Slip length and drag reduction of superhydrophobic surfaces in shear-thinning fluid flows.

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Tác giả: Colin R Crick, Henry C-H Ng, Robert J Poole, Linsheng Zhang, Weixing Zhou

Ngôn ngữ: eng

Ký hiệu phân loại: 658.3134 Personnel management (Human resource management)

Thông tin xuất bản: United States : Journal of colloid and interface science , 2025

Mô tả vật lý:

Bộ sưu tập: NCBI

ID: 61178

HYPOTHESIS: We hypothesise that superhydrophobic surfaces can achieve effective interfacial slip and drag reduction even under non-Newtonian, shear-thinning fluid flows. Unlike Newtonian fluids, where slip is primarily influenced by viscosity and surface tension, we anticipate that the shear-thinning nature of these fluids may enhance slip length and drag reduction. EXPERIMENTS AND NUMERICAL ANALYSIS: The superhydrophobic surfaces used in this study, featuring a dual-scale random topography, were fabricated via a spray coating process, and low-concentration xanthan gum solutions (50-250 ppm) were used as model shear-thinning fluids of low elasticity. Drag reduction was experimentally measured using a rheometric cone-and-plate system, while slip length was calculated through a newly developed integral expression for power-law fluids. FINDINGS: Experimental results revealed a significant increase in slip length for xanthan gum solutions compared to distilled water, indicating that shear-thinning effects lead to substantial increases in slip length. Specifically, xanthan gum solutions with a power-law index of approximately 0.8 achieved over a 25% increase in slip length compared to equivalent Newtonian fluids. Furthermore, analytical and numerical analyses confirmed that shear-thinning fluids enhance the slip effect over superhydrophobic surfaces while shear-thickening fluids diminish it. The strong agreement between theoretical and experimental results underscores the potential of superhydrophobic surfaces to reduce drag in shear-thinning fluid flows.
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