Effect of oxygen partial pressure on the marangoni flow of molten metals

Hibiya, Taketoshi; Ozawa, Shumpei

doi:10.1002/crat.201200514

Cited by 11 publications

(6 citation statements)

References 19 publications

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“…The relevant curve for a sulfur concentration of 150 ppm is plotted in figure 2. Experimentally, such a behaviour with a sign change at a critical temperature has been shown to occur in steels [42,43] and pure iron [44], as well as other metals such as silver [44] and nickel [45].…”

Section: Momentummentioning

confidence: 94%

Marangoni driven turbulence in high energy surface melting processes

Kidess

Kenjereš

Righolt

et al. 2016

International Journal of Thermal Sciences

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Experimental observations of high-energy surface melting processes, such as laser welding, have revealed unsteady, often violent, motion of the free surface of the melt pool. Surprisingly, no similar observations have been reported in numerical simulation studies of such flows. Moreover, the published simulation results fail to predict the post-solidification pool shape without adapting non-physical values for input parameters, suggesting the neglect of significant physics in the models employed. The experimentally observed violent flow surface instabilities, scaling analyses for the occurrence of turbulence in Marangoni driven flows, and the fact that in simulations transport coefficients generally have to be increased by an order of magnitude to match experimentally observed pool shapes, suggest the common assumption of laminar flow in the pool may not hold, and that the flow is actually turbulent. Here, we use direct numerical simulations (DNS) to investigate the role of turbulence in laser melting of a steel alloy with surface active elements. Our results reveal the presence of two competing vortices driven by thermocapillary forces towards a local surface tension maximum. The jet away from this location at the free surface, separating the two vortices, is found to be unstable and highly oscillatory, indeed leading to turbulence-like flow in the pool. The resulting additional heat transport, however, is insufficient to account for the observed differences in pool shapes between experiment and simulations.

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Section: Momentummentioning

confidence: 94%

Marangoni driven turbulence in high energy surface melting processes

Kidess

Kenjereš

Righolt

et al. 2016

International Journal of Thermal Sciences

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“…A realistic relationship 10,25 between the surface tension temperature coefficient ∂γ/∂T and temperature for a binary liquid metal -surfactant mixture, as shown in figure 2, will be used in the simulations:…”

Section: B Boundary Conditionsmentioning

confidence: 99%

“…The shape of the surface tension-temperature curve and thus the system behavior is not specific to the iron-sulfur system, but also applies to e.g. silver 25 and nickel 26 in the presence of oxygen.…”

Section: B Boundary Conditionsmentioning

confidence: 99%

The influence of surfactants on thermocapillary flow instabilities in low Prandtl melting pools

2016

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Flows in low Prandtl number liquid pools are relevant for various technical applications, and have so far only been investigated for the case of pure fluids, i.e. with a constant, negative surface tension temperature coefficient ∂γ/∂T . Real-world fluids containing surfactants have a temperature dependent ∂γ/∂T > 0, which may change sign to ∂γ/∂T < 0 at a critical temperature T c . Where thermocapillary forces are the main driving force, this can have a tremendous effect on the resulting flow patterns and the associated heat transfer.Here we investigate the stability of such flows for five Marangoni numbers in the range of 2.1 × 10 6 ≤ M a ≤ 3.4 × 10 7 using dynamic large eddy simulations (LES), which we validate against a high resolution direct numerical simulation (DNS). We find that the five cases span all flow regimes, i.e. stable laminar flow at M a ≤ 2.1 × 10 6 , transitional flow with rotational instabilities at M a = 2.8 × 10 6 and M a = 4.6 × 10 6 and turbulent flow at M a = 1.8 × 10 7 and M a = 3.4 × 10 7 .

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“…[ 110–112 ] Further effects like O absorption could also have a decisive influence on the surface tension. [ 110,113 ] However, under the assumption of higher surface tension for Ag than for AgCaLa, a reduced difference in surface tension between Fe and Ag, compared to Fe and AgCaLa, is conclusive. This reduces the necessary surface energy and the formation of narrow Ag phases with a large surface is simplified.…”

Section: Resultsmentioning

confidence: 99%