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  1. Article ; Online: Interaction between a rising bubble and a stationary droplet immersed in a liquid pool using a ternary conservative phase-field lattice Boltzmann method.

    Zhao, Chunheng / Lee, Taehun

    Physical review. E

    2023  Volume 107, Issue 2-2, Page(s) 25308

    Abstract: When a stationary bubble and a stationary droplet immersed in a liquid pool are brought into contact, they form a bubble-droplet aggregate. Its equilibrium morphology and stability largely depend on the combination of different components' surface ... ...

    Abstract When a stationary bubble and a stationary droplet immersed in a liquid pool are brought into contact, they form a bubble-droplet aggregate. Its equilibrium morphology and stability largely depend on the combination of different components' surface tensions, known as the "spreading factor." In this study, we look at the interaction between a rising bubble and a stationary droplet to better understand the dynamics of coalescence and rising and morphological changes for the bubble-droplet aggregate. A systematic study is conducted on the interaction processes with various bubble sizes and spreading factors in two dimensions. The current simulation framework consists of the ternary conservative phase-field lattice Boltzmann method (LBM) for interface tracking and the velocity-pressure LBM for hydrodynamics, which is validated by benchmark cases such as the liquid lens and parasitic currents around a static droplet with several popular surface tension formulations. We further test our LBM for the morphology changes of two droplets initially in contact with various spreading factors and depict the final morphologies in a phase diagram. The separated, partially engulfed, and completely engulfed morphologies can be replicated by systematically altering the sign of the spreading factors. The rising bubble and stationary droplet interaction are simulated based on the final morphologies obtained under stationary conditions by imposing an imaginary buoyancy force on the rising bubble. The results indicate that the bubble-droplet aggregate with double emulsion morphology can minimize the distortion of the bubble-droplet aggregate and achieve a greater terminal velocity than the aggregate with partially engulfed morphology.
    Language English
    Publishing date 2023-03-17
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2844562-4
    ISSN 2470-0053 ; 2470-0045
    ISSN (online) 2470-0053
    ISSN 2470-0045
    DOI 10.1103/PhysRevE.107.025308
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: General wetting energy boundary condition in a fully explicit nonideal fluids solver.

    Zhao, Chunheng / Limare, Alexandre / Zaleski, Stephane

    Physical review. E

    2023  Volume 108, Issue 5-2, Page(s) 55307

    Abstract: We present an explicit finite-difference method to simulate the nonideal multiphase fluid flow. The local density and momentum transport are modeled by the Navier-Stokes equations and the pressure is computed by the van der Waals equation of the state. ... ...

    Abstract We present an explicit finite-difference method to simulate the nonideal multiphase fluid flow. The local density and momentum transport are modeled by the Navier-Stokes equations and the pressure is computed by the van der Waals equation of the state. The static droplet and the dynamics of liquid-vapor separation simulations are performed as validations of this numerical scheme. In particular, to maintain the thermodynamic consistency, we propose a general wetting energy boundary condition at the contact line between fluids and the solid boundary. We conduct a series of comparisons between the current boundary condition and the constant contact angle boundary condition as well as the stress-balanced boundary condition. This boundary condition alleviates the instability induced by the constant contact angle boundary condition at θ≈0 and θ≈π. Using this boundary condition, the equilibrium contact angle is correctly recovered and the contact line dynamics are consistent with the simulation by applying a stress-balanced boundary condition. Nevertheless, unlike the stress-balanced boundary condition for which we need to further introduce the interface thickness parameter, the current boundary condition implicitly incorporates the interface thickness information into the wetting energy.
    Language English
    Publishing date 2023-12-19
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2844562-4
    ISSN 2470-0053 ; 2470-0045
    ISSN (online) 2470-0053
    ISSN 2470-0045
    DOI 10.1103/PhysRevE.108.055307
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Book ; Online: Spreading and engulfment of a viscoelastic film onto a Newtonian droplet

    Zhao, Chunheng / Lee, Taehun / Carlson, Andreas

    2024  

    Abstract: We use the conservative phase-field lattice Boltzmann method to investigate the dynamics when a Newtonian droplet comes in contact with an immiscible viscoelastic liquid film. The dynamics of the three liquid phases are explored through numerical ... ...

    Abstract We use the conservative phase-field lattice Boltzmann method to investigate the dynamics when a Newtonian droplet comes in contact with an immiscible viscoelastic liquid film. The dynamics of the three liquid phases are explored through numerical simulations, with a focus on illustrating the contact line dynamics and the viscoelastic effects described by the Oldroyd-B model. The droplet dynamics are contrasted with the case of a Newtonian fluid film. The simulations demonstrate that when the film is viscoelastic, the droplet dynamics become insensitive to the film thickness when the polymer viscosity and relaxation time are large. A viscoelastic ridge forms at the moving contact line, which evolves with a power-law dependence on time. By rescaling the interface profile of the ridge using its height and width, it appears to collapse onto a similar shape. Our findings reveal a strong correlation between the viscoelastic stress and the interface shape near the contact line.
    Keywords Physics - Fluid Dynamics
    Subject code 612
    Publishing date 2024-01-31
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Book ; Online: The Effect of Dust and Sand on the 5G Terrestrial Links

    Abuhdima, Esmail M M / Comert, Gurcan / Pisu, Pierluigi / Huang, Chin-Tser / Qaouaq, Ahmed El / Zhao, Chunheng / Alston, Shakendra / Ambrose, Kirk / Liu, Jian

    2021  

    Abstract: Wireless connections are a communication channel used to support different applications in our life such as microwave connections, mobile cellular networks, and intelligent transportation systems. The wireless communication channels are affected by ... ...

    Abstract Wireless connections are a communication channel used to support different applications in our life such as microwave connections, mobile cellular networks, and intelligent transportation systems. The wireless communication channels are affected by different weather factors such as rain, snow, fog, dust, and sand. This effect is more evident in the high frequencies of the millimeter-wave (mm-wave) band. Recently, the 5G opened the door to support different applications with high speed and good quality. A recent study investigates the effect of rain and snow on the 5G communication channel to reduce the challenge of using high millimeter-wave frequencies. This research investigates the impact of dust and sand on the communication channel of 5G mini links using Mie scattering model to estimate the propagating wave's attenuation by computing the free space loss of a dusty region. Also, the cross-polarization of the propagating wave with dust and sand is taken into account at different distances of the propagating length. Two kinds of mini links, ML-6363, and ML-6352, are considered to demonstrate the effect of dust and sand in these specific operating frequency bands. The 73.5 GHz (V-band) and (21.5GHz (K-band) are the ML-6352 and ML-6363 radio frequency, respectively. Also, signal depolarization is another important radio frequency transmission parameter that is considered heroin. The numerical and simulation results show that the 5G ML-6352 is more effect by dust and sand than ML6363. The 5G toolbox is used to build the communication system and simulate the effect of the dust and sand on the different frequency bands.

    Comment: 6 pages, 10 figures, IEEE WiSEE 2021
    Keywords Electrical Engineering and Systems Science - Signal Processing ; Electrical Engineering and Systems Science - Systems and Control
    Publishing date 2021-08-20
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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