Can triply periodic minimal surface inserts reduce turbulence-induced effects in high-Reynolds-number internal flows?

Turbulence in high-Reynolds-number internal flows generates broadband pressure fluctuations that induce structural vibrations, acoustic noise, and even structural fatigue. To mitigate these effects, triply periodic minimal surfaces (TPMSs) and other porous inserts are considered promising for efficient turbulence reduction in internal flows. This relies heavily on numerical predictions of reduced turbulent kinetic energy and lacks rigorous experimental validation in high-Reynolds-number regimes. This study challenges this assumption by quantifying the efficiency of porous inserts in a well-controlled turbulence regime driven by geometric inhomogeneities in pipes. Specifically, we study high-Reynolds (Re=15 000) turbulent flows in pipes with a sudden expansion and a 90° miter bend through 3D-printed resin TPMS inserts. We evaluate various porosities, insert lengths, and unit cell sizes by measuring pressure fluctuations in the local and up- and downstream regimes. Our findings demonstrate that, compared to a honeycomb insert, the tested TPMS inserts offer no advantage in pressure-fluctuation attenuation and increase pressure levels upstream of the insert. Furthermore, while the relative performance of TPMS inserts improves with larger pore sizes, this effectively minimizes flow interactions and renders the structural contribution of the TPMS matrix negligible. Therefore, for the considered sheet-based geometries and flow regime up to (Re≤15 000) shown here, the TPMS inserts cannot be recommended for passive acoustic and hydrodynamic mitigation in internal high-Reynolds-number flows, disproving the initial assumptions regarding their reduction in wall pressure fluctuations in these particular configurations.