TY - GEN

T1 - Drag reduction in spatially developing turbulent boundary layers by blowing at constant mass-flux

AU - Kametani, Yukinori

AU - Orlii, Ramis

AU - Fukagata, Koji

AU - Schlatter, Philipp

N1 - Funding Information:
This project is financially supported by the Japan Society for the Promotion of Science (JSPS). Computer time is provided by SNIC (Swedish National Infrastructure for Computing).

PY - 2015

Y1 - 2015

N2 - A series of large-eddy simulations of spatially developing turbulent boundary layers with uniform blowing at moderate Reynolds numbers (based on free-stream velocity, U∞ and momentum thickness, θ) up to Reθ ∼ 2500 were performed with the special focus on the effect of intermittent (separated in streamwise direction) blowing sections. The number of blowing sections, N, investigated is set to be 3, 6, 20, 30 and compared to N = 1, which constitutes the reference case, while the total wall-mass flux is constrained to be the same for all considered cases, corresponding to a blowing amplitude of 0.1% of U∞ for the reference case. Results indicate that the reference case provides a net-energy saving rate of around 18%, which initially decreases at most 2 percentage points for N = 3 but recovers with increasing N. The initial reduction of the drag reduction is due to the shorter streamwise length of intermittent blowing sections. The physical decomposition of the skin friction drag through the FIK identity (Fukagata et at, 2002), shows that the distribution of all components over each blowing section has similar trends, resulting in similar averaged values over the whole control region.

AB - A series of large-eddy simulations of spatially developing turbulent boundary layers with uniform blowing at moderate Reynolds numbers (based on free-stream velocity, U∞ and momentum thickness, θ) up to Reθ ∼ 2500 were performed with the special focus on the effect of intermittent (separated in streamwise direction) blowing sections. The number of blowing sections, N, investigated is set to be 3, 6, 20, 30 and compared to N = 1, which constitutes the reference case, while the total wall-mass flux is constrained to be the same for all considered cases, corresponding to a blowing amplitude of 0.1% of U∞ for the reference case. Results indicate that the reference case provides a net-energy saving rate of around 18%, which initially decreases at most 2 percentage points for N = 3 but recovers with increasing N. The initial reduction of the drag reduction is due to the shorter streamwise length of intermittent blowing sections. The physical decomposition of the skin friction drag through the FIK identity (Fukagata et at, 2002), shows that the distribution of all components over each blowing section has similar trends, resulting in similar averaged values over the whole control region.

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M3 - Conference contribution

AN - SCOPUS:85034441023

T3 - 9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015

BT - 9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015

PB - TSFP-9

T2 - 9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015

Y2 - 30 June 2015 through 3 July 2015

ER -