Random wave and Schell model for the mean RCS of bent chaotic ducts with a homogeneous scattered aperture field distribution

It is shown how a Schell model can be constructed to estimate the mean radar cross-section (RCS) of long bent engine ducts. A consistent random wave model is also provided to determine representative RCS distributions of such ducts. In both cases it is assumed that the duct has an aperture which is approximately normal to the duct axis and a scattered field distribution which is homogeneous across the aperture. It is believed that such a model is often valid for long chaotic bent ducts when most rays (in a ray representation) undergo many reflections before escaping the duct. A comparison is made with a nonconvergent shooting-and-bouncing prediction of a complex duct