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Institute of Turbomachinery and Fluid Dynamics
Logo Leibniz Universität Hannover
Institute of Turbomachinery and Fluid Dynamics
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Constant Temperature Anemometry (CTA)

Field of Application

  • Measurement of flow velocities and turbulent flow parameters
  • High temporal resolution allows the investigation of highly turbulent flows
  • Using small probes very small vortex structures can be detected

Measured Quantities

  • Three dimensional flow vector
  • Turbulent fluctuation values

Description

Constant Temperature Anemometry (CTA) is one type of hot-wire anemometry. It is based on the temperature dependence of the ohmic resistance of a metallic sensor, which is electrically heated while fluid passes it. This leads to convective heat transfer between the sensor wire and fluid. The heat transfer results in a change of the ohmic resistance that is measured by an electrical circuit. The relationship between heat transfer and flow field parameter enables the measurement of the flow velocity.

In general hot wire anemometry is divided into two types, Constant Current Anemometry (CCA) and Constant Temperature Anemometry (CTA). CTA is used at the TFD. In this method the electrical resistance of the sensor is kept constant by adjusting the voltage with a Wheatstone bridge. Hence, the temperature of the wire remains constant even if there is heat transfer into the flow. Therefore it is possible to determine the flow velocity from the change in voltage. Due to the high temporal resolution even turbulent parameters can be determined. Using multiple wire probes allows the study of three-dimensional flow velocities.

Three-dimensional hot-wire probes are currently used in the low speed diffuser test rig in order to study the unsteady flow field in an exhaust diffuser. Furthermore, hot-wire probes are used in the air turbine rig to measure the turbulence intensity. The CTA-system is mobile and therefore can be used on every test rig at the institute.

Contact

Dipl.-Ing. Lars Wein

  • Phone:                 +49 (0) 511 762 2347
  • Mail:                      weintfd.uni-hannover.de