Yahya Erkan Akansu

Control of the Flow Around Square Cylinders at Incidence by Using a Rod

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 x 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

Flow Around a Rotatable Circular Cylinder-Plate Body at Subcritical Reynolds Numbers

The behavior of a stationary circular cylinder with an attached plate, under conditions where the entire cylinder‐ plate body rotates about the cylinder axis, has been investigated experimentally for Reynolds numbers between 8 × 10 3 and 6 × × 10 4 .T osee 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 =7 5deg, whereas it has a minimum value at θ =1 5deg. The lift coefficient has two maximums, at θ =1 5and 165 deg, depending on the plate position. The values of CL at about θ =4 5and 160 deg are zero as in the case of the cylinder without a plate.

Flow Around a Rotatable Square Cylinder-Plate Body

The flow around a square cylinder with a plate attached to it has been investigated experimentally in the Reynolds number range between 7.5 × 10 3 and 5.5 × 10 4 . The plate was located at the center of the front face of the square cylinder at the beginning. To determine the effects of the incidence angle of the square cylinder‐plate body on the pressure distributions and vortex shedding, the square cylinder with the plate was rotated. The incidence angle was varied from 0 to 180 deg, corresponding to the position of the plate in the front and back face of the cylinder, respectively. The width of the cylinder and the plate were chosen to be the same at 28 mm. Measurements of shedding frequency and pressures on the surface of the cylinder were obtained. The results indicate that the Strouhal number based on D, the side length of the square cylinder, has a strong peak at θ = 12 deg. After that, it decreases and remains nearly constant in the range from 50 to 105 deg. Two weaker peaks have also been observed at θ = 112 and 162 deg. The positions of flow attachments, separations, and reattachments on the square cylinder due to the attached plate and the inclination of the body have been clearly obtained from the pressure distributions on the square cylinder and from the flow visualization photographs. Also, drag and lift coefficients of the square cylinder are calculated from the pressure distributions. Drag coefficient of the square cylinder has minimum and maximum values at approximately θ = 20 and 80 deg, respectively, whereas the lift coefficient has a minimum and a maximum at approximately θ = 110 and 150 deg, depending on the plate position. The reducing effects of the plate on the drag and lift forces are discussed.

The passive flow control around a truck-trailer model / Bir kamyon römork modeli etrafındaki pasif akış kontrolü

In this study the aerodynamic characteristics of 1/32 scale truck and trailer model were examined in a wind tunnel. The acting drag force to model truck and trailer combination is calculated and aerodynamic drag coefficient is determined. The wind tunnel tests were carried out in the range of 160 000 - 449 000 Reynolds numbers. In order to improve the aerodynamics structure of truck- trailer, one spoiler, one passive air channel and three different redirector is produced in three dimensional printer. These aerodynamic parts respectively added to base truck-trailer model and obtaining aerodynamic improvement rates compared. According to wind tunnel test results, the aerodynamic improvement rates are respectively 15,62 %, 18,80 %, 23,58 % and 21,54 %. The lowest drag coefficient was determined as 0,588 on model-3 of truck-trailer model. Ozet: Bu calismada, 1/32 olcekli kamyon ve treyler modeli aerodinamik ozellikleri bir ruzgar tunelinde incelenmistir. Model kamyon ve treyler kombinasyonu hareket surtunme kuvveti hesaplanir ve aerodinamik surtunme katsayisi belirlenir. 449 000 Reynolds sayilari - ruzgar tuneli testleri 160 000 araliginda gerceklestirilmistir. KAMYON romork, tek spoiler, tek pasif hava kanali ve uc farkli yonlendiricisi aerodinamik yapisini iyilestirmek amaciyla uc boyutlu yazicidan uretilmektedir. Bu aerodinamik parcalar sirasiyla taban kamyon romork modeline eklenmis ve elde aerodinamik iyilestirme oranlari karsilastirildi. Ruzgar tuneli testi sonuclarina gore, aerodinamik iyilestirme oranlari sirasiyla 15,62,% 18,80,% 23,58 ve% 21,54% bulunmaktadir. Dusuk surtunme katsayisi modeli-3 kamyon romork model uzerinde 0,588 olarak belirlendi.