Viscous Flow Past a Circular Cylinder Below a Free Surface

2014 ◽  
Author(s):  
Benjamin Bouscasse ◽  
Andrea Colagrossi ◽  
Salvatore Marrone ◽  
Antonio Souto-Iglesias
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Mixing Processes ◽  
Surface Evolution ◽  
Flow Past ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Karman Vortex ◽  
Drag And Lift

Flow past a circular cylinder close to a free surface at low Reynolds and large Froude numbers is investigated numerically using the Smoothed Particle Hydrodynamics model. This meshless method allows for a non-diffusive computation of the free surface evolution, even while breaking and fragmentation may occur. The distance of the cylinder to the free surface, submergence, is varied in order to investigate the detached flow patterns dependence with this factor. Vorticity shed by the cylinder, vortex generation due to free surface breaking, mixing processes, and drag and lift coefficients behavior are discussed. It has been found that, for small submergences, the classical Von Karman vortex shedding from the cylinder does not take place. In turn, moderate vortex shedding occurs, departing not from the cylinder but from vorticity generated at the free surface. This shedding takes places simultaneously with the transport of free surface fluid elements into the bulk of the fluid. It has been also found that for even smaller depth ratios, a vorticity layer remains spatially localized between the cylinder and the free surface, and a stagnation recirculating area develops behind the cylinder. Results are compared with literature finding reasonable qualitatively agreement with experimental works conducted with similar geometrical configuration but larger Reynolds number.

High Froude Number Viscous Flow Past a Circular Cylinder

2015 ◽  
Author(s):  
Benjamin Bouscasse ◽  
Andrea Colagrossi ◽  
Salvatore Marrone ◽  
Antonio Souto-Iglesias
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Mixing Processes ◽  
Surface Evolution ◽  
Flow Past ◽  
Gap Ratio ◽  
Particle Hydrodynamics ◽  
Wake Instability ◽  
Smoothed Particle ◽  
Drag And Lift

Two-dimensional monophasic flow past a circular cylinder intersecting or close to a free surface at Reynolds 180 is numerically investigated using the Smoothed Particle Hydrodynamics (SPH) method. The wake behaviour for a range of conditions with Froude numbers between 0.3 and 2.0, a gap ratio of 0.55 and for a half-submerged cylinder are studied. The SPH technique allows for a non-diffusive computation of the free surface evolution, even while breaking and fragmentation may occur. Vorticity shed by the cylinder, vortex generation due to free surface breaking, mixing processes, and drag and lift coefficients behaviour are discussed. It has been found that, for certain Froude numbers and for the analysed submergence ratio, a vorticity layer remains spatially localized between the cylinder and the free surface and a large recirculating wake area develops, which eventually gets detached after several shedding cycles, being advected downstream, a previously unreported form of wake instability, to the authors’ knowledge. This behaviour is blocked when the cylinder is intersecting the free surface.

scholarly journals Simulation of flow past a sphere on a rough bed using smoothed particle hydrodynamics (SPH)

2021 ◽  
Author(s):  
Gerhard Bartzke ◽  
Georgios Fourtakas ◽  
Ricardo Canelas ◽  
Benedict D. Rogers ◽  
Katrin Huhn
Keyword(s):  
Free Surface ◽  
Smoothed Particle Hydrodynamics ◽  
Surface Flow ◽  
Large Sphere ◽  
Natural Sediment ◽  
Flow Past ◽  
Rough Bed ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Flow Past A Sphere

AbstractThis paper presents an investigation of flow past a sphere on a rough surface by means of simulation using the meshless numerical method, smoothed particle hydrodynamics (SPH) in the presence of a free surface. A representative of natural and engineered objects is spherical wall-mounted bodies. These are ideal to study the flow conditions around hydraulic structures, boulders, fish habitat structures or even architectural structures. The aim is to understand their effect on the hydrodynamics around the larger object sphere resting on them and their interaction. The Lagrangian particle-based scheme SPH using the open-source code DualSPHysics is validated against datasets from a laboratory-based flume experiment. The validation case was selected from the family of the flow past a sphere test cases since it reproduces the flow features in a simplified manner that can be observed in the vicinity of natural sediment grains or larger bodies. The validation results include flow velocity profiles in the vicinity of the large sphere and comparison with experiment data. The results stand in overall agreement with the experimental velocity and force measurements that demonstrates the applicability of SPH in aquatic environments. An SPH investigation on a rough bed in combination with objects/body near the bed in the presence of a free-surface flow has not been shown before in the literature. This is a novel application with insight into the fluid mechanics made possible by using DualSPHysics solver.

Numerical Simulation of Die Swell of Second-Order Fluids Using Smoothed Particle Hydrodynamics

2010 ◽  
Author(s):  
Samir Hassan Sadek ◽  
Mehmet Yildiz
Keyword(s):  
Free Surface ◽  
Smoothed Particle Hydrodynamics ◽  
Second Order ◽  
Rheological Parameters ◽  
Die Swell ◽  
Two Dimensional ◽  
Polymeric Fluid ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Second Order Fluids

This work presents the development of both weakly compressible and incompressible Smoothed Particle Hydrodynamics (SPH) models for simulating two-dimensional transient viscoelastic free surface flow which has extensive applications in polymer processing industries. As an illustration with industrial significance, we have chosen to model the extrudate swell of a second-order polymeric fluid. The extrudate or die swell is a phenomenon that takes place during the extrusion of polymeric fluids. When a polymeric fluid is forced through a die to give a polymer its desired shape, due to its viscoelastic non-Newtonian nature, it shows a tendency to swell or contract at the die exit depending on its rheological parameters. The die swell phenomenon is a typical example of a free surface problem where the free surface is formed at the die exit after the polymeric fluid has been extruded. The swelling process leads to an undesired increase in the dimensions of the extrudate. To be able to obtain a near-net shape product, the flow in the extrusion process should be well-understood to shed some light on the important process parameters behind the swelling phenomenon. To this end, a systematic study has been carried out to compare constitutive models proposed in literature for second-order fluids in terms of their ability to capture the physics behind the swelling phenomenon. The effect of various process and rheological parameters on the die swell such as the extrusion velocity, normal stress coefficients, and Reynolds and Deborah numbers have also been investigated. The models developed here can predict both swelling and contraction of the extrudate successfully. The die swell problem was solved for a wide range of Deborah numbers and for two different Re numbers. The numerical model was validated through the solution of fully developed Newtonian and Non-Newtonian viscoelastic flows in a two-dimensional channel, and the results of these two benchmark problems were compared with analytic solutions, and good agreements were obtained.

Numerical Simulation of Vortex Shedding From a Circular Cylinder in the Presence of a Free Surface

2003 ◽  
Author(s):  
S. Nagaya ◽  
R. E. Baddour
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Free Surface ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Fluid Flows ◽  
Reynolds Numbers ◽  
Cfd Simulations ◽  
Induced Drag

CFD simulations of crossflows around a 2-D circular cylinder and the resulting vortex shedding from the cylinder are conducted in the present study. The capability of the CFD solver for vortex shedding simulation from a circular cylinder is validated in terms of the induced drag and lifting forces and associated Strouhal numbers computations. The validations are done for uniform horizontal fluid flows at various Reynolds numbers in the range 103 to 5×105. Crossflows around the circular cylinder beneath a free surface are also simulated in order to investigate the characteristics of the interaction between vortex shedding and a free surface at Reynolds number 5×105. The influence of the presence of the free surface on the vortex shedding due to the cylinder is discussed.

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