Drag reduction study of naturally occurring oscillating axial flow induced by helical corrugated surface in Taylor–Couette flow

This study investigates drag reduction capability of naturally occurring-oscillating axial secondary flow (ASF) induced by helical-corrugated surface in Taylor–Couette (TCFHelical) for three values pitch to wavelength ratios (P* = 1, 2, and 3) amplitude ratio(A*) 0.25. As reported Razzak et al. [“Numerical Taylor Couette with longitudinal corrugated surface,” Phys. Fluids 32(5), 053606 (2020)], emergence ASF longitudinal-corrugated TCF (TCFLongitudinal) increasing trend on its magnitude Reynolds number (Re) results the occurrence reduction. has motivated us possibility enhancing maintaining a consistently Re stationary outer cylinder TCF. From structures, steady non-zero mean is observed at 60, which suppresses strength azimuthal vorticities > 85, contributed increased 100, 90, 85 P* 3, respectively, formation periodic oscillating further, contributes maximum 13%. For 165, 145, 140 non-periodic observed, remains nearly unchanged or decreases slightly Re, suppression effect vortices be weaker. decrease Oscillating TCFHelical found occur earlier it stronger than that TCFLongitudinal, higher TCFHelical.