In curvilinear coordinates, the divergences of a vector field v and a second-order tensor field S are ∇ ∇ ⋅ ⋅ v = ( ∂ ∂ v i ∂ ∂ ξ ξ i + v k Γ Γ i k i ) ∇ ∇ ⋅ ⋅ S = ( ∂ ∂ S i k ∂ ∂ ξ ξ i − − S l k Γ Γ i i l − − S i l Γ Γ i k l ) g k