Papers by Mostafa Bakhoday Paskyabi
Journal of Physics: Conference Series, 2020
In this paper, the primary objective is to investigate flow structures in the wake of wind turbin... more In this paper, the primary objective is to investigate flow structures in the wake of wind turbines based on applying a truncated Proper Orthogonal Decomposition (POD) approach. This scheme decomposes the three-dimensional velocity fields produced by the high-fidelity PArallelized LES Model (PALM) into a number of orthogonal spatial modes and time-dependent weighting coefficients. PALM has been combined with an actuator disk model with rotation to incorporate the effects of a turbine array. The time-dependent deterministic weights from applying the POD scheme are replaced by stochastic weights, estimated from two independent stochastic techniques that aim to account for unresolved small-scale features for a number of POD modes. We then reconstruct the flow field by a small number of stochastic modes to investigate how well the applied stochastic methodologies can reproduce the flow field compared to the original LES results.
The impact of ocean surface gravity waves on the near-surface currents and on the upper ocean mix... more The impact of ocean surface gravity waves on the near-surface currents and on the upper ocean mixed layer is investigated using the one-dimensional general ocean turbulence model (GOTM). The goal of the investigation is to determine coupling methodology which required theories, modifications and parameterizations to incorporate the influence of surface wave forcing into an ocean dynamic model. To this end, some well-known theories of air-sea interaction are applied to modify momentum and energy equations to include the surface wave stress, wind energy input, wave dissipation, and Stokes drift. A two dimensional wave energy spectrum is used as a representative sea state for a sufficiently large fetch. The performance of the wave-modified model is tested by a series of model experiments which cover a number of features of the upper ocean boundary layer on diurnal and seasonal time scales. These sets of model experiments include both some idealized test cases to show the importance and sensitivity of the upper ocean to wave parameterizations, and some additional observation-oriented experiments which highlight the role of the modifications in improving the prediction of the upper ocean dynamical variability. The results confirm again the dominant role of Stokes drift in influencing both the magnitude and the angular turning of the surface Ekman current and the evolution of the upper ocean boundary layer (mixed layer depth and temperature evolution), in comparison with other wave induced parameters. Meanwhile, it is shown that the modified model is sensitive to wave parameterizations and the wave energy spectrum. However, there remain a number of uncertainties due to choice of wave energy spectrum, wave forcing parameterization, the surface eddy viscosity, momentum and energy surface boundary conditions, and the role of some important processes excluded from this study, such as the effect of Langmuir circulations.
In this paper, split step wavelet Galerkin method (SSWGM)is proposed for solving underwater wave ... more In this paper, split step wavelet Galerkin method (SSWGM)is proposed for solving underwater wave propagation in range-independent fluid/solid media. Parabolic equation model is applied for transforming elliptic wave to parabolic wave equation that enable us to use marching approaches in numerical algorithms. Wavelet Galerkin method is used to discretize the depth operators by using 1-periodic Daubechies scaling basis as shape functions. This discretization leads to circulant and bandlimit system which can be solved by fast Fourier transformations and this improves the accuracy and cost of computation. The numerical solution of SSWGM is applied for deep and shallow water environment involving water column over bottom.
Journal of The Acoustical Society of America, Jan 1, 2008
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Papers by Mostafa Bakhoday Paskyabi