By defining the deflection angles of exhaust flow on each cascades, efflux-pattern describes the circumferential distribution of the exhaust flow from the thrust reverser around a nacelle. The determination of the efflux pattern must take into account the requirements for efficiency, re-ingestion characteristics and effective area,as well as the impact imposed by the exhaust flow on the aircraft aerodynamic characteristics. Whether or not certain efflux design provides sufficient thrust efficiency and effective area can be evaluated by separate thrust reverser static test while re-ingestion characteristics and engine/aircraft aerodynamic interference can only be studied in an installed wind tunnel test.