Thermostratified Wind-Wave Tank
The Thermostratified Wind-Wave Tank (TsWiWaT) is a unique experimental facility, which allows laboratory modeling of hydrophysical processes in the subsurface layer of the ocean, marine atmosphere boundary layer, as well as wind-wave interaction under a wide range of conditions. One of the main feature of the facility is the possibility to prepare conditions of temperature stratification (which strongly affects on the processes in hydrosphere) and maintain it for a long time. Extreme conditions concerning with high winds such as intensive wavebreaking, spray of droplets generation at the interface between the atmosphere and the hydrosphere (for storms and hurricanes) can also be simulated on this unique facility.
The following research fields belongs this facility:
- study of the processes in the subsurface layer of the ocean, including natural phenomena and anthropogenic effects;
- laboratory modeling of the interaction of the atmosphere and the hydrosphere for a wide range of conditions;
- development of the methods of remote sensing of marine boundary layer;
- tests of measuring equipment used in meteorological and hydrologic environments.
TsWiWaT is equipped with towing trolleys and internal and surface wavemakers. Unique measuring complex of TsWiWaT includes various instruments for contact measurements, and original laser-optical systems for air and water flow visualization. The complex is automated and includes equipment for precision positioning of sensors ang gauges using step motors.
For the present time no analogs of LTST exist, neither in Russia, nor abroad compared on proximity of parameters of temperature distribution to real conditions and sizes of stratified-water volume.
There are a few operating experimental facilities abroad, which model wind-wave interaction, including LASIF (France), the Heidelberg Aelotron (Germany), and the recently built world-largest tank SUSTAIN (USA).
Large Thermostratified Test Tank
The Large Thermostratified Test Tank (LTST) is the world-largest hydrophysical facility that realizes the possibility to create stratification, i.e., vertical temperature distribution. The unique system including three high-power cooling fridges acts as a thermal pump, drawing the heat from the bottom water layer and transferring it to the top layer. After approximately 20 hours of continuous operation, stratification of the thermocline type is achieved from the initially uniform mixed water thickness having a temperature of 15 degrees. The resulting temperature gradient is from 27 degrees on the surface to 6 degrees at the bottom, with a sharp density jump at a depth of about 60 cm. These unique conditions allow one to study dynamics of internal waves and their manifestation in the surface-wave field and analyze evolution of turbulent flows under the stratification conditions. The tank is equipped with a towing trolley for studying wake flows behind bodies and installing measuring equpment, as well as wavemakers of internal and surface gravity waves. The internal-wave generator is a vertical plate that performs angular oscillations relative to the horizontal axis at the level of the thermocline center. The surface wavemaker employs cylinders with different diameters and oscillating on the water surface in the vertical direction.
- Dimensions: 20 m × 4 m × 2 m
- Fridge power: 150 kW
- Temperature difference between the bottom and the surface: up to 21°С
- Depth of the temperature step position: 0.6 m
- Maximum value of the buyoancy frequency: 0.3 rad/s
- Speed of the towing trolley: 0.02...1.0 m/s
- Diameters of the cylinders of the surface-wave generator: 5, 10, and 16 mm
- Frequency of the surface-wave generator: 1...4 Hz
- Amplitude of vertical oscillations of the wave generator: up to 5 cm
- Dimensions of the plate of the internal-wave generator: 3.5 × 0.7 m
- Frequency of the internal-wave generator: 0.008 … 0.05 Hz
- Amplitude of internal waves: 0.1 … 4 cm
High-speed Wind-wave Flume
The High-speed Wind-Wave Flume (HSWWF) is designed to model the effects of interaction of atmospheric air flows with the sea surface for a wide range of conditions, including extreme ones (storms and hurricanes). The flume is located in the middle of LTST. On the 12 meters length crosssection increase from 0.7 m × 0.7 m inlet to 0.7× 0.9 m outlet due to the inclined ceilling. The side walls of the channel are submerged in the water to 0.6 m, and there is no bottom. Installation of the channel directly in the LTST reservoir with a large external water volume prevents underwater counterflow. This feature is an advantage of HSWWF as compared with typical wind-wave facilities characterized by the above-mentioned drawback. The air track is equipped with flexture deflector blades and an acoustic damper. An expanding/narrowing section with a set of honeycombs and nets is installed in front of the exit to the water surface. All these systems guarantee a high quality of the air flow at the channel entrance with a fluctuation level of about 1% and a high degree of the flow uniformity over its crosssection. The channel is equipped with a special system for accurate controllable tuning of the fan rotation frequency, which supply air flow to the aerodynamic line. Thus, the centerline wind speed can be ajusted in the range up to 33 m/s, which in terms of the equivalent velocity corresponds to wind speeds of up to 50 m/s at a height of 10 m for real conditions. At such winds, the regime of regular wave breaking can be realized with formation of foam and sprays of droplets. The channel makes it possible to organize controllable mixing of the air from the outdoors and the laboratory room in order to adjust the temperature and the air volume flow rate. As a result, the temperature of the air flow at the channel entrance is controlled in the range from -2°C до +45°C depending on the operation regime and the season of the year. Combining it with the possibility of adjust the temperature of the subsurface water layer in the range from +5°C up to +25°C, one can study the processes of wind-wave interaction in a wide range of temperature gradients between air and water in the channel, which are typical, in particular, for the extreme conditions of the polar regions.
General view of the wind-wave channel
- Dimensions of the straight section of the air channel above the water surfce: 0.7 m × 0.7 m inlet and 0.7 m × 0.9 m outlet
- Total length 12 m
- Range of axis wind speed in the working section of the flume: 0 … 33 m/s
- Corresponding equivalent 10 m wind speed for real conditions: 0 ... 50 m/s
- Temperature of the air flow in the channel: -2°C … +45°C
- Temperature of the water surface in the channel: +5°C … +25°C
- Frequency of the surface wavemaker: 0.5 … 2.5 Hz
- Amplitude of vertical oscillations of the wavemaker: up to 5 cm