Effect of the spacing on forced convection heat transfer for flow around a row of heated square cylinders

Abstract

This work reports impact of spacing on forced convection heat transmission for flow around the row of heated square cylinders for s/d = 1.0 to 8.0 at Re = 80, Ri = 0, and Pr = 0.71. The thermal lattice Boltzmann method (TLBM) is used to perform numerical analysis. The focus is to explore heat transfer physics and to comprehend influence of spacing on transitions in heat transfer through signals of the Nusselt number. Synchronous, quasi-periodic, and chaotic heat transfer regimes have been documented here as a function of the spacing between cylinders. The contribution of modulation frequency to the cylinder Nusselt number signals and their power spectra are used to assess these heat transfer regimes. The distinguishing feature of a synchronous heat transfer regime (s/d = 6.0 to 8.0) is development of independent heat wakes behind cylinders with a single frequency in Nusselt number signal. In quasi-periodic heat transfer regimes, thermal blobs coalesce directly downstream of the cylinder at a short distance. In a chaotic heat transfer regime, due to small spacing between cylinders, thermal blobs merge immediately behind cylinders leading to chaotic heat transfer between the cylinders just like a jet. It is noticed that average cylinder Nusselt number recognized by all cylinders grows as spacing reduces. It is important to note that at 6.0 ≤ s/d ≤ 8.0 the transfer of heat is dominated by the presence of a single frequency in the Nusselt number signal while at 3.0 ≤ s/d ≤ 5.0 another frequency is called secondary frequency appears in the signal which dominates at low s/d = 1.0. The most important discovery from current numerical research is that heat transfer method is unsteady and periodic in nature. The unsteadiness in the heat transport process can be explained through transient variation of Nusselt number.