We have various equipment components available for research in our wind tunnel laboratory. The most notable systems are listed below.
Particle image velocimetry allows us to measure the velocity field of the flow in our wind tunnel. By adding small oil droplets to the airflow and shining a laser sheet on them, we can record these tracer particles over time with a high-speed camera as they move through space. The biggest advantage of this technique is that it is predominantly non-intrusive and very accurate.
We have 2 laser systems available. The first system consists of low-speed 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 at a maximum frequency of 15 Hz. The second system allows us to operate a dual-cavity high-speed laser type DM30-527-DH with a maximum repetition rate of 10 kHz emitting with a wavelength of 527 nm.
We generate seeding particles using a PIVTEC PIVpart45 seeder. Spherical particles with an average diameter of 0.9 micrometer are generated using an oily, colorless liquid (Di-Ethyl-Hexyl-Sebacat). We track particles using either Phantom v611 high-speed cameras or Imager SX 9M (low-speed) cameras. The Phantom camera can record up to 1,000,000 FPS at a resolution of 128 x 8 pixels and 6,242 fps at full 1280 x 800 pixels wide-screen resolution. The Imager SX 9M operated with a resolution of 3360 x 2712 pixels at a maximum frame rate of 18 FPS. The laser optics can be guided with an optical arm.
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 91N10 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.