Particle Image Displacement Velocimetry Research Articles

INVESTIGATION OF THE FLOWFIELD OF A SCRAMJET COMBUSTOR WITH PARALLEL H2-INJECTION THROUGH A STRUT BY PARTICLE IMAGE DISPLACEMENT VELOCIMETRY

The flow field in a supersonic combustor with H2-injection through a strut is investigated by particle image displacement velocimetry. The flowfield is characterized by shock trains which originate at the leading edge of the strut, an expansion originating at the interaction of the fuel and the air flows. PIV recordings are taken without and with ignition of the fuel/oxidizer mixture. Velocities up to 900 m/s were measured. The measured velocity fields are compared with the flow structures in the shadow photographs.

Experimental examinations of the 2D-thermal-hydraulic code FRECON for single phase natural convection flows in complex structures

An experimental program for the verification of the 2D-thermal-hydraulic code FRECON is being carried out. This code serves for the simulation of single phase natural convective flows in complex structures. As a special application it has already been used in the analyses of severe LWR accidents. For this, the code has been coupled with the KESS code system describing the core behaviour during such an accident. While strong improvements have been reached meanwhile concerning the FRECON code itself as well as its application to the reactor problem, experimental verification has not yet been performed. Such a verification is strongly required because of the basic assumption of a quasi-continuum approach for the solid structures in FRECON and the problem of describing local characteristic properties of the structures within this approach. In contrast to integral experiments aiming to simulate the real reactor situation as closely as possible, the present experiments aim to check specific structures and aspects in detail. Thus, in a first step, natural convective flows in a rod bundle with imposed solid temperature profiles are being analysed. In addition to temperature measurements in the solid as well as in the gas, the flow patterns are visualized by means of light-weight glass spheres as tracers, illuminated with a laser-light-sheet. After recording the tracers by a video system the analysis of the flow patterns is made either directly at the TV-monitor or by using the digital image processing technique PIDV (Particle Image Displacement Velocimetry). First comparisons between code calculations and experimental results support the code development in general, but need further refinement.

Measurement of two-dimensional velocity fields in porous media by particle image displacement velocimetry

Local measurements of the phase function and of two components of the velocity can be performed in transparent porous media by means of particle image displacement velocimetry (P.I.D.V.). Some preliminary results are presented and discussed.

Holographic instrumentation for monitoring crystal growth in space

Refinements of holographic instruments for the First International Microgravity Laboratory Spaceflight, scheduled for February 1992, are described. The refinements include addition of holographic optical elements (HOEs) to incorporate tomographic analysis of the solution concentration and particle image displacement velocimetry to measure convection. A variety of advanced diagnostic instruments were designed for future spaceflights and possibly in the space station. These new instruments employ fiber optics, diode lasers, and HOEs to enhance miniaturization and ruggedness and to reduce power requirements. The instruments can measure concentration, temperature, convection, and crystal growth rate. Instruments currently in use as well as the conceptual designs and applications of future laser- and holography-based instrumentation are described.

Experimental investigation of the flow in the vaneless diffuser of a centrifugal pump by particle image displacement velocimetry

This work presents the application of particle image displacement velocimetry to the measurement of fluid velocities in a centrifugal pump diffuser. Measurements are taken at different operating points and allow to define the variation of radial and tangential velocity components along a pitch. They are further processed to determine the relative velocity and vorticity fields. Results are also compared with laser Doppler measurements taken in the same facility.

Particle image displacement velocimetry measurements of a three-dimensional jet

A whole field experimental technique, commonly referred to as particle image displacement velocimetry (PIDV), is used for the measurement of the instantaneous two-dimensional velocity fields in the transition region of a three-dimensional jet issuing from a rectangular nozzle with aspect ratio 4. The experiments were performed using an air jet at a Reynolds number based on the hydraulic diameter of 3600. The rollup of the laminar shear layer into vortices and their subsequent interactions are examined.

Improving the accuracy and resolution of particle image or laser speckle velocimetry

Particle Image Displacement Velocimetry (PIDV) or Laser Speckle Velocimetry (LSV) is a non-intrusive 2-D method of obtaining instantaneous fluid velocities over an extended region. This method involves lighting a particle seeded flow with a sheet of light (usually from a laser) and photographing the particles at two instants of time on the same film. This film is then analyzed to determine the displacement of the particle over the known time interval. Applications of PIDV and LSV have been diverse, including flow past cylinders and airfoils by Lourenco et al. (1986) and Smith et al. (1986), transient Benard convection by Simpkins and Dudderar (1978), vortex pairing in jets by Meynart (1983) and internal gravity waves by Gartner et al. (1986). These studies however, have all been two dimensional. The velocities along the lighted plane were measured, from which the two dimensional vorticity fields and streamlines were calculated using finite differencing (Lourenco et al. 1986, and Smith et al. 1986).

Noninvasive experimental technique for the measurement of unsteady velocity fields

The novel technique of particle image displacement velocimetry allows visualization of two-dimensional flows as well as the quantification of the instantaneous velocity and vorticity fields. The method's principles of operation are then presented; the method is shown to be suited to the gathering of both temporal and spatial data, as is required in the case of complex flow fields. 6 references.