Navier-Stokes and Euler Investigations for a Wing/Body/Engine/Pylon Model of the Fairchild/Dornier 728 Jet Aircraft with a Short and a Long Pylon

A numerical investigation is carried out to analyze the engine/airframe interference phenomena of closely coupled engines on a twin-jet regional transport aircraft in cruise flight conditions. Two configurations are considered respectively with a short pylon of and with a long pylon. The short pylon has a stronger pylon curvature than the long one. The calculations are performed by using the FLOWer-code for Euler and Navier-Stokes computations without and with jet. In general, the viscous effects cause a decambering of the wing. The flow on the upper wing is decelerated, while on the lower wing is accelerated, except and in the region, where the flow is super sonic. This occurs in jet condition on the present configuration due to the engine position close to the wing. The jet effects cause a strong flow acceleration on the lower wing in the pylon region. The flow acceleration characterized by pressure peak is quite harmful in inviscid flow as well as in viscous flow. Therefore, for such a closely coupled engine, it is very necessary to simulate the flow around the configuration with jet condition. Results without jet simulation, which the wind tunnel test belongs to, may underestimate the jet effects on the engine interference on the wing. For the configuration with the short pylon, the pressure peaks provoke strong shock waves and lead to flow separations on the pylon, which increase drag significantly. For the configurations with the long pylon, the pressure peaks are weaker and no flow separation occurs, which indicates an advantage of the long pylon with respect to the short pylon. The pylon drag ofthe lift of the long pylon decreases with respect to the short pylon due to the lift loss on the wing rear loading in the pylon region, which indicates a disadvantage. Since the investigation is performed at the same angle of attack, it is meaningful to continue the investigation performed at the same lift, to verify the advantage respectively the disadvantage of both pylons