Extensive research has been conducted on the flow control of bluff bodies to address negative imp... more Extensive research has been conducted on the flow control of bluff bodies to address negative impacts such as vibration, acoustic noise, and resonance caused by wake flow. The circular cylinder, due to its simple geometry, is frequently studied as a bluff body and is utilized in various engineering applications including cooling system pipes, electrical pylons, industrial flue systems, overpasses, satellite antennas, electrical cables, and marine drilling platforms. In this investigation, a perforated splitter plate was strategically positioned at different downstream locations to manage the wake flow of the cylinder. The experiments were conducted in a sophisticated, closed-loop water channel at the Fluid Mechanics Laboratory of Cukurova University, providing a controlled environment for precise flow analysis. To measure the instantaneous velocity vector field in the wake region of the cylinder at a Reynolds number (Re) of 5000 (based on the cylinder diameter, D), particle image velocimetry (PIV) was employed. Three different permeability values for the splitter plate (e=0.30, 0.50, 0.70) and three lengths (ls*=1, ls*=2, ls*=3) were tested, maintaining a constant gap (G/D=1) between the splitter plate's leading edge and the cylinder surface. The splitter plates were aligned with the flow direction (ϴ=0°). The permeable separator plates minimize the interaction of boundary layers formed around the cylinder, enhancing their effect in downstream regions where shear layer interaction is more pronounced. Consequently, this results in reduced fluctuations and a more stabilized wake flow downstream of the cylinder.
Titreşim ve akustik gürültü veya rezonans gibi iz akışının olumsuz etkilerini ortadan kaldırmak i... more Titreşim ve akustik gürültü veya rezonans gibi iz akışının olumsuz etkilerini ortadan kaldırmak için batık gövdelerin akış kontrolü kapsamlı bir şekilde incelenmiştir. Isı eşanjör boruları, enerji nakil hatları, baca bacaları, köprüler, radyo teleskoplar, enerji hatları, açık deniz sondaj kuleleri vb. birçok mühendislik uygulamalarında kullanılan, silindir gövdenin iz akışını kontrol etmek için çeşitli art iz konumuna geçirgen bir ayırıcı plaka yerleştirilmiştir. Tüm deneyler, Çukurova Üniversitesi Akışkanlar Mekaniği Laboratuvarı'ndaki büyük ölçekli bir kapalı devre su kanalında, PIV kullanılarak, silindir çapına (D) bağlı olarak Re=5000'de gerçekleştirilmiştir. Dört farklı ayırıcı plaka açısı (θ =0°; 15°; 30°; 45°), üç farklı gözeneklilik (ε=0.30; 0.50; 0.70) incelenmiştir. Ayırıcı plakaların geçirgenliği (ε) plaka üzerindeki toplam delik alanının, plaka toplam alanına oranı olarak belirlenmiştir. Tüm değişkenler silindir çapına (D) bölünerek boyutsuzlaştırılmış ve * indisi ile gösterilmiştir. Ayırıcı plaka uzunluğu da deney sırasında ls*=1 olarak sabit tutulmuştur. Ayırıcı plaka ile silindir arasındaki mesafe, ayırıcı plakanın art iz eksenine göre açısı değişken olduğundan sabit değildir. Bunun üstesinden gelebilmek için silindir ile ayırıcı plaka dönme ekseni arasındaki mesafe ele alınmış ve ** indisi ile gösterilmiştir. Ayırıcı plaka orta noktası ile silindir (lg**) arasındaki boşluk, deneyler boyunca lg**=1.5 olarak sabit tutulmuştur. Plakalar döndürüldüğünde akışa paralel kesit azalmakta, bu da sınır tabakalar arasındaki etkileşimi artırmaktadır. Geçirgen ayırıcı plakalar, silindir etrafındaki akışta oluşan sınır tabakaların etkileşimini engellediğinden, sınır katmanların etkileşiminin arttığı ardıl bölgelerde geçirgen ayırıcı plakaların etkisi artmaktadır. Böylece dalgalanmalar azalmakta ve silindirin akış aşağısında daha kararlı bir iz akışı oluşmaktadır. Ayırıcı plaka açısının artmasıyla çevrinti oluşumunun geciktiği gözlenmiştir. Bu çalışmada ayırıcı plaka açısının etkisi ve plaka geçirgenliğinin etkisi net bir şekilde gözlemlenmiştir.
Flow control of bluff bodies has been studied extensively to eliminate adverse effects of wake fl... more Flow control of bluff bodies has been studied extensively to eliminate adverse effects of wake flow such as vibration and acoustic noise or resonance. The circular cylinder has been studied as the bluff body since it is basic geometry and has been used in engineering applications such as heat exchanger tubes, power transmission lines, chimney stacks, bridges, radio telescopes, power lines, offshore drilling rigs etc. In this study, a permeable splitter plate was located at various downstream locations to control the wake flow of the cylinder. All experiments were carried out in a large-scale closed-loop water channel in the Fluid Mechanics Laboratory at Cukurova University. PIV was used to measure the instantaneous velocity vector field in the wake region of the cylinder at Reynolds number Re=5000, which is based on the cylinder diameter, D. Four different splitter plate angle values (θ =0°; 15°; 30°; 45°), three different porosity values (ε=0.30; 0.50; 0.70) were investigated. The porosity (ε) of the separator plates is defined as the ratio of the total hole area to the plate surface area. All lengths are nondimensionalized by dividing by the cylinder diameter and shown with the * index. The splitter plate length kept to constant during the experiment as ls*=1. The distance between the leading edge of the splitter plate and the cylinder (lg*) is variable due to the rotation of the separator plate at certain angles in the flow direction. To overcome this, the distance between the splitter plate rotation axis and the cylinder was taken as a parameter and shown with the **. The gap between splitter plate midpoint and cylinder (lg**) kept to constant during the experiments as lg**=1.5. When the plates are rotated, the cross-section parallel to the flow decreases, which increases the interaction between the boundary layers. Since the permeable separator plates prevent the interaction of the boundary layers formed in the flow around the cylinder, the effect of the permeable separator plates increases in the downstream regions where the interaction of the boundary layers increases. Thus, the fluctuations are reduced, and a more stabilized trail flow occurs downstream of the cylinder. It was observed that the vortex formation was delayed with the increase of the separator plate angle. In this study, the effect of the separator plate angle and the effect of the plate permeability were clearly observed.
Hydroforming is a technique in which sheet or tube shaped metalmaterials is formed by the use of ... more Hydroforming is a technique in which sheet or tube shaped metalmaterials is formed by the use of fluid pressure (water,oil, viscous polymericmaterials etc.) in a closed die. Since 1890's some variety of this technique has beenused in industry in somewaybut the real
progress of this technique is proved by German and Japan scientists after theWorld War II. By the use of this technique,advantages like high forminglimits, lower thinning and manufacturing ability of complex geometries make possible tomanufacture lighter and rigid designs. Especially for the last 15 yearsmany scientists have begun to make their studies in this field and by these studieshydroforming becameindispensable technique in
automotive industry.The purpose of this paper is that to explain the hydroforming
terminology, basic types of hydroforming
Present experimental investigation aims to reduce the shedding of vortex in the near wake region ... more Present experimental investigation aims to reduce the shedding of vortex in the near wake region of a circular cylinder using a perforated splitter plate. Perforated plates were placed in the wake region of the cylinder and aligned with the streamwise direction. The length of the plates was equal to the diameter of the cylinder. Different plate porosities and locations were examined and obtained results were compared to the baseline cylinder. Flow measurements downstream of the cylinder were performed in a water channel by employing a particle image velocimetry technique (PIV) at a Reynolds number of Re=5×103. It is observed that the effect of the porosity on the flow characteristics of the cylinder depends on the location of the plate. The strength of shear layers and flow fluctuations in the near wake region of the cylinder are considerably diminished by the perforated splitter plate. It is found that the porosity of ε=0.3 is the most effective control element for gap ratio of G/D=0.5. On the other hand, proper gap ratio is determined as G/D=2 for porosity of ε=0.7. It is concluded in the present study that the perforated splitter plate could be used as alternative passive flow control technique in order to reduce vortex shedding of the cylinder.
Extensive research has been conducted on the flow control of bluff bodies to address negative imp... more Extensive research has been conducted on the flow control of bluff bodies to address negative impacts such as vibration, acoustic noise, and resonance caused by wake flow. The circular cylinder, due to its simple geometry, is frequently studied as a bluff body and is utilized in various engineering applications including cooling system pipes, electrical pylons, industrial flue systems, overpasses, satellite antennas, electrical cables, and marine drilling platforms. In this investigation, a perforated splitter plate was strategically positioned at different downstream locations to manage the wake flow of the cylinder. The experiments were conducted in a sophisticated, closed-loop water channel at the Fluid Mechanics Laboratory of Cukurova University, providing a controlled environment for precise flow analysis. To measure the instantaneous velocity vector field in the wake region of the cylinder at a Reynolds number (Re) of 5000 (based on the cylinder diameter, D), particle image velocimetry (PIV) was employed. Three different permeability values for the splitter plate (e=0.30, 0.50, 0.70) and three lengths (ls*=1, ls*=2, ls*=3) were tested, maintaining a constant gap (G/D=1) between the splitter plate's leading edge and the cylinder surface. The splitter plates were aligned with the flow direction (ϴ=0°). The permeable separator plates minimize the interaction of boundary layers formed around the cylinder, enhancing their effect in downstream regions where shear layer interaction is more pronounced. Consequently, this results in reduced fluctuations and a more stabilized wake flow downstream of the cylinder.
Titreşim ve akustik gürültü veya rezonans gibi iz akışının olumsuz etkilerini ortadan kaldırmak i... more Titreşim ve akustik gürültü veya rezonans gibi iz akışının olumsuz etkilerini ortadan kaldırmak için batık gövdelerin akış kontrolü kapsamlı bir şekilde incelenmiştir. Isı eşanjör boruları, enerji nakil hatları, baca bacaları, köprüler, radyo teleskoplar, enerji hatları, açık deniz sondaj kuleleri vb. birçok mühendislik uygulamalarında kullanılan, silindir gövdenin iz akışını kontrol etmek için çeşitli art iz konumuna geçirgen bir ayırıcı plaka yerleştirilmiştir. Tüm deneyler, Çukurova Üniversitesi Akışkanlar Mekaniği Laboratuvarı'ndaki büyük ölçekli bir kapalı devre su kanalında, PIV kullanılarak, silindir çapına (D) bağlı olarak Re=5000'de gerçekleştirilmiştir. Dört farklı ayırıcı plaka açısı (θ =0°; 15°; 30°; 45°), üç farklı gözeneklilik (ε=0.30; 0.50; 0.70) incelenmiştir. Ayırıcı plakaların geçirgenliği (ε) plaka üzerindeki toplam delik alanının, plaka toplam alanına oranı olarak belirlenmiştir. Tüm değişkenler silindir çapına (D) bölünerek boyutsuzlaştırılmış ve * indisi ile gösterilmiştir. Ayırıcı plaka uzunluğu da deney sırasında ls*=1 olarak sabit tutulmuştur. Ayırıcı plaka ile silindir arasındaki mesafe, ayırıcı plakanın art iz eksenine göre açısı değişken olduğundan sabit değildir. Bunun üstesinden gelebilmek için silindir ile ayırıcı plaka dönme ekseni arasındaki mesafe ele alınmış ve ** indisi ile gösterilmiştir. Ayırıcı plaka orta noktası ile silindir (lg**) arasındaki boşluk, deneyler boyunca lg**=1.5 olarak sabit tutulmuştur. Plakalar döndürüldüğünde akışa paralel kesit azalmakta, bu da sınır tabakalar arasındaki etkileşimi artırmaktadır. Geçirgen ayırıcı plakalar, silindir etrafındaki akışta oluşan sınır tabakaların etkileşimini engellediğinden, sınır katmanların etkileşiminin arttığı ardıl bölgelerde geçirgen ayırıcı plakaların etkisi artmaktadır. Böylece dalgalanmalar azalmakta ve silindirin akış aşağısında daha kararlı bir iz akışı oluşmaktadır. Ayırıcı plaka açısının artmasıyla çevrinti oluşumunun geciktiği gözlenmiştir. Bu çalışmada ayırıcı plaka açısının etkisi ve plaka geçirgenliğinin etkisi net bir şekilde gözlemlenmiştir.
Flow control of bluff bodies has been studied extensively to eliminate adverse effects of wake fl... more Flow control of bluff bodies has been studied extensively to eliminate adverse effects of wake flow such as vibration and acoustic noise or resonance. The circular cylinder has been studied as the bluff body since it is basic geometry and has been used in engineering applications such as heat exchanger tubes, power transmission lines, chimney stacks, bridges, radio telescopes, power lines, offshore drilling rigs etc. In this study, a permeable splitter plate was located at various downstream locations to control the wake flow of the cylinder. All experiments were carried out in a large-scale closed-loop water channel in the Fluid Mechanics Laboratory at Cukurova University. PIV was used to measure the instantaneous velocity vector field in the wake region of the cylinder at Reynolds number Re=5000, which is based on the cylinder diameter, D. Four different splitter plate angle values (θ =0°; 15°; 30°; 45°), three different porosity values (ε=0.30; 0.50; 0.70) were investigated. The porosity (ε) of the separator plates is defined as the ratio of the total hole area to the plate surface area. All lengths are nondimensionalized by dividing by the cylinder diameter and shown with the * index. The splitter plate length kept to constant during the experiment as ls*=1. The distance between the leading edge of the splitter plate and the cylinder (lg*) is variable due to the rotation of the separator plate at certain angles in the flow direction. To overcome this, the distance between the splitter plate rotation axis and the cylinder was taken as a parameter and shown with the **. The gap between splitter plate midpoint and cylinder (lg**) kept to constant during the experiments as lg**=1.5. When the plates are rotated, the cross-section parallel to the flow decreases, which increases the interaction between the boundary layers. Since the permeable separator plates prevent the interaction of the boundary layers formed in the flow around the cylinder, the effect of the permeable separator plates increases in the downstream regions where the interaction of the boundary layers increases. Thus, the fluctuations are reduced, and a more stabilized trail flow occurs downstream of the cylinder. It was observed that the vortex formation was delayed with the increase of the separator plate angle. In this study, the effect of the separator plate angle and the effect of the plate permeability were clearly observed.
Hydroforming is a technique in which sheet or tube shaped metalmaterials is formed by the use of ... more Hydroforming is a technique in which sheet or tube shaped metalmaterials is formed by the use of fluid pressure (water,oil, viscous polymericmaterials etc.) in a closed die. Since 1890's some variety of this technique has beenused in industry in somewaybut the real
progress of this technique is proved by German and Japan scientists after theWorld War II. By the use of this technique,advantages like high forminglimits, lower thinning and manufacturing ability of complex geometries make possible tomanufacture lighter and rigid designs. Especially for the last 15 yearsmany scientists have begun to make their studies in this field and by these studieshydroforming becameindispensable technique in
automotive industry.The purpose of this paper is that to explain the hydroforming
terminology, basic types of hydroforming
Present experimental investigation aims to reduce the shedding of vortex in the near wake region ... more Present experimental investigation aims to reduce the shedding of vortex in the near wake region of a circular cylinder using a perforated splitter plate. Perforated plates were placed in the wake region of the cylinder and aligned with the streamwise direction. The length of the plates was equal to the diameter of the cylinder. Different plate porosities and locations were examined and obtained results were compared to the baseline cylinder. Flow measurements downstream of the cylinder were performed in a water channel by employing a particle image velocimetry technique (PIV) at a Reynolds number of Re=5×103. It is observed that the effect of the porosity on the flow characteristics of the cylinder depends on the location of the plate. The strength of shear layers and flow fluctuations in the near wake region of the cylinder are considerably diminished by the perforated splitter plate. It is found that the porosity of ε=0.3 is the most effective control element for gap ratio of G/D=0.5. On the other hand, proper gap ratio is determined as G/D=2 for porosity of ε=0.7. It is concluded in the present study that the perforated splitter plate could be used as alternative passive flow control technique in order to reduce vortex shedding of the cylinder.
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Papers by Serdar Sahin
progress of this technique is proved by German and Japan scientists after theWorld War II. By the use of this technique,advantages like high forminglimits, lower thinning and manufacturing ability of complex geometries make possible tomanufacture lighter and rigid designs. Especially for the last 15 yearsmany scientists have begun to make their studies in this field and by these studieshydroforming becameindispensable technique in
automotive industry.The purpose of this paper is that to explain the hydroforming
terminology, basic types of hydroforming
progress of this technique is proved by German and Japan scientists after theWorld War II. By the use of this technique,advantages like high forminglimits, lower thinning and manufacturing ability of complex geometries make possible tomanufacture lighter and rigid designs. Especially for the last 15 yearsmany scientists have begun to make their studies in this field and by these studieshydroforming becameindispensable technique in
automotive industry.The purpose of this paper is that to explain the hydroforming
terminology, basic types of hydroforming