The Centre díEssais des Propulseurs (CEPr), Saclay, France, is dedicated to the comparison and ground testing of aeronautical aerobic motors, their components, assemblies and sub-assemblies, and associated equipment.

One application where CFD is used is in drone calculation. In the example illustrated here, flight conditions are: altitude of 700 m, speed of 55 m/s, and attack angle of 0 degrees. These factors can not be entirely reproduced in a test chamber, where only the flow submerging the drone can be analyzed. CFD complements ground testing because it simulates the entire jet (free jet testing), and real flight (free field flight) conditions.

The comparison between CFD and test data is made at the inlet of the engine ventilation scoops where the total pressure rakes are compared. Very good agreement between the free jet and free field simulations and test data is achieved along the body of the drone. However, the free jet and free field simulations diverge at 1.7 m from the nozzle outlet, where the fluid region representative of fight is a cylinder with a radius of 0.5 m for an initial nozzle exit radius of 0.9 m. Thus, for the part of the drone outside the cylinder, the ground test is not representative of flight conditions.

Total pressure at the scoop inlet of the jet engine.

CEPr is also studying ejector performance using CFD. The objective of these studies is to gather data that enable them to adapt the test chamber for ramjet tests. Simulations are run for steady, compressible, viscous flow using the k-epsilon turbulence model.

There is very good agreement between experimental and computed data. Expansion of the flow at the outlet of the nozzle and static pressure oscillations (compression and expansion waves) of the flow are correctly estimated. At the ejector outlet, FLUENT calculates the turbulent boundary layer expansion and captures the resulting shock. The center at Saclay continues to use CFD in innovative ways to expand their analysis capabilities and complement experimental testing.

Results (above) of CFD simulation of ejector performance show good correlation with ground testing.

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