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Prediction of the drag forces acting on truck trailer with/without spoiler is carried out by using artificial neural network (ANN). ANN model data set include the experiments of spoiler positions which have zero level to trailer front corner, -2 mm, -4.5 mm, -9 mm, +4.5 mm and +9 mm offset and truck trailer without spoiler. The experiments were carried out in the wind tunnel for number of ten free stream velocities of 4.6, 6.2, 7.8, 9.4, 11.0, 12.6, 14.2, 15.8, 17.45 and 19.3 m/s which are corresponds to Reynolds numbers range between 1.0x105 and 5.0x105. Mean absolute percentage error (MAPE) is obtained as 2.24% for training, 3.75% for validation and 7.58% for testing in the prediction of the drag forces. Prediction performance of the developed ANN model has very good accuracy. According to drag coefficients results, Reynolds independent for truck trailer model is obtained at Reynolds number between 1.97x105 and 4.89x105. For spoiler position cases, while minimum drag coefficient acting truck trailer with spoiler is seen at – 2mm offset, maximum drag coefficient is seen at -9 mm offset. The maximum drag reduction is 22.6 % at the position of -2 mm spoiler offset in Re = 3.2x105.

In this study, aerodynamic structures of the heavy vehicle consisting of truck and trailer was investigated with computational fluid mechanics method. The force measurement were performed on the model car and aerodynamic drag coefficient (CD) were determined numerically in 4 different speeds on the Fluent® program. Numerical analysis of flow were made on the 59 000 - 844 000 Reynolds number. The effect of trailer additional to truck was determined to aerodynamic drag coefficient. The friction and pressure induced distributions were determined of total aerodynamic resistance. The images of flow structure were obtained around the truck trailer. The zones that was forming aerodynamic resistance were determined., Buçalışmada, kamyon ve treyler oluşan ağır aracın aerodinamikyapısı hesaplamalı akışkanlar mekaniği yöntemi ilearaştırılmıştır. Kuvvet ölçüm model araba yapıldı veaerodinamik sürtünme katsayısı (CD) Fluent® programı 4 farklıhızlarda sayısal belirlendi. 844 000 Reynolds sayısı - akışınınSayısal analiz 59 000 yapılmıştır. Kamyon ek römork etkisiaerodinamik sürükleme katsayısı tespit edildi. Sürtünme vebasınç kaynaklı dağılımları toplam aerodinamik dirençbelirlenmiştir. Akış yapısının görüntüleri kamyon römorketrafında elde edilmiştir. Aerodinamik direnç oluşturan edildibölgeleri tespit edilmiştir.