An introduction to heat transfer

The development of the method of particle image velocimetry (PIV) is traced by describing some of the milestones that have enabled new and/or better measurements to be made. The current status of PIV is summarized, and some goals for future advances are addressed.

Twenty years of particle image velocimetry

The size specifications for suitable tracer particles for particle image velocimetry (PIV), particularly with respect to their flow tracking capability, are discussed and quantified for several examples. A review of a wide variety of tracer materials used in recent PIV experiments in liquids and gases indicates that appropriately sized particles have normally been used. With emphasis on gas flows, methods of generating seeding particles and for introducing the particles into the flow are described and their advantages are discussed.

https://iopscience.iop.org/article/10.1088/0957-0233/8/12/005/pdf

Tracer particles and seeding for particle image velocimetry

To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows

Very large-scale motions in the form of long regions of streamwise velocity fluctuation are observed in the outer layer of fully developed turbulent pipe flow over a range of Reynolds numbers. The premultiplied, one-dimensional spectrum of the streamwise velocity measured by hot-film anemometry has a bimodal distribution whose components are associated with large-scale motion and a range of smaller scales corresponding to the main turbulent motion. The characteristic wavelength of the large-scale mode increases through the logarithmic layer, and reaches a maximum value that is approximately 12–14 times the pipe radius, one order of magnitude longer than the largest reported integral length scale, and more than four to five times longer than the length of a turbulent bulge. The wavelength decreases to approximately two pipe radii at the pipe centerline. It is conjectured that the very large-scale motions result from the coherent alignment of large-scale motions in the form of turbulent bulges or packets of...

Very large-scale motion in the outer layer

Space and energy-based turbulent scale-resolving simulations of flow in a 5 × 5 nuclear reactor core fuel assembly with a spacer grid

Experimental study of a simplified 3 × 3 rod bundle using DPTV

An accurate wall temperature measurement using infrared thermometry with enhanced two-phase flow visualization in a convective boiling system

Pressure Measurements in a Wire-Wrapped 61-Pin Hexagonal Fuel Bundle

Experimental study on bubble dynamics and wall heat transfer arising from a single nucleation site at subcooled flow boiling conditions – Part 1: Experimental methods and data quality verification

Yassin A. Hassan

Papers

Space and energy-based turbulent scale-resolving simulations of flow in a 5 × 5 nuclear reactor core fuel assembly with a spacer grid

Experimental study of a simplified 3 × 3 rod bundle using DPTV

An accurate wall temperature measurement using infrared thermometry with enhanced two-phase flow visualization in a convective boiling system

Pressure Measurements in a Wire-Wrapped 61-Pin Hexagonal Fuel Bundle

Experimental study on bubble dynamics and wall heat transfer arising from a single nucleation site at subcooled flow boiling conditions – Part 1: Experimental methods and data quality verification