Updated CFD interface in ShipIR (v4.2)

Most existing platform signature models use semi-empirical correlations to predict flow convection on internal and external surfaces, a key element in the prediction of accurate skin signature. Although these convection algorithms are capable of predicting bulk heat transfer coefficients between each surface and the designated flow area, they are not capable of capturing local effects such as flow stagnation, flow separation, and flow history. Most computational fluid dynamics (CFD) codes lack the ability to predict changes in background solar and thermal irradiation with variations in the environment and sun location, and do not include the thermal / optical properties of the surfaces and multi-bounce radiative surface exchanges with their solvers (by default). Existing interfaces between CFD and signature prediction tend to simply map the CFD predicted temperatures onto the signature model. This paper describes the latest efforts to develop a fully functional interface between the NATO-standard ship signature model (ShipIR) and the ANSYS Fluent CFD solver. Our previous work (Vaitekunas et al, 2011) has been updated to include a parallel version of the ShipIR User-Defined Function (UDF) library, which now transfers the net radiative and other non-conducting sources of heat flux to the Fluent solver, using either a wall heat flux for adiabatic walls or a heat generation rate for coupled and backside convection wall boundaries. The resultant wall temperatures and convective fluid heat fluxes are used to either iterate the coupled solution (coupled-T) or refine the local-area heat transfer coefficients and fluid temperatures in ShipIR (coupled-h). The updated interface is analysed using a detailed thermal/IR simulation of a commercial Bell 407 helicopter with a standard engine and tailpipe.