Investigation and Improvement of T-Tail Junction Flow Separation for a Demonstration Aircraft

Flow separation is easily induced at the junctions of aircraft components, and for aircraft with T-type tails, in particular, it can lead to loss of directional stability under a small sideslip angle. In the reported study, improved delayed detached eddy simulation with a shear-layer-adapted length scale based on the k-omega shear-stress transport method was used to analyze and rectify the corner separation at the junctions of the horizontal and vertical parts of the tail of a demonstration aircraft. This was done to (i) suppress the flow separation caused by the complex interaction of the boundary layers on the horizontal and vertical tail parts at their junctions, and (ii) prevent the vertical tail parts from having any separated flow on their pressure and suction sides. The results showed that the main cause of the loss of directional stability was separation flow on the suction sides of the vertical tail parts. The corner flow separation was suppressed significantly by only using fairing cones at the junctions of the horizontal and vertical tail parts, thereby allowing the aircraft to maintain directional stability under a small sideslip angle.