AKIŞ KAYNAKLI TİTREŞİMDE İKİ ARDIŞIK SİLİNDİRDEN ELDE EDİLEN GÜCÜN PARAMETRİK OLARAK İNCELENMESİ

Abstract

Enine akışlarda silindirler özellikle çevri kaynaklı titreşim ve hızlı artış (galloping) adı verilen bölgeden oluşan akış kaynaklı titreşim sergilerler. Hızlı artış bölgesinde, osilatörlerde mekanik enerjiye çevrilen hidrokinetik enerji akışın hızı ve Re sayısıyla artar. Türbülanslı serbest su yüzeyli kanalda yapılan deneylerde arkalı önlü bulunan ardışık silindirlerin hareketi 30,000<Re <120,000 aralığında farklı parametreler için incelenmiş ve özellikle hızlı artış bölgesindeki 0.9<U<1.3 m/s akış hızı aralığında elde edilen güçte lokal artış ve düşüşler tespit edilmiştir. Bu çalışmanın amacı bu artış/azalışların sebeplerini açıklamaktır. Bunun için tüm deneyler incelenerek bu ani değişim olan parametreler (Kütle oranı, yay sabiti, hız oranı vb. gibi) belirlenerek bir matris oluşturulmuştur. Hem öndeki silindir hem de arkasındaki silindir için elde edilen güç, genlik oranı, frekans oranları ve zamana bağlı hareket grafikleri oluşturulmuştur. Yüksek çözünürlüklü kamera ile görüntüleme tekniği kullanılmış ve elde edilen sonuçlar tartışılmıştır. Bu değişimlerin ana sebebinin iki silindir arasındaki etkileşim olduğu tespit edilmiştir. Bu değişimlerde hızlı artış dengesizliği kaybolmakta ve elde edilen güçte ve genlikte ani düşüşler oluşmaktadır.     

Keywords

• Çevri kaynaklı titreşim,hızlı artış dengesizliği,güç

Parametric Investigation of Harnessed Power of Two Tandem Cylinders in Flow Induced Vibration

Abstract

In transverse flow, cylinders respond in FIV (Flow Induced Vibrations); particularly VIV (Vortex Induced Vibrations) and galloping. Typically, in the galloping region, the hydrokinetic power converted to mechanical in the oscillators increases with increasing flow velocity and Reynolds number. Flow Induced Vibrations (FIVs) of two tandem, rigid and circular cylinder with end-springs are studied for  30,000<Re <120,000 with different damping, mass ratio and stiffness as parameters in the Low Turbulence Free Surface Water (LTFSW) Channel of the Marine Renewable Energy Laboratory (MRELab). Typical local drops and jumps in harnessed power were observed in the velocity range of 0.9<U<1.3 m/s within the galloping region. The main objective of this paper is to explain the reason for the presence of these drops and jumps. To achieve this objective, the points of changing in harnessed power in an extensive set of data with spacing, damping, stiffness, and flow velocity as parameters are identified. For both up and downstream cylinders, the harnessed power, amplitude-ratio, frequency-ratio and time history graphs are obtained to define the reason of these drop/jumps. Visualization with high-resolution camera has been used and the assumption which may affect the phenomena were studied and presented. As a conclusion, there is a big interaction between cylinders. Galloping instability disappears at this drops and harnessed power decreases sharply and amplitude as well.

Keywords

• Vortex Induced Vibrations,galloping instability,harnessed power

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