Effect of metal additive manufacturing surface roughness on laminar flows

Purpose Surface roughness inherent to additive manufacturing (AM) is frequently overlooked in the design of components for thermal management and fluid transport, particularly under laminar flow conditions where its effects are often assumed negligible. This study aims to systematically evaluate the impact of different AM roughness scales on flow resistance in such applications. Design/methodology/approach The roughness of side-skin surfaces produced by laser-based powder bed fusion of metals (PBF-LB/M) is decomposed into three components: a base profile with dominant sinusoidal or smoother features from inter-layer meltpool stitching; small-scale roughness caused by partially melted or adhered powder particles; and large-scale random roughness due to process instabilities such as spatter. Laminar flow simulations are performed in circular channels generated from both analytical sinusoidal profiles and profilometry scans of vertically printed AlSi10Mg samples, enabling isolation and quantification of each roughness component’s contribution to flow resistance. Findings Results show that spatter-induced large-scale roughness is the primary contributor to drag, accounting for nearly two-thirds of the total pressure loss in AM channels. Powder–scale roughness is responsible for more than half of the remaining pressure loss, while the base profile contributes the least. These findings provide quantitative insight into the role of each roughness scale in AM-fabricated components. Originality/value This work provides the first systematic decomposition and quantification of multi-scale AM roughness effects on laminar flow resistance, supporting targeted roughness mitigation strategies to enhance the hydraulic performance of AM components.