The Effect of Biofilms on Turbulent Flow Over Permeable Beds
The Effect of Biofilms on Turbulent Flow Over Permeable Beds
复制标题
DOI：
10.1029/2019wr026032
复制
发表时间：
2020-12
影响因子：
5.4
通讯作者：
F. Kazemifar;G. Blois;M. Aybar;Patricia Perez Calleja;R. Nerenberg;S. Sinha;R. Hardy;J. Best;G. S. Sambrook Smith;K. Christensen
中科院分区：
文献类型：
--
作者：
F. Kazemifar;G. Blois;M. Aybar;Patricia Perez Calleja;R. Nerenberg;S. Sinha;R. Hardy;J. Best;G. S. Sambrook Smith;K. Christensen
尽管越来越多的工作促进了我们对在可渗透床上的湍流界面上发生的流动相互作用的理解，但关于生物膜的存在如何影响这种流动的了解很少，生物膜几乎存在于所有的水环境中。这项研究量化了在实验室实验渗透床上生长的生物膜在生物膜脱离之前对流动的影响，然后将其与生物膜脱离后的残余影响进行了比较。研究是在流动通道中进行的，通过浸泡具有理想几何形状和不同孔隙率的二维渗透床来探索不同的床层渗透率。考虑了流速越高，流量越小的顺序，以探索剥离的影响。使用粒子图像测速仪进行测量。在相同的泵浦频率下，预生生物膜的存在使壁面总剪应力和摩擦速度增大，生物膜剥离后壁面总剪应力和摩擦速度减小。在泵浦频率不变时，外层不同床型的无量纲雷诺应力发生崩塌，而内层生物膜的存在导致无量纲雷诺应力的降低。象限分析表明，这一下降主要是由于第二季度强劲贡献的减少。这些结果表明，水环境中可渗透介质上的流动和传输模型不能忽视生物膜在修正湍流中的作用。
Despite an increasingly large body of work advancing our understanding of flow interactions occurring at the interface of a turbulent flow overlying a permeable bed, little is known concerning how such flow may be affected by the presence of biofilms, which exist in nearly all aquatic environments. This study quantifies the effects on flow exerted by biofilms grown over experimental laboratory permeable beds until biofilm detachment, and then compares this to the residual effects after its detachment. The investigation is conducted in a flow channel by immersing two‐dimensional permeable beds with idealized geometry and different porosities in order to explore different bed permeabilities. Sequences of increasingly higher flow velocity conditions, followed by lower flow, were considered to explore the effect of detachment. Measurements were performed using particle image velocimetry. The total wall shear stress and friction velocity were found to increase in the presence of pregrown biofilm, and decrease after biofilm detachment, when compared at the same pump frequency. The dimensionless Reynolds stresses, at constant pump frequency, collapsed for different bed configurations in the outer layer, while for the inner layer, the presence of biofilm led to a decrease in dimensionless Reynolds stress. Quadrant analysis shows that this decrease was primarily due to a reduction in strong Q2 contributions. These results suggest that models for flow and transport over permeable media in aquatic environments cannot neglect the role of biofilms in modifying turbulence.