LDTRAN/CB: A Model for the Assessment of the Impact of the Chemical/Biological Environment on Military Rotorcraft Operations

Assessing the influence of the Chemical/Biological (CB) environment on the mission effectiveness of current and projected Army rotorcraft requires the direct modeling of the rotor wake flowfield (or rotorwash) as well as wake/fuselage interaction. Rotorwash effects may have a significant influence on CB agent deposition on the fuselage, affecting both CB survivability design features as well as decontamination procedures. In generating a predictive tool to address these issues, it is desirable to use an analysis with a track record of successful application to rotor/fuselage modeling while developing a user-friendly input and a code structure suitable for taking input from the current generation of CB cloud dispersion models. The project described here constructed a coupled model of rotor wake/ airframe effects and cloud droplet transport, building on software previously developed for both U.S. Army and industry users. The general aim was to tailor this model to the requirements of CB cloud interaction problem and to implement appropriate interface software to produce a practical mission simulation tool. The work to date has led to the development of the LDTRAN/CB computer program (Lagrangian Deposition and TRajectory ANalysis/Chemical-Biological). This paper presents a technical description of LDTRAN/CB and its supporting software, an overview of its operation, and examples of its application to representative rotorcraft in typical mission operating scenarios.