Optimum Nose Shape of High-speed Train Using Vehicle Modeling Function for the Reduction of the Aerodynamic Drag

초록

Nose shape optimizations are performed numerically to reduce the aerodynamic drag of the high speed train with the Vehicle Modeling Function. Vehicle Modeling Function can model various 3D nose shapes and extract engineering models of the existing 3D shapes. 3-car train model is used for the nose shape optimization of the basic train and 10-car train model is composed for that of the commercial high speed train, KTX-Sancheon. Through nose shape optimization of 3-car basic train with Broyden-Fletcher-Goldfarb-Shanno algorithm, the aerodynamic drag with the optimized shape was reduced by 5.8% when compared to the base model. The low-risen and long vertical nose shape of the optimized shape weakens the whirled flow around the nose tip behind the train rear nose and reduces the total aerodynamic drag. For the shape optimization of the commercial high speed train, 2D characteristic shapes of KTX Sancheon nose were extracted and the base model of KTX Sancheon was constructed with the Vehicle Modeling Function. The design space was constructed with the base model and doesn’t violate the shape constraint. By the nose shape optimization of the commercial train, the aerodynamic drag of the optimized shape is reduced by 6% when compared to the base model. The longer nose and sharper edge of the optimized shape weakens the vortices behind the last car and can reduce the aerodynamic drag. Through two optimizations, the three dimensional modeling is very necessary for shape optimization of the train nose in that the wake area behind the train must be simulated as accurately as possible. In doing so, Vehicle Modeling Function is a valuable tool in successful three-dimensional shape optimization since it can functionalize three-dimensional shape thus efficiently enables the various models of the three-dimensional train shape.