This paper provides the theoretical basis for modeling tangential injection into ideal tubular flames. For most practical tubular combustors, the present formulation provides significant advantages compared to the traditional model formulation. The mass, momentum, and energy associated with tangential injectors are represented as Gaussian-shaped source terms in the appropriate conservation equations. Incorporating the source terms alters the governing equations, but does not affect the similarity properties associated with ideal tubular flow. The system of equations form a nonlinear boundary-value problem, which can be solved computationally. (c) 2007 The Combustion Institute. Published by Elsevier Inc. All rights reserved.