ETH- Two-phase flows in flexible porous media
Project code: ETH-35 12-2
Title of project: Two-phase flows in flexible porous media: wicking of water in micro-textiles
Principal Investigator: Jan Carmeliet
Project duration (from- to): 2013 - 2016
Micro-textiles with higher added values, like protective clothing, sports or medical textiles are worn next to the human skin and, therefore, the interface between the fibrous materials and the skin has to be optimized. Removal of moisture produced by the skin is of primary importance for the comfort of the wearer but also in preventive medicine. Wicking of water in advanced textiles for protective clothing or performance clothing is understood as the non-saturated flow of water, or two-phase flow of water and air, in a flexible porous media, where a surface film flow occurs from a limited reservoir ahead of bulk liquid flow. Textiles show a double porosity, an intra-yarn porosity between the fibers and an inter-yarn porosity between the yarns and by applying multiple layers their specific behavior and performance may be specifically designed for. The modeling and prediction of the wicking behavior is therefore very challenging, given the complex configuration of the liquid phase within this flexible porous medium. Since continuum approaches need an unsaturated permeability as input obtained from e.g. measurements, their use as predictive tools is limited.
We propose a multi-scale framework to understand and capture the physics of the wicking process in multilayer textiles by combining advanced high resolution X-ray tomographic imaging and levelset lattice Boltzmann modeling and then to upscale this information to a continuum model validated by neutron radiography experiments. The project builds upon the recent successes in the development of the Entropic lattice Boltzmann method (ELBM) as a general novel paradigm in computational fluid dynamics, and is focused on the creation, validation and application of new ELBM models for multi-phase flows in textiles. To be able to separate the water and the textile material phases in the X-ray phase contrast results, we will apply morphometry for segmentation allowing to distinguish between air, polymer and water, followed by affine and non-affine registration to obtain the deformation of the fiber network upon wetting.
The results of the proposed project will be used to develop new technical and advanced textiles with improved moisture transport properties which will be beneficial thanks to better adapted solutions for sports, leisure activities as well as in the field of heat and cold protective clothing, and specially adapted textiles for the geriatric and paraplegic population.