The facilities are equipped with cutting-edge modern measurement techniques: 3D-PTV, 3D-PIV, LDV, torque sensors, optical probes, hot-film anemometry.
Facilities and equipment
T3C (Twente Turbulent Taylor-Couette System)
The Twente Turbulent Taylor-Couette system consisting of two independently rotating cylinders has been operational since 2010. The gap in between the cylinders has a height of 0.927 m, an inner radius of 0.200 m and a variable outer radius (from 0.279 m to 0.220). The maximum angular rotation rates of the inner and outer cylinder are respectively 20 Hz and 10 Hz, resulting in Reynolds numbers up to 3.4 × 106 with water as working fluid. With this Taylor-Couette system, the parameter space (Rei, Reo, η) can be pushed to (2.0 × 106, ±1.4 × 106, 0.716 - 0.909). The system is equipped with bubble injectors, temperature control, skin-friction drag sensors, and several local sensors for studying turbulent single-phase and two-phase flows. The inner cylinder is able to sense the skin-friction drag by means of measuring the cylinder's torque with load cells. The dynamics of the liquid flow and the dispersed phase (bubbles, particles, fibers etc.) inside the gap can be investigated with specialized local sensors and nonintrusive optical imaging techniques, enabled by the clear acrylic outer cylinder. The system allows for studying Taylor-Couette flow in high Reynolds number regime and the mechanisms behind skin-friction drag alterations due to bubble injection, polymer injection, and surface hydrophobicity and roughness. Various liquids (including FC-liquids) will be used for the experiments.
We provide the following measurement equipment in the facilities: a 3D-PIV/PTV system consisting of 4 Photron cameras (1k × 1k at 1 kHz). A Dantec LDV system, a Dantec hot-film velocimetry and shear stress system, a Nd-YLF laser with a repetition rate of 20 kHz and high power 100W, a computer cluster for data analysis.
TWT (Twente Water Tunnel)
The Twente Water Tunnel is an 8m high facility in which strong turbulence (up to a Taylor-Reynolds number of 300) can be created thanks to an active grid. Light particles including bubbles (from now on all called particles) can be injected into the turbulent flow with a concentration up to 10%. The size of the mono-disperse particles can be varied. These light particles rise with the flow and can be observed and followed in the measuring section. The instrumentation includes 3D Particle Tracking Velocimetry, hot-film anemometry, and optical probes. A traverse system enables the movement of the cameras (up to 30 kg) and other devices with the operated mean flow.
The control parameters in the TWT are the density ratio between particles and water, the particle size and concentration, and the Reynolds number. The questions that we address with the TWT facility are the Lagrangian particle dynamics in the flow and in particular particle clustering, velocity and acceleration statistics, effect of particles on spectra and collision rates, average rise/sink velocity of particles, further Lagrangian aspects, and finally also bubbly drag reduction.
The TWT is a unique facility for two-phase turbulence studies. The bubble and light particle regime of the phase space: relative particle density vs. Stokes number is only accessible in the TWT. For these reasons, the TWT should be made accessible to a broader turbulence community.