Control of Flow Separation in a Turbulent Boundary Layer Using Time-Periodic Forcing

被引:13
作者
Cho, Minjeong [1 ]
Choi, Sangho [1 ]
Choi, Haecheon [2 ]
机构
[1] Seoul Natl Univ, Dept Mech & Aerosp Engn, 1 Gwanak Ro, Seoul 08826, South Korea
[2] Seoul Natl Univ, Dept Mech & Aerosp Engn, Inst Adv Machines & Design, 1 Gwanak Ro, Seoul 08826, South Korea
来源
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME | 2016年 / 138卷 / 10期
基金
新加坡国家研究基金会;
关键词
BACKWARD-FACING STEP; SYNTHETIC-JET; NUMERICAL-SIMULATION; ACTUATION FREQUENCY; AIRFOIL; EXCITATION; DYNAMICS; VORTEX; DELAY;
D O I
10.1115/1.4033977
中图分类号
TH [机械、仪表工业];
学科分类号
0802 ;
摘要
A time-periodic blowing/suction is provided to control turbulent separation in a boundary layer using direct numerical simulation. The blowing/suction is given just before the separation point, and its nondimensional forcing frequency ranges from F* = fL(b)/U-infinity = 0.28-8.75, where f is the forcing frequency, L-b is the streamwise length of uncontrolled separation bubble, and U1 is the freestream velocity. The size of separation bubble is minimum at F* = 0.5. At low forcing frequencies of F* <= 0.5, vortices generated by the forcing travel downstream at convection velocity of 0.32-0.35 U1, bring high momentum toward the wall, and reduce the size of separation bubble. However, at high forcing frequencies of F* >= 1.56, flow separation disappears and appears in time during the forcing period. This phenomenon occurs due to high wall-pressure gradients alternating favorably and adversely in time. A potential flow theory indicates that this rapid change of the wall pressure in time occurs through an inviscid mechanism. Finally, it is shown that this high-frequency forcing requires a large control input power due to high pressure work.
引用
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页数:10
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