TY - GEN

T1 - Resolvent analysis of turbulent friction drag reduction by manipulation of mean velocity profile

AU - Uekusa, Riko

AU - Kawagoe, Aika

AU - Nabae, Yusuke

AU - Fukagata, Koji

PY - 2019/1/1

Y1 - 2019/1/1

N2 - In the present study, we numerically manipulate the mean velocity profile of a turbulent channel flow and assess the friction drag reduction performance by using resolvent analysis. Building on the implication obtained from Kühnen et al. (Nat. Phys., Vol. 14, 2017, pp. 386-390) that modifying mean velocity profile flat leads to significant drag reduction, we first introduce two functions for turbulent mean velocity, which can express flattened profiles: one is derived based on the turbulent viscosity model proposed by Reynolds & Tiederman (J. Fluid Mech., Vol. 658, 2010, pp. 336-382), and the other is based on the mean velocity profile of laminar flow. These functions are used as the mean velocity profile for the resolvent analysis, and the flatness of the resulting profiles is characterized by two different measures. As a result, we confirm that, friction drag reduction is achieved if the turbulent mean velocity profile is’flattened’. However, we also find that the flatness of the mean velocity profile in the center of the channel alone is not enough to evaluate the drag reduction performance.

AB - In the present study, we numerically manipulate the mean velocity profile of a turbulent channel flow and assess the friction drag reduction performance by using resolvent analysis. Building on the implication obtained from Kühnen et al. (Nat. Phys., Vol. 14, 2017, pp. 386-390) that modifying mean velocity profile flat leads to significant drag reduction, we first introduce two functions for turbulent mean velocity, which can express flattened profiles: one is derived based on the turbulent viscosity model proposed by Reynolds & Tiederman (J. Fluid Mech., Vol. 658, 2010, pp. 336-382), and the other is based on the mean velocity profile of laminar flow. These functions are used as the mean velocity profile for the resolvent analysis, and the flatness of the resulting profiles is characterized by two different measures. As a result, we confirm that, friction drag reduction is achieved if the turbulent mean velocity profile is’flattened’. However, we also find that the flatness of the mean velocity profile in the center of the channel alone is not enough to evaluate the drag reduction performance.

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U2 - 10.1115/ajkfluids2019-5125

DO - 10.1115/ajkfluids2019-5125

M3 - Conference contribution

AN - SCOPUS:85076392049

T3 - ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019

BT - Fluid Mechanics

PB - American Society of Mechanical Engineers (ASME)

T2 - ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019

Y2 - 28 July 2019 through 1 August 2019

ER -