Boundary Layer Hydrodynamics and Mass Transfer Rates in Flax Roving Swelling
Hydynamic boundary layer reduction in wet-spinning troughs accelerates core hydration, stabilizing swelling and lowering yarn count CV percent.
Inter Fiber Capillary Transport
Pore Flow
Liquid movement through the narrow gaps between adjacent flax filaments is driven by surface tension forces during the wet-spinning process. This mechanism of inter fiber capillary transport carries moisture from the outer boundary of the bundle into the dry core. Uniform penetration must occur before the roving reaches the draft rollers to ensure even yarn drawing.
Twist Impedance
High twist levels in the roving reduce the capillary size and hinder the entry of the wetting agent. When the roving twist is too high, the capillary pathways compress, which slows down the rate of inter fiber capillary transport and leaves the center of the bundle dry. This dry core resists drafting, which creates thick and thin places in the spun linen yarn and increases the frequency of thread breakages during spinning.
Lowering the twist level or adding a wetting surfactant to the bath restores the capillary flow rate by reducing the contact angle of the liquid on the flax surface.
Drafting Stability
Moisture uniformity across the roving cross-section determines the friction between individual fibres during drafting. If inter fiber capillary transport fails to distribute the liquid evenly, some fibres slide past each other too easily while dry fibres resist the draft forces. This uneven resistance results in high yarn mass variation.
Controlling the immersion time in the warm water bath ensures that capillary flow reaches the center of every fiber bundle.