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

Yıl 2018, Cilt: 23 Sayı: 1, 329 - 344, 24.04.2018

Erinç Dobrucalı

https://doi.org/10.17482/uumfd.377444

Öz

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.     

Anahtar Kelimeler

Çevri kaynaklı titreşim, hızlı artış dengesizliği, güç

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

Öz

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.

Anahtar Kelimeler

Vortex Induced Vibrations, galloping instability, harnessed power

Kaynakça

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