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Flow over an oscillating cylinder has been the subject of various studies as well as its heat transfer characteristics due to the lock-in phenomenon which occurs as a result of multiple frequencies being present in the system. The motivation was to investigate the effect of superhydrophobicity on heat transfer and wake dynamics of partially superhydrophobic oscillating cylinder. Applying the slip condition causes the drag and root-mean-square lift coefficients to reduce by 46 and 75% in comparison to the no-slip case, respectively. It also augments the average Nusselt number by 55% accompanied by a 21% increase of the natural shedding frequency compared to the no-slip cylinder. Considering the reduction of force coefficients, it is shown that the application of slip over a 135° segment of the surface is an optimum case, resulting in 47% and 85% decrease of the drag and root-mean-square lift coefficients, respectively. Application of slip over the surface of the cylinder also causes the average Nusselt number to become nearly 6 times greater than the no-slip oscillating cylinder at the lock-in condition. Further analysis based on thermal performance index (TPI) proves that a high value of TPI = 6 can be reached for the superhydrophobic cylinder. [ABSTRACT FROM AUTHOR]

Hydroacoustic analysis of three-dimensional, turbulent flow over superhydrophobic and oscillating cylinders has been performed at Re = 3900. A third-type Robin boundary condition has been utilized to apply superhydrophobicity over the surfaces including two different slip coefficients of 0.425 and 0.1. Regarding the acoustical analysis, the Ffowcs Williams–Hawkings acoustic analogy has been used to investigate the generation and propagation of sound. For the case of a stationary cylinder, superhydrophobicity leads to an 8 percent increase in the Strouhal number. Furthermore, the overall sound pressure level is reduced by an amount of around 6 decibels. It is indicated that at a constant amplitude, the mean drag coefficient and the root-mean-square lift coefficient experience a 40% and 750% increase, respectively. Also, the maximum and the overall sound pressure levels escalate as the frequency ratio increases. The maximum amount of elevation in terms of the generated sound is 25 decibels for the synchronized case. Further analysis of the sound directivity proves that both the stationary cylinder and the lock-in cases of the transversely oscillating cylinder demonstrate symmetrical patterns in the dipole form. However, the non-synchronized states of the oscillation exhibit asymmetrical trends and deviate from the dipole pattern. • The aim is to predict the effect of superhydrophobicity and boundary movement on SPL. • The force coefficients, the shedding frequency, the peak/overall SPLs are analyzed. • The shedding modes, behavior of the sound spectra in oscillating conditions are presented. • The maximum amount of elevation in terms of the generated sound is 25 dB. • The directivity of sound will be studied using polar diagrams. [ABSTRACT FROM AUTHOR]