TY - JOUR
T1 - Composite active drag control in turbulent channel flows
AU - Yao, Jie
AU - Chen, Xi
AU - Hussain, Fazle
N1 - Publisher Copyright:
© 2021 American Physical Society.
PY - 2021/5
Y1 - 2021/5
N2 - A composite drag control (CDC) combining the opposition (OC) and spanwise opposed wall-jet forcing (SOJF) methods is studied in a turbulent channel flow via direct numerical simulation of the incompressible Navier-Stokes equations. A maximum drag reduction of about 33% is obtained for CDC - much higher than that produced by either individual method (namely, 19% for SOJF and 23% for OC). Due to the small power input required for both OC and SOJF methods, a significant net power saving (about 32%) is achieved via CDC. Flow analysis shows that CDC can take advantage of both OC and SOJF methods to better suppress drag producing near-wall turbulent structures - vortices and streaks. In particular, due to the presence of the large-scale coherent swirls generated by SOJF, it is more effective than OC in suppressing the random turbulence. Moreover, due to the OC's role in suppressing random small-scale turbulence, CDC requires weaker large-scale coherent swirls than those using SOJF only - hence decreasing the drag contribution associated with large-scale swirls. In summary, our results suggest prospects of employing composite control strategy for effective skin friction drag reduction, particularly at very high Reynolds numbers.
AB - A composite drag control (CDC) combining the opposition (OC) and spanwise opposed wall-jet forcing (SOJF) methods is studied in a turbulent channel flow via direct numerical simulation of the incompressible Navier-Stokes equations. A maximum drag reduction of about 33% is obtained for CDC - much higher than that produced by either individual method (namely, 19% for SOJF and 23% for OC). Due to the small power input required for both OC and SOJF methods, a significant net power saving (about 32%) is achieved via CDC. Flow analysis shows that CDC can take advantage of both OC and SOJF methods to better suppress drag producing near-wall turbulent structures - vortices and streaks. In particular, due to the presence of the large-scale coherent swirls generated by SOJF, it is more effective than OC in suppressing the random turbulence. Moreover, due to the OC's role in suppressing random small-scale turbulence, CDC requires weaker large-scale coherent swirls than those using SOJF only - hence decreasing the drag contribution associated with large-scale swirls. In summary, our results suggest prospects of employing composite control strategy for effective skin friction drag reduction, particularly at very high Reynolds numbers.
UR - http://www.scopus.com/inward/record.url?scp=85106358796&partnerID=8YFLogxK
U2 - 10.1103/PhysRevFluids.6.054605
DO - 10.1103/PhysRevFluids.6.054605
M3 - Article
AN - SCOPUS:85106358796
SN - 2469-990X
VL - 6
JO - Physical Review Fluids
JF - Physical Review Fluids
IS - 5
M1 - 054605
ER -