We investigate the modifications in the dynamics of liquid film flow, resulting from the addition... more We investigate the modifications in the dynamics of liquid film flow, resulting from the addition of soluble surfactants. We use aqueous solutions of iso-propanol (IP) and of sodium dodecyl sulfate (SDS), and perform experiments in two inclined flow facilities, a 3000 mm long by 450 mm wide channel and a 800 mm long by 250 mm wide channel. Both facilities may operate with adjustable width up to the above maximum values. Regular disturbances with frequency in the range 0.15-1.50 Hz are introduced at the inlet, and their temporal evolution at various downstream locations is recorded by conductance probes. Recent experiments [1] indicate that, unlike classical predictions based on Squire's theorem, the primary instability of film flow in channels of finite width depends on surface tension. Using IP solutions of varying concentrations, we have shown [2] that this dependence scales with Kapitza number, which expresses the ratio of capillary to viscous stresses as shown at the followi...
Experimental results are reported on the formation and characteristics of solitary waves on liqui... more Experimental results are reported on the formation and characteristics of solitary waves on liquid films flowing along a periodically corrugated wall. The effect of the wall is manifested in the regularity of the resulting wavetrain and also in the shape of individual humps. At high Re, travelling waves recede in favor of a stationary three-dimensional structure, a phenomenon that has no counterpart in film flow along flat walls.
This work has been undertaken in the frame of Marie-Curie Initial Training Network "Multiflo... more This work has been undertaken in the frame of Marie-Curie Initial Training Network "Multiflow", which is investigating multiscale complex fluid flows and interfacial phenomena. We presently report the effect on liquid film flow of two apparently innocuous geometric constraints, a finite channel width and a periodically corru-gated bottom wall. The work has an experimental and a computational /analytical component, and documents some unexpected finding: (i) The finite channel width introduces long-range transverse coherence of traveling disturbances, particularly so for high-surface tension liquids. As a consequence, the primary instability for film flow along a flat wall deviates in the order of 100% from the classical prediction. (ii) Steeply corrugated walls modify the above long-wave instability, but, most impor-tant, introduce at high enough inclination angles a new, oscillatory energy-transfer mechanism that results in an absolute instability at low Re. Film flows at ...
A 1.7kW CO2 laser was used for the study of bead-on-plate welds in D36 ship steel. The effect of ... more A 1.7kW CO2 laser was used for the study of bead-on-plate welds in D36 ship steel. The effect of welding heat input and focal point position on weld geometrical features and microstructure was determined. It was found that weld penetration as well as the width of weld pool and heat-affected-zone (HAZ) increase with heat input. Microstructure and hardness in the weld pool, Partial fusion zone and HAZ are also influenced by heat input. As the heat input is increased, the associated cooling rate is decreased, resulting in the formation of softer microstructures. Simple analytical models describing heat flow during welding were used to calculate the above mentioned geometrical features. The agreement between the calculated and experimentally determined weld penetration, as well as weld pool width, is sufficiently good and depends on weld heat input. The optimum experimental conditions defined from the bendon-plate study were applied to Laser welding of butt joints in 4mm D36 steel.
ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Associat... more ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
ABSTRACT We investigate experimentally the modifications in the dynamics of liquid film flow, res... more ABSTRACT We investigate experimentally the modifications in the dynamics of liquid film flow, resulting from the addition in water of the soluble surfactants iso-propanol (IP) and Sodium Dodecyl Sulfate (SDS). Recent experiments indicate that, the primary instability of film flow in channels of finite width depends on surface tension. Using IP solutions of varying concentrations, we have shown that this dependence scales with Kapitza number. Based on the high solubility and diffusivity of iso-propanol in water, we argue that these solutions behave as pure liquids with reduced surface tension. Indeed, low-frequency inlet disturbances turn in the unstable regime into solitary humps preceded by capillary ripples, with the scaling predicted by theory for simple liquids. Aqueous solutions of SDS exhibit a remarkably different behavior, with more pronounced feature of strong damping of all inlet disturbances. The dominant structures for the entire range of inlet frequencies tested, even at surprisingly high Re, are sinusoidal traveling waves of very small amplitude.
We investigate the modifications in the dynamics of liquid film flow, resulting from the addition... more We investigate the modifications in the dynamics of liquid film flow, resulting from the addition of soluble surfactants. We use aqueous solutions of iso-propanol (IP) and of sodium dodecyl sulfate (SDS), and perform experiments in two inclined flow facilities, a 3000 mm long by 450 mm wide channel and a 800 mm long by 250 mm wide channel. Both facilities may operate with adjustable width up to the above maximum values. Regular disturbances with frequency in the range 0.15-1.50 Hz are introduced at the inlet, and their temporal evolution at various downstream locations is recorded by conductance probes. Recent experiments [1] indicate that, unlike classical predictions based on Squire's theorem, the primary instability of film flow in channels of finite width depends on surface tension. Using IP solutions of varying concentrations, we have shown [2] that this dependence scales with Kapitza number, which expresses the ratio of capillary to viscous stresses as shown at the followi...
Experimental results are reported on the formation and characteristics of solitary waves on liqui... more Experimental results are reported on the formation and characteristics of solitary waves on liquid films flowing along a periodically corrugated wall. The effect of the wall is manifested in the regularity of the resulting wavetrain and also in the shape of individual humps. At high Re, travelling waves recede in favor of a stationary three-dimensional structure, a phenomenon that has no counterpart in film flow along flat walls.
This work has been undertaken in the frame of Marie-Curie Initial Training Network "Multiflo... more This work has been undertaken in the frame of Marie-Curie Initial Training Network "Multiflow", which is investigating multiscale complex fluid flows and interfacial phenomena. We presently report the effect on liquid film flow of two apparently innocuous geometric constraints, a finite channel width and a periodically corru-gated bottom wall. The work has an experimental and a computational /analytical component, and documents some unexpected finding: (i) The finite channel width introduces long-range transverse coherence of traveling disturbances, particularly so for high-surface tension liquids. As a consequence, the primary instability for film flow along a flat wall deviates in the order of 100% from the classical prediction. (ii) Steeply corrugated walls modify the above long-wave instability, but, most impor-tant, introduce at high enough inclination angles a new, oscillatory energy-transfer mechanism that results in an absolute instability at low Re. Film flows at ...
A 1.7kW CO2 laser was used for the study of bead-on-plate welds in D36 ship steel. The effect of ... more A 1.7kW CO2 laser was used for the study of bead-on-plate welds in D36 ship steel. The effect of welding heat input and focal point position on weld geometrical features and microstructure was determined. It was found that weld penetration as well as the width of weld pool and heat-affected-zone (HAZ) increase with heat input. Microstructure and hardness in the weld pool, Partial fusion zone and HAZ are also influenced by heat input. As the heat input is increased, the associated cooling rate is decreased, resulting in the formation of softer microstructures. Simple analytical models describing heat flow during welding were used to calculate the above mentioned geometrical features. The agreement between the calculated and experimentally determined weld penetration, as well as weld pool width, is sufficiently good and depends on weld heat input. The optimum experimental conditions defined from the bendon-plate study were applied to Laser welding of butt joints in 4mm D36 steel.
ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Associat... more ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
ABSTRACT We investigate experimentally the modifications in the dynamics of liquid film flow, res... more ABSTRACT We investigate experimentally the modifications in the dynamics of liquid film flow, resulting from the addition in water of the soluble surfactants iso-propanol (IP) and Sodium Dodecyl Sulfate (SDS). Recent experiments indicate that, the primary instability of film flow in channels of finite width depends on surface tension. Using IP solutions of varying concentrations, we have shown that this dependence scales with Kapitza number. Based on the high solubility and diffusivity of iso-propanol in water, we argue that these solutions behave as pure liquids with reduced surface tension. Indeed, low-frequency inlet disturbances turn in the unstable regime into solitary humps preceded by capillary ripples, with the scaling predicted by theory for simple liquids. Aqueous solutions of SDS exhibit a remarkably different behavior, with more pronounced feature of strong damping of all inlet disturbances. The dominant structures for the entire range of inlet frequencies tested, even at surprisingly high Re, are sinusoidal traveling waves of very small amplitude.
Uploads