Göttingen Turbulence Facilities Germany

Facilities and equipment

Overview

The facilities are exceptional in providing both Eulerian and Lagrangian measurements with the highest technologically realizable speed and resolution. They are versatile and flexible in the installation of other flow generators and instruments.

  • Highest turbulence levels under well-controlled conditions 
  • Flow resolvable over all scales by current measurement technology;
  • High-pressure compatible measurement systems: 3D LPT, Tomo PIV, LDV, PDPA, hot-wire.

The facilities are housed in a newly constructed experimental hall that is vibration isolated and temperature stabilized. Safety control systems are installed to support daily use of pressurized gases and high-power lasers. High bandwidth fibre optics links the facilities to a 288-processor data analysis cluster. A 36m2 class 1000 clean room is available for micro fabrication of sensors. The institute installed a gas liquefaction system in a separate building, where 13 tons of SF6 gas are stored. The operational pressure of the system ranges from 1mbar to 19bar.

The facilities include the following equipment: a 3D Lagrangian particle tracking system consisting of 4 phantom V7b cameras (800x600 at 6k fps and 256x256 at 36k fps), a Tomo-PIV system (LaVison) with 4 Phantom cameras (2000x2000 at 500fps), a 3 component LDV system (TSI) with a PDPA for particle sizing, a Dantec hot-wire system, nano-fabricated hot-wires (Princeton). All of the above equipment is compatible with high pressure up to 15 bar. In addition, 2 frequency doubled, high-repetition-rate and high-power Nd:YAG lasers (100kHz and 50W), 2x5W argon-ion lasers, 2 linear optical rails (7m, 9m) with linear motors (capable of driving 350kg at speeds up to 5m/s), optics, data analysis software, and a computing and storage cluster are available.

GTF1 (Variable Density Turbulence Tunnel)

In GTF1, Reynolds numbers of up to Rλ ~7000 are possible when filled with SF6 at 15bar. The tunnel is upright and consists of two measurement sections with a cross-sectional area of 1.9m2 and lengths of 9m and 7m, respectively. A passive grid is mounted at the entrance of one measurement section to generate the turbulence (Rλ up to 1700). An active grid has been designed, constructed, and pre-assembled. It will replace the passive grid in order to increase the Reynolds number up to Rλ~7000. The wind tunnel has been designed to contain sleds in each of the measurement sections, carrying up to 350kg and driven by linear motors, which allows measurement devices (e.g. cameras and optics) to be moved with the mean velocity of the circulating gas (up to 5m/s). Appropriate test systems (outside the wind tunnel) and optical benches (inside the wind tunnel) exist. The tunnel is pressure and temperature controlled, and has optical and electrical interfaces. The circulating gas can be filtered to <1μm in order to gurantee the cleanness. Measurement equipment can be installed along the measurement sections. Beside several pressure sensors, nano-fabricated hot-wires from Princeton University have been installed on a 3D traversing system. Other measurement devices to be used in the tunnel are Lagrangian particle tracking systems, LDV/PDPA systems, and cantilever velocimeters. Specifications: Total length 18m, height 6m, measurement section lengthes 9m and 7m, inner diameter 1.8m, pressure range 1mbar-15bar, temperature 20-35°C, mechanical power of the fan 210kW, cooling capacity 280kW, kinematic viscosity of SF6 at 15bar: 1.5x10-7m2/s. Turbulence properties: <u>max =5m/s, urms,max=1m/s, Lmax=0.70m, Rλ,max=7500, εmax =1.2W/kg, η >8μm, τη>0.4msec.

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GTF2 (High-pressure Convection Facility)

GTF2 is a general-purpose pressure vessel. It has been designed to house different experiments. As in the turbulence tunnel, all equipment, from heat transport and PIV to 3D-Langrangian Particle Tracking (LPT), can be used inside the vessel. Experimental inserts available include two turbulent cylindrical Rayleigh-Bénard experiments (diameter 1.1m, height 2.2m and 1.1m respectively) that reach Rayleigh numbers as large as Ra~1015. Specifications: length 5.3m, max. height 4.0m, outer diameter 2.5m, straight cylinder length 4m, dome 1.5m high and 1.2m diameter, pressure range 1mbar-19bar, temperature 20-35°C, cooling power up to 50kW, kinematic viscosity of SF6 at 15bar:  1.5x10-7m2/s. Properties of the Rayleigh-Benard cell: Ramax = 7x1014 with very weak non-Boussinesq effects; Lagrangian stirrer: <u>max =0m/s, urms,max=1m/s, Lmax=0.1m, Rλ,max=4500, εmax =5.5W/kg, η >5μm, τη>0.2msec.

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A photo of the pressure vessel in blue wrapped in black foam to provide additional thermal isolation. The vessel itself is fully pressure and temperature controlled. The 'turret' on top and the porthole on the left provide means to insert equipment into the vessel. Electrical/optical cables and gas/water pipes can be fed through the wall of the vessel.
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Dimensions of the pressure vessel in two different configurations. The configuration on the right has an extended turret, resulting in a maximum interior height of 5.1 m as measured from the flat support floor. The main cylinder has an inner diameter of 2.46 m and the turret has an inner diameter of 1.46 m.

GTF3 (von Karman Flow Apparatus)

GTF3 generates high Reynolds number turbulent water flows between two counter-rotating baffled disks. Large glass windows provide access for LPT or PIV measurements. The apparatus can be pumped down to reduced-pressure for the study of bubble dynamics. A frequency doubled high-power (50W), high-repetition-rate Nd:YAG laser is devoted to measurements in this apparatus. Specifications: Inner diameter 0.5m, height 0.63m, propeller diameter 0.25m, urms,max=1.4m/s, Lmax=0.07m, Rλ,max=1200, εmax =10W/kg, η >20μm, τη>0.3msec.

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The von Karman swirling flow apparatus
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The optical windows