SIMULATIONS OF AIR PERMEABILITY OF MULTILAYER TEXTILES BY THE COMPUTATIONAL FLUID DYNAMICS

摘要

The article concerns the ventilation aspect of biophysical comfort. In the paper, multilayer textiles (built of three layers of different destination) were investigated with potential application in uniforms addressed to firefighters. Studied materials were constructed with the following raw materials: Kevlar, Nomex, PTFE, PU, and carbon fiber. Different variants of textiles used to protect firefighters against heat and flame were tested for air permeability. First, materials were tested experimentally in specific constant ambient conditions using an air permeability tester. The main goal of this paper was to design 3D models of multilayer textiles to determine the air permeability of real textiles and predict it for clothing made of these materials. For this purpose two 3D models (monofiber model and multifiber model) were designed. The models differed in degree of yarn structure in woven fabrics, whereas nonwoven fabrics (due to their complicated random arrangement of fibers) and membranes were mapped as a porous media of isotropic porosity. The simpler model treated the yarn as monofilament, while in the second, more accurate model the yarn was made of fibers. The main objective of the experiment was to verify the utility of the models and to investigate the impact of a degree of mapping yarn geometry on air permeability. Obtained outcomes of the simulations for both models showed correlation with the experimental results; however, values of calculated air permeability obtained by simulations performed on more precise model were clearly closer to the experimental outcomes and show which parameters of geometric structure of the yarn could be an important factor in the modeling of airflow through the textiles.