The Bulk Synchronous Parallel (BSP) model provides a theoretical framework to accurately predict the execution time of parallel programs. In this paper we describe a BSP programming library that has been developed and contrast two approaches to analysing performance: (1) a pencil and paper method; (2) a profiling tool that analyses trace information generated during program execution. These approaches are evaluated on an industrial application code that solves fluid dynamics equations around a complex aircraft geometry on IBM SP2 and SGI Power Challenge machines. We show how the profiling tool can be used to explore the communication patterns of the CFD code and accurately predict the performance of the application on any parallel machine.