AN ADHESIVE PROBLEM FOR A POWER-LAW FLUID

Abstract

The flow caused by the pulling of a circular disk away from a plane rigid surface is investigated when the disk and the surface are separated by a thin layer of power-law fluid of thickness h(t). It is observed that the force exerted by the fluid on the disk is a suction force F, which tends to make the disk adhere to the rigid surface. The variation of F/k (where k is the power-law consistency index) with time t is computed for h(t) = t + 5.0 for both pseudoplastic (with power-law exponent n satisfying 0 < n < 1) and dilatant fluids (with n > 1). It is found that at a given instant, |F|/k for any pseudoplastic fluid is larger than that for a dilatant fluid. Further, the values of F for several realistic pseudoplastic fluids are computed at a given instant for both linear and quadratic variation of h(t) with t. The analysis further reveals that for a realistic pseudoplastic fluid, |F| at a given instant corresponding to a linear variation of h(t) is larger for a layer of given thickness than |F| at that instant for a layer of larger thickness.

Keywords:

• Adhesive force
• Power-law fluid

Acknowledgments

One of the authors (A. S. G.) acknowledges the financial assistance of Indian National Science Academy, New Delhi for carrying out this work. The authors would like to acknowledge the use of the facilities and technical assistance of the Center for Theoretical Studies at Indian Institute of Technology, Kharagpur.

Notes

CMC carboxy methyl cellulose.