Thermo-Fluid Management under Low-gravity Conditions (2nd Report, Free-Surface Flows Driven by Surface Forces)

武洋, 姫野; 紀徳, 渡辺

doi:10.1299/kikaib.69.2400

Cited by 12 publications

(9 citation statements)

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“…The level-set method is combined with the MARS (Multi-interface Advection and Reconstruction Solver) method, 31 a kind of VOF (Volume of Fluid) methods, to improve the mass conservation. 22,32 Surface tension is modeled by the CSF (Continuum Surface Force) method. 33 The surface tension force is…”

Section: A Mathematical Formulations and Numerical Proceduresmentioning

confidence: 99%

Physics of puffing and microexplosion of emulsion fuel droplets

et al. 2014

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The physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation. Varying the dispersed-phase (water) sub-droplet size/location and the initiation location of explosive boiling (bubble formation), the droplet breakup processes have been well revealed. The bubble growth leads to local and partial breakup of the parent oil droplet, i.e., puffing. The water sub-droplet size and location determine the after-puffing dynamics. The boiling surface of the water sub-droplet is unstable and evolves further. Finally, the sub-droplet is wrapped by boiled water vapor and detaches itself from the parent oil droplet. When the water sub-droplet is small, the detachment is quick, and the oil droplet breakup is limited. When it is large and initially located toward the parent droplet center, the droplet breakup is more extensive. For microexplosion triggered by the simultaneous growth of multiple separate bubbles, each explosion is local and independent initially, but their mutual interactions occur at a later stage. The degree of breakup can be larger due to interactions among multiple explosions. These findings suggest that controlling microexplosion/puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed. The current study also gives us an insight into modeling the puffing and microexplosion of emulsion droplets and sprays.

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Section: A Mathematical Formulations and Numerical Proceduresmentioning

confidence: 99%

Physics of puffing and microexplosion of emulsion fuel droplets

et al. 2014

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“…The material derivative term in the governing equations

\frac{normalD ϕ}{normalD t} = \frac{\partial ϕ}{\partial t} + bold-italicU \cdot \nabla ϕ

is often discretized using a semi‐Lagrangian scheme in pressure‐based unified solvers based on the CIP‐CUP method, for example, the works of Yabe et al, Himeno and Watanabe, and Jemison et al Unlike them, in the present method, the term is written as

\frac{normalD ϕ}{normalD t} = \frac{\partial ϕ}{\partial t} + bold-italicU \cdot \nabla ϕ = \frac{\partial ϕ}{\partial t} + \nabla \cdot false(bold-italicU ϕ false) - ϕ \nabla \cdot bold-italicU

by dividing the advection term U ·∇ ϕ into the conservation part ∇·( U ϕ ) and into the rest − ϕ ∇· U . Equation is discretized as

\frac{normalD ϕ}{normalD t} = \frac{ϕ^{n + 1} - ϕ^{n}}{italicΔ t} + \frac{1}{V} \sum_{f} Φ_{normalf}^{n} ϕ_{normalf}^{n + 1} - \frac{ϕ^{n + 1}}{V} \sum_{f} Φ_{normalf}^{n} .

In Equation ,

ϕ_{normalf}^{n + 1}

is interpolated using conventional difference schemes such as central‐difference schemes, upwind schemes, and TVD schemes.…”

Section: Methodsmentioning

confidence: 99%

“…The CIP‐CUP method solves the pressure equation derived from the nonconservation form of the governing equations to stabilize the calculations of the high density ratio between a gas and a liquid, unlike conventional pressure‐based unified solvers for single‐phase flows, such as that done in the works of Harlow and Amsden and Issa . The CIP‐CUP method was modified by Himeno as the thermo–CIP‐CUP method for thermofluid analyses . The pressure‐based unified solvers based on the CIP‐CUP method such as the thermo–CIP‐CUP method have been applied to various flows, for example, sloshing of liquid fuel in spacecraft and injection of liquid fuel in diesel engines .…”

Section: Introductionmentioning

confidence: 99%

“…4 The CIP-CUP method was modified by Himeno as the thermo-CIP-CUP method for thermofluid analyses. [5][6][7] The pressure-based unified solvers based on the CIP-CUP method such as the thermo-CIP-CUP method have been applied to various flows, for example, sloshing of liquid fuel in spacecraft 8 and injection of liquid fuel in diesel engines. 9 However, these methods have not sufficiently shown its effectiveness for large-eddy simulation (LES) of turbulence and supersonic flows and have not been applied for unstructured grids composed of arbitrary polyhedra because it discretizes the advection term of the nonconservation form using a semi-Lagrangian scheme such as the cubic interpolated propagation (CIP) method.…”

Section: Introductionmentioning

confidence: 99%

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Pressure‐based unified solver for gas‐liquid two‐phase flows where compressible and incompressible flows coexist

Yamamoto

Takatani

2018

Numerical Methods in Fluids

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Summary We propose a pressure‐based unified solver for gas‐liquid two‐phase flows where compressible and incompressible flows coexist. Unlike the original thermo–Cubic Interpolated Propagation Combined Unified Procedure (CIP‐CUP) method proposed by Himeno et al (Transactions of the Japan Society of Mechanical Engineers, Series B, 2003), we split the advection term of the governing equations into a conservation part and into the rest. The splitting of advection term has two advantages. One is the high degree of freedom in choosing discretization schemes such as central‐difference schemes, upwind schemes, and Total Variation Diminishing (TVD) schemes. The other is the ease of implementation on unstructured grids. The advantages enable the analyses of various flows such as turbulent and supersonic ones in actual complicated boundaries. Therefore, the solver is useful for practical analyses. The solver was validated on the following test cases: subsonic single‐phase flows, incompressible single‐phase turbulent flows, and incompressible gas‐liquid two‐phase flows. With unstructured grids, we obtained the equivalent results as the ones with structured grids. After the validations, subsonic jet impinging on a water pool was calculated and compared with experimental results. It was confirmed that the calculated results were consistent with the experimental ones.

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“…Reconstruction Solver) method (Kunugi, 1997), a kind of VOF (Volume of Fluid) methods, to improve mass conservation (Himeno and Watanabe, 2003).…”

Section: The Level-set Methods Is Combined With the Mars (Multi-interfmentioning

confidence: 99%

Modeling Temperature Distribution Inside an Emulsion Fuel Droplet Under Convective Heating: A Key to Predicting Microexplosion and Puffing

et al. 2016

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Microexplosion/puffing is rapid disintegration of a water-in-oil emulsion droplet caused by explosive boiling of embedded superheated water sub-droplets. To predict microexplosion/puffing, modeling the temperature distribution inside an emulsion droplet under convective heating is a prerequisite, since the temperature field determines the location of nucleation (vapor bubble initiation from superheated water). In the first part of the present study, convective heating of water-in-oil emulsion droplets under typical combustor conditions is investigated using high-fidelity simulation in order to accurately model inner-droplet temperature distribution. The shear force due to the ambient air flow induces internal circulation inside a droplet. It has been found that for droplets under investigation in the present study, the liquid Peclet number PeL is in a transitional regime of 100

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Thermo-Fluid Management under Low-gravity Conditions (2nd Report, Free-Surface Flows Driven by Surface Forces)

Cited by 12 publications

References 0 publications

Physics of puffing and microexplosion of emulsion fuel droplets

Physics of puffing and microexplosion of emulsion fuel droplets

Pressure‐based unified solver for gas‐liquid two‐phase flows where compressible and incompressible flows coexist

Modeling Temperature Distribution Inside an Emulsion Fuel Droplet Under Convective Heating: A Key to Predicting Microexplosion and Puffing

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