Liquid Surface Velocity Research Articles

Hydraulic Jump Behavior during Filling Process of Cast Start II

This paper presents a 0.25-scale quasi-three-dimensional hydraulic model experiment of transient fluid flow phenomena during continuous casting of steel under solidification. Water cooling is performed at the bottom of the mold, and saturated sodium acetate solution is covered on the spring and particle arrangement at the bottom of the mold/on the dummy bar to simulate the solidification phenomenon in the actual continuous casting process. The results show that the solidification on the dummy bar surface is very important to the early stage of the filling process and cannot be ignored. Its influence gradually decreases with the rise of the liquid level, and basically disappears when the liquid level rises to a certain height (steady liquid level, SLL). In SLL, the interface morphology of the solidified layer is more affected by the flow, while the interface morphology of the solidified layer has no significant effect on the liquid surface velocity.

Optimizing of Submerged Entry Nozzle for Bloom Continuous Casting Based on Physical and Numerical Simulation

Herein, a physical model with a geometric similarity ratio of 1:1 and a 3D numerical model of macrosegregation are established to study the initial metallurgy behavior of the 410 mm × 530 mm section bloom continuous casting (CC). The results show that the average wave height, liquid surface velocity, and washing velocity of the five‐port nozzle are greater than those of the straight nozzle, but the center temperature and the temperature gradient at the solidification front are lower. Meanwhile, the diagonally installed five‐port nozzle can avoid the excessive washing effect under the orthogonally installed five‐port nozzle, which improves the minimum subsurface negative segregation index, which is increased from 0.753 to 0.802. For the Steel 45 bloom CC process, when the straight nozzle is changed to the diagonally installed five‐port nozzle, the length of the equiaxed crystal zone is increased from 97.5 to 198.5 mm, and the asymmetry of the solidification structure is improved.

Study on Multiphase Flow in a Wide-Width Continuous Casting Mold

The multiphase flow in the mold has a significant impact on the surface quality of the slab. In this paper, the multiphase flow in the mold is studied by establishing a one-quarter scale water mold, with the aid of a high-speed camera and particle image velocimetry (PIV). The oil phase will make the liquid surface velocity around the nozzle smaller. The greater the viscosity of the oil, the greater the critical water model casting speed and the shallower the critical immersion depth of submerged entry nozzle (SEN). Blowing will enhance the turbulence of the flow field in the mold and have a suppressing effect on the surface velocity. However, the vertical velocity of the narrow surface does not change significantly. The randomness of the bubble entering the mold from the nozzle can easily cause asymmetry of the instantaneous flow. The number of bubbles with a diameter less than 1 mm increase with the increase in gas flow rate. The larger the bubble size, the more buoyant around the nozzle when it escapes. The larger the diameter of bubble, the closer the vortex center of the upper circulation is to the nozzle and the closer the center of the lower circulation is to the narrow surface.

The Role of Liquid Properties on Lifetime of Levitated Droplets.

It is known that the temperature difference between a droplet and a liquid surface can extend the levitation time of that droplet by providing a thin air film between the surface and the droplet. However, the effect of fluid properties, liquid surface velocity, and air film thickness on the lifetime of droplets is still not well understood. Also, there is inconsistency in the literature about the role of vapor pressure in noncoalescence. Here we test a variety of liquids including silicone oil, Fluorinert, and water to understand the effect of surface tension, density ratio, viscosity, and heat capacity on the lifetime of a droplet. Droplets with larger heat capacity and vapor pressure like water remain floating for a longer time compared to oils. Similarly, higher surface velocity, which is seen in low viscous liquids, helps the air to replenish into the interstices beneath droplet and delay the drainage process. We also discuss the air film variation with temperature manipulation, and propose a correlation for the minimum thickness required to balance the droplet weight.

Mathematical Simulation on Slag Entrainment in Bottom-blowing Gas Ladle with Immersed Cylinder

A flow field mathematical model of the molten steel in a 150 t bottom blowing gas ladle has been established. The ladle blowing argon process was simulated by mixture multiphase model. The flow of the liquid steel and the phenomenon of slag entrainment on the surface of the liquid steel in bottom blowing gas ladle with immersed cylinder were studied. On the basis of the effects of the gas flow rate and the way of blowing on the flow state of the top slag and mixing of molten steel, the critical gas flow rate with the immersed cylinder was determined. The results show that the flow distribution of the liquid steel tends to be uniform, the liquid surface velocity decreases, the critical gas flow of slag entrainment increases and the mixing time is shortened in the ladle when an immersed cylinder is applied.

Passive mixing enhancement of microliter droplets in a thermocapillary environment

Fast and efficient mixing of reagents and bioassays is of great importance in micro total analysis systems and in particular, open-surface microfluidics. This is the first study of droplet collision and mixing phenomenon of levitated droplets on an immiscible thin liquid substrate undergoing Marangoni convection. The mixing percentage was determined by monitoring the changing color during chemical reaction that occurs in the resultant coalesced droplet. The thermocapillary effect of the liquid substrate plays a significant role in mixing in that the liquid surface velocity and the droplet velocity increase with an increase in the surface temperature gradient. This, in turn, increases the mixing of the coalesced droplet, which is further enhanced when the drop size is smaller. Since the collision is convection dominated, an appropriate time scale is proposed, which provides a universal correlation of the non-dimensional mixing time in terms of Reynolds number.

Measurement of liquid sheet using laser tagging method by photochromic dye

Liquid atomization system has been extensively applied as the most significant process in many industrial fields. In the internal combustion engine, the combustion phenomenon is strongly influenced by the spray characteristics of the fuel given by the atomization process. In order to completely understand the whole atomization process, a detail investigation of relations between the liquid jet characteristics and the breakup phenomenon is required. In this study, a non-intrusive method called as laser tagging method by photochromic dye has been developed with aim to study the breakup process of liquid sheet in detail, covering from the behavior in film until disintegrated into ligament and droplets. The laser tagging method by photochromic dye is based on a shift in the absorption spectrum of photochromic dye molecules tagged by ultraviolet laser. The shift results a color change at the tagged region of liquid containing the dye. In this study, the motions of the dye traces were analyzed as the liquid surface velocity. As a result, liquid sheet was found to keep its velocity constantly in film before suddenly increase around broken point. However, it then decreased after broken into droplets. By forming a set of four points of dye traces on the liquid sheet, the change of relative position of the set enabled the measurement of deformation and rotational motion of the liquid sheet. As a result, the normal strain of the liquid sheet parallel to the flow direction depended on the flow behavior of ligament formation.

Simultaneous Measurement of Liquid Surface and Wave Velocities for Falling Liquid Films

We propose a simultaneous measurement of liquid surface and wave velocities for falling liquid films on inclined wall The liquid surface velocity was measured using a non―intrusive technique called as laser tagging method by photochromic dye. The movement of the dye trace tagged by UV laser(λ=355nm)was recorded by a high speed video camera and analyzed together with the movement of wave passing over the dye trace. As a result,velocity difference between wave and liquid film before the wave passing over was found to increase with increasing wall inclination angle.

Generation of a Wave on a Liquid Film Flowing Down a Heated Inclined Plane. 2nd Report, Disturbance and Marangoni Waves.

An investigation was conducted into the generation of a disturbance wave on a liquid film flowing down a heated inclined plane. Theoretical analysis shows that the Marangoni effect due to the surface tension gradient contributes to reduction of the critical flow rate of the liquid on the generation of a disturbance wave. Theoretical results also suggest the existence of two boundaries for generation of a disturbance wave, at a fixed inclined angle. The lower boundary, however, could not be observed for thin water film because liquid film breakdown occurred before the lower critical flow rate was achieved. In this paper, silicone oil with high viscosity was used as the working fluid instead of water. Small waves were observed under the lower critical flow rate. The surface temperature gradient along a wave is one order of magnitude larger than that of a disturbance wave under the higher critical flow condition. We defined a wave under lower critical condition as a Marangoni wave. The measured velocity of a Marangoni wave is almost the same as the liquid surface velocity.

Stratified gas-liquid two-phase electrohydrodynamics in horizontal pipe flow

Stratified gas-liquid two-phase electrohydrodynamics in pipe flow has been studied experimentally and numerically. Experimental studies were conducted using 1.27 and 1.9*10/sup -2/ m-inner diameter horizontal tubes with air-water two-phase flow for the range of gas surface velocity of 10+or-/sup 2/-10 m/s, liquid surface velocity of 10/sup -2/-2*10/sup -1/ m/s, and applied voltage of 0-20 kV. Experimental results are analysed by an area-averaged two-fluid one-dimensional model. The results show that the effect of the applied electric field is significantly influenced by the flow regime transition boundaries between stratified smooth-to-wavy and stratified wavy-to-intermittent flow. However, the time-averaged void fraction was not observed to be significantly influenced by applied electric fields.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Laminar-turbulent transition in a radial free liquid film flow. (3rd report. Velocity measurements on transition from laminar to turbulent flow).

The laminar-turbulent transition in the radial flow of a free liquid film is studied. The liquid film flow is generated in the same way as in the previous papers. When the Reynolds number which is based on the liquid surface velocity and the film thickness at the disk edge is high, the transition from laminar to turbulent flow takes place several millimeters downstream of the disk edge. The change of the velocity distribution in the process of the transition is examined by LDV. It is found that the reduction of the radial velocity component due to the occurrence of very small vortices starts at the higher velocity side of the liquid film a few millimeters downstream of the disk edge, and thereafter the velocity distribution becomes uniform immediately.

Liquid Films Flowing Concurrently with Air in Horizontal Duct : 3rd Report, The relation between occurrence of viscous wave and breakdown of liquid film

A thin liquid film flowing concurrently with an air stream was investigated with regard to waves generated when superficial velocity of air was less than about 10 m/s and water flow rate was considerably low. It was made clear theoretically and verified by an experiment that a special wave, named viscous wave by the authors, is generated on the thin liquid film when film thickness was less than a definite value which depended on liquid properties, i.e., 0.255 mm at 20°C for water. Theory shows that the occurrence of a viscous wave depends more on liquid viscosity than on surface tension, and that the wave velocity is lower than liquid surface velocity. The viscous wave occurs always in the vicinity of the nonwetting region, signifying that the occurrence of it reduces the minimum film thickness, which causes a breakdown of liquid film.

Measuring liquid—liquid interfacial behavior with the deep-channel surface viscometer

The analysis for the liquid—gas deep-channel surface viscometer has been extended to the liquid—liquid—gas case with two interfaces for a class of interfacial behaviors that describes the surface stress as a function of the surface rate of deformation. The analysis takes into account the viscous effects in all three phases. By measuring the gas—liquid surface velocity distribution, the liquid—liquid interfacial behavior can be determined, if the shear stress distribution at the gas—liquid interface has been previously determined. Experimental results for a Petrostep Sulfonate solution-decane-air system are presented.

Impingement of an axisymmetric liquid jet on a barrier

In some metallurgical and chemical engineering technologies utilization of heavy liquid jets impinging onto a wall appears to be an effective tool for the enhancement of heat- and mass-transfer processes. The aim of the present work was to study, both theoretically and experimentally, hydrodynamics and mass transfer of a radial liquid jet impinging onto a horizontal plane. The whole field of the flow—from the stagnation point to the hydraulic jump—is described within the scope of approximations of the boundary-layer theory for both laminar and turbulent regimes of flow in a thin liquid layer. Simple formulas have been obtained for calculation of the friction factor, liquid layer thickness and the liquid surface velocity as a function of discharge parameters. Solution has been offered to the problem of mass transfer from the wall to a liquid layer for the whole laminar flow region upstream of the jump and simple working formulas have been obtained for calculation of the mass-transfer coefficient. Wall shear stresses, local and mean mass-transfer coefficients within the entire flow region have been measured by an electrodiffusion method in a wide range of liquid flow rates and the conditions at which the flow leaves the barrier. Hydrodynamic characteristics of the jet at the location of impact and of the hydraulic jump have also been studied. The experimental results are given in terms of generalized coordinates and compared with the appropriate theoretical equations.