Abstract
In dyeing yarns coiled on a cylindrical bobbin or reel or in immersing in water raw silk or pot cake packed in the form of a cylinder before rereeling, water permeability is one of the most important problems.
In this paper, we deal with this problem, especially the method of its measurement. The flow through layers of cylindrical yarn may be expressed in the following equation, the gravity flow being neglected.
where Q: total flux through the yarn layers in unit time, k: constant, l: width of layer, p: pressure head, μ: coefficient of viscosity, γe and γw: outer and inner radii respectively.
It has been experimentaly found that this equation is fit for sufficiently thick layers (more than 3 rolls) at the low Reynolds numbers.
In case the thickness of yarn layer is not uniform, for instance barrel or cone package, γe is the function of Z (axis coincides with bobbin axis), and so when this function is known, we can obtain Q-γe (Z) relation from the integration of γe (Z) along Z axis.
