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Proposing Institution

DLR Oberpfaffenhofen
Project Manager

Dr.-Ing Frank Holzäpfel
Münchner Str.
82234 Oberpfaffenhofen
As an unavoidable consequence of lift aircraft generate a pair of counter-rotating and long-lived wake vortices that pose a potential risk to following aircraft. The therefore prescribed aircraft separations contribute significantly to capacity restrictions of large airports. A particular risk prevails during final approach, where the vortices can not descend below the flight path, but tend to rebound due to the interaction with the ground. In this project wake vortex evolution in ground proximity is investigated employing the Large Eddy Simulation (LES) code MGLET for different situations of crosswind and/or headwind. First turbulent boundary layer profiles are simulated and then the wake vortices are superimposed to the established boundary layer flow. These investigations will be continued with more realistic simulations of final approach and landing. For this purpose a method is developed allowing flying a highly resolved flow around an aircraft model (established with a RANS method) through the LES domain. Of special interest is whether so-called end effects travel along the vortices and weaken the vortices. End effects are initiated by disturbances of the pressure field within the vortex caused by the decrease of the circulation of the wake vortices during touchdown. During the roll-up process the exhaust jets are entrained into the wake vortices. Under cruise conditions ice crystals are generated from the exhaust jets that may give rise to long-lived contrails or even induce cirrus clouds (contrail cirrus). The turbulent mixing and detrainment of the ice crystals during the vortex descent is an important parameter in order to quantify the vertical extent, optical thickness, and lifetime of the contrails. Currently, it is not yet clear how strong the contribution of contrails and contrail cirrus to global warming might be. A comprehensive investigation of the turbulent detrainment processes will be conducted for different conditions of environmental turbulence and temperature stratification.

Impressum, Conny Wendler