Numerical study on flow-drag-reduction mechanism of resident microbubble array
A numerical simulation study was conducted using the finite volume method and large eddy simulation(LES)method to analyze the complex turbulent flow near the wall of a flat plate and with the resident microbubble array in order to improve the theoretical mechanism of drag reduction by the resident microbubble array.The proper orthogonal decomposition(POD)method was used to extract and compare the near-wall turbulent quasi-coherent structure.Results showed that the wall shear stress of the resident microbubble array was more stable and decreased by 13.7%approximately compared with the flat plate.The dynamic deformation of the gas/liquid interface of the microbubbles caused intermittent flow separation and reattachment in the boundary layer,which suppressed the"bursting"phenomenon of low-speed fluid upcast and high-speed fluid down-sweep,leading to a 5.6 Hz reduction in the bursting frequency of turbulent coherent structures.The POD method can effectively extract the main distribution characteristics of the near-wall turbulent quasi-coherent structures.The presence of microbubbles strengthens the small-scale structure in the near-wall turbulent region,promoting a more homogeneous distribution of turbulent kinetic energy within the flow field,suppressing the development of quasi-coherent structure and demonstrating the good drag-reduction property.
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维普
