Flow structure evolution for laminar vortex rings impinging onto a fixed solid wall
Flow structure evolution for laminar vortex rings impinging onto a fixed solid wall
复制标题
层流涡环撞击固定固体壁的流动结构演化
DOI：
10.1016/j.expthermflusci.2016.02.010
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发表时间：
2016-07
影响因子：
3.2
通讯作者：
Wang Jin Jun
中科院分区：
文献类型：
--
作者：
Xu Yang;Wang Jin Jun
利用激光诱导荧光(LIF)和粒子图像测速(PIV)技术研究了合成射流驱动的层流涡环撞击固体壁面的过程。采用四种不同冲程长度的情况(19 mm、⩽L0⩽和50 mm)，在雷诺数(Rev_0、≈、151)和孔壁间距(H=0.40 mm)不变的情况下，产生层流涡环。研究发现，孔板与壁面距离(L0/H)归一化的无量纲行程长度对冲击合成射流近壁流动结构的演变有重要影响。具体地说，由于冲程长度较小(L0/H=0.475和0.775)，撞击涡环只能在壁面附近诱导较弱的二次涡度，不能卷起形成相干结构。LIF可视化和有限时间李雅普诺夫指数(FTLE)表明，在这两种情况下，近壁区都产生了一个大尺度的螺旋涡环，这是首次发现的。然而，随着冲程长度的增加(L0/H=0.95和1.25)，强二次涡度卷曲并与撞击涡环配对形成涡偶极子。从而防止了撞击涡环与壁面附近涡团的融合，导致近壁涡强迅速降低。对径向壁面射流的分析表明，在较小冲程下诱导的大尺度螺旋涡环可以减缓径向质量流量和动量通量的衰减率，这可能有利于冲击合成射流时壁面的传质和换热。
Laser Induced Fluorescence (LIF) and Particle Image Velocimetry (PIV) techniques are used to investigate the synthetic jet actuated laminar vortex rings impinging onto a solid wall. Four cases with different stroke lengths (19 mm ⩽L0⩽ 50 mm) are adopted to generate laminar vortex rings with Reynolds number (ReV0≈ 151) and orifice-to-wall distance (H= 40 mm) unchanged. It is found that the dimensionless stroke length normalized by the orifice-to-wall distance (L0/H) has a significant influence on the evolution of near wall flow structure of the impinging synthetic jet. Specifically, as the stroke length is relatively small (L0/H= 0.475 and 0.775), the impinging vortex ring could only induce a weak secondary vorticity near the wall, which cannot roll up into a coherent structure. It is illustrated with LIF visualization and Finite Time Lyapunov Exponents (FTLEs) that a large-scale spiral vortex ring is generated in the near wall region for these two cases, which is explored for the first time. However, as the stroke length becomes larger (L0/H= 0.95 and 1.25), the strong secondary vorticity rolls up and pairs with the impinging vortex ring to form a vortex dipole. As a result, the impinging vortex rings are prevented to merge with the vorticity clustering near the wall causing a rapid reduction of the near wall vortex strength. The analysis of the radial wall jet shows that the induced large-scale spiral vortex ring at the case of the smaller stroke length could slow down both the decay rates of radial mass flow rate and momentum flux, and this might be of benefit for the mass and heat transfer of wall surface when applying the impinging synthetic jet.
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DOI：
--
发表时间：
1983-10
期刊：
--
影响因子：
--
作者：
A. Cerra;C. Smith
通讯作者：
A. Cerra;C. Smith
影响因子：
3.2
作者：
Alan McGuinn;R. Farrelly;T. Persoons;D. Murray
通讯作者：
Alan McGuinn;R. Farrelly;T. Persoons;D. Murray
影响因子：
4
作者：
Haller, G
通讯作者：
Haller, G
影响因子：
3.7
作者：
J. Walker;C. R. Smith;A. W. Cerra;T. Doligalski
通讯作者：
J. Walker;C. R. Smith;A. W. Cerra;T. Doligalski
影响因子：
3.7
作者：
P. Orlandi;R. Verzicco
通讯作者：
P. Orlandi;R. Verzicco