internal die geometry influences both the severity and pattern. For a given die geometry, the severity of instability increases with structure asymmetry and some polymers are more susceptible to unstable flow than others. 

Thresholds of changes in behavior can be expected (no contact contact "wavy" interface and separation). These changes may be connected with changes in the FCI mode boiling, decoupled propagation, and steam explosion. 

For simplifying the problem, the simulated object is the liquid-gas contacting falling film with wavy interface as shown in Fig. 8.51. The simulation is on the two-dimensional x-z plane. Xiao [12] established the model equation and give the simulated results as follows. 

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