Abstract
In this study, numerical analysis of forced convective pulsating nanofluid flow over a backward-facing step with different nanoparticle shapes was performed by the finite volume method. The effects of the Strouhal number (between 0.1 and 2), solid nanoparticle volume fraction (between 0 and 0.04) and nanoparticle shapes (spherical, blade and cylindrical) on the heat transfer and fluid flow were examined with the aid of numerical simulation. It was observed that the average Nusselt number is a decreasing function of the Strouhal number for the considered range, and it enhances for higher solid particle fractions. Using nanofluids with spherical particles is advantageous in pulsating flow, whereas cylindrically-shaped particles are preferred in steady flow configurations. Average Nusselt number enhancements up to 30.24% and 27.95% are achieved with cylindrical- and spherical-shaped particles at the highest volume fraction.
Highlights
In a wide range of engineering applications, flow separation and subsequent reattachment play an important role such as in cooling of electronic devices, flow around buildings, solar collectors, combustion chambers and many other systems
For the nanofluid with the cylindrically-shaped particles, higher viscosity resulted in a lower Reynolds number, and the reattachment length was lower
The number of cycles to reach the steady oscillation state was higher for higher Strouhal numbers. This is due to the flow adaptation time becoming significant for higher frequencies, which were shown in the previous studies for pulsating flow over a backward-facing step [30,31]
Summary
In a wide range of engineering applications, flow separation and subsequent reattachment play an important role such as in cooling of electronic devices, flow around buildings, solar collectors, combustion chambers and many other systems. A vast amount of numerical and experimental research studies related to fluid flow and heat transfer over a backward-facing step can be found in various references. In the experimental study of [1], laminar flow over a backward-facing step in a two-dimensional configuration was studied by measuring the reattachment length and velocity distribution. Their results indicated that different flow regimes can be identified by the variation of the separation length. In the experimental work of [2], flow over a forward-facing step was analyzed, and the mechanisms that played an important role in the reattachment length were highlighted
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