A Numerical Strategy for Investigating Internal Circulation in Droplets

Lin, Yushu; Setiya, Meha; Palmore, John

doi:10.2514/6.2022-1443

Cited by 4 publications

(5 citation statements)

References 8 publications

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“…However, due to the uncertainty of the drag coefficient caused by droplet deformation, the velocity reached will still be lower than the terminal velocity. To ensure constant terminal velocity was reached, Lin, Setiya and Palmore [14,28] developed a gravity update scheme to balance the changing drag force. Since the drag force is unknown explicitly, their method is based on a feedback control loop:…”

Section: Artificial Gravitymentioning

confidence: 99%

“…Hence, the gas density change represents the physical process of the pressure change. In addition, studies such as [5,13,14] have revealed that internal circulation is dependent on density ratio. Therefore, we choose the gas density to be the controlling parameter for changing the strength of internal circulation.…”

Section: E Quantification Of Internal Circulationmentioning

confidence: 99%

“…To quantify the strength of internal circulation, several common physical quantities are considered, including the maximum liquid velocity, the maximum and mean vorticity of the droplet, and the droplet enstropy. Based on our previous work, maximum velocity and vorticity are not good choices due to their sensitivity to numerical errors, while volumeaveraged variables are better in representing internal circulation strength [14]. Thus, we only use volume-averaged variables in this study.…”

Section: E Quantification Of Internal Circulationmentioning

confidence: 99%

“…As a result, the evaluation of e is not accurate. Besides, results from literature have no ρ * is the quantification of internal circulation strength [14], and is correlated to pressure through ideal law, indicating the coupling between liquid and gas phases. This correlation can be found in Fig.…”

Section: Aspect Ratiomentioning

confidence: 99%

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The effect of droplet deformation and internal circulation on drag coefficient

Lin¹,

Palmore²

2022

Preprint

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The current study uses numerical approaches to investigate the effect of droplet deformation and internal circulation on droplet dynamics. Although droplet drag is a classical area of study, there are still theoretical gaps in understanding the motion of large droplets. In applications like spray combustion, droplets of various sizes are generated and move with the flow. Large droplets tend to deform in the flow, and have complex interactions with the flow because of this deformation. To better model spray, the physical understanding of droplets need to be improved.Under spray conditions, droplets are subjected to a high temperature and pressure environment, and the coupling between liquid and gas is enhanced. Therefore, the deformation and internal circulation will affect droplet drag coefficient more significantly than in atmospheric conditions.To study the mechanism on how droplet shape and internal circulation influence droplet dynamics, we will use direct numerical simulation (DNS) to simulate a droplet falling at its terminal velocity in high pressure air. An in-house code developed for interface-capturing DNS of multiphase flows will be employed for the simulation. The drag coefficient is calculated, and the results are consistent with existing literature for slightly deformed droplets. The results show that the drag coefficient is directly related to the droplet deformation and droplet internal circulation. The paper also develops a theory to account the effect of Weber number and liquid/gas properties in droplet deformation.

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Section: Artificial Gravitymentioning

confidence: 99%

Section: E Quantification Of Internal Circulationmentioning

confidence: 99%

Section: E Quantification Of Internal Circulationmentioning

confidence: 99%

Section: Aspect Ratiomentioning

confidence: 99%

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The effect of droplet deformation and internal circulation on drag coefficient

Lin¹,

Palmore²

2022

Preprint

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“…This method of keeping the droplet stationary is called "Gravity update method". More details of this can be found in previous works [33], [34]. An outflow boundary condition is applied on the positive x-face of the domain.…”

Section: Fig 1: a Sketch Of Numerical Setup And Boundariesmentioning

confidence: 99%

Evaporation of deformable liquid fuel droplets

Setiya¹,

Palmore²

2022

Preprint

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This work covers the effect of droplet deformation on its evaporation rate under convective flow conditions. A single component jet fuel surrogate n-decane is used as a liquid fuel. The large droplets in sprays tend to deform due to an imbalance of aerodynamic force and surface tension, hence deviate from a spherical shape. This influence of the deformation and planar flow on evaporation is investigated by varying the relevant non-dimensional groups such as Weber number (W e) ranging from 1 − 12 and Reynolds number (Re) ranging from 25 to 120. These numerical studies utilize a numerical framework for interface capturing Direct Numerical Simulation (DNS) for multiphase flows. The framework is built upon an in-house code NGA. A grid-independent study is performed in order to find an accurate and computationally feasible grid for this work.Furthermore, the numerical results are compared against the analytical correlations by Abramzon and Sirignano (Int. Journal of heat and mass transfer, 1989) to validate the accuracy of the solver.The results for grid size N d = 24 are found to be in good agreement with the analytical solution with 5% of difference.Finally, the effect of droplet shape on the evaporation rate at various Re is quantified in terms of total evaporation rate and its contributors: local evaporation rate and the total surface area.Results suggest that the evaporation of the droplet has a weak dependency with Weber number at low Re. However, as the deformation is significant for W e = 4, 8, 12 at Re = 120, it plays a key role in altering the total evaporation rate ( ṁ) by altering the flow around it.

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Interface-capturing numerical studies of multicomponent spray and droplet vaporization

Palmore

Lin

2022

AIAA SCITECH 2022 Forum

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A Numerical Strategy for Investigating Internal Circulation in Droplets

Cited by 4 publications

References 8 publications

The effect of droplet deformation and internal circulation on drag coefficient

The effect of droplet deformation and internal circulation on drag coefficient

Evaporation of deformable liquid fuel droplets

Interface-capturing numerical studies of multicomponent spray and droplet vaporization

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