We perform direct numerical simulations (DNS) to investigate how cubic-lattice porous substrates influence momentum and heat transfer in turbulent channel flows. The simulations span friction Reynolds numbers from 260 to 1500, Prandtl numbers of 0.5, 1, and 2, and substrate porosities of 50%, 71%, and 87%. We show that theories developed for rough- wall turbulence can be extended to porous surfaces by replacing the roughness height with the inverse of the streamwise Forchheimer coefficient. The shifts in the mean velocity and temperature profiles follow existing fully rough momentum and thermal theories, enabling their prediction with rough-wall models. Combining these models with synthetic temperature and velocity profiles, we derive analytical formulas for the friction coefficient and Stanton number that agree with our DNS data to within 5%. The performance enhancement factor, which measures heat-transfer augmentation relative to the pressure-drop penalty at constant pumping power, is comparable to that obtained for rough surfaces. This suggests that porous substrates provide an alternative method for enhancing heat transfer in turbulent flows.
Wall-resolved Large Eddy Simulations are performed to investigate turbulent heat transfer in a rough pipe over a range of Pr. The roughness is generated using a controlled numerical procedure that allows independent specification of roughness correlation length, amplitude, and skewness; a statistically Gaussian heigh...
Himani Garg· Journal of turbomachinery· 0 citations
Matrix cooling is an internal cooling concept for gas turbine blades that combines structural reinforcement with enhanced heat transfer through a rib-crossing lattice geometry. The repeated flow redirection generates strong shear layers, impingement, and vortical structures that significantly influence turbulent tran...
Himani Garg, Romain Seppey, M. Mihaescu et al.· Journal of turbomachinery· 0 citations
Unstable thermal stratification modifies near-wall momentum and heat transport, causing the mean velocity profile to depart from the classical logarithmic law and complicating wall modelling for turbulent mixed convection. We develop a buoyancy-modified logarithmic-quadratic wall model for incompressible Poiseuille--Ra...
This study numerically investigates laminar forced convection in a porous channel with elliptic wavy cavities, a geometry relevant to compact heat exchangers and energy systems. The governing equations, expressed in vorticity–stream function form, are solved using a finite difference method on a boundary-fitted curvili...
Muhammad Irshad, M. Hussan, Humayoun Shahid et al.· Canadian journal of physics...· 0 citations
We investigate turbulent boundary layers at Mach 2.5 over sinusoidal roughness at matched $Re_\tau=784$. We considered three wall temperatures, $T_w/T_r=$ 1.0, 0.7, and 0.4. Each wall temperature was repeated with a smooth and rough surface, the latter following a three-dimensional sinusoidal profile with effective slo...
Mateus A. R. Braga, Robyn L. Macdonald· 0 citations
Abstract Content of image described in text. We investigate pressure-driven turbulent flow in a square duct using wall-modelled large-eddy simulations (WMLES) of the Navier–Stokes equations. An equilibrium wall model based on the logarithmic law is employed, yielding results in close agreement with direct numerical sim...
F. Verolini, Mao-Chao Xiao, S. Pirozzoli· Journal of Fluid Mechanics· 0 citations
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