scholarly journals Interactions between Two Deformable Droplets in Tandem Fixed in a Gas Flow Field of a Gas Well

2021 ◽  
Vol 11 (23) ◽  
pp. 11220
Author(s):  
Zhibin Wang ◽  
Tianli Sun ◽  
Zhongwei Yang ◽  
Guo Zhu ◽  
Hongyan Shi
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Drag Coefficient ◽  
Drag Force ◽  
High Reynolds Number ◽  
Droplet Breakup ◽  
Gas Well ◽  
Body Forces ◽  
Simulation Results ◽  
High Reynolds

Knowing the droplet-deformation conditions, the droplet-breakup conditions, and the drag force in the interaction between two droplets with a high Reynolds number is of importance for tracking droplet movement in the annular flow field of a gas well. The interactions between two droplets with a high Reynolds number in a tandem arrangement fixed in flowing gas was investigated. The volume of fluid (VOF) method was used to model the droplets’ surface structure. Two different body forces were exerted on both droplets to hold them suspended at a fixed location, which eliminated the effect of droplet acceleration or deceleration on the drag and decreased the amount of computation required. The exerted body forces were calculated using the Newton iteration procedure. The interactions between the two droplets were analyzed by comparison with the simulation results of a single isolated droplet. The effect of the separation distance on the drag force was investigated by changing the separation spacing. The simulation results showed that for droplets with a small separating space between them, the dynamics of the downstream droplet were influenced significantly by the upstream droplet. The drag coefficient of the downstream droplet decreased considerably to a small, even negative, value, especially for droplets with higher Weber numbers and smaller initial separating spaces between them, while the drag force of the upstream droplet was influenced only slightly. In addition, a formula for predicting the final drag coefficient of the downstream droplet was devised.

scholarly journals Numerical Investigation of the Flow around a Feather Shuttlecock with Rotation

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 28
Author(s):  
John Hart ◽  
Jonathan Potts
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Numerical Investigation ◽  
Computational Fluid Dynamic ◽  
High Reynolds Number ◽  
Fluid Dynamic ◽  
Flow Structures ◽  
Drag Forces ◽  
High Reynolds

This paper presents the first scale resolving computational fluid dynamic (CFD) investigation of a geometrically realistic feather shuttlecock with rotation at a high Reynolds number. Rotation was found to reduce the drag coefficient of the shuttlecock. However, the drag coefficient is shown to be independent of the Reynolds number for both rotating and statically fixed shuttlecocks. Particular attention is given to the influence of rotation on the development of flow structures. Rotation is shown to have a clear influence on the formation of flow structures particularly from the feather vanes, and aft of the shuttlecock base. This further raises concerns regarding wind tunnel studies that use traditional experimental sting mounts; typically inserted into this aft region, they have potential to compromise both flow structure and resultant drag forces. As CFD does not necessitate use of a sting with proper application, it has great potential for a detailed study and analysis of shuttlecocks.

Numerical Simulation of an Oscillating Cylinder at High Reynolds Number

2013 ◽  
Author(s):  
Simone Mandelli ◽  
Sara Muggiasca ◽  
Stefano Malavasi
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Flow Field ◽  
High Reynolds Number ◽  
Fluid Dynamic ◽  
Numerical Results ◽  
Experimental Results ◽  
Dynamic Conditions ◽  
High Reynolds ◽  
Lock In

In this work a numerical investigation of the main flow field characteristics around a free oscillating rigid circular cylinder immersed in a turbulent flow is proposed (Re ≈ 5 · 104). The cylinder is characterized by high value of mass ratio and mass damping (m* = 145; ξ = 0.6 ÷ 1.14 · 10−3; m*ξ = 0.1 ÷ 0.25). The numerical results are compared with experimental data obtained in the wind tunnel under very similar fluid dynamic conditions. There are few works in literature that consider both numerical and experimental results under these conditions. This is probably due to the experimental facilities limitations and the computational difficulties correlated to modeling the flow at high Reynolds number. A numerical URANS model was developed through a CFD commercial code using a k–ω SST turbulence model in a 3D domain with the aim of matching the experimental results in the last years in the Politecnico di Milano Wind Tunnel on a suspended oscillating cylinder. The numerical setup is characterized by the use of the DFBI-Morphing (Dynamic Fluid Body Interaction) model that allows reproducing the body motion in response to fluid forces treating the cylinder as a mass-damping-spring system by introducing spring and damping forces acting on it. A preliminary check of this numerical setup was provided by a benchmark case involving a simple case of fixed cylinder at the same Reynolds number, where the movements of the cylinder were disabled. The numerical results of this case have been compared with experimental and numerical results reported in literature in terms of Drag and Lift coefficients and Strouhal number at high Reynolds numbers (Re ≈ 5 · 104). After that benchmark, the full setup has been checked by considering specific fluid dynamic conditions out of the lock in region in which the oscillations of the cylinder are negligible. Finally two points of the cylinder steady state response curve in the lock in region were investigated. The numerical model gave good results in terms of amplitude response of the cylinder and aerodynamic forces in agreement with experimental results. The analysis of the numerical reconstruction of the flow field evolution are therefore considered to have more information on the vortex shedding mode especially in the transition region between 2S and 2P mode.

Grid sensitivity of flow field and noise of high-Reynolds-number jets computed by large-eddy simulation

2018 ◽  
Vol 17 (4-5) ◽  
pp. 399-424 ◽  
Author(s):  
Christophe Bogey
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Flow Field ◽  
High Reynolds Number ◽  
Mean Velocity ◽  
Laminar Jet ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Reynolds ◽  
Jet Axis

Three isothermal round jets at a Mach number of 0.9 and a diameter-based Reynolds number of 105 are computed by large-eddy simulation using four different meshes in order to investigate the grid sensitivity of the jet flow field and noise. The jets correspond to two initially fully laminar jets and one initially strongly disturbed jet considered in previous numerical studies. At the exit of a pipe nozzle of radius r0, they exhibit laminar boundary-layer mean-velocity profiles of thickness [Formula: see text] and [Formula: see text], respectively. For the third jet, a peak turbulence intensity close to 9% is also imposed by forcing the boundary layer in the nozzle. The grids contain up to one billion points, and, compared to the grids used in previous simulations, they are finer in the axial direction downstream of the nozzle and in the radial direction on the jet axis and in the outer region of the mixing layers. The main flow field and noise characteristics given by the simulations, including the mixing-layer thickness, the centerline mean velocity, the turbulence intensities on the nozzle lip line and the jet axis, spectra of velocity and far-field pressure obtained from the jet near field by solving the isentropic linearized Euler equations, are presented. With respect to those from previous studies, the results are very similar for the initially laminar jet with thick boundary layers, but they differ significantly for the initially laminar jet with thin boundary layers and for the initially disturbed jet. For the latter two jets, using a finer grid leads to a faster flow development, to higher turbulence intensities in the shear layers and at the end of the potential core, to stronger large-scale structures, and to the generation of more low-frequency noise. Moreover, very small mesh spacings appear to be necessary all along the jet mixing layers, and in particular during their early stages of growth, to properly capture the formation and dynamics of the flow coherent structures and thus obtain results in good agreement with measurements available for high-Reynolds-number jets.

scholarly journals Numerical modeling of flow around a heated cylinder with a rough surface

2020 ◽  
Vol 313 ◽  
pp. 00046
Author(s):  
Lenka Lausová ◽  
Vladimíra Michalcová ◽  
Ivan Kološ
Keyword(s):  
Reynolds Number ◽  
Numerical Modeling ◽  
Drag Coefficient ◽  
Numerical Solution ◽  
Rough Surface ◽  
High Reynolds Number ◽  
Pressure Coefficient ◽  
Flow Properties ◽  
Heated Cylinder ◽  
High Reynolds

The article deals with the numerical solution of the load of a heated chimney from wind effects. The paper examines flow around a heated cylinder with the rough surface in high Reynolds number regime. The results of drag coefficient, pressure coefficient and other related flow properties are compared with the calculations of the flow around the unheated cylinder.

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