Effect of steady and transient wind shear on the wake structure and performance of a horizontal axis wind turbine rotor

This paper presents an investigation of the effect of steady and transient free-stream wind shear on the wake structure and performance characteristics of a horizontal axis wind turbine rotor. A new three-dimensional unsteady vortex-panel method potential flow solver based on a free-vortex wake methodology, AeroSIM+, is used for this purpose. The code is validated using the experimental data from the National Renewable Energy Laboratory Unsteady Aerodynamics Experiments. The effects of vortex core model, core size, expansion, and filament stretching on torque and thrust predictions are investigated. Three-different wind shear cases, i.e., uniform inflow (no wind shear), steady vertical wind shear that uses a power law velocity profile (Normal Wind Profile, NWP) and transient Extreme Wind Shear (EWS), are investigated. The results show that the existence of wind shear can create a very complex wake structure with substantial asymmetries, streamwise vorticity generation, and non-periodicities downstream of the turbine rotor. In addition, the blades are subjected to asymmetrical surface pressure variations that in turn result in high amplitude fluctuations in power and thrust levels generated by the turbine. Copyright (C) 2011 John Wiley & Sons, Ltd

Panel-Method-Based Path Planning and Collaborative Target Tracking for Swarming Micro Air Vehicles

This paper presents an application of the potential field panel method commonly used in aerodynamics analysis to obtain streamlinelike trajectories and use them for path planning and collaborative target tracking for swarming micro air vehicles in an urban environment filled with complex shaped buildings and other architectural structures. In addition, we introduce a performance matching technique that relates the flu id velocities, which are obtained as a part of the panel method solution, to vehicle velocities along each trajectory. The approach is further extended to track moving targets yet avoid obstacles and collision between the vehicles. Because of the inherent nature of streamlines, obstacle avoidance is automatically guaranteed. To make the micro air vehicles follow and track a moving target, dynamically changing streamline patterns are calculated for each and every one of the micro air vehicles within a swarm. To prevent vehicle-to-vehicle collisions, each micro air vehicle is represented using a point source singularity element within the potential field. The simulation results are quite encouraging, in the sense that micro air vehicle swarms quickly locate and track the assigned target in an environment filled with complex-shaped structures while avoiding obstacles and collisions among themselves. One benefit of the method is that the trajectory computations can be relatively fast and even have the potential to be applied in real time, depending on the number and complexity of the urban structures

Yatay eksenli rüzgar türbini kanadı ve kanat profillerinin BEM ve CST metodları ve genetik algoritma kullanarak aerodinamik optimizasyonu

Bu çalışmada yatay eksenli rüzgar türbini palalarının ve kanat kesitlerinin aerodinamik optimizasyonu yapılmaktadır. Kanat kesit geometrisi tasarımında Sınıf-Şekil Transformasyonu Metodu (CST) kullanılmıştır. Aerodinamik veriler, bir potansiyel akış çözücüsü olan XFOIL yazılımı ile elde edilmiştir. Rotor güç hesaplamaları için Pala Elemanı-Momentum (BEM) teorisi kullanılmıştır. Genetik Algoritma (GA), rotor maksimum güç üretimi amacıyla, pala kanat kesitigeometrisi optimizasyonunda kullanılmıştır.Bu bildiride, seçilen rotorlariçin doğrulama çalışmaları yapılmış, ve yapılan optimizasyon çalışmaları ve aerodinamik performans karakteristikleri hesaplamaları ve sonuçlar literatürdeki mevcut test rüzgar türbinleri ilekarşılaştırılmıştır.Kalın ve ince kanat kesiti optimize tasarımlarını da kullanan üç kanat kesitli tasarlanan yeni rotor için analizler yapılmış ve aerodinamik performans artırımları incelenmiştir