Experimental and numerical investigation of the effect of periodic checkerboard patterns on diffusion properties of Khaya ivorensis tropical species

Dimensional variations in wooden structures caused by water absorption or desorption can lead to damage, especially when moisture diffusion mechanisms are not well understood. This limitation affects the reliable use of optical measurement methods, particularly when they operate under variable humidity. This study examined the longitudinal diffusion behavior of Khaya ivorensis wood and evaluates how a checkerboard-pattern surface treatment alters its diffusion response. Diffusion experiments were conducted using a custom setup designed to minimize external exchanges. The diffusion coefficient and surface exchange coefficient were identified through Siau's analytical approximation and an inverse numerical approach based on Fick's law combined with the Nelder–Mead simplex algorithm. A generalized analytical solution was also formulated and validated using numerically determined parameters. The longitudinal diffusion coefficient was about 6.68×10−10m2/s analytically and 5.54×10−10m2/s numerically. For untreated samples, the surface exchange coefficient was around 9.32×10−7m/s, while the surface treatment reduced it to 4.05×10−7m/s. The analytical method represented the early diffusion stage well, whereas the numerical model captured long-term behavior. Under the experimental tested conditions of this paper, the generalized analytical model describes the full diffusion process and shows that the checkerboard pattern reduces water flux at the wood surface by a factor of 2.3.