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  1. Article ; Online: Effects of spatially-varying substrate anchoring on instabilities and dewetting of thin nematic liquid crystal films.

    Lam, Michael-Angelo Y-H / Kondic, Lou / Cummings, Linda J

    Soft matter

    2020  Volume 16, Issue 44, Page(s) 10187–10197

    Abstract: Partially wetting nematic liquid crystal (NLC) films on substrates are unstable to dewetting-type instabilities due to destabilizing solid/NLC interaction forces. These instabilities are modified by the nematic nature of the films, which influences the ... ...

    Abstract Partially wetting nematic liquid crystal (NLC) films on substrates are unstable to dewetting-type instabilities due to destabilizing solid/NLC interaction forces. These instabilities are modified by the nematic nature of the films, which influences the effective solid/NLC interaction. In this work, we focus on the influence of imposed substrate anchoring on the instability development. The analysis is carried out within a long-wave formulation based on the Leslie-Ericksen description of NLC films. Linear stability analysis of the resulting equations shows that some features of the instability, such as emerging wavelengths, may not be influenced by the imposed substrate anchoring. Going further into the nonlinear regime, considered via large-scale GPU-based simulations, shows however that nonlinear effects may play an important role, in particular in the case of strong substrate anchoring anisotropy. Our simulations show that instability of the film develops in two stages: the first stage involves formation of ridges that are perpendicular to the local anchoring direction; and the second involves breakup of these ridges and formation of drops, whose final distribution is influenced by the anisotropy imposed by the substrate. Finally, we show that imposing more complex substrate anisotropy patterns allows us to reach basic understanding of the influence of substrate-imposed defects in director orientation on the instability evolution.
    Language English
    Publishing date 2020-10-24
    Publishing country England
    Document type Journal Article
    ZDB-ID 2191476-X
    ISSN 1744-6848 ; 1744-683X
    ISSN (online) 1744-6848
    ISSN 1744-683X
    DOI 10.1039/d0sm01416h
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: On the Problem of Modeling the Boat Wake Climate: The Florida Intracoastal Waterway

    Forlini, Carola / Qayyum, Rizwan / Malej, Matt / Lam, Michael‐Angelo Y.‐H. / Shi, Fengyan / Angelini, Christine / Sheremet, Alex

    Journal of geophysical research. 2021 Feb., v. 126, no. 2

    2021  

    Abstract: Quantifying and forecasting the impact of boat traffic on the health of coastal ecosystems must account for the multiscale nature of the process: from minutes (individual wakes), to days (tidal phase), weeks, and longer (tide modulation, seasonal traffic) ...

    Abstract Quantifying and forecasting the impact of boat traffic on the health of coastal ecosystems must account for the multiscale nature of the process: from minutes (individual wakes), to days (tidal phase), weeks, and longer (tide modulation, seasonal traffic). Direct numerical simulations covering all these scales are difficult, not in the least because specifying the vessel type and navigation characteristics for every wake is practically impossible. To overcome this problem, we propose a statistical‐mechanics description of the wake field that focuses on classes of wakes, defined by a set of characteristic parameters, and their joint probability density in the characteristic‐parameter space. Here, we demonstrate the first steps of the approach using existing numerical tools and parametrizations. Because vessel type and navigation characteristics are not available, an investigation of wake parameter space is not possible at this time. Instead, we use the leading‐order Froude‐number parametrization defined by a linear model to classify the wake population observed during the field experiment. Numerical tests applying the FUNWAVE‐TVD model across all wake‐classes identified show excellent skills for weakly dispersive wakes. The model is challenged by the short waves generated by small, slow boats. However, simulations suggest that the problem is confined to the deeper water domain and linear evolution. Nonlinear wake shoaling, essential for modeling wake‐induced sediment transport and wake impact on the environment, is described well.
    Keywords boats ; climate ; environmental impact ; field experimentation ; geophysics ; linear models ; probability distribution ; research ; sediment transport ; traffic ; Florida
    Language English
    Dates of publication 2021-02
    Publishing place John Wiley & Sons, Ltd
    Document type Article
    Note JOURNAL ARTICLE
    ZDB-ID 161667-5
    ISSN 2169-9291 ; 2169-9275 ; 0148-0227 ; 0196-2256
    ISSN (online) 2169-9291
    ISSN 2169-9275 ; 0148-0227 ; 0196-2256
    DOI 10.1029/2020JC016676
    Database NAL-Catalogue (AGRICOLA)

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