Flow confinement effect and heat transfer around square cylinder with downstream control cylinders
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Flow confinement effect and heat transfer around square cylinder with downstream control cylinders T. S. Nikhil1 · Amit Varakhedkar1 · Rajendran Senthil Kumar1 Received: 18 July 2020 / Accepted: 2 November 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract A two-dimensional numerical investigation on flow past a heated square cylinder at different confinements has been carried out in the presence of two control cylinders placed on the rear side of the cylinder near the wake to control the shedding phenomena. The confined flow has been simulated with a blockage ratio from 4 to 8 (i.e., ratio of the computational domain height to the diameter of the square). The effects of Reynolds number (Re) range 100 ≤ Re ≤ 150 on various flow and heat transfer characteristics are studied and analyzed in the form of streamline plots, variations of pressure and viscous drag coefficients, Strouhal number (St), total pressure drop and Local and average Nusselt number. Different varieties of flow pattern were observed under laminar conditions with different combinations of Re, Blockage ratio (BR), size of the control cylinder and placement of the control cylinder. The St for geometry with control cylinder of size d—30% decreases by 6.5% when shifted from L = 0.6 to L = 1.6 for least BR 4 and maximum Reynolds number 150. The pressure difference decreases by 10.2% for further control cylinder position from 0.6 to 1.6, size from 20 to 30% at BR 4 and Re 100. The control cylinder closer to the bluff body maintains the pressure difference in increasing BR. The convective heat transfer is higher for L = 1.6 for lower BR. An increase of 8.6% observed for Re 150 at d—30%. The increase in BR reduces the effect of the positioning of the control cylinder and its size becomes the decisive factor. Keywords Nusselt number · Square cylinder · Control cylinder · Strouhal number List of symbols BR Blockage ratio (H/D) Cd Total drag coefficient Cdp Pressure drag coefficient Cdv Viscous drag coefficient D Characteristic length (m) d Length of control cylinder/D (in %) f Vortex shedding frequency (s−1) Fdp Pressure drag force (N) Fdv Viscous drag force (N) H Height of confinement (m) h Convective heat transfer coefficient (Wm−2 K−1)) k Thermal conductivity of fluid (Wm−1 K−1) L Center distance for main and control cylinder (m) NuD Average Nusselt number p Dynamic pressure (Pa) Re Reynolds number * Rajendran Senthil Kumar [email protected] 1
Department of Mechanical Engineering, SRM Institute of Science and Technology, Kattankulathur 603 203, India
St Strouhal number T0 Cylinder surface temperature (K) U∞ Freestream velocity (ms−1) u Stream-wise velocity (ms−1) v Cross-stream velocity (ms−1) x Stream-wise dimension of coordinates (m) y Cross-stream dimension of coordinates (m Greek symbols ρ Density of fluid (kgm−3) µ Dynamic viscosity (Nsm−2) α Thermal diffusivity (m2s−1)
Introduction The bluff bodies like circular cylinders, rectangular prisms, etc. are the foremost common engineering structural config
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