H41 – Laser PIV System

 

H41 – Laser PIV System

The H41 consists of two main assemblies: the nanoLase light sheetprojector and the rtCam camera, with built-in timing synchroniser.

Description

The H41 consists of two main assemblies: the nanoLase light sheet projector and the rtCam camera, with built-in timing synchroniser. The rtCam interfaces to the rtControl software package, which runs on a standard PC under Windows XP (not supplied by Armfield).

The nanoLase consists of a low-power solid-state laser, together with optics to form the beam into a ~3mm thick, 45° wide light sheet. The laser is modulated to produce pairs of pulses, with an adjustable delay (known as Δt) of between 100μs and 5s. Both the pulse separation and pulse width can be set directly from the rtControl software.

The nanoLase and rtCam are arranged orthogonally around the flow to be measured, with the laser being used to illuminate flow-following ‘seeding’ particles that have been mixed into the water. The system is supplied with 100g of 100μm polyamide particles, which are suitable for the majority of water-based flows. These particles scatter light toward the rtCam, which acquires a pair of images every time the laser emits a pulse pair.

Each pair of particle images are immediately sent to the control PC using a standard FireWire (IEEE 1394) connection. The rtControl software then subdivides the images into ‘tiles’, which are cross-correlated in order to measure the displacement of the seeding particles in that area.

Because the delay between the images is known, a velocity map can be calculated for the whole of the camera’s field of view. While most PIV systems take several minutes to get to this point, rtCam and rtControl can repeat the entire process up to 16 times a second.

In addition to the real-time velocity vector maps, rtControl can calculate and display derived statistical data (such as vorticity or time-averaged velocity) with options to superimpose vectors, scalars, and video on top of each other. Similarly, there are options to record data as either raw images (in BMP format), or as processed vectors or scalars (in AVI movie, CSV spreadsheet, or Matlab® archive format). Previously recorded data sets can be loaded into rtControl for subsequent display and analysis.

Both the rtCam and the nanoLase are fitted with standard mountings suitable for a selection of different mounting mechanisms. The system is supplied with two small desktop tripods; larger tripods and various snake-arm mounts are available as accessories. Also available are purpose-designed mounts designed for use with Armfield flow channels.

The system is provided complete with all cables and packed into an aluminium flight case for safe storage and easy transport.

Technical Specifications

Lasers:

  • Solid-state air-cooled 200mW, 660nm laser diode (Class 3b)
  • Standard optics produce a ca 3mm thick, 45° light sheet (ca 200mm wide at 250mm)
  • Interchangeable 20° light sheet optic available (H41-3)
  • Pulse separation (Δt) of between 100μs and 5s (in steps of 10μs)
  • Pulse width of between 10μs and 32ms (in steps of 10μs)

Camera:

  • Super-sensitive VGA CMOS sensor:
    – 640×480, 6.0μm pixels (1/3” format);
    – ~50% quantum efficiency at 660nm;
    – 75-110dB dynamic range;
    – 4.8 V/lux-sec sensitivity
  • Trigger input enables image pair acquisition to be synchronised with external events
  • Accepts standard CS or C-mount lenses (12.5mm f/1.4 lens supplied)
  • Camera exposure can be linked to the laser’s pulsing, thereby enabling operation in a lit room

Features & Benefits

  • The H41 uses particle image velocimetry (PIV) to measure, non-intrusively, fluid velocities at multiple points in a flow,
    at a rate of up to 16Hz.
  • The compact and portable hardware (which uses a safe, non-pulsed Class 3b laser) and extremely easy-to-use software
    with real-time display, make this an ideal tool for undergraduate teaching and demonstration.
  • With its sophisticated multipass processing, the H41 matches the performance of higher power PIV systems costing several times more.
  • It is therefore also an ideal, cost-effective tool for experimental fluid dynamics research.
  • The intuitive software provides a wide range of processing, display and recording functions for both velocity and derived statistical data, using a standard PC.

Downloads

  • Easily set up and calibrated
  • High dynamic accuracy
  • Linear calibration over a large range
  • Outputs for high speed recorders and data loggers
  • Can be operated at different energisation frequencies to avoid mutual interaction between two or more closely spaced probes
  • Supplied as a complete working system, with the option of 1, 2, or 3 channels of measurement

Options

  • A range of further options are available to suit specific user applications, including:
  • Waterproof enclosure for the rtCam, to enable complete submersion in water, eg for use with a large towing tank
  • Flashlamps can be supplied in place of the nanoLase, for surface velocimetry measurements
  • Higher power versions of the nanoLase are available for measuring larger areas or faster flows
  • The rtCam can be supplied with macro or telephoto lenses
  • A light-sheet thickness adjuster is available for micro-PIV measurements

Please contact Armfield for further details of these options.

Optional accessories

  • H41-3 20° Light sheet Optics for nanoLase
    The standard 45° light sheet optics can be replaced with item H41-3 in order to produce a narrower 22° fan angle. This can be useful in cases where the nanoLase needs to be placed farther away from the measurement area.
  • H41-5 1.5m tripod for rtCam
  • H41-6 S nake-arm with magnetic base for nanoLase
  • H41-7 Snake-arm with G-Clamp base for nanoLase
  • C4-12 Mounting system for Armfield
  • C4-MkII flume (requires H41-2 submersible nanoLase and H41-3 optics option)
  • S16-12 Mounting system for Armfield S16 Hydraulic Flow Demonstrator (requires H41-2 submersible nanoLase and H41-3 optics option)

  • Particle Image Velocimetry (PIV) system, comprising a laser light sheet projector, a camera system and processing software
  • 200mW (Class 3b) 660nm laser, with variable pulse width and pulse spacing
  • 45° light sheet optics as standard with optional optics to produce a 20° sheet
  • Real-time 2D display of flow velocity vectors updated at up to 16Hz
  • Data can be recorded in video (avi), bitmap (bmp), text (csv) and Matlab (mat) formats
  • Option of submersible light sheet projector

Ordering Details

  • H41-1 Laser PIV System for Flow Measurement and Visualisation
  • H41-2 Laser PIV System for Flow Measurement and Visualisation with submersible nanoLase light sheet projector

Electrical supply:

  • H41-1-A, H41-2-A: 220-240V/1ph/50Hz

Voltage Variants:

  • H41-1, H41-2: 90-264V, 47-63Hz

A PC running Windows 98 or above, with a FireWire port. Laptop FireWire ports require a suitable four to six-pin cable.

It is recommended the PC has at least 2GB RAM with a processing speed of at least 2GHz. The display resolution should be at least 1024×768, true colour.

The data refresh rate achievable is dependent on the specification of this computer. For example, to achieve 16Hz data refresh and recording rate, a 2.66GHz Intel dual core processor or better is required, and the hard drive must support sustained writes at 9.5 Mb/s.

Consumables

  • H41-4 Seeding particles suitable for water flows (200g)

PACKED AND CRATED SHIPPING SPECIFICATIONS

H41-1 / H41-2

  • Volume: 0.01m³
  • Gross Weight: 5Kg

nanoLase:

  • Length 0.05mm
  • Width 0.05mm
  • Height 0.085mm

Submersible nanoLase:

  • Length 0.05mm
  • Width 0.05mm
  • Height 0.095mm

rtCam:

  • Length 0.05mm
  • Width 0.05mm
  • Height 0.09mm

  • H41-1
  • H41-2
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