Type II and IV fluids exhibit which behavior to release from surfaces at takeoff?

Type II and IV fluids exhibit which behavior to release from surfaces at takeoff?

• A. Newtonian
• B. Shear-thinning (pseudoplastic)
• C. Bingham
• D. Dilatant

Answer: (B)

Shear-thinning behavior is what allows Type II and IV de-icing fluids to work as the aircraft accelerates. These fluids are designed to stay on surfaces at low shear (helping protect against ice) but become less viscous as shear rate increases, so the flow thins and sheds off the surfaces during takeoff. This thinning with increased shear means the fluid can release from wings and other surfaces as speed rises, reducing residual film and drag. The other types don’t fit: a Newtonian fluid keeps the same viscosity regardless of shear, a Bingham fluid has a yield stress and behaves like a solid until that stress is exceeded, and a dilatant fluid becomes more viscous with more shear.

Shear-thinning behavior is what allows Type II and IV de-icing fluids to work as the aircraft accelerates. These fluids are designed to stay on surfaces at low shear (helping protect against ice) but become less viscous as shear rate increases, so the flow thins and sheds off the surfaces during takeoff. This thinning with increased shear means the fluid can release from wings and other surfaces as speed rises, reducing residual film and drag. The other types don’t fit: a Newtonian fluid keeps the same viscosity regardless of shear, a Bingham fluid has a yield stress and behaves like a solid until that stress is exceeded, and a dilatant fluid becomes more viscous with more shear.