Discrete Vortex Method Of Flow Around A Cylinder In A Channel Using Simple Grid System

Modelling of unidirectional and oscillatory flows around a cylinder in a channel using a simple overlapping grid system are carried out. The importance of this cylinder-wall configuration is the effect of blockage which suppress the development of the vortex shedding The polar grid system of the cylinder is then overlapped with the rectangular grid system of the wall. The length of rectangular grid element is about the same as the length of the polar grid system in the cylinder surface. The use of such overlapping grid system is for reducing the CPU time, i.e. in calculating the vortex velocity since the CPU time in calculating the vortices velocity takes the longest time. This method is not only time efficient, but also gives a better distribution of surface vorticity as the scattered vortices around the body are now concentrated on grid point. In this study there is no vortex-to-vortex interaction, but instead it uses node-to-node interactions. Velocity calculation also uses this overlapping grid in which the new incremental shift position then summed up to get the total new vortices position. In this overlapping system the grid can be either off or on depend on process involved to get rid of the nodes not being used. The engineering applications of this topic is to simulate the loading pipeline placed in the channel such as in the heat exchanger or simulation of U-tube experiment or other system. The in-line and transverse force coefficients are found by integrating the pressure around the cylinder surface. The flow patterns are then can be obtained and presented. The comparison of the results with experimental evidence is presented and also the range of good results is discussed.

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Discrete Vortex Prediction of Flows around a Cylinder Near a Wall Using Overlapping Grid System

Fluids ◽

10.3390/fluids6060211 ◽

2021 ◽

Vol 6 (6) ◽

pp. 211

Author(s):

Wisnu Wardhana ◽

Ede Mehta Wardhana ◽

Meitha Soetardjo

Keyword(s):

Grid Point ◽

The Body ◽

Cylinder Surface ◽

Grid System ◽

Vortex Interaction ◽

Discrete Vortex ◽

Cpu Time ◽

Comparison Of The Results ◽

Circular Grid ◽

Interaction Velocity

Modelling of unidirectional and oscillatory flows around a cylinder near a wall using an overlapping grid system is carried out. The circular grid system of the cylinder was overlapped with the rectangular grid system of the wall. The use of such an overlapping grid system is intended to reduce the CPU time compared to the cloud scheme in which vortex-to-vortex interaction is used, i.e., especially in calculating the shedding vortex velocity, since calculating the vortices velocity takes the longest CPU time. This method is not only time efficient, but also gives a better distribution of surface vorticity as the scattered vortices around the body are now concentrated on a grid point. Therefore, grid-to-grid interaction is used instead of vortex-to-vortex interaction. Velocity calculation was also carried out using this overlapping grid in which the new incremental shift position was summed up to obtain the total new vortices position. The engineering applications of this topic are to simulate the loading of submarine pipeline placed close to the seabed or to simulate the flow as a result of the scouring process below the cylinder since there is space for the fluid to flow beneath it. The in-line and transverse force coefficients are found by integrating the pressure around the cylinder surface. The flow patterns are then obtained and presented. The comparison of the results with experimental evidence is presented and the range of good results is discussed.

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Vortex Simulation of Two Cylinders in Tandem Using Overlapping Grid System

10.21203/rs.3.rs-113057/v1 ◽

2020 ◽

Author(s):

Wisnu Wardhana ◽

Ede Wardhana ◽

Meitha Soetardjo

Keyword(s):

Grid Point ◽

The Body ◽

Structural Elements ◽

Grid System ◽

Considerable Time ◽

Discrete Vortex ◽

Cpu Time ◽

Tandem Cylinders ◽

Flow Phenomena ◽

Comparison Of The Results

Abstract To give a considerable time reduction in the calculation of the vortex velocity and in the CPU time, discrete vortex modelling of flows using overlapping grid system for two tandem cylinders is carried out. This simple and time efficient method gives a better scatter of surface vorticity as the vortices around the body are now calculated on grid point. This research is to simulate the loading on structural elements of the structures due to their interaction with anodes or with other members. To show the flow phenomena and interactions involved, the in-line and transverse force coefficients are presented. The comparison of the results with experimental and numerical results and the range for good results is presented.

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NUMERICAL SIMULATION OF THE FLOW AROUND A SQUARE CYLINDER USING THE VORTEX METHOD

Revista de Engenharia Térmica ◽

10.5380/reterm.v3i2.3537 ◽

2004 ◽

Vol 3 (2) ◽

pp. 161

Author(s):

V. G . Guedes ◽

G . C. R. Bodstein ◽

M. H. Hirata

Keyword(s):

Reynolds Number ◽

Incompressible Flows ◽

Pressure Coefficient ◽

Vortex Method ◽

Panel Method ◽

The Body ◽

Cylinder Surface ◽

Square Cylinder ◽

Aerodynamic Forces ◽

Discrete Vortex

The study of external incompressible flows around bluff bodies finds extensive applicability to real-life problems. Such flows are characterized by unsteady flow separation for high values of the Reynolds number, where a Von Karman-type periodic wake is formed. The prediction of these flows is very difficult, and one has usually to rely on specific experimental data to calculate the aerodynamic forces on the body. In order to numerically simulate this flow, this paper uses a new mesh-free two-dimensional Discrete Vortex Method associated with a Panel Method to calculate the lift and drag coefficients, as well as the pressure coefficient on a square cylinder, for a high Reynolds number flow. Lamb vortices are generated along the cylinder surface, whose strengths are determined to ensure that the no-slip condition is satisfied and that circulation is conserved. The impermeability condition is imposed through a source panel method, so that mass conservation is explicitly enforced. The dynamics of the body wake is computed using the convection-diffusion splitting algorithm, where the diffusion process is simulated using the random walk method, and the convection process is carried out with a lagrangian second-order time-marching scheme. Results for the aerodynamic forces and pressure distribution are presented.

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NUMERICAL SIMULATION OF THE FLOW AROUND A SQUARE CYLINDER USING THE VORTEX METHOD

Revista de Engenharia Térmica ◽

10.5380/ret.v3i2.3537 ◽

2004 ◽

Vol 3 (2) ◽

Author(s):

V. G . Guedes ◽

G . C. R. Bodstein ◽

M. H. Hirata

Keyword(s):

Reynolds Number ◽

Incompressible Flows ◽

Pressure Coefficient ◽

Vortex Method ◽

Panel Method ◽

The Body ◽

Cylinder Surface ◽

Square Cylinder ◽

Aerodynamic Forces ◽

Discrete Vortex

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Numerical Simulation of Rivulet Dynamics Associated With Rain-Wind Induced Vibration

ASME 2010 7th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, and Flow-Induced Vibration and Noise: Volume 3, Parts A and B ◽

10.1115/fedsm-icnmm2010-30663 ◽

2010 ◽

Author(s):

Ian J. Taylor ◽

Andrew C. Robertson

Keyword(s):

Flow Field ◽

Thin Liquid Film ◽

Vortex Method ◽

The Body ◽

Wind Loading ◽

External Loading ◽

Discrete Vortex ◽

Unsteady Aerodynamic ◽

Karman Vortex ◽

Wind Induced Vibration

On wet and windy days, the inclined cables of cable-stayed bridges can experience large amplitude, potentially damaging oscillations known as Rain-Wind Induced Vibration (RWIV). The phenomenon is believed to be the result of a complicated nonlinear interaction between rivulets of rain water that run down the cables and the wind loading on the cables due to the unsteady aerodynamic flow field. A numerical method has been developed at the University of Strathclyde, to simulate aspects of RWIV, the results of which can be used to assess the importance of the water rivulets on the instability. This combines a Discrete Vortex Method solver to determine the external flow field and unsteady aerodynamic loading and a pseudo-spectral solver based on lubrication theory to model the water on the surface of the body and which is used to determine the evolution and growth of the water rivulets under external loading. These two models are coupled to simulate the interaction between the aerodynamic field and the thin liquid film on a horizontal circular cylinder. The results illustrate the effects of various loading combinations, and importantly demonstrate rivulet formation in the range of angles previous research has indicated that these may suppress the Karman vortex and lead to a galloping instability. These rivulets are found to be of self limiting thickness in all cases.

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Effect of vortex shedding on the coupled roll response of bodies in waves

Journal of Fluid Mechanics ◽

10.1017/s0022112088000990 ◽

1988 ◽

Vol 189 ◽

pp. 243-261 ◽

Cited By ~ 38

Author(s):

M. J. Downie ◽

P. W. Bearman ◽

J. M. R. Graham

Keyword(s):

Vortex Shedding ◽

Degrees Of Freedom ◽

Rectangular Cross Section ◽

Vortex Method ◽

The Body ◽

Wave Radiation ◽

Viscous Damping ◽

Discrete Vortex ◽

Hydrodynamic Damping ◽

Main Component

Hydrodynamic damping of floating bodies is due mainly to wave radiation and viscous damping. The latter is particularly important in controlling those responses of the body for which the wave damping is small. The roll response of ship hulls near resonance in beam seas is an example of this. The present paper applies a discrete vortex method as a local solution to model vortex shedding from the bilges of a barge hull of rectangular cross-section and hence provides an analytic method for predicting its coupled motions in three degrees of freedom, including the effects of the main component of viscous damping. The method provides a frequency-domain solution satisfying the full linearized boundary conditions on the free surface.

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Conformal Mapping-Based Discrete Vortex Method for Simulating 2-D Flows around Arbitrary Cylinders

Journal of Marine Science and Engineering ◽

10.3390/jmse9121409 ◽

2021 ◽

Vol 9 (12) ◽

pp. 1409

Author(s):

Guoqing Jin ◽

Zhe Sun ◽

Zhi Zong ◽

Li Zou ◽

Yingjie Hu

Keyword(s):

Conformal Mapping ◽

Vortex Method ◽

Reynolds Numbers ◽

Mapping Method ◽

Mirror Image ◽

The Body ◽

Time Step ◽

Discrete Vortex ◽

Fluid Field ◽

Pressure Distributions

A novel technique based on conformal mapping and the circle theorem has been developed to tackle the boundary penetration issue, in which vortex blobs leak into structures in two-dimensional discrete vortex simulations, as an alternative to the traditional method in which the blobs crossing the boundary are simply removed from the fluid field or reflected back to their mirror-image positions outside the structure. The present algorithm introduces an identical vortex blob outside the body using the mapping method to avoid circulation loss caused by the vortex blob penetrating the body. This can keep the body surface streamlined and guarantees that the total circulation will be constant at any time step. The model was validated using cases of viscous incompressible flow passing elliptic cylinders with various thickness-to-chord ratios at Reynolds numbers greater than Re = 1 × 105. The force and velocity fields revealed that this boundary scheme converged, and the resultant time-averaged surface pressure distributions were all in excellent agreement with wind tunnel tests. Furthermore, a flow around a symmetrical Joukowski foil at Reynolds number Re = 4.62 × 104, without considering the trailing cusp, was investigated, and a close agreement with the experimental data was obtained.

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The Influence of Viscous Effects on the Motion of a Body Floating in Waves

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.2920087 ◽

1993 ◽

Vol 115 (1) ◽

pp. 40-45 ◽

Cited By ~ 1

Author(s):

M. J. Downie ◽

J. M. R. Graham ◽

X. Zheng

Keyword(s):

Three Dimensional ◽

Vortex Method ◽

Inviscid Flow ◽

The Body ◽

Viscous Effects ◽

Local Flow ◽

Discrete Vortex ◽

Outer Flow ◽

Viscous Forces ◽

Singularity Distribution

This paper describes a method for calculating the forces experienced by a body floating in waves, including those due to vortex shedding from its surface. The method uses a purely theoretical approach, incorporating viscous forces, for calculating the motions of the body in the frequency domain. It involves the matching of an outer inviscid flow with the local flow in the regions of flow separation on the body, which must be well defined. The outer flow is computed by a three-dimensional singularity distribution technique and the inner flow by the discrete vortex method. The technique has been applied to the prediction of the motion response of barges floating in waves. The results compare favorably with experimental data.

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