Showing papers by "Yulia Peet published in 2021"

Verification and convergence study of a spectral-element numerical methodology for fluid-structure interaction

Abstract: A high-order in space spectral-element methodology for the solution of a strongly coupled fluid-structure interaction (FSI) problem is developed. A methodology is based on a partitioned solution of incompressible fluid equations on body-fitted grids, and nonlinearly-elastic solid deformation equations coupled via a fixed-point iteration approach with Aitken relaxation. A comprehensive verification strategy of the developed methodology is presented, including h-, p- and temporal refinement studies. An expected order of convergence is demonstrated first separately for the corresponding fluid and solid solvers, followed by a self-convergence study on a coupled FSI problem (self-convergence refers to a convergence to a reference solution obtained with the same solver at higher resolution). To this end, a new three-dimensional fluid-structure interaction benchmark is proposed for a verification of the FSI codes, which consists of a fluid flow in a channel with one rigid and one flexible wall. It is shown that, due to a consistent problem formulation, including initial and boundary conditions, a high-order spatial convergence on a fully coupled FSI problem can be demonstrated. Finally, a developed framework is applied successfully to a Direct Numerical Simulation of a turbulent flow in a channel interacting with a compliant wall, where the fluid-structure interface is fully resolved.

Streamwise inhomogeneity of spectra and vertical coherence of turbulent motions in a finite-size wind farm

Abstract: In a finite size wind farm turbulence is streamwise inhomogeneous. This paper examines the evolution of large scale motions on the order of 10 turbine rotor diameters influenced by wake-mixing from turbine rows. Using wavelet-based methods, the analysis illustrates that streamwise and vertically coherent length scales grow significantly past the first row of turbines. The first observation is primarily due to turbulence from the superposition of turbine wakes while the latter one is associated with the development of a global energy transfer mechanism (``sweeps'') between the outer layer and the wind turbine region.

A Constraint Handling Approach with Guaranteed Feasibility for Surrogate Based Optimization

Abstract: Gradient-free optimization methods, such as surrogate based optimization (SBO) methods, and genetic (GAs), or evolutionary (EAs) algorithms have gained popularity in the field of constrained optimization of expensive black-box functions. However, constraint-handling methods, by both classes of solvers, do not usually guarantee strictly feasible candidates during optimization. This can become an issue in applied engineering problems where design variables must remain feasible for simulations to not fail. We propose a constraint-handling method for computationally inexpensive constraint functions which guarantees strictly feasible candidates when using a surrogate-based optimizer. We compare our method to other SBO, GA/EA and gradient-based algorithms on two (relatively simple and relatively hard) analytical test functions, and an applied fully-resolved Computational Fluid Dynamics (CFD) problem concerned with optimization of an undulatory swimming of a fish-like body, and show that the proposed algorithm shows favorable results while guaranteeing feasible candidates.