The behavior of a stationary circular cylinder with an attached plate, under conditions where the entire cylinderplate body rotates about the cylinder axis, has been investigated experimentally for Reynolds numbers between 8 × × 10 3 and 6 × × 10 4 . To see the effect of the plate inclination on the pressure distributions and vortex shedding, the cylinder-plate body was rotated from 0 to 180 deg, unlike freely rotatable cases in previous studies. The plate was located at the center plane of the cylinder, upstream of the cylinder, at the beginning. The diameter of the cylinder and the width of the plate were both chosen to be 35 mm. Measurements of shedding frequency and pressures on the surface of the cylinder were obtained. The results indicate that the shedding frequency was nearly constant in the range of 50-120 deg and, by further increasing the angle from 120 to 160 deg, it strikingly increases and then again decreases at angles larger than 160 deg. The plate also causes important changes in pressures on the surface of the cylinder with increasing inclination angle. For different plate angles, five different types of pressure distributions have been observed. Characteristics of the vortex formation region and location of flow attachments, reattachments, and separations were observed by means of the flow visualizations. The drag coefficient of the cylinder has a maximum value at approximately θ = 75 deg, whereas it has a minimum value at θ = 15 deg. The lift coefficient has two maximums, at θ = 15 and 165 deg, depending on the plate position. The values of C L at about θ = 45 and 160 deg are zero as in the case of the cylinder without a plate. Nomenclature C D = drag coefficient 1 2 2π 0 C p · cos α dα C L = lift coefficient − 1 2 2π 0 C p · sin α dα C p = pressure coefficient, (P − P st )/ 1 2 ρU 2 D = diameter of circular cylinder D = projected cross-stream dimension of the cylinder-plate body f = vortex-shedding frequency L = width of the plate P = surface pressure P st = static pressure in the test section Re = Reynolds number based on D, U D/ν Sr = Strouhal number, f D/U Sr = Strouhal number, f D /U U = freestream velocity x, y = streamwise and lateral coordinates α = circumferential angle measured from the stagnation point of the cylinder θ = plate angle ν = kinematic viscosity of fluid ρ = density of air

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Aerodynamic characteristics of a square cylinder at incidence were investigated experimentally in the wake of a small rod at a Reynolds number of 3.4 × × 10 4 . The dimensionless gap L/D was varied from 1.71 to 8.00. Depending on the spacing L/D, two flow patterns with and without vortex shedding from the rod were observed. Pressure measurements on the rod and square cylinder and hot-film measurements in the wake of the cylinder were carried out. The combined influences of the rod and angle of incidence on the pressure distributions and vortex-shedding phenomenon were investigated. Without the rod, as the incidence increases from 0 deg, the reattachment on the lower side surface of the square cylinder occurs at the vicinity of 13 deg, and this corresponds to a jump in the Strouhal number. However, when the rod was set upstream of the square cylinder, the reattachment occurs at smaller angles of incidence depending on L/D. At zero angle of incidence, the minimum value of drag on the square cylinder is obtained for L/D = 2.0 and produces a drag that is 30% that of the square cylinder without rod. For L/D = 1.71, with increasing the angle of incidence C D values approximate to those of the square cylinder without rod. In the case of L/D > -2.7, there is a considerable decrease in C D in the region θ < -10 deg; however, the effect of the rod on C D decreases beyond θ = 10 deg. NomenclatureC D = drag coefficient of square cylinder based on D as the reference length C DR = drag coefficient of rod C DT = total drag coefficient, = C D + C DR (d/D) C L = lift coefficient of square cylinder based on D as the reference length C p = pressure coefficient, = (P − P st )/ 1 2 ρU 2 D = length of side of square cylinder D = projected cross-stream dimension of the square cylinder in incidence d = diameter of rod f = vortex-shedding frequency L = distance between the axes of square cylinder and rod P = surface pressure P st = static pressure in the test section Re = Reynolds number based on D, U D/ν Sr = Strouhal number based on D Sr = Strouhal number based on D U = freestream velocity x, y = streamwise and lateral coordinates α = circumferential angle measured from the front stagnation point of the rod θ = angle of incidence ν = kinematic viscosity of fluid ρ = density of air

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Prediction of the drag forces acting on a 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 and truck trailer without spoiler. The experiments were carried out in the wind tunnel in the range of the free stream velocity between 4.6 m/s and 19.3 m/s, corresponding the Re number range, 1.0×10 5-5.0×10 5. Mean absolute percentage error (MAPE) for training, validation and testing is 2.24%, 3.75% and 4.58% in the prediction of the drag forces, respectively. Prediction performance of the developed ANN model has a very good accuracy. According to the drag coefficients results, Reynolds number independence for truck trailer model is obtained at Reynolds number between 1.97×10 5 and 4.89×10 5. For spoiler position cases, while minimum drag coefficient acting on truck trailer with spoiler is seen at-2mm offset, maximum drag coefficient is seen at-9 mm offset.

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