SOLUTION SHEETFlexLDA systems

Factory aligned and calibrated

FlexLDA system measuring the air flow around a wing profile

Pre-aligned and calibrated LDA solution for flow velocity measurements
Laser Doppler Anemometry (LDA) is an optical technique ideal for non-intrusive point
measurement of velocity and turbulence in a wide range of fluid dynamics applications.
The FlexLDA system is a full featured turn-key solution for working distances up to 500
mm and velocities up to 68 m/s. It uses compact lasers and Bragg cells integrated intothe stable and robust design. The system is very easy to set up due to the factory alignedand calibrated optics. Signal processing is done by the well proven BSA (Burst SpectrumAnalyzer) using robust real time FFT (Fast Fourier Transform) processing. The calibration
data are loaded into the BSA Flow software package providing the most accurate results
directly in velocity units (m/s or ft/s).

Key benefits•

Factory aligned and turn-key operation for fast setup•

Calibrated to 0.11% uncertainty•

1 and 2 velocity component configurations•Measurement distances from 300 mm to 500 mm•Robust real-time FFT signal processing•

On-line end-results thanks to real-time processing•

Extensive graphics and data exchange features•Real-time display of signals, validation and data rate•

Wi-Fi, LAN or USB connection to PC

The FlexLDA solution
The LDA method uses the Doppler effect which occurs when laser light isscattered from seed particles in a gas or liquid flow. Inside the FlowExplorer, alaser beam is split in two and then focused to a point to form a measurement
volume. The Doppler-shifted scattered light of each particle passing themeasurement volume is collected and then sent to the signal processor todetermine their velocity. The main benefits of LDA over other flow velocity
measurement methods include: the optical technique does not disturb theflow, the transfer function is linear and can be determined to high accuracy,
small measurement volumes are possible, high frequency response is possible
in well-seeded flows, and the absolute accuracy of the measurement results
are unmatched due to calibrated optics and signal processor performance.
The solution is based on three core components: optics, signal processor, andsoftware.
Configurations for one or two component measurements are available.

FlexLDA system including FlowExplorer
optics, BSA processor and BSA Flowsoftware.

1D and 2D FlexLDA configurations

OpticsCalibrated LDA solution
Since the optical transceiver is factory aligned and calibrated, the FlexLDA
system is the ideal solution for applications requiring documentation of themeasurement uncertainty.
The velocity calibration uncertainty is 0.11% (coverage factor 2). The velocity
resolution is better than 0.002% of the chosen velocity range.
The systems have a single optical head with one or two lasers, connected toa BSA processor with one or two channels.

Processor
Fast & powerful all-in-one processor

Air jet experiment with FlexLDA

The BSA F100 processor is a fast and powerful all-in-one processor. With
Ethernet, Wi-Fi and USB interfaces included, the processor can be connected
to a PC via a local area network or a wireless or cabled connection. In large
facilities or in situations where remote access is required, these features makeit easy to have the processor near the experiment while keeping the PC at agreater distance away for safety and/or convenience.
The processor covers a velocity range up to more than 68 m/s depending on
the optical configuration. Robust FFT (Fast Fourier Transform) processing isused.
System setup is very easy and user friendly: the setup is done directly in
velocity units, based on a center velocity and a velocity span value.
The processor software includes an on-line signal monitor which provides
the user with real-time information about signal quality, data rate, validation,
coincidence between channels, PM sensitivity, and anode current. This results
in a powerful tool for optimizing the user adjustable parameters during set-up
and monitoring of measurement results.
For more details on the signal processor, please refer to the data sheet on“Burst Spectrum Analyzer (BSA)” available at our website.
Page 2Plot of velocity profile in an air jet

Data Analysis
The most flexible and comprehensive software for LDA measurements

Calibration of a water flowmeter

BSA Flow with Advanced Graphics add-on, included in the FlexLDA solution.

The BSA Flow software is easy to use thanks to its workflow-based userinterface and includes extensive graphics and data exchange features.
The system setup, including the optical configuration as well as processor
settings, is controlled via the software. Tools are provided which enableuser-defined data analysis and display, dynamically updated during
measurements.
Data analysis can be customized with a built-in Calculation module,with Python or via a MatLab link for ultimate flexibility. Graphical output
includes vector plots, 2D line and scatter plots, and 3D plots. Both plots
and numerical results can be transferred to a measurement report in PDFor HTML format. Numerical output includes binary, ASCII, MS Excel, andTecPlot formats.
For further details on the software’s performance and capabilities, please
see the data sheet on “BSA Flow Software” available on our website.

Plot of velocity profile in a turbulent
pipe flow in water

FlexLDA configurations
The FlexLDA solution is being offered in the following 1D and 2D
configurations.
Item noItem name

Description

9061N0011 FlexLDA 1D																		FlowExplorer 1D 90mW (660nm)
BSA F100 1D 660nm
BSA Flow Software
Advanced Graphics Add-on
Laser Alignment Eyewear
Laser Protective Eyewear
Front Lens for FlowExplorer (300 mm or 500 mm)

9061N0021 FlexLDA 2D															FlowExplorer 2D 90/70mW (660/785nm)
BSA F100 2D 660/785nm
BSA Flow Software
Advanced Graphics Add-on
Laser Protective Eyewear
Front Lens for FlowExplorer (300 mm or 500 mm)

Calibration of a pitot tube and a
flywheel anemometer

Options
The FlexLDA system offers several options to meet the requirements of theapplication. The options include:
Optics mounts: adjustable supports for rotating a FlowExplorer head around an axis
Page 3perpendicular to its optical axis (panning) as well as for fine-adjustable pan, tilt andtranslation are available.
Processor upgrade: The BSA F100 processor can be upgrade to BSA F600 which
offers 120 MHz max. frequency, allowing for measurements of higher velocities.
Software add-ons: Spectrum/Correlation Add-on, Cyclic Phenomena Add-on, Scripting
and MATLAB link Add-on, LIF and Parametric Analysis Add-on. Please see separate data
sheet on our website.
Traverse: A software-controlled automatic traversing mechanism with 1D, 2D or 3D
capability for flow mapping can be added to the system. Several standard traverse
controllers are supported in the software. Please see separate data sheet on ourwebsite.
Seeding: For air flows, a range of liquid droplet and solid particle seeders are available.
For liquid flows, we offer a variety of seeding particles. Please see the separate datasheets on our website.

Technical specifications
OpticsFlowExplorer

Laser

Diode

Laser power

90/70 mW (1D/2D)

Laser wavelength

660/785 nm (1D/2D)

Focal length

300, 500 mm

Measurement volume dimensions

0.09 x 0.09 x 0.92 mm3 (300 mm focal length)0.15 x 0.15 x 2.55 mm3 (500 mm focal length)

Optics weight (excl. laser controller)

5 kgProcessor

BSA F100

Max. Velocity>40 m/s (300 mm focal length)>68 m/s (500 mm focal length)

Data rate>100,000 bursts/sec

Resolution>16 bits

SoftwareFeatures

BSA Flow

Workflow-based user interface
Real-time oscilloscope display of signals
On-line display of data validation, data rate, coincidence
rate, photomultiplier anode current
Real-time end results thanks to multi-threading and decimation of displayed dataSet up of BSA processor
Acquisition of data from BSA,
Control of traversing system
Statistics of results (mean, RMS, Skewness and Flatness)
Listing of results
Export of data

Advanced Graphics
Add-onX-Y plots, vector plots, 3D plots, profile plots

Solution Sheet SS_0736_v4. Subject to change without notice. Copyright © 2021.
Dantec Dynamics. All Rights Reserved. www.dantecdynamics.com