Juan B. V. Wanderley

A Two-Dimensional Numerical Investigation of the Hysteresis Effect on Vortex Induced Vibration on an Elastically Mounted Rigid Cylinder

The hysteresis effect on the vortex induced vibration (VIV) on a circular cylinder is investigated by the numerical solution of the two-dimensional Reynolds averaged Navier-Stokes equations. An upwind and total variation diminishing (TVD) conservative scheme is used to solve the governing equations written in curvilinear coordinates and the k-e turbulence model is used to simulate the turbulent flow in the wake of the body. The cylinder is supported by a spring and a damper and free to vibrate in the transverse direction. In previous work, numerical results for the amplitude of oscillation and vortex shedding frequency were compared to experimental data obtained from the literature to validate the code for VIV simulations. In the present work, results of practical interest are presented for the power absorbed by the system, phase angle, amplitude, frequency, and lift coefficient. The numerical results indicate that the hysteresis effect is observed only when the frequency of vortex shedding gets closer to the natural frequency of the structure in air.

Validation of a finite difference method for the simulation of vortex-induced vibrations on a circular cylinder

Abstract The Karman Vortex Street generated by a circular cylinder is investigated by the numerical solution of the compressible Navier–Stokes equations in the incompressible Mach number range (Mach Chorin, 1968 ) is fairly good while convergence time is very much better. The investigation suggests that the compressible Navier–Stokes equations may be used as an efficient alternative to study incompressible flows as well. Mach numbers just below 0.3 are enough to simulate incompressible flow behavior and at the same time do not cause numerical ill-conditioning in the solution. In addition, some relevant features of the vortices generated and carried by the wake of the cylinder could be fairly well captured.

Numerical Simulation of Roll Damping of a FPSO

The viscous flow problem of roll damping of a FPSO is investigated by means of numerical solution of the unsteady two-dimensional Navier-Stokes equations. The finite volume method using unstructured grid is used to solve the integral form of the governing equations. The cross section of the FPSO hull with an initial roll displacement is left free to oscillate in roll, heave and sway in an initially still fluid. The numerical simulation provides a realistic picture of the physics of the phenomenon, capturing the vortex formation around the bilge keel. The numerical results are compared with experimental data showing a fairly good qualitative and quantitative agreement of the motion damping.Copyright

The Robustness of the Added Mass in VIV Models

In this paper we show that added mass coefficient, Ca , is robust, i.e., is a first measure of model consistency. Regardless of the model type, phenomenological as well as CFD models, the general trend of the added mass coefficient plot is always the same.Copyright

A Numerical Investigation of Vortex Induced Vibration on an Elastically Mounted Rigid Cylinder

The Vortex-Induced Vibration on an elastically mounted circular cylinder is investigated by the numerical solution of the two-dimensional Reynolds Averaged Navier-Stokes equations and results are compared with experimental data. The upwind TVD scheme of Roe – Sweby is used to solve the governing equations and the k-e turbulence model is used to simulate the turbulent flow in the wake of the cylinder. The cylinder is laterally supported by a spring and a damper and is free to oscillate in the transverse direction. Results for the lift coefficient amplitude, displacement amplitude, frequency, phase angle, and power absorbed by the system are presented and compared to experimental data. The code was tested for the fixed cylinder case, and for the moving cylinder. The comparison with experimental data obtained from the literature showed the good quality of the numerical results and validated the code for simulations of vortex-induced vibration.Copyright

A Two-Dimensional Numerical Simulation of Roll Damping Decay of a FPSO Using the Upwind TVD Scheme of Roe-Sweby

The study of roll damping is investigated for a Floating Production Storage and Offloanding (FPSO). For this purpose, a roll decay test of FPSO is simulated by means of the numerical solution of the slightly compressible Navier-Stokes equations in 2D. The governing equations are solved using the finite volume method and the upwind TVD scheme of Roe-Sweby. The roll damping for rectangular hulls is dominated by viscous effects. Strong vortices are formed around the bilge keel. Hence, in this zone, there is a discontinuity of pressure that the TVD scheme will resolve and capture the physics of the phenomenon without spurious oscillations. The numerical results are compared with experimental data for validating the numerical scheme implemented.Copyright

A Numerical Investigation of the Hysteresis Effect on Vortex Induced Vibration on an Elastically Mounted Rigid Cylinder

The hysteresis effect on the vortex induced vibration (VIV) on a circular cylinder is investigated by the numerical solution of the Reynolds average Navier-Stokes equations. An upwind and Total Variation Diminishing (TVD) conservative scheme is used to solve the governing equations written in curvilinear coordinates and the k-e turbulence model is used to simulate the turbulent flow in the wake of the body. The cylinder is supported by a spring and a damper and free to vibrate in the transverse direction. In previous work, numerical results for the amplitude of oscillation and vortex shedding frequency were compared to experimental data obtained from the literature to validate the code for VIV simulations. In the present work, results of practical interest are presented for the power absorbed by the system, phase angle, amplitude, frequency, and lift coefficient. The numerical results indicate that the hysteresis effect is observed only when the frequency of vortex shedding gets closer to the natural frequency of the structure in air.Copyright

Chapter 27 – Calculation of the flow around ship hulls using a parallel CFD code

Publisher Summary This chapter discusses calculation of the flow around ship hulls using a parallel computational fluid dynamics (CFD) code. A free surface is used for simulating the flow around ship hulls. The working environment with the specific compilation options is used to assess their efficiency. Several configurations of the 4-nodes cluster are compared in terms of speed. The free surface incompressible turbulent flow around the hull is investigated by the numerical solution of the unsteady Navier–Stokes equations for slightly compressible flows, and the results are compared with different numerical and experimental results. The “beam” and “warming” implicit factorized scheme is used to solve the governing equations. Large eddy simulation is used together with the Smagorinsky subgrid scale model to simulate the turbulent flow. The free surface is treated through the re-meshing technique, using an algebraic routine for accompanying the displacements. The complexity and high sensitivity of such a physical flow phenomenon require an accurate and robust numerical model. The proposed numerical solution is able to provide a good picture of the real physics of the turbulent flow. The numerical results compare fairly well with experimental results from various sources.

Roll Damping Decay of a FPSO With Bilge Keel

The roll damping decay is investigated for a Floating Production Storage and Offloading (FPSO). For this purpose, a roll decay test of a middle section of FPSO with bilge keel is simulated by means of the numerical solution of the incompressible two-dimensional Navier–Stokes equations. The governing equations are solved using the finite volume method and the upwind Total Variation Diminishing (TVD) scheme of Roe–Sweby. The upwind TVD scheme resolves and captures the physics of the fluid dynamics without spurious oscillations in regions of the flow field with strong pressure gradients. The numerical results are compared with experimental data for validating the numerical scheme implemented. The simulations indicated the strong influence of the bilge radius in the damping coefficient of the FPSO section. Interesting results were obtained regarding the time series of the displacement of the body and vortex shedding around the bilge keel.

A Numerical Investigation on 2D and 3D Sloshing Effects

In this paper, we study the effect of sloshing in a compartment of a naval artifact. The sloshing is of great importance in the dynamics of ships and offshore platforms, it is one of the factors that may cause the capsizing. This happens when the ship is under undesirable conditions, such as progressive flooding or fault conditions. The goal is to represent numerically the effect of sloshing. The numerical code is validated through comparisons with numerical and experimental data obtained in the literature. The numerical model is based on the finite difference method, where the Euler equations are solved using the upwind scheme and TVD (Total Variation Diminishing) Roe (1984) and Sweby (1984). The computer code for 2D represents the effect of sloshing in a closed vessel. To adequately represent the reservoir of the naval artifact, we used a structured computational mesh, where the fluid is forced to move by the excitation applied to the tank, this type of excitation is harmonic in sway. For the 3D computer code, a sloped free surface elevation is used as initial condition. Another attempt to realize the versatility of the computer code was the fall of a sphere of water on the free surface of the tank.Copyright