General Description

The aerodynamic shape of wind turbine blades is designed based on 2D and 3D aerodynamic simulations and wind tunnel measurements. Often, due to time, budget and computational power restrictions, these simulations include simplifications and assumptions. A typical example is the fact that airfoil performance polars are measured in wind tunnels with very low turbulence or by means of CFD methods that do not include realistic turbulence modeling. However these airfoil sections operate in the field under severe turbulence, gusts, surface contamination e.t.c. Their real-life-performance therefore can vary significantly from the theoretical predictions.

A great assistance for the development of reliable aerodynamic designs would be the introduction of aerodynamic experimental field testing, much similar to the aircraft prototype testing procedure. Unfortunately, however the experimental analysis of wind turbine prototypes with respect to detailed aerodynamic performance is very costly and often technically impractical. 

Low-cost techniques, such are flow-tuft visualization are currently employed but these give only qualitative, approximate results that do not really allow the quantification of the aerodynamic characteristics of wind turbine blades. What is therefore needed is the development of a cost-effective, easy to perform, quantitative flow analysis with high spatial and temporal resolution. 

 

 

SMARTviz >> Developed by SMART BLADE & HFI TU Berlin

The use of modern high resolution digital optics, advanced image processing techniques and high quality materials allowed the SMART BLADE & HFI TU Berlin researchers to develop SMARTviz. This is an innovative technique that allows wind turbine manufacturers as well as operators to analyze the aerodynamics of wind turbines in the field under real-life conditions with unprecedented detail.

Basic schematic representation of the SMARTviz setup. Optic, wind and other sensors are used for the spatial and temporal analysis of rotorblade aerodynamics.
The post processing process of several tens of thousands of images involves sophisticated image processing and flow analysis algorithms.

SMARTviz Results

The results of a SMARTviz process include various spatial and temporal aerodynamic flow characteristics and higher order statistical information. Some of the typical results are presented bellow:

>> Mean flow direction (streamlines)

>> Streamline variation in different wind speed regions

>> Streamline variation for various rotor positions

>> Statistical information for the mean position and standard deviation of each flow tuft

>> Crossflow iso-contours along the blade

>> Turbulence level (flow tuft activity) contours along the blade

 

 

(Left) Crossflow iso-lines and turbulence contour plots. (Right) Single flow tuft statistics.
Rotorblade streamline analysis depicting strong cross-flow, local stall and flow stagnation region. The turbulence contour plots are also overlaid.