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Wen Binghai - One of the best experts on this subject based on the ideXlab platform.

  • lateral migration and nonuniform rotation of biconcave particle suspended in poiseuille flow
    Chinese Physics Letters, 2013
    Co-Authors: Wen Binghai, Chen Yanyan, Zhang Renliang, Zhang Chaoying, Fang Haiping
    Abstract:

    A biconcave particle suspended in a Poiseuille flow is investigated by the multiple-relaxation-time lattice Boltzmann method with the Galilean-invariant momentum exchange method. The lateral migration and equilibrium of the particle are similar to the Segre-Silberberg effect in our numerical simulations. Surprisingly, two lateral equilibrium positions are observed corresponding to the releasing positions of the biconcave particle. The upper equilibrium positions significantly decrease with the increasing Reynolds number, whereas the lower ones are almost insensitive to the Reynolds number. Interestingly, the Regular Wave accompanied by nonuniform rotation is exhibited in the lateral movement of the biconcave particle. It can be attributed to the fact that the biconcave shape in various postures interacts with the parabolic velocity distribution of the Poiseuille flow. A set of contours illustrate the dynamic flow field when the biconcave particle has successive postures in a rotating period.

  • lateral migration and nonuniform rotation of biconcave particle suspended in poiseuille flow
    arXiv: Computational Physics, 2013
    Co-Authors: Wen Binghai, Chen Yanyan, Zhang Renliang, Zhang Chaoying, Fang Haiping
    Abstract:

    A biconcave particle suspended in a Poiseuille flow is investigated by the multiple-relaxation-time lattice Boltzmann method with the Galilean-invariant momentum exchange method. The lateral migration and equilibrium of the particle are similar to the Segr\'e-Silberberg effect in our numerical simulations. Surprisingly, two lateral equilibrium positions are observed corresponding to the releasing positions of the biconcave particle. The upper equilibrium positions significantly decrease with the growth of the Reynolds number, whereas the lower ones are almost insensitive to the Reynolds number. Interestingly, the Regular Wave accompanied by nonuniform rotation is exhibited in the lateral movement of the biconcave particle. It can be attributed to that the biconcave shape in various postures interacts with the parabolic velocity distribution of the Poiseuille flow. A set of contours illustrate the dynamic flow field when the biconcave particle has successive postures in a rotating period.

Dag Myrhaug - One of the best experts on this subject based on the ideXlab platform.

Fang Haiping - One of the best experts on this subject based on the ideXlab platform.

  • lateral migration and nonuniform rotation of biconcave particle suspended in poiseuille flow
    Chinese Physics Letters, 2013
    Co-Authors: Wen Binghai, Chen Yanyan, Zhang Renliang, Zhang Chaoying, Fang Haiping
    Abstract:

    A biconcave particle suspended in a Poiseuille flow is investigated by the multiple-relaxation-time lattice Boltzmann method with the Galilean-invariant momentum exchange method. The lateral migration and equilibrium of the particle are similar to the Segre-Silberberg effect in our numerical simulations. Surprisingly, two lateral equilibrium positions are observed corresponding to the releasing positions of the biconcave particle. The upper equilibrium positions significantly decrease with the increasing Reynolds number, whereas the lower ones are almost insensitive to the Reynolds number. Interestingly, the Regular Wave accompanied by nonuniform rotation is exhibited in the lateral movement of the biconcave particle. It can be attributed to the fact that the biconcave shape in various postures interacts with the parabolic velocity distribution of the Poiseuille flow. A set of contours illustrate the dynamic flow field when the biconcave particle has successive postures in a rotating period.

  • lateral migration and nonuniform rotation of biconcave particle suspended in poiseuille flow
    arXiv: Computational Physics, 2013
    Co-Authors: Wen Binghai, Chen Yanyan, Zhang Renliang, Zhang Chaoying, Fang Haiping
    Abstract:

    A biconcave particle suspended in a Poiseuille flow is investigated by the multiple-relaxation-time lattice Boltzmann method with the Galilean-invariant momentum exchange method. The lateral migration and equilibrium of the particle are similar to the Segr\'e-Silberberg effect in our numerical simulations. Surprisingly, two lateral equilibrium positions are observed corresponding to the releasing positions of the biconcave particle. The upper equilibrium positions significantly decrease with the growth of the Reynolds number, whereas the lower ones are almost insensitive to the Reynolds number. Interestingly, the Regular Wave accompanied by nonuniform rotation is exhibited in the lateral movement of the biconcave particle. It can be attributed to that the biconcave shape in various postures interacts with the parabolic velocity distribution of the Poiseuille flow. A set of contours illustrate the dynamic flow field when the biconcave particle has successive postures in a rotating period.

Poul Jorgensen - One of the best experts on this subject based on the ideXlab platform.

  • molecular response properties from a hermitian eigenvalue equation for a time periodic hamiltonian
    Journal of Chemical Physics, 2015
    Co-Authors: Filip Pawlowski, Jeppe Olsen, Poul Jorgensen
    Abstract:

    The time-dependent Schrodinger equation for a time-periodic perturbation is recasted into a Hermitian eigenvalue equation, where the quasi-energy is an eigenvalue and the time-periodic Regular Wave function an eigenstate. From this Hermitian eigenvalue equation, a rigorous and transparent formulation of response function theory is developed where (i) molecular properties are defined as derivatives of the quasi-energy with respect to perturbation strengths, (ii) the quasi-energy can be determined from the time-periodic Regular Wave function using a variational principle or via projection, and (iii) the parametrization of the unperturbed state can differ from the parametrization of the time evolution of this state. This development brings the definition of molecular properties and their determination on par for static and time-periodic perturbations and removes inaccuracies and inconsistencies of previous response function theory formulations. The development where the parametrization of the unperturbed sta...

  • molecular response properties from a hermitian eigenvalue equation for a time periodic hamiltonian
    Journal of Chemical Physics, 2015
    Co-Authors: Filip Pawlowski, Jeppe Olsen, Poul Jorgensen
    Abstract:

    The time-dependent Schrodinger equation for a time-periodic perturbation is recasted into a Hermitian eigenvalue equation, where the quasi-energy is an eigenvalue and the time-periodic Regular Wave function an eigenstate. From this Hermitian eigenvalue equation, a rigorous and transparent formulation of response function theory is developed where (i) molecular properties are defined as derivatives of the quasi-energy with respect to perturbation strengths, (ii) the quasi-energy can be determined from the time-periodic Regular Wave function using a variational principle or via projection, and (iii) the parametrization of the unperturbed state can differ from the parametrization of the time evolution of this state. This development brings the definition of molecular properties and their determination on par for static and time-periodic perturbations and removes inaccuracies and inconsistencies of previous response function theory formulations. The development where the parametrization of the unperturbed state and its time evolution may differ also extends the range of the Wave function models for which response functions can be determined. The simplicity and universality of the presented formulation is illustrated by applying it to the configuration interaction (CI) and the coupled cluster (CC) Wave function models and by introducing a new model—the coupled cluster configuration interaction (CC-CI) model—where a coupled cluster exponential parametrization is used for the unperturbed state and a linear parametrization for its time evolution. For static perturbations, the CC-CI response functions are shown to be the analytical analogues of the static molecular properties obtained from finite field equation-of-motion coupled cluster (EOMCC) energy calculations. The structural similarities and differences between the CI, CC, and CC-CI response functions are also discussed with emphasis on linear versus non-linear parametrizations and the size-extensivity of the obtained molecular properties.

Chris Swan - One of the best experts on this subject based on the ideXlab platform.

  • second order Wave maker theory using force feedback control part ii an experimental verification of Regular Wave generation
    Ocean Engineering, 2009
    Co-Authors: Johannes Spinneken, Chris Swan
    Abstract:

    This paper provides an experimental verification of the new Wave maker theory outlined by Spinneken and Swan [2009. Second-order Wave maker theory using forcefeedback control. Part I. A new theory for Regular Wave generation. Ocean Engineering, in press, doi:10.1016/j.oceaneng.2009.01.019]. This theory concerns the generation of Regular Waves by a flap-type Wave maker using force-feedback control, providing the first quantitative evidence of the inherent advantages of this latter approach. When the Wave maker is controlled by a first-order force command signal, comparisons between the theory and experimental observations confirm two key points: (i) The first-order behaviour is crucial for the absorption characteristics of the machine. (ii) The second-order behaviour leads to a spurious, or unwanted, freely propagating second harmonic that is substantially smaller in amplitude when compared to an identical Wave paddle operating with first-order position control. Both aspects of this work, effective absorption and reduced second-order spurious Wave generation, are investigated over a broad range of Wave frequencies and shown to be widely applicable. Furthermore, the theory also provides a force command signal correct to second order. This is introduced in a separate set of experiments and shown to provide further improvement in the quality of the Wave generation.

  • second order Wave maker theory using force feedback control part i a new theory for Regular Wave generation
    Ocean Engineering, 2009
    Co-Authors: Johannes Spinneken, Chris Swan
    Abstract:

    Abstract Second-order Wave maker theory has long been established; the most extensive and detailed approach given by Schaffer [1996. Second-order Wave maker theory for irRegular Waves. Ocean Engineering 23, 47–88]. However, all existing theories assume the Wave paddle is driven by a position-feedback motion controller. Early research in the Wave power field led to the design of a force-controlled absorbing Wave machine [Salter, S., 1982. Absorbing Wave-makers and wide tanks. In: Directional Wave Spectra Applications, pp. 185–200]. In addition to operating as an excellent absorber, this machine seemed to introduce very little spurious harmonic content when driven with a first-order command signal. The present paper provides a mathematical model for the operation of Wave makers using force-feedback control and seeks to explain this apparent advantage. The model is developed to second-order so that a command signal compensating for the remaining spurious Wave is also provided. Due to the complexity of the problem, the model has been limited to flap-type Wave machines and the generation of Regular Waves. A variety of numerical tests in force-control mode have been conducted, indicating that the spurious Wave content is greatly reduced when compared to the position-control mode. A separate experimental study validating the theory is presented in a part II paper by the same authors.