Flow Field Diagnostics
Constant Temperature Anemometry Solutions

Boundary layer hotwire probe with gold-plated sensors.

Turbulence diagnostics is an important step in research and development because it
has great impact in numerous applications from aerodynamics to passenger comfort.
Hotwire anemometers provide the best spatial and temporal resolution for turbulence
investigations.

Constant Temperature Anemometry (CTA)
CTA is a well-established point measurement techniquewith commercial systems available for several decades.
Application areas include temperature, shear stress, velocity
and turbulence measurements in e.g. jets, boundary layers,transitional flows.
Even though the CTA technique is intrusive and its response
is non-linear; it is still the best option for accurate
turbulence investigations, boundary layer diagnostics, highfrequency temperature fluctuations and simultaneous multipoint velocity measurements.

We offer:• High quality research grade anemometers• Low cost, educational and mobile anemometers• Automatic and manual calibration systems for air• Manual calibration systems for water• Probes with wire, fiber-film and film sensors• Data acquisition and control systems• Dedicated software package that reduces the burden ofexperiments; incl. hardware control, automatedcalibration and automated acquisition.
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CTA Measurement Principle

The CTA measurement principle is based on heat transfer from a heated sensor.

The CTA measurement principle is based on the cooling of
small sensors placed in the flow:
The temperature (resistance) of the sensor is kept constantby an advanced feedback control loop that contains
an electronic bridge circuit. This way, the anemometerproduces a continuous voltage that is proportional to theinstantaneous flow velocity. The output signal is sampledwith high resolution so the flow velocity is determinedaccurately both in the amplitude domain and in thefrequency domain.

StreamLine Pro - the most reliable research-grade CTAsystem.

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Three different anemometer systems cover a wide variety
of applications, from extremely accurate turbulence
investigations in a thin boundary layer to measuring mean
wind profiles out in the open field. The MiniCTA systems
are quite popular in field applications as well as foreducational use.
Each anemometer system consists of a mainframe, CTA
modules, calibration equipment, hotwire probes andaccessories, a data acquisition and control system, and a
dedicated software package.

MultichannelCTA - the multiple channel version of theMiniCTA system.

MiniCTA - the most compact CTA system for educational use.

Calibration is Key in CTA Measurements

StreamLine Pro Automatic (Air) Calibrator.

Water Calibrator.

An accurate CTA measurement requires an accurate
calibration. With decades of experience Dantec
Dynamics has designed an automatic and a manual
calibrator for air applications and a water calibrator.
The air calibrators are able to produce speeds up toMach 1 and the water calibrator up to 2 m/s, and thecalibrators are delivered with exchangable nozzles tocover their individual velocity range. All calibrators arecompatible with the Pitch/Yaw – Roll (PYR) manipulators,
which are required for directional calibrations.

Directional calibrations are required for multiple-sensor
hotwire and hotfilm probes. A single axis rotation(Pitch/Yaw) is sufficient for 2-sensor probes, whereas a
two-axis rotation (Pitch/Yaw & Roll) is required forcalibrating 3-sensor probes. These operations are madesimpler by the manual and motorised PYR manipulators.
The motorised PYR manipulator is compatible with the aircalibrators whereas the manual version is recommended
for the water calibrator. Both versions are supported in
the CTA software StreamWare Basic and StreamWare Pro.

Manual and motorized pitch-yaw manipulators allow probe rotation around two axes during directional calibration.

5Probes

Triaxial Parallel-flow probe with gold-plated wire sensors.

Triaxial cross-flow probe with fiber-film sensors.

Dantec Dynamics has a comprehensive probe program.
The hotwire and hotfilm probes are a result of more thanhalf-a-century design and manufacturing experience.
The product range is complete with accessories: probe
supports, mounting tubes and guide tubes.

Dantec’s probe manufacturing precision manifests itself
during directional calibration events. For multi-sensor
probes, the sensors should be placed perpendicular toeach other in space to achieve a balanced directional
sensitivity. This dictates the prong placement with tight
manufacturing tolerances.

Standard probes are available with different sensormaterials for use in gaseous or liquid media, addressing
different applications and challenges. For demanding
applications where standard probes are not sufficient,custom designs can be provided upon request.

Dantec Dynamics’ probe manufacturing precision manifests itself in directional
calibration events.
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If the prong and sensor placement is close to ideal a low
residual error during directional calibration is observed.
The result is near-textbook values for the pitch and yaw
coefficients and an accurate velocity measurement.

Thin film coating in Dantec Dynamics’ clean room facility.

Software

StreamWare Pro software has a modern look and an intuitive interface, which guides the user through system configuration, hardware setup, probe calibration, and data acquisition.

StreamWare Basic and StreamWare Pro are dedicatedsoftware platforms that help the user to design, organize
and document CTA measurements as well as post process
the results. StreamWare Basic supports MiniCTA andMultichannel CTA systems, and StreamWare Pro supports
the StreamLine system family. They perform hardware
set-up, automatic probe calibration, data acquisition,conversion and reduction. Raw and reduced data can bepresented in StreamWare Basic and StreamWare Pro orthey can be exported to other applications (e.g. Excel andTecPlot ®) for further manipulations.

CTA is still the preferred technique for turbulence
investigations due to its unmatched frequency response.
The power spectrum calculation in StreamWare Basic andStreamWare Pro provides a one-sided power spectral
density per unit time. The computation combines features
like block averaging, data windowing, zero padding anddata overlapping in a smart fashion to reduce uncertainty
inherent to Fourier analysis, while satisfying the Parseval’s
theorem for each signal block. The result is a clean power
spectrum where dominant frequencies and harmonics areobtained.

Flow field downstream of a cylinder in cross flow in Tecplot: mean velocity field &turbulence intensity.

Power Spectral Density computation downstream of cylinder in cross flow, data
courtesy of Technical University of Denmark.
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About Dantec Dynamics
Dantec Dynamics is the leading provider of laser optical measurement systems and sensors.
Since 1947 we have provided solutions for customers to optimize their component testingand products. Our large number of customers benefit from our quality solutions within:

Fluid
Mechanics

Spray andParticle
Characterization

Combustion
Diagnostics

Microfluidics

3D Shape
Deformation,
Strain andVibration
Measurement

Strain andStressMeasurement

DISATAC
Tachometers

ThermalComfortNon
Destructive
Testing

Worldwide representation
From our six offices and more than 30 representatives worldwide we approach ourcustomers individually. We examine the specific needs and find the best solution for you.
For us you are a long-term partner in improving efficiency, safety and quality of life.
A list of representatives is available at our website.
DENMARK (headquarters)
Dantec Dynamics A/S
info@dantecdynamics.com

UNITED KINGDOM
Dantec Dynamics Ltd.
uk@dantecdynamics.com

FRANCE
Dantec Dynamics S.A.S.
france@dantecdynamics.com

USA
Dantec Dynamics Inc.
usa@dantecdynamics.com

GERMANY
Dantec Dynamics GmbHgermany@dantecdynamics.com
JAPANDantec Dynamics K.K.
japan@dantecdynamics.com

www.dantecdynamics.com

Publication No.: 346 v1
The specifications in this document are subject tochange without notice.
Dantec Dynamics is trademark of Dantec Dynamics A/S.

Dantec Dynamics, a Nova Instruments company