Numerical study of flow regimes and force characteristics for cruciform cylinder in oscillatory flow

Abstract

Oscillatory flow past cruciform cylinder is numerically investigated using the Large-eddy simulation (LES) technique. The flow regimes and force characteristics of the cruciform cylinder are analyzed in detail for β (frequency parameter) numbers ranging from 200 to 500 and KC (Keulegan–Carpenter) number equals 10. Three vortex shedding modes are observed at different β values, which affect the torques exerted on the cruciform cylinder. At sections far from the node, two vortices shed within each cycle. The transverse force curve exhibits a regular pattern and a significant dominant frequency is observed in the transverse force spectra. However, as the node is approached, the vortex shedding becomes increasingly complex, leading to significant changes in the amplitudes and shapes of the transverse forces. Additionally, the sectional force coefficients agree well with those on the isolated cylinder at sections far from the node, whereas they exhibit significant increases at the sections near the node. Finally, the force coefficients of the cruciform cylinder are compared with those of the isolated cylinder for 2 < KC < 30 at β = 500. The results indicate that the cruciform cylinder experiences an increase in force coefficients, attributed to the influence of the node in cruciform cylinder.