Effects of oscillation frequency, phase difference, and arrangement of two triangular cylinders on the hydrothermal performance of a channel

This study aims to numerically explore the effects of two cylinders with triangular cross sections, undergoing transverse oscillation on the heat and fluid flow within a channel. The governing equations along with the pertinent initial and boundary conditions are solved using the finite element method. The results are validated against the available data in the literature, demonstrating admissible agreement. Different oscillation frequencies, phase differences, and arrangement of the cylinders are considered. The results are presented in terms of temperature, pressure, and vorticity contours, alongside the Nusselt (Nu) number and thermal performance index (TPI). The Reynolds number based on the triangle's side length (Reb=200) is deliberately chosen to induce the vortex shedding phenomenon in the wake of the cylinders. For a single oscillatory cylinder, an optimal oscillation frequency fr=0.5 was found resulting in a remarkable increase in 22.3% and 33.1% in the Nu number and TPI, respectively, when compared to the fixed single cylinder. Using the obtained optimal oscillation frequency fr=0.5, the side-by-side arrangement of two cylinders gives rise to a higher TPI than the tandem one. The maximum TPI in side-by-side arrangement corresponds to the oscillation phase of φ=π/6, which is about 1.69. In tandem arrangement, it corresponds to φ=π/3, which is approximately 1.3. Furthermore, the oscillation phase φ=π exhibits the lowest TPI for both arrangements.