We use a singular perturbation method to study the interface dynamics of a nonconserved order parameter (NCOP) system, of the reaction-diffusion type, for the case where an external bias field or convection is present. We find that this method, developed by Kawasaki, Yalabik, and Gunton [Phys. Rev. A 17, 455 (1978)] for the time-dependent Ginzburg-Landau equation and used successfully on other NCOP systems, breaks down for our system when the strength of convective nonlinearity gets large enough.

• Received 21 September 1993

DOI:https://doi.org/10.1103/PhysRevE.49.3480