Figure 2 - uploaded by Janek Meyer
Content may be subject to copyright.
Source publication
Simulating free-surface flow around ships in sea waves using RANSE-Methods usually requires damping of the waves in front of the outlet to avoid reflections.
It has been shown, that common damping methods like sponge layer methods deliver a reliable damping for monochromatic waves, but require a parameter adjustment by the user for different wave s...
Context in source publication
Context 1
... scale factor χ is varied from 0.008 to 1.0 for each wave to achieve the least reflections and to show the dependency of our wave damping method from the wave characteristics. Figure 2 shows the results of all simulations. Sub- figure b shows the results of the common linear sponge layer method (with f 2 = 0.0 = const), also implemented in our solver. ...
Similar publications
This article presents results of the free surface flow around ship hull on two different types of computational grid. Each type of mentioned grid has its own advantages and disadvantages in particular cases, mostly in one phase simulation. Omitting cases with capitation, there is no free surface involved in one phase simulation. Multiphase simulati...
In various fields of applications one is often interested in solving a fluid flow
problem computationally in a domain which is much smaller than the actual domain where
the governing equations hold. This approach is employed in order to reduce computational
time and usually results in possibility to use more complex mathematical model of given
phys...
This paper verifies a mathematical model that is developed for the open source CFD-toolbox OpenFOAM, which couples turbulent combustion with conjugate heat transfer. This feature already exists in well-known commercial codes. It permits the prediction of the flame’s characteristics, its emissions, and the consequent heat transfer between fluids and...
This work presents the implementation and verification of a new solver in the OpenFOAM®open source computational library. The new solver allows the numerical solution of the integral viscoelastic constitutive equations, and their coupling with the continuity and momentum equations. This solver is also more stable when compared to the previous imple...
Citations
... In Söding's paper, the need for an explicit added mass matrix for numerical stability is explained, and an iteration-based method for its determination is formulated. In a study by Meyer et al. [25], this algorithm was applied to calculate the motion of a yacht in head waves. To the best of our knowledge, no thorough demonstration of the stability properties exists in the literature, and no open-source CFD implementation is available to the scientific community. ...
We present a non-iterative algorithm, FloatStepper, for coupling the motion of a rigid body and an incompressible fluid in computational fluid dynamics (CFD) simulations. The purpose of the algorithm is to remove the so-called added mass instability problem, which may arise when a light, floating body interacts with a heavy fluid. The idea underlying the presented coupling method is to precede every computational time step by a series of prescribed probe body motions in which the fluid response is determined, thus revealing the decomposition of the net force and torque into two components: (i) an added mass contribution proportional to the instantaneous body acceleration and (ii) all other forces and torques. The algorithm is implemented and released as an open-source extension module to the widely used CFD toolbox, OpenFOAM, as an alternative to the existing body motion solvers. The accuracy of the algorithm is investigated with several single-phase and two-phase flow benchmark cases. The benchmarks demonstrate excellent stability properties, allowing simulations even with massless bodies. They also highlight aspects of the implementation, such as the mesh motion method, where it can be improved to further enhance the flexibility and predictive capabilities of the code.
... In Söding's paper, the need for an explicit added mass matrix for numerical stability is explained and an iteration based method for its determination is formulated. In a study by Meyer et al. [25] this algorithm was applied to calculate the motion of a yacht in head waves. To the best of our knowledge, no thorough demonstration of the stability properties exists in the literature, and no open source CFD implementation is available to the scientific community. ...
... The pressure parts of the hydrodynamic force and torque contain components, that are proportional to the instantaneous body acceleration, and which go into the total force-torque vector, f , in Eqn. (25). Just as we did in the introductory 1-DoF example, we can conceptually split f into a part, −Av b , containing all terms that are proportional tov b , and another part, f other , containing all other forces and torques, ...
... Inserting the decomposed force from Eqn. (27) into the body equations of motion, Eqn. (25), and isolating the acceleration, we geṫ ...
We present a non-iterative algorithm, FloatStepper, for coupling the motion of a rigid body and an incompressible fluid in computational fluid dynamics (CFD) simulations. The purpose of the algorithm is to remove the so-called added mass instability problem, which may arise when a light floating body interacts with a heavy fluid. The idea underlying the presented coupling method is to precede every computational time step by a series of prescribed probe body motions in which the fluid response is determined, thus revealing the decomposition of the net force and torque into two components: 1) An added mass contribution proportional to the instantaneous body acceleration, and 2) all other forces and torques. The algorithm is implemented and released as an open source extension module to the widely used CFD toolbox , OpenFOAM, as an alternative to the existing body motion solvers. The accuracy of the algorithm is investigated with several single-phase and two-phase flow benchmark cases. The benchmarks demonstrate excellent stability properties, allowing simulations even with massless bodies. They also highlight aspects of the implementation, such as the mesh motion method, where more work is needed to further enhance the flexibility and predictive capabilities of the code.
... Details of the theory and implementation of the new solver are given in [3] and [4]. Only an overview is given here. ...
... A new approach for the wave damping in the exit zone has been developed, which has been published only recently [4]. Available methods usually damp the sea waves by adding some external force into the momentum equation. ...
... The methods mentioned here are described in detail in [3] and [4]. They are implemented as a new OpenFOAM solver and as enhancements of existing boundary conditions. ...
This paper presents a method for the simulation of scour around arbitrary offshore structures. It is based on the solution of the Reynolds-Averaged-Navier-Stokes equations implemented in the OpenFOAM framework. The sediment is simulated with the help of a Bingham model, which basically models a solid sediment behavior by introducing a very high viscosity. The relative pressure used by the Bingham model is estimated with a new approach based on the solution of a Poisson equation. The position of the sediment surface is calculated with the Volume-of-Fluid approach using a high-resolution scheme. To keep the typical wall characteristics without demanding a fine grid, the common wall functions are transferred to the domain internal sediment walls. Furthermore, additional modifications are applied to model a solid sediment wall inside the solution domain. The new internal wall function implementation is validated with a 2D test case. The results show a very good agreement to common wall functions and a significant improvement compared to its negligence. Furthermore the solver is used to simulate the scour downstream of an apron and the scour around a vertical cylinder in current. The results are compared to experiments presented in the literature and show good agreement. The applicability onto arbitrary structures is demonstrated by applying the solver onto a vertical cylinder with a mudplate. The current development state is able to resolve all important physical flow and scour phenomena. The results also unveil that modeling of the suspension and the treatment of the internal wall need additional attention.
This paper presents a new flow simulation method for the simulation of scour around arbitrary offshore structures. It is based on the solution of the Reynolds-Averaged-Navier-Stokes equations implemented in the OpenFOAM framework. The sediment is simulated with the help of a Bingham model, which basically models a solid sediment behavior by introducing a very high viscosity. The relative pressure used by the Bingham model is estimated with a new approach based on the solution of a Poisson equation. The position of the sediment surface is calculated with the Volume-of-Fluid approach using a high-resolution scheme. To keep the typical wall characteristics without demanding a fine grid the common wall functions are transferred to the domain internal sediment walls. Furthermore, additional modifications are applied to model a solid sediment wall inside the solution domain. The new internal wall function implementation is validated with a 2D test case. The results show a very good agreement to common wall functions and a significant improvement compared to its negligence. Furthermore the solver is used to simulate the scour downstream of an apron and the scour around a vertical cylinder in current. The results are compared to experiments presented in the literature and show good agreement. The applicability onto arbitrary structures is demonstrated by applying the solver onto a vertical cylinder with a mudplate. The current development state is able to resolve all important physical flow and scour phenomena. The results also unveil that modeling of the suspension and the treatment of the internal wall need additional attention.
