A numerical investigation of internal surface roughness and its influence on additively manufactured inlet manifold performance

Purpose The purpose of this paper is to numerically investigate the effect of interior surface roughness on an additively manufactured (AM) intake manifold’s performance. This study attempts to empirically assess the impact of different interior surface roughness on an intake manifold’s performance using simulation tool. Design/methodology/approach Computational fluid dynamics analysis of an intake manifold is carried out at different internal surface roughness using Ansys Fluent software. An arbitrary surface roughness value (Ra) is translated into an equivalent roughness of sand grain height for simulation. The k–Ɛ turbulence model with a standard wall function was used in this research because of solver limitations. It is one of the few models in Fluent that completely enables surface roughness specification. Findings Outcome of the investigation indicates that air flow velocity close to the intake manifold’s outlet was affected by surface roughness. The maximum velocity at the intake manifold outlet of a 1.25 mm rough surface is found to be 18% lower than that of a smooth surface. Practical implications This study offers a numerical method for determining how internal surface roughness affects the performance of intake manifolds manufactured using AM. This work is restricted to single-phase, steady-state flow, and experimental validation has been noted as a crucial next step. Originality/value Internal surface roughness of an intake manifold has received relatively little research attention. This numerical study establishes maximum permissible internal surface roughness value for a given complicated geometry during AM process of intake manifold to achieve an optimum performance.