METHOD FOR DERIVING BUCKLING CONDITION OF FIBERS MOVING IN FLUID, BREAKING CONDITION CALCULATION METHOD, AND FIBER LENGTH DISTRIBUTION PREDICTION METHOD

摘要

In a method of deriving the buckling condition of a cylindrical fiber moving in a fluid, a method of calculating the breakage condition thereof, and a method of forecasting the fiber length distribution, the flow field around a cylindrical fiber in a contraction flow is determined by a stricter method.;The method of deriving the buckling condition, which is a condition under which buckling occurs, of a cylindrical fiber moving in a fluid, includes the step of multiplying a dimensionless fluid stress distribution, uniquely determined with regard to the aspect ratio r₀' of the cylindrical fiber, by µk (where µ represents fluid viscosity and k represents the contraction rate (velocity gradient in the length direction at the location where the fiber is present)) at a location where the cylinder is present, to obtain the fluid stress distribution acting on the cylinder surface in a contraction flow, and the step of using a minimum eigenvalue λ₀, which is the threshold for buckling derived from the fluid stress distribution on the cylinder surface, to derive the buckling condition, wherein the buckling condition is represented by µk ≥ -(λ₀Er₀'⁴log r₀")/4 (where E is Young's modulus and r₀' is the aspect ratio of the cylinder).