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Application and Selection
Published in Béla G. Lipták, Flow Measurement, 2020
The two main limitations are line size and Reynolds number. The frequency of fluid oscillation drops off as the line size increases. For this reason meters in excess of 8 to 12 in. (200 to 300 mm) diameter are not very practical. The other limitation is that vortices form only at Reynolds numbers exceeding 10,000, and therefore this meter is not usable under that limit. Vortex shedding meters are gaining increasing acceptance and are used as a general-purpose, low-cost alternative to the orifice plate and dp transmitter, but they are also used for many demanding applications in the chemical industry.
Instrumentation and Controls
Published in Siddhartha Mukherjee, Process Engineering and Plant Design, 2021
Vortex flowmeters work on the principle of vortex shedding. When a non-streamlined obstruction, called the “shredder,” is placed in between a flowing fluid, vortex formation occurs. As the fluid flows, it is divided into two paths by the shredder. The high-velocity fluid parcels flow past the low-velocity parcels in the vicinity of the element to form a shear layer. After a certain length of travel, the shear layer breaks down into well-defined vortices [5].
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
The basic differential equations also may be nondimensionalized to obtain dimensionless groups. Dynamic similarity is ensured when two flows are governed by the same differential equations with the same dimensionless coefficient values in the equations and boundary conditions. Strouhal number St is a frequency parameter that arises from boundary conditions for external flow with vortex shedding.
A New Method for the Simulation of High Reynolds Number Effects on Cooling Tower Models in Wind Tunnels
Published in Structural Engineering International, 2023
Xiao-Xiang Cheng, Lin Zhao, Yaojun Ge, Gang Wu
To avoid the end effects, the 8th section with a full-scale height 151.42 m, which was closest to the throat part in the middle of the cooling tower model (see Fig. 3b), was chosen as the characteristic section of the model, and the mean and the fluctuating wind pressure distributions obtained from that section are shown in Fig. 5. According to Fig. 5b, most fluctuating wind pressure distribution patterns basically are slightly descending slopes with big obtuse crests in the circumferential range [35°, 130°] (the second zone marked in Fig. 5b). The reason that big obtuse crests exist in the second zone of the fluctuating wind pressure distributions is that vortices are formed and separated in that region.19 The physical phenomenon of vortex shedding has been defined in Ref. [12] as alternating vortex shedding from the cylinder and a clear “vortex trail” formed downstream. Obviously, vortex shedding can cause strong turbulence in the position where it is produced, leading to magnified pressure fluctuations on the surface of a bluff body near that position.
Transient vortex shedding behaviour of non-reacting flow over V-gutter bluff bodies with a central slit
Published in International Journal of Ambient Energy, 2022
K. George Luckachan, K. Raja Sekar, A. R. Srikrishnan, R. Kannan
The non-reacting fluid flow field over the V-gutter bluff body was analysed for 30° and 60°. To examine the wake-manipulation potential of central slits, the configuration was analysed for four slit dimensions: 1, 0.75, 0.5, and 0.25 mm. The fluid flow velocity at the inlet was maintained at 100 m/s. The main thrust of this work is on understanding the impact of mass flux entering through a central slit of different dimensions present in the V-gutter bluff body on the spatial spreading and shedding dynamics of the vortices downstream. The analysis has been performed based on the streamline distribution extracted for the different time intervals of the single shedding vortex cycle, in addition to the temporal and spatial variations of fluid flow parameters, such as streamwise velocity, static pressure, stagnation pressure, turbulent kinetic energy, and shedding frequency of the vortexes. Strouhal number, as defined below, is used to quantify the vortex shedding frequency. In (5) f is the frequency of oscillation and is estimated by calculating the period of one complete cycle. h represents the characteristic length and U, the freestream velocity.
Effect of multiple control cylinders on the transient flow behind a translationally and rotationally started cylinder
Published in Ships and Offshore Structures, 2021
Jialiang Zhou, Guoyong Jin, Tiangui Ye, Huahua Zhou, Boyi Zhang
Vortex shedding is known to cause an unsteady pulsating pressure on cylinder, causing vibration and fatigue damage. Studies have been found that cross-sectional shape, surface roughness and proximity to other bodies are factors affecting the transient flow around a bluff body. The separation of boundary layer and the formation and shedding of vortexes are affected by the cross-section shape of the cylinder (Parkinson and Dicker 1971; Parkinson and Sullivan 1979; Bokaian and Geoola 1984). The intensity of the vortex can be selectively enhanced or weakened by changing the surface roughness (Zdravkovich 1997; Hover et al. 2001; Chang et al. 2011; Quadrante and Nishi 2014; Vinod et al. 2018). Many experimental and theoretical methods have been used to investigate transient flows between multiple same cylinders arranged in different ways, and the number of cylinders is two (Assi et al. 2006; Harichandan and Arnab 2010; Okajima et al. 2007; Prasanth and Sanjay 2009), three (Bao et al. 2010) or four (Liu et al. 2008; Yu 2008). The flow around the main cylinder controlled by small cylinders is also concerned (Rahmanian et al. 2012; Wu et al. 2012a; Wu et al. 2012b; Zhao et al. 2005).