Increased demand for higher performance from airbreathing propulsion systems, and in particular ramjets, has resulted in a need to upgrade existing technologies to meet more stringent design requirements. The criteria for higher performance include reduced volume and weight, leading to the use of shorter comhustors and high energy, high density fuels. Systems constraints have dictated the use of sudden-expans ion (dump) combustors capable of operating effectively at high combustion intensities over wide ranges of conditions; problems of flame stabilization, flame propagation and spray combustion have been encountered. This paper describes how the development and application of modeling techniques can be used to interpret experimental results and to assist in the design of ramjet combustors and combustor components. ONTROL of flame stabilization and flame propagation in a turbulent flow represents a key element in combustion-chamber design. The placement and geometry of fuel injectors, flameholders, and air distribution ports are basic design parameters that govern the performance of a particular combustor. Therefore, it is desirable to compute combustion chamber flowfields in order to understand the phenomena that occur in existing combustors and to predict the performance of new combustor design concepts. In ad- dition to the overall combustor flowfield, modeling can also be used to provide insight into the behavior of portions of the combustor, such as flameholders and fuel injectors, under a variety of conditions. The insight gained through the use of these unit analyses can be of substantial use in the planning of a combustor test program and in the interpretation of combustor and combustor-component test data. The computation of a generalized combustor flowfield is a formidable task, involving a number of complex, coupled physical and chemical processes. The obvious difficulties include not only sorting out the multitude of coupled mechanisms but also involve the typical disparity in characteristic length and time scales in combustion chamber flows. Despite the problems involved, considerable progress has been made in recent years in the development of calculation methods for these flows, using technologies for the solution of the elliptic governing equation and simpler yet physically perceptive modular modeling techniques. A unified model of an overall combustion chamber flowfield requires the numerical solution of the elliptic form of the governing equations, since most practical combustion- chamber flows involve large regions of recirculation, in which