In our wind tunnel laboratory, we have a various range of equipment available for research. The most notable systems are listed below.
With particle image velocimetry we are able to obtain instantaneously velocity measurements of the flow in our wind tunnel. By adding small oil droplets to the airflow, shining a laser sheet on them and recording the particles over time with a high speed camera the flow is visualized. The biggest advantage of this technique is that it is non-intrusive and very accurate.
The current laser system consists of a Litron Nano 135-15 PIV laser (135 mJ), which is a dual cavity laser allowing the creation of high intensity, closely spaced pulses with a wavelength of 532 nm. Seeding particles are generated using a PIVTEC PIVpart45 seeder. The particles are injected into the stream using a hose that connects to the closed wind tunnel test section. Spherical particles with an average diameter of 0.9 micrometerare generated using an oily colorless liquid (Di-Ethyl-Hexyl-Sebacat). Particles are tracked using two Phantom v611 high speed camera’s. These camera’s can record up to 1,000,000 FPS at a resolution of 128 x 8 pixels, 6,242 fps at full 1280 x 800 widescreen resolution. Both the laser and high speed camera’s are provided by LaVision.
Hot wire anemometry uses a very small wire which is heated electronically. The wire will be cooled as air flows past the wire changing the wire's resistance. Through this, a relationship between wire resistance and flow is obtained. Consequently, very accurate flow measurements can be performed at a high sampling frequency.
A Dantec Streamline 90N10 frame with various one wire and cross-wire probes are available for measurements. The streamline frame consists of two channels each with a Wheatstone bridge. The sampling rate extends more than 105 Hz which is well beyond frequencies of interest for acoustic purposes. Real-time temperature corrections can be applied to increase accuracy.
With an acoustic camera, we can visualize noise sources using the principle of phase delay. It is a very effective tool for localizing and quantifying noise sources on many different kinds of applications. We currently mainly apply it to airfoil noise for wind turbine or aircraft applications.
At the moment we have the availability of the following acoustic cameras:
- CAE Systems Bionic M-112 Array
- In-House developed array using digital MEMS microphones.
- The possibility of creating a custom array using LinearX M51 microphones.
- 64 GRAS 40PH microphones.
Direct image correlation system (DIC) is an optimal technique used to measure 2D and 3D displacement and strains. The StrainMaster system consists of a 3D-DIC system type provided by LaVision capable of determining 2D in-plane deformation or full 3D surface measurements. It can be used to investigate for example acoustics caused by structural vibrations of an airfoil.