Review of Computer-Aided Numerical Simulation in Wind Energy

Many advances have been made during the last decade in the development and application of computational fluid dynamics (CFD), finite element analysis (FEA), numerical weather modeling, and other numerical methods as applied to the wind energy industry. The current information about this area of study may help researchers gage research efforts. Specifically, micro-siting, wind modeling and prediction, blade optimization and modeling, high resolution turbine flow modeling, support structure analysis, and noise prediction have been the main focuses of recent research. The advances in this area of research are enabling better designs and greater efficiencies than were possible previously. The trends toward system coupling, parallel computing, and replacing experiments are discussed. The shortcomings of recent research and areas of possible future research are also presented

Monopile Foundation Offshore Wind Turbine Simulation and Retrofitting

Offshore wind turbines (OWT) provide a renewable source of energy with great proximity to many large cities. This has caused a major increase in OWT development and implementation, primarily in Europe, but spreading throughout the world. There are a multitude of different foundation options, each with their own benefits. The most common types are: monopile, jacket, TLP, Semi-Submersible, and SPAR. The monopile foundation OWT has been proven to be the most economic selection for water depths up to approximately 25m. This thesis has analyzed strictly monopile foundations due to their previous success and popularity. Three different chapters have been created to cover the two different research papers contained in this thesis. Chapter one utilizes the software ANSYS to complete a multi-hazard computational fluid dynamic (CFD) analysis of a monopile foundation OWT. A dynamic analysis was performed on the structure, with a p-y curve soil-structure interaction implemented. Chapter two aims to verify the plausibility of a retrofit solution to a significant problem certain previously installed monopiles have developed. The annulus grout of the transition zone of the structure has been determined to be under-designed, and thus has experienced crushing. This allows the tower to slightly slide down the monopile, increasing the chances of total structural failure. A retrofit bolted connected has been implemented, and proven to significantly increase the limiting shear capacity of the structure. The research paper in chapter three is focused on developing the retrofit solution into a more applicable design. Using a response surface methodology (RSM) an optimized design criteria has been generated based on six geometric/material parameters of the bolted connection: horizontal spacing, vertical spacing, bolt diameter, number of bolts in vertical columns, pre-tensioning load on bolt, and modulus of elasticity

Optimization of Support Structures for Offshore Wind Turbines Using Genetic Algorithm with Domain-Trimming

The powerful genetic algorithm optimization technique is augmented with an innovative “domain-trimming” modification. The resulting adaptive, high-performance technique is called Genetic Algorithm with Domain-Trimming (GADT). As a proof of concept, the GADT is applied to a widely used benchmark problem. The 10-dimensional truss optimization benchmark problem has well documented global and local minima. The GADT is shown to outperform several published solutions. Subsequently, the GADT is deployed onto three-dimensional structural design optimization for offshore wind turbine supporting structures. The design problem involves complex least-weight topology as well as member size optimizations. The GADT is applied to two popular design alternatives: tripod and quadropod jackets. The two versions of the optimization problem are nonlinearly constrained where the objective function is the material weight of the supporting truss. The considered design variables are the truss members end node coordinates, as well as the cross-sectional areas of the truss members, whereas the constraints are the maximum stresses in members and the maximum displacements of the nodes. These constraints are managed via dynamically modified, nonstationary penalty functions. The structures are subject to gravity, wind, wave, and earthquake loading conditions. The results show that the GADT method is superior in finding best discovered optimal solutions