High Reynolds Number Oscillating Flow by Cylinders

Abstract

In order to determine the added mass, drag and lift coefficients of a smooth cylinder at various distances from a plane boundary, the forced cylinder oscillation tests at high Reynolds number 105 to 106 and the wave force tests at moderate Reynolds number 101* to 105 have been carried out at the Wave Research Facility at Oregon State University. It is found that the drag, lift and added mass coefficients are all strongly Reynolds number dependent. The effect of the near by plane boundary is to increase all of the force coefficients two to four times as compared to the free stream flow values. This is a most important factor to be aware of for design purposes.

Fluid–structure interactions of a circular cylinder in a stratified fluid

“…The drag coefficient is considered constant and equal to 1, which is the value for a static cylinder and for Reynolds numbers between and (von Wieselsberger 1921; Blevins 1984). The drag coefficient varies when the cylinder oscillates (Khalak & Williamson 1996, 1999) but its mean value is found to remain not far from 1, as observed experimentally (Bishop & Hassan 1964; Yamamoto & Nath 1976; Bearman et al. 1985), and numerically for low Reynolds numbers (Guilmineau & Queutey 2002; Zheng & Zhang 2008; Placzek, Sigrist & Hamdouni 2009).…”

Nanocomposite Thin Films for Solar Energy Conversion

“…Recently, United Solar Ovonic Corporation in the USA has shown an initial active-area efficiency over 15% using an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure [48], which is higher than the champion cell with an a-Si:H/a-SiGe:H/a-SiGe:H triple-junction structure [24]. In Japan, Canon and Kaneka Corporation have demonstrated large-area a-Si:H/nc-Si:H/nc-Si:H triple-junction and a-Si:H/nc-Si:H double-junction modules with initial aperture-area efficiency over 13% [49,50]. It appears that nc-Si:H based solar cells will become an important technology in thin film solar cell manufacturing.…”

Quadratically damped oscillators with non-linear restoring force

“…To model the phenomenon of damping, specially at higher velocities it is necessary to introduce a quadratic non-linearity and the corresponding term is in general of the form -sgn( ẋ) ẋ2 [16,20]. In recent times, such systems have gained much attention because of vast range of applications in engineering, specially in the problems involving hydrological drag and aerodynamics [22,14].…”

“…The first term is the inertial force and the second term gives the drag force on the object. In [22], Yamamoto and Nath studied the oscillatory flows around a cylinder and they determined the drag force as being directly proportional to the signed velocity squared where the coefficients were determined experimentally. In [14], Madison used a quadratic damping force caused by fluid friction to study isenthalpic oscillations in a saturated two-phase fluid.…”