Abstract
As marine biofouling seriously affects the development and utilization of oceans, the antifouling technology of microstructured surface has become a research hotspot due to its green and environmentally friendly advantages. In the present research, the motion models of microorganisms on the surfaces of five rectangular micropits, in co-current and counter-current flow direction, were established. Dynamic mesh technology was used to simulate the movements of microorganisms with different radii in the near-wall area, and the fluid kinematics and shear stress distributions in different-sized micropits were compared. Furthermore, moving microorganisms were included in the three-dimensional microstructure model to achieve the real situation of biofouling. Simulation results revealed that the vortex flow velocity in the micropits increased with the increase of the inlet flow velocity and the existence of the vortex flow effectively reduced the formation of conditioning layers in the micropits. In the downstream and countercurrent directions, the average shear stresses on the wall decreased with the increase of the micropit depth and width, and the shear stress on the inner wall of the Mp1 micropit (a patterned surface arranged with cubes of 2 µm × 2 µm × 2 µm) was found to be the largest. A low shear stress region with a low flow velocity was formed around microorganisms in the process of approaching the microstructured surface. The shear stress gradient of micro-ridge steps increased with the approach of microorganisms, indicating that microridge edges had a better effect on reducing microbial attachment.
Highlights
Scardino et al [15] found the best antifouling performance when the characteristic size of the microstructure was slightly smaller than that of the attached organisms and proposed the “attachment contact theory”, which is the basis of the engineered roughness index (ERI) model, the ERIII model, the nano-force gradient model, and the surface energetic attachment (SEA) model
In the nano-force gradient model, it is not considered that microorganisms may be smaller than the characteristic size or can adjust their directions to adhere to grooves
We only focus on the situation where a single microorganism is affected by the fluid on the microstructured surface to analyze the factors of the antifouling mechanism, which does not mean replacing all the microorganisms in the flow field with a single microorganism
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Scardino et al [15] found the best antifouling performance when the characteristic size of the microstructure was slightly smaller than that of the attached organisms and proposed the “attachment contact theory”, which is the basis of the engineered roughness index (ERI) model, the ERIII model, the nano-force gradient model, and the surface energetic attachment (SEA) model. The two ERI models can only predict the attachment of Ulva Lactuca spores without considering surface wettability, the microbial characteristic size, and other parameters. In the nano-force gradient model, it is not considered that microorganisms may be smaller than the characteristic size or can adjust their directions to adhere to grooves This model only considers rectangular protruded structures of different lengths and arrangements. CFD was employed to simulate the movement of microorganisms in the near-wall zone and explain the antifouling mechanism of a microstructured surface
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