1. 南京理工大学 瞬态物理国家重点实验室,南京,210094
2. 帝国理工学院 数学系,伦敦,英国,SW7 2AZ
张成龙(1995-), 男, 江苏海安人, 研究生, 研究方向:流动控制.E-mail:zhangcl0115@foxmail.com
张辉(1981-), 教授, 研究方向:流动控制.E-mail:zhanghui1902@126.com
纸质出版:2020
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张成龙, 张辉, 江代文. 电磁力作用下槽道流速度响应的放大机理[J]. 空气动力学学报, 2020, 38(3): 490-499.
ZHANG Chenglong, ZHANG Hui, JIANG Daiwen. Amplification mechanism of the velocity response with the effect of electro-magnetic force in channel flow[J]. 2020, 38(3): 490-499.
张成龙, 张辉, 江代文. 电磁力作用下槽道流速度响应的放大机理[J]. 空气动力学学报, 2020, 38(3): 490-499. DOI: 10.7638/kqdlxxb-2019.0165.
ZHANG Chenglong, ZHANG Hui, JIANG Daiwen. Amplification mechanism of the velocity response with the effect of electro-magnetic force in channel flow[J]. 2020, 38(3): 490-499. DOI: 10.7638/kqdlxxb-2019.0165.
在电解质溶液中,电磁场产生的电磁力可以控制流体的运动,从而达到很好的减阻、增升、减振等效果。但由于所施加的电磁力较大,导致控制效率很低,因此以较小的电磁力诱导出大的流动响应成为提高流动控制效率的关键。以层流槽道流动作为研究对象,在槽道的下壁面施加沿展向余弦分布的展向电磁力,推导了线性条件下流向响应速度的解析解,并通过直接数值模拟对非线性条件下的响应进行了计算。结合解析解和数值解,揭示了流场中速度响应的放大机制,讨论了电磁力和流场参数对响应放大效果的影响。结果表明:当振幅较小时,速度响应处于线性范围内,其放大倍数与
Re
2
成正比,随着渗透深度的增大,先迅速增大后缓慢减小;随着展向波数
K
z
的增大单调减小。随着振幅的增大,放大倍数进入非线性范围,其值逐渐减小,但速度响应值先增大后减小。在振幅处于10
-3
~10
-2
量级时,速度响应可达到的最大值超过0.2,此时的放大倍数在10
2
量级。因此,利用流场的放大效应,是实现高效流动控制的重要环节。
The flow of the weak electrolyte solution can be controlled by electromagnetic forces generated by the suitably chosen magnetic and electric fields
which has significant effects for applications in the drag reduction
lift amplification
and oscillatory suppression. However
the control efficiency is very low due to the application of a large amplitude for the electromagnetic force. Therefore
the large response
induced by a small electromagnetic force
is the key to enhance the flow control effic
iency. In this paper
based on the laminar flow of a weakly conductive fluid in a channel
the flow responses are induced by the electromagnetic force
which is applied on the lower wall of the channel and is cosine distribution along the spanwise direction. The analytic solutions of the velocity responses in linear stage are deduced with linear stability theory
and the numerical solutions of these responses in nonlinear stage are calculated with direct numerical simulation (DNS). For the periodic characters of the channel flow in the streamwise and spanwise directions
the dealiased Fourier method is used in these two directions
while the Chebyshev-tau method is used in the wall-normal direction. Moreover
the usual no-slip and no-penetration conditions are used on the walls. The time advancement is performed with third-order accuracy by using a semi-implicit back-differentiation formula method. To eliminate residual divergence
the pressure term and the linear term are solved with a Chebyshev-tau influence matrix method. For the non-linear term
a spectral truncation method is used to remove aliasing errors. Combing the analytic and numerical solutions
the amplification mechanisms are revealed
and the influences of the parameters of electromagnetic forces and flow field are discussed. The results show that the amplification of velocity response along the streamwise direction is proportional to
Re
2
for small amplitude
i.e.
the responses in the linear stage. Moreover
the amplification of response increases firstly and then decreases with the increase of the effective penetration
Δ
while the amplification monotonically decreases with the increase of wave number along the spanwise direction. However
with the increase of amplitude
the response amplification approaches the nonlinear stage. The amplification monotonically decreases
while the amplitude value of velocity response increases firstly and then decreases. Moreover
the amplitude value reaches the maximum which is more than
0.2
and the corresponding amplification is the order of 10
2
. Therefore
the flow induced by the electromagnetic force is amplified with the effect of flow field
which is the key to enhance the efficiency of flow control.
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