Experimental investigation of the Eckert-Weise effect (aerodynamic cooling) of pair side-by-side circular cylinders in a compressible cross-flow

The rear surface of a thermally insulated circular cylinder placed in a subsonic high-velocity cross-flow is significantly cooled, this phenomenon is known as aerodynamic cooling or the Eckert-Weise effect. This effect is associated with the redistribution of the stagnation temperature (energy separation) in the unsteady vortex wake. Experiments show that the effect is maximal at Mach numbers of the free-stream flow of 0.5-0.7, resulting in negative values of the temperature recovery factor (the temperature of the cylinder rear surface becomes lower than the static temperature of the free-stream flow). In this case, the cooling of the rear surface can reach tens of degrees. This effect can be utilized as the basis for a novel energy separation device, as it enables heat transfer between flows with the same stagnation temperatures. As shown in a numerical study (Aleksyuk, 2021), the effect is highly sensitive to the flow interference behind side-by-side cylinders, this is especially important for its practical application. In this study, the aerodynamic cooling of a pair identical circular cylinders in side-by-side arrangement, is experimentally investigated within the Mach and Reynolds number ranges of M = 0.34-0.58 and ReD = 1.6 center dot 105-3.1 center dot 105. The cylinder spacing considered in this study (P/D = 1.1; 1.5; 2.0; 3.0; and 4.0, where P is the center-to-center cylinder spacing and D is the diameter) covered the key regimes of vortex interference, that is, single, bistable, and coupled vortex streets. Also, investigations were conducted for a single circular cylinder with the same diameter within the Mach and Reynolds number ranges of M = 0.34-0.68 and ReD = 1.6 center dot 105-3.4 center dot 105. The channel blockage ratio was found to be 8% for a single cylinder and 16% for a pair of cylinders. Consequently, this study focuses on confined flow or flow past a confined cylinder with a uniform profile of oncoming flow velocity. It is shown that the Eckert-Weise effect for the pair of cylinders can either increase or decrease depending on the interference regimes and is sensitive to the blockage ratio value.