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Yong Zhao - One of the best experts on this subject based on the ideXlab platform.

  • an unstructured mesh arbitrary lagrangian eulerian unsteady incompressible flow solver and its application to insect flight aerodynamics
    Physics of Fluids, 2016
    Co-Authors: Xiaohui Su, Yong Zhao
    Abstract:

    In this paper, an unstructured mesh Arbitrary Lagrangian-Eulerian (ALE) incompressible flow solver is developed to investigate the aerodynamics of insect hovering flight. The proposed finite-volume ALE Navier-Stokes solver is based on the artificial compressibility Method (ACM) with a High-Resolution Method of characteristics-based scheme on unstructured grids. The present ALE model is validated and assessed through flow passing over an oscillating cylinder. Good agreements with experimental results and other numerical solutions are obtained, which demonstrates the accuracy and the capability of the present model. The lift generation mechanisms of 2D wing in hovering motion, including wake capture, delayed stall, rapid pitch, as well as clap and fling are then studied and illustrated using the current ALE model. Moreover, the optimized angular amplitude in symmetry model, 45°, is firstly reported in details using averaged lift and the energy power Method. Besides, the lift generation of complete cyclic cl...

  • an unstructured mesh arbitrary lagrangian eulerian unsteady incompressible flow solver and its application to insect flight aerodynamics
    Physics of Fluids, 2016
    Co-Authors: Yuanwei Cao, Yong Zhao
    Abstract:

    In this paper, an unstructured mesh Arbitrary Lagrangian-Eulerian (ALE) incompressible flow solver is developed to investigate the aerodynamics of insect hovering flight. The proposed finite-volume ALE Navier-Stokes solver is based on the artificial compressibility Method (ACM) with a High-Resolution Method of characteristics-based scheme on unstructured grids. The present ALE model is validated and assessed through flow passing over an oscillating cylinder. Good agreements with experimental results and other numerical solutions are obtained, which demonstrates the accuracy and the capability of the present model. The lift generation mechanisms of 2D wing in hovering motion, including wake capture, delayed stall, rapid pitch, as well as clap and fling are then studied and illustrated using the current ALE model. Moreover, the optimized angular amplitude in symmetry model, 45°, is firstly reported in details using averaged lift and the energy power Method. Besides, the lift generation of complete cyclic clap and fling motion, which is simulated by few researchers using the ALE Method due to large deformation, is studied and clarified for the first time. The present ALE model is found to be a useful tool to investigate lift force generation mechanism for insect wing flight.

  • parallel multigrid computation of unsteady incompressible viscous flows using a matrix free implicit Method and high resolution characteristics based scheme
    Computer Methods in Applied Mechanics and Engineering, 2005
    Co-Authors: Yong Zhao, K M Liew
    Abstract:

    Abstract A three-dimensional parallel unstructured non-nested multigrid solver for solutions of unsteady incompressible viscous flow is developed and validated. The finite-volume Navier–Stokes solver is based on the artificial compressibility approach with a High-Resolution Method of characteristics-based scheme for handling convection terms. The unsteady flow is calculated with a matrix-free implicit dual time stepping scheme. The parallelization of the multigrid solver is achieved by multigrid domain decomposition approach (MG-DD), using single program multiple data (SPMD) and multiple instruction multiple data (MIMD) programming paradigm. There are two parallelization strategies proposed in this work, first strategy is a one-level parallelization strategy using geometric domain decomposition technique alone, second strategy is a two-level parallelization strategy that consists of a hybrid of both geometric domain decomposition and data decomposition techniques. Message-passing interface (MPI) and OpenMP standard are used to communicate data between processors and decompose loop iterations arrays, respectively. The parallel-multigrid code is used to simulate both steady and unsteady incompressible viscous flows over a circular cylinder and a lid-driven cavity flow. A maximum speedup of 22.5 could be achieved on 32 processors, for instance, the lid-driven cavity flow of Re  = 1000. The results obtained agree well with numerical solutions obtained by other researchers as well as experimental measurements. A detailed study of the time step size and number of pseudo-sub-iterations per time step required for simulating unsteady flow are presented in this paper.

Xiaohui Su - One of the best experts on this subject based on the ideXlab platform.

  • an unstructured mesh arbitrary lagrangian eulerian unsteady incompressible flow solver and its application to insect flight aerodynamics
    Physics of Fluids, 2016
    Co-Authors: Xiaohui Su, Yong Zhao
    Abstract:

    In this paper, an unstructured mesh Arbitrary Lagrangian-Eulerian (ALE) incompressible flow solver is developed to investigate the aerodynamics of insect hovering flight. The proposed finite-volume ALE Navier-Stokes solver is based on the artificial compressibility Method (ACM) with a High-Resolution Method of characteristics-based scheme on unstructured grids. The present ALE model is validated and assessed through flow passing over an oscillating cylinder. Good agreements with experimental results and other numerical solutions are obtained, which demonstrates the accuracy and the capability of the present model. The lift generation mechanisms of 2D wing in hovering motion, including wake capture, delayed stall, rapid pitch, as well as clap and fling are then studied and illustrated using the current ALE model. Moreover, the optimized angular amplitude in symmetry model, 45°, is firstly reported in details using averaged lift and the energy power Method. Besides, the lift generation of complete cyclic cl...

Yuanwei Cao - One of the best experts on this subject based on the ideXlab platform.

  • an unstructured mesh arbitrary lagrangian eulerian unsteady incompressible flow solver and its application to insect flight aerodynamics
    Physics of Fluids, 2016
    Co-Authors: Yuanwei Cao, Yong Zhao
    Abstract:

    In this paper, an unstructured mesh Arbitrary Lagrangian-Eulerian (ALE) incompressible flow solver is developed to investigate the aerodynamics of insect hovering flight. The proposed finite-volume ALE Navier-Stokes solver is based on the artificial compressibility Method (ACM) with a High-Resolution Method of characteristics-based scheme on unstructured grids. The present ALE model is validated and assessed through flow passing over an oscillating cylinder. Good agreements with experimental results and other numerical solutions are obtained, which demonstrates the accuracy and the capability of the present model. The lift generation mechanisms of 2D wing in hovering motion, including wake capture, delayed stall, rapid pitch, as well as clap and fling are then studied and illustrated using the current ALE model. Moreover, the optimized angular amplitude in symmetry model, 45°, is firstly reported in details using averaged lift and the energy power Method. Besides, the lift generation of complete cyclic clap and fling motion, which is simulated by few researchers using the ALE Method due to large deformation, is studied and clarified for the first time. The present ALE model is found to be a useful tool to investigate lift force generation mechanism for insect wing flight.

Dale L Boger - One of the best experts on this subject based on the ideXlab platform.

  • a simple high resolution Method for establishing dna binding affinity and sequence selectivity
    Journal of the American Chemical Society, 2001
    Co-Authors: Dale L Boger, Brian E Fink, Steven R Brunette, Michael Hedrick
    Abstract:

    Full details of the development of a simple, nondestructive, and high-throughput Method for establishing DNA binding affinity and sequence selectivity are described. The Method is based on the loss of fluorescence derived from the displacement of ethidium bromide or thiazole orange from the DNA of interest or, in selected instances, the change in intrinsic fluorescence of a DNA binding agent itself and is applicable for assessing relative or absolute DNA binding affinities. Enlisting a library of hairpin deoxyoligonucleotides containing all five base pair (512 hairpins) or four base pair (136 hairpins) sequences displayed in a 96-well format, a compound's rank order binding to all possible sequences is generated, resulting in a High-Resolution definition of its sequence selectivity using this fluorescent intercalator displacement (FID) assay. As such, the technique complements the use of footprinting or affinity cleavage for the establishment of DNA binding selectivity and provides the information at a hi...

  • a simple high resolution Method for establishing dna binding affinity and sequence selectivity
    Journal of the American Chemical Society, 2001
    Co-Authors: Dale L Boger, Brian E Fink, Steven R Brunette, Winston C Tse, Michael P Hedrick
    Abstract:

    Full details of the development of a simple, nondestructive, and high-throughput Method for establishing DNA binding affinity and sequence selectivity are described. The Method is based on the loss of fluorescence derived from the displacement of ethidium bromide or thiazole orange from the DNA of interest or, in selected instances, the change in intrinsic fluorescence of a DNA binding agent itself and is applicable for assessing relative or absolute DNA binding affinities. Enlisting a library of hairpin deoxyoligonucleotides containing all five base pair (512 hairpins) or four base pair (136 hairpins) sequences displayed in a 96-well format, a compound's rank order binding to all possible sequences is generated, resulting in a High-Resolution definition of its sequence selectivity using this fluorescent intercalator displacement (FID) assay. As such, the technique complements the use of footprinting or affinity cleavage for the establishment of DNA binding selectivity and provides the information at a higher resolution. The merged bar graphs generated by this rank order binding provide a qualitative way to compare, or profile, DNA binding affinity and selectivity. The 96-well format assay (512 hairpins) can be conducted at a minimal cost (presently ca. $100 for hairpin deoxyoligonucleotides/assay with ethiduim bromide or less with thiazole orange), with a rapid readout using a fluorescent plate reader (15 min), and is adaptable to automation (Tecan Genesis Workstation 100 robotic system). Its use in generating a profile of DNA binding selectivity for several agents including distamycin A, netropsin, DAPI, Hoechst 33258, and berenil is described. Techniques for establishing binding constants from quantitative titrations are compared, and recommendations are made for use of a Scatchard or curve fitting analysis of the titration binding curves as a reliable means to quantitate the binding affinity.

S Collin - One of the best experts on this subject based on the ideXlab platform.

  • a transmission electron microscope study of neel skyrmion magnetic textures in multilayer thin film systems with large interfacial chiral interaction
    Scientific Reports, 2018
    Co-Authors: S Mcvitie, Sean Hughes, K Fallon, S Mcfadzean, D Mcgrouther, M Krajnak, William Legrand, Davide Maccariello, S Collin
    Abstract:

    Skyrmions in ultrathin ferromagnetic metal (FM)/heavy metal (HM) multilayer systems produced by conventional sputtering Methods have recently generated huge interest due to their applications in the field of spintronics. The sandwich structure with two correctly-chosen heavy metal layers provides an additive interfacial exchange interaction which promotes domain wall or skyrmion spin textures that are Neel in character and with a fixed chirality. Lorentz transmission electron microscopy (TEM) is a high resolution Method ideally suited to quantitatively image such chiral magnetic configurations. When allied with physical and chemical TEM analysis of both planar and cross-sectional samples, key length scales such as grain size and the chiral variation of the magnetisation variation have been identified and measured. We present data showing the importance of the grain size (mostly < 10 nm) measured from direct imaging and its potential role in describing observed behaviour of isolated skyrmions (diameter < 100 nm). In the latter the region in which the magnetization rotates is measured to be around 30 nm. Such quantitative information on the multiscale magnetisation variations in the system is key to understanding and exploiting the behaviour of skyrmions for future applications in information storage and logic devices.