Enhanced fluid chaotic mixing and heat transfer with vibrating blade coupled with flexible plate

doi:10.11949/0438-1157.20250295

Abstract

Abstract:

To optimize the oscillating flow field formed by the vibrating blade (VB) and improve fluid mixing and comprehensive heat transfer performance, a coupling structure of a vibrating blade with a flexible plate (VBFP) was proposed. The mechanism of fluid mixing and heat transfer enhancement is revealed through experiments, numerical simulations and chaos analysis. The results showed that the VB induces periodic vortex shedding and breakdown, forming a high-velocity oscillating flow with chaotic characteristics, which promotes chaotic mixing of the fluid. However, the uneven vortex distribution results in weaker heat transfer in the central region. Driven by the oscillating flow, the passive oscillation and deformation of the flexible plate induce secondary and near-wall vortices, generating a secondary high-velocity flow that enhances nonlinearity and energy cascade effects. This process further strengthens chaotic mixing and improves heat transfer performance. Compared to the smooth channel, the VBFP reduces the time-averaged maximum temperature(T_max,av) by 16.7℃, improves the time-averaged Nusselt number (Nu_av) by 69.1%, and ultimately enhances the comprehensive heat transfer performance factor (η) by 42%. Additionally, for comparable maximum temperatures, the VBFP reduces power consumption and noise by 6.4 W and 20 dB, respectively, offering significant energy-saving and noise-reduction advantages.

Key words: vibrating blade, flexible plate, chaos, mixing, heat transfer

摘要：

为优化振动叶片（VB）形成的振荡流场，提升流体混合能力与综合传热性能，提出一种振动叶片与柔性板的耦合结构（VBFP）。通过实验、数值模拟及混沌分析，揭示流体混合与传热强化机制。结果表明，VB诱导周期性旋涡脱落与破碎，形成具有混沌特性的高速振荡流，使流动演化为混沌混合，但旋涡分布不均导致中心区域传热较差。在振荡流的驱动下，柔性板的被动变形振荡诱导次级和近壁旋涡，形成二次高速气流，增强非线性特征和能量级联效应，从而强化流体混沌混合，改善传热。相较光滑通道，VBFP降低时均最高温度（T_max，av）16.7℃，改善时均Nusselt数（Nu_av）69.1%，最终提升综合传热因子（η）42%；最高温度相当时，功耗和噪声分别降低6.4 W和20 dB，具备显著节能降噪优势。

关键词: 振动叶片, 柔性板, 混沌, 混合, 传热

CLC Number:

TK 124

Jinqi HU, Chunhua MIN, Xiaolong LI, Yuanhong FAN, Kun WANG. Enhanced fluid chaotic mixing and heat transfer with vibrating blade coupled with flexible plate[J]. CIESC Journal, 2025, 76(9): 4824-4837.

胡金琦, 闵春华, 李小龙, 范元鸿, 王坤. 振动叶片耦合柔性板强化流体混沌混合与传热研究[J]. 化工学报, 2025, 76(9): 4824-4837.

Figures/Tables 21

Fig.1 Structures of vibrating blade and flexible plate

Fig.2 Experiments on energy saving and noise level of a vibrating blade coupled with a flexible plate

Table 1 Error sources and maximum uncertainties in the experiment

误差来源	测试范围	最大不确定度
加热表面温度	40~85℃	±0.5℃
环境温度变化	27℃	±0.5℃
气流速度	1~6 m·s^-1	±2%
风机功耗	0.2~10 W	±2.3%
噪声水平	28~80 dB	±1 dB

Fig.3 Numerical calculation model

Table 2 Critical settings in FLUENT

参数	设置
压力-速度耦合	COUPLED
梯度	基于最小二乘
压力、动量、能量	二阶迎风
湍动能、比耗散率	二阶迎风
收敛残差	1×10^-6
时间步长	1×10^-4

Fig.4 Calculation model mesh view

Fig.5 Mesh independence and model validation

Fig.6 Distribution of stress and displacement of the flexible plate driven by oscillating flow

Fig.7 Airflow velocity distribution of z = 0 mm section

Fig.8 Airflow velocity distribution of z = -9.9 mm section

Fig.9 Distributions of vortical structure and wall convective heat transfer coefficient at different phases for VB

Fig.10 Comparison of vortical structure and wall convection heat transfer coefficients for VB and VBFP

Fig.11 Turbulent kinetic energy distribution of z = 0 mm section

Fig.12 Turbulent kinetic energy distribution of z = -9.9 mm section

Fig.13 Variation of maximum airflow velocity with time for VB and VBFP

Fig.14 Fourier spectrograms for VB and VBFP

Fig.15 Phase space trajectories of velocity for VB and VBFP

Fig.16 Variation of wall maximum temperature with time for VB and VBFP

Fig.17 Instantaneous temperature distribution of heated surfaces

Table 3 Time-averaged results of heated surfaces for different cases

工况	T_max,av/℃	Nu_av	f_av	η
光滑通道	86.9	36.6	0.24	1
VB	80.7	48.1	0.31	1.2
VBFP	70.2	61.9	0.39	1.42

Table 4 Temperatures， power consumption and noise levels of measurement point

工况	气流速度/(m·s^-1)	温度/℃			功耗/W	噪声/dB
工况	气流速度/(m·s^-1)	点 1	点 2	点 3	功耗/W	噪声/dB
光滑通道	3	82.7	65.8	65.2	2.2	55
VB	3	53.5	53.9	76.2	2.5	55
VBFP	3	54.9	67.5	37.3	2.6	55
光滑通道	4.7	67.7	58.7	58.2	9	75

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