In gas turbine engines, the management of critical fluid (oil, cooling air, etc.) temperatures is accomplished with heat exchangers (HEX). One of the major thermal sinks is accomplished by ducting bypass air to a HEX or placing it in the bypass air flow path. The fan duct bypass flow is a major contributor to engine thrust in a commercial gas turbine engine. Heat exchangers can have an impact on overall duct performance as a result of size (blockage), porosity (flow thru Hex), and position in the duct. The sponsor would like to have a reduced order mathematical model of the flow around a heat exchanger in a duct as a way to conduct preliminary design studies before a final design is established.