Localized deformation in yield-stress fluids (Bingham / Herschel-Bulkley model)
0.30
0.80
0.50
1.00
0.05
Shear stress: 0.00
Band width: --
Flowing fraction: --
Physics
Viscoplastic materials (mayonnaise, cement, lava, blood) flow only when stress exceeds a yield stress τ_y. The Bingham model: τ = τ_y + η·γ̇ (for |τ|>τ_y), otherwise solid. The Herschel-Bulkley model: τ = τ_y + K·γ̇ⁿ allows shear-thinning (n<1) or thickening (n>1). When loaded non-uniformly (e.g., pipe flow), only a shear band flows while the rest remains rigid — leading to plug flow with a liquid sheath.