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

• Main Author: Erinç Dobrucalı
• Format: Article
• Language: English
• Published: Bursa Uludag University 2018-04-01
• Series: Uludağ University Journal of The Faculty of Engineering
• Subjects: vortex induced vibrations; galloping instability; harnessed power; çevri kaynaklı titreşim; hızlı artış dengesizliği; güç
• Online Access: https://dergipark.org.tr/tr/pub/uumfd/issue/36268/377444
• ISSN: 2148-4147; 2148-4155

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.