SOLUTION SHEET

Integrated 3D LDA System

Flow velocity measurements with minimum disturbanceStreamlined 3D LDA optics for water channels
Laser Doppler Anemometry (LDA) is an optical technique ideal for non-intrusive point
measurement of velocity and turbulence in flows. It is based on the Doppler effect oflaser light scattered from seed particles that follow the flow.
Simultaneous measurement of 3 velocity components in a water flow is often acomplicated task using standard optical probes. Keeping individual probes alignedin a flow with strong flow forces is difficult and often results in mounting structures
disturbing the flow and misalignment due to the flow forces on the probes or thermaleffects.
With the integrated streamlined probe, these problems are minimized. The integrationof all transmitting and receiving optics in one probe ensures stable alignment and asimpler mounting structure. The streamlined probe design ensures minimum flow
disturbance.

Key benefits• Minimum flow disturbance due to streamlined submerged optics.
• High resolution of all three-velocity components due to large angle between measuredcomponents• Adjustable orientation of measurement plane• Simple to align and mechanically stable• High laser power for high data quality• Alignment and calibration tools included

Integrated solution with simple cabling and few adjustments
The Integrated 3D LDA System is based on four core components: Probe,transmitter/laser, signal processor, and software. Tools for alignment of thelaser beams to the receiver optics are included.
The probe is usually connected to a traverse mechanism above the water
via a streamlined strut. We can offer a traverse mechanism adapted to theexperimental rig, as well as a strut with length and stiffness adapted toyour requirements.

The integrated 3D LDA system in brief
Tools for alignment of the laser
beams and the receiver optics areincluded.

Overview of the system components

Integrated 3D probe
The streamlined submersible probe emits 6 laser beams, which interferein pairs. The beams all intersect in a common measurement volume. One
receiving optic detects light scattered from particles passing through themeasurement volume. Optical fibers guide the laser light to the probe andthe optical signal back to the detectors in the BSA Processor.
The geometry ensures high accuracy of all 3 velocity components. The offaxis receiver ensures high spatial resolution and the ability to measure close
to surfaces.
A calibration basin and calibration tools are included. The calibration factors(fringe spacings) of the three beam pairs, and the coordinate transformation
matrix for conversion from the measured to ortogonal velocity components
are defined in a single process.

Transmitter/laser
Fiber lasers offer high laser power in compact packages, without need
for water cooling or three-phase power. Equal laser power in the three
wavelengths used in 3D optics ensure similar signal quality and data rates
for all three measured velocity components.
The units are designed with focus on user safety and ease-of-use with aminimum of adjustments.
The laser light is blocked automatically by shutters when the optical fiberconnectors are detached.
A built-in attenuator reduces the laser power 99% to protect the user duringalignment.

BSA Processor
The new third generation Burst Spectrum Analyzer (BSA) from Dantec
Dynamics is the fastest and most powerful signal processor for LDA systems
ever. Using the latest developments in signal processing technology, we offer
a robust and accurate processor for LDA.
For further details on the BSA Processor, please consult separate data sheet
on our website.
Page 2The probe is attached to a streamlined strut (optional) connected to a
traverse (optional).

BSA Flow software
The BSA Flow Software is Windows-based, easy to use, and features themost complete and comprehensive interface for Laser Doppler Anemometry
measurement systems. The software is an integral part of our LDA andPDA systems using BSA F/P signal processors. The modular design ofthe software provides the user with many add-ons so that the system
functionality can be enhanced to meet your measurement needs now and in
the future.
For further details on BSA Flow software, please consult separate data sheet
on our website.

Options
Streamlined Strut
A streamlined strut for stable connection of the probe to a traverse
mechanism can be offered on request. The strut must be designed for themax. depth and max. flow velocity that the probe will be exposed to. Pleasecontact you Dantec Dynamics prepresentative for further details.
Traverse Mechanism
The measurement position is controlled by a traverse mechanism. We canoffer a traverse mechanism on request, or an existing traverse mechanism
may be used. In the latter case, we can offer adaptation of our software tothe protocol of the traverse mechanism so that measurement campaigns
with predefined measurement position grids can be done automatically.
Phase locked measurements
Phase locking measurements to eg. a rotating propeller or a wavemakercan be done by adding the Synchronization Option to the BSA processor
and the Cyclic Phenomena add-on to the BSA Flow software. For further
details on this, please consult separate data sheets about the BSA
Processor and about BSA Flow software on our website.
Phase sorted and phase averaged
velocity data from a 3 blade impeller.

Technical specifications

Dimensions of the LDA probe
Page 3

3D submersible probe
Probe length

1165 mm

Probe diameter

80 mm

Weight (excl. strut)

20 kg

Material

Stainless steel

Measurement distance from axis (in water)

600 mmProbe volume

Ø 0.3 mm x 2 mm

Manual probe rotation (around longitudinal axis)

270°

Optical fiber length

15 m

Laser/transmitter
Laser power

1W per wavelength

Laser wavelengths

520/532/546 nm

Laser safety classification

Class 4Safety shutter

Laser light automatically blocked when fiberconnector is removed

Attenuator

Open, attenuated (to 1%), closed

Software control

Laser on/off, laser power

Processor		

BSA F100

Velocity span

30 m/sMin. velocity-60 m/sMax. velocity

60 m/sData rate>100,000 bursts/sec

Resolution>16 bits

Software			

BSA Flow

Features

Online oscilloscope display of signals
Online display of data validation, data rate,coincidence rate
Photomultiplier anode current
Set up of BSA processor
Acquisition of data from BSA
Control of traversing system
Statistics of results (Mean, RMS, Skewness andFlatness)
Listing of results
Set up of analysis sequences
Export of data

Advanced Graphics Add-on

X-Y plots, vector plots, 3D plots, velocity profileplots

Solution Sheet 0709_v1 . Subject to change without notice. Copyright © 2021
Dantec Dynamics. All Rights Reserved. www.dantecdynamics.com