Prediction and comparison of aerodynamic performance and flow control for smooth and wavy tube banks in crossflow at subcritical Reynolds numbers using a 3D RANS approach

This paper investigates the effects of introducing wavy cylinders of appropriate wavelength into tube bundles for the passive control of flow-induced vibration. The Reynolds-averaged Navier-Stokes approach RANS was used to study the turbulent flow characteristics within staggered tube bundles having transverse and longitudinal pitch-to-diameter ratios of 3.8 and 2.1, respectively. Two wavy models are tested with different wavelength-to-mean diameter ratios, namely: Model-A with lambda/Dm=2 and Model-B with lambda/Dm=1, and their performances are compared with those of a smooth circular tube bundle Model-C (lambda/D=infinity), in a range of subcritical Reynolds numbers 0.5x104 <= Re <= 4.1x104. Mean velocity and pressure fields as well as aerodynamic coefficients are presented and compared. According to the obtained results, the wavy tube bundle with lambda/Dm=2 exhibits the best performance, with slightly smaller CD values than the smooth tube bundle. However, results show that the wavy model with lambda/Dm=1 is clearly the worst with an increase of CD up to 40%. Numerical outcomes also reveal that the interaction of neighboring rows and columns affects the fluctuation of CD values relative to each tube position. Moreover, CD evolutions depend significantly on the variation of Re as well, where drag reduction is more substantial by increasing Re. Thus, wavy-shaped tubes with optimum parameters could be more suitable for flow control by enhancing the secondary flow, turbulence and fluid mixing.