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DGV System Specifications

Recording Principle

• optimized for time-averaging (integrating) velocity measurements
• applicable to stationary (steady) flows
• single receiver - three light sheet approach
• exposure times from a few milliseconds up to 1 minute per image pair
• phase-averaged measurements possible by laser modulation using Bragg cell

Measurement Characteristics

• measurement uncertainty better than 1 m/s RMS
• measurement reproducability better than 0.1 m/s RMS (based on spatial velocity average)
• field of view typically 10 - 50 cm (in principle >1m²)

DGV Receiver

• single objective system with internal beam-splitter and relay lens
• Detectors: thermoelectrically-cooled CCD sensors:
  1) LaVision LightStar
      dynamic range = 14 bits (16384 levels)
      spatial resolution: 384 × 292 pixels
      signal-to-noise better than 400:1
  2) PCO Sensicam Long-Exposure
      dynamic range = 12 bits (4096 levels)
      spatial resolution: 1280 × 1024 pixels
      signal-to-noise better than 150:1 (600:1 with 4x4 pixel binning)
      fiber optic data transmission (5 m to >1000 m)

Laser

• CW Argon-ion laser operating in single frequency mode at l = 514,5 nm, Pmax = 2 Watts.
• stabilization better than +/- 1 MHz using temperature controlled etalon and iodine absorption cell
• stabilization on hyperfine structure of iodine possible for calibration of absorption cells

Light sheet generators

• based on scanning beam approach
• essentially top-hat intensity profile
• scanning frequencies up to 400 Hz
• parallel light sheet height up to 140 mm
• fiber optic light delivery from laser head