On the behaviour of the elongational viscosity of a nematic polymer in elongational flow

For nematic materials, the elongational viscosity depends on the orientation of the director field relative to the velocity field. A computation of the elongational viscosity for various flow geometries is presented. It is shown that for uniaxial elongational flow the director aligns along the flow direction with a characteristic time τ E = −2γ 1 /(3γ 2 ϵ); for planar elongational flow, the director aligns perpendicular to the flow with a characteristic time τ E2 = ‐γ 1 /(γ 2 ϵ).