Flow characteristics of diamond and lambda wings at different flight conditions

TEZ7583Tez (Doktora) -- Çukurova Üniversitesi, Adana, 2009.Kaynakça (s.120-125) var.xiii, 132 s. : rnk.res. ; 29 cm.The aim of this study is to investigate the time-averaged flow structure around a nonslender diamond and lambda wing using a laser based 3-dimessional Particle Image Velocimetry (PIV) technique. The flow structure in close region of the stationary diamond wing surface and formation of the vortex breakdown were studied by varying the yaw angle of the wing within the range of 0°???15°for the angle of attack of ?=7° and 10°. Secondly, the flow structure in the near-surface and other crosssections of the wing and formation of the vortex breakdown were investigated by varying the angle of attack of the wing within the range of 7o???17o. Finally, a lambda wing is subjected to small-amplitude perturbations over a range of periods to simulate leading-edge vortex control concepts. Perturbations near the inherent frequency of the predominantly unsteady flow event on the stationary wing yield substantial changes of the near surface flow structure. Experimental analyses are composed of time-average patterns of streamlines, contours of vorticity distributions, Reynolds stress correlations, transverse and streamwise velocity components, distribution of fluctuating velocities and turbulent kinetic energyBu çalışmada, 3 boyutlu parçacık görüntülemeli hız ölçme tekniği (PIV) kullanılarak düşük süpürme açısına sahip elmas ve lambda kanat üzerindeki ortalama akış yapısı incelenmiştir. Elmas kanat yüzeyine yakın bölgede akış yapısı ve girdap çökmesinin oluşumu hücum açısı ?=7° ve 10° değeri için kanatların sapma açısı 0°???15° aralığında değiştirilerek çalışılmıştır. İkinci olarak, lambda kanat için deneyler üstten ve arkadan görünüş düzlemlerinde gerçekleştirilmiştir. Kanat yüzeyine yakın bölgede ve diğer kesitlerde akış yapısı ve girdap çökmesinin oluşumu kanat hücum açıları 0°???17° aralığında değiştirilerek incelenmiştir. Son olarak, kanat uç girdap kontrol kavramlarını benzeştirmek için, lambda kanat birkaç farklı periyotta küçük salınıma tabi tutulmuştur. Sabit kanat üzerinde çoğunlukla daimi olmayan akış yapısının doğal frekansına yakın değerde kanata salınım hareketi verilmesi halinde yüzeye yakın bölgede ve akış yapısında temel değişiklikler meydana gelmektedir. Deneysel analizler; zaman-ortalama eşdeğer akım çizgileri, girdap eğrileri dağılım konturları, Reynolds stres korelasyonları, akış yönündeki u ve akışa dik yöndeki v hız bileşenleri, çalkantı hız dağılımları ve türbülans kinetik enerjisi gibi akış karakteristiklerinden meydana gelmektedir.Bu çalışma Ç.Ü. Bilimsel Araştırma Projeleri Birimi Tarafından Desteklenmiştir. Proje No:MMF2007D13 TÜBİTAK 105M22

Investigation of Effect of Boundary Layer on Flow Structure Around a Cylinder with a Strip

In this study, the flow characteristic of the circular cylinder was placed vertically in channel which has dimensions as 8000 mm, 1000 mm, 750 mm, lenght, width and height repectively, was investigated. The cylinder was located in boundary layer with a diameter of 60 mm (D) and a elastic stripwhich has a 1400 N/mm2 modulus of elasticity vinyl PVC transperent film was attached behind the cylinder. Lenght of the strip (L) was 240 mm L/D=4. The Reynolds number was fixed at Re=7500. The time-averaged and instantaneous velocity vector maps, vorticity contours, Reynold shear and normal stresses, turbulent kinetic energy and frequency of shedding were obtained using the particle image velocimetry (PIV) technique. It was found that the elastic plate which exists behind the cylinder has a slight influence on the flow structure of the wake-boundary layer interaction. Values of turbulent kinetic energy, streamwise Reynold stress, transverse Reynold stresses were decreased by attaching strip

Comparison of Flow Structures in the Downstream Region of a Cylinder with Flexible Strip

The present study investigates the details of flow structure to downstream of a circular cylinder mounted on a flat surface, in successive plan-view plane both in the boundary layer and up level region. The behavior of the flow in the wake of the bare cylinder and attached a flexible strip which has a 1400 N/mm2 modulus of elasticity vinyl PVC transperent film. The length of strip 240 mm (L/D=4) is investigated using Particle Image Velocimetry (PIV) technique for Reynolds numbers based on the cylinder diameter of 2500. The flow data downstream of the cylinder are presented using time-averaged velocity vector map, Vavg, streamline patterns, ψavg, vorticity contours, ωavg, and Reynolds stress correlations, u’u’ avg, v’v’ avg, u’v’ avg and rms velocity values. The locations of the peak values of Reynolds stress correlations and other data are also presented in both bare cylinder and attached body in order to determine the regions under high fluctuations. Another L/D ratios will be investigated in other experiments

Investigation of Flow Structure Around a Cylinder with a Strip by Effect of Boundary Layer

In this study, the flow characteristic of the circular cylinder was placed vertically in channel which has dimensions as 8000 mm, 1000 mm, 750 mm, lenght, width and height repectively, was investigated. The cylinder was located in boundary layer with a diameter of 60 mm (D) and a elastic stripwhich has a 1400 N/mm2 modulus of elasticity vinyl PVC transperent film was attached behind the cylinder. Lenght of the strip (L) was 240 mm L/D=4. The Reynolds number was fixed at Re=7500. The time-averaged and instantaneous velocity vector maps, vorticity contours, Reynold shear and normal stresses, turbulent kinetic energy and frequency of shedding were obtained using the particle image velocimetry (PIV) technique. It was found that the elastic plate which exists behind the cylinder has a slight influence on the flow structure of the wake-boundary layer interaction. Values of turbulent kinetic energy, streamwise Reynold stress, transverse Reynold stresses were decreased by attaching strip

Effects of Flexible Splitter Plate in the Wake of a Cylindrical Body

In the wake of the bluff bodies rigid splitter plates are known to control vortex shedding. In this study, the problem of flexible splitter plate in the wake of circular cylinder was investigated using Particle Image Velocimetry (PIV) experimentally. In this case; the splitter plate which has a certain amount of modulus of elasticity freely deforms along its length because of the fluid forces on plate. The diameter of cylinder, D was 60 mm while the Reynolds number based on the cylinder diameter is kept constant as 2500, the characteristics length of the control element, L was tested for four different cases that the values of L/D were 0, 1.25, 2.25, 2.5 in the investigation. As a consequence, turbulent kinetic energy, TKE, velocity vector field , vortex, Reynolds stress , root mean square of streamwise and transverse velocities, / U, / U were analyzed. It is found that the variable parameter of L/D affects the flow structures and also noted that it decreased maximum level of all characteristic values

Flow measurement around a cylindrical body by attaching flexible plate: A PIV approach

In this study, flow structures and downstream wake behind a flexible splitter plate attached to a circular cylinder have been qualitatively and quantitatively investigated at three different Reynolds numbers of 2500, 5000 and 7500. The Particle Image Velocimetry (PIV) technique was implemented to examine the flow field downstream of the bluff body in deep water. Laser sheet illuminated the region 5 mm below the top of the cylinder. All results were compared with a bare cylinder case to analyze differences in flow characteristics. Time-averaged velocity vector field , vorticity contours , turbulent kinetic energy, TKE, rms of streamwise, u(rms), transverse, v(rms), velocity components were acquired and also frequency, f of vortex shedding was carried out using single point spectral analysis from PIV data to indicate flow structures. It was observed that the flexible splitter plate had a considerable effect on vortex shedding and fluctuations were prominently weakened by the use of control material

Comparison of Flow Structures in the Downstream Region of a Cylinder with Flexible Strip

The present study investigates the details of flow structure to downstream of a circular cylinder mounted on a flat surface, in successive plan-view plane both in the boundary layer and up level region. The behavior of the flow in the wake of the bare cylinder and attached a flexible strip which has a 1400 N/mm2 modulus of elasticity vinyl PVC transperent film. The length of strip 240 mm (L/D=4) is investigated using Particle Image Velocimetry (PIV) technique for Reynolds numbers based on the cylinder diameter of 2500. The flow data downstream of the cylinder are presented using time-averaged velocity vector map, Vavg, streamline patterns, ψavg, vorticity contours, ωavg, and Reynolds stress correlations, u’u’ avg, v’v’ avg, u’v’ avg and rms velocity values. The locations of the peak values of Reynolds stress correlations and other data are also presented in both bare cylinder and attached body in order to determine the regions under high fluctuations. Another L/D ratios will be investigated in other experiments

Effects of flexible plate attached to the rear of the cylinder on flow structure

In this experimental study, the flow structure in the wake flow region was investigated with the Particle image velocimetry technique (PIV) by attaching elastic plates at different lengths behind the cylinder. The flow structure occurred at the wake flow region altered depending on the length of the flexible matter. In this experiment, the strips with the lengths of 75, 90, 120, 135 and 180 mm were used to control instabilities. Diameter of the cylinder (D) is 60 mm and the water height (h(w)) is 600 mm. Reynolds number was kept constant as 5000 based on cylinder diameter. The images were captured at mid-height of the cylinder (h(m)) which is 250 mm. As a result of experimental studies, attached flexible strip suppressed vortex shedding occurred in the behind of the cylinder and it is observed that effect of the length flexible of the strip is pretty much. Maximum level of flow characteristics such as Reynolds stress, fluctuation velocities and turbulent kinetic energy were decreased with flexible splitter plate and shifted through the downstream region