Integrated 3D LDA

Streamlined 3D LDA optics for wind tunnels and water channels

Simultaneous measurement of 3 velocity components using standard optical probes is a challenge. When the optics are exposed to the flow forces, keeping individual probes aligned is difficult, and the optics and mounting structure typically disturb the flow significantly.

The integrated streamlined probe mitigates these challenges. The integration of all transmitting and receiving optics in one probe ensures stable alignment and a simpler mounting structure. The streamlined probe design ensures minimum flow disturbance.

In combination with a traverse and a rigid fixture of the probe, the system can be moved while maintaining alignment and calibration. The entire system – traverse, calibration, automatic measurements and analysis – is operated from dedicated software – BSA Flow.

Components for submersible 3D LDA system

• 3 FiberFlow Laser Transmitters
  • generate 3 pairs of beams (with/without frequency shift) at 3 wavelengths
• Fiber-optical connection to the probe
• Streamlined strut
  • Holds the probe
  • Carries cables
  • Connects to a traverse
  • Allows rotation of the probe around its axis
• Streamlined probe containing
  • Optics for emitting 6 laser beams
  • Receiver optics
  • Alignment screws
• Burst Spectrum Analyzer
  • connection to receiving fiber from probe
  • color separation and filtering of received light
  • Photomultipliers
• BSA Flow Software
  • Controls hardware, data acquisition and storage, analysis and presentation of results
• PC
• Calibration tools
  • Pinhole on 3-axis manual traverse for measurement of beam directions
  • Spreadsheet for calculation of fringe spacings (calibration factors) for each wavelength and calculation of the co-ordinate transformation matrix

• Traverse mechanism (optional)