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Comparison of dynamic mesh methods in OpenFOAM for a WEC in extreme waves
Published in C. Guedes Soares, Developments in Renewable Energies Offshore, 2020
The diffusivity parameter, k, is a measure for mesh deformation and quality (Davidson et al. 2019), control how the motion of a moving boundary (WEC) is diffused into the domain, finding an efficient way to distribute the mesh motion. In OpenFOAM, the morphing mesh area is defined by specifying innerDistance and outerDistance parameters.The mesh motion solver applies SLERP interpolation to define the mesh displacement based on the distance of each cells from the moving body.
Fluid dynamics and wave-structure interactions
Published in Dezhi Ning, Boyin Ding, Modelling and Optimization of Wave Energy Converters, 2022
Malin Göteman, Robert Mayon, Yingyi Liu, Siming Zheng, Rongquan Wang
Dynamic mesh morphing is a technique employed to allow for the displacement of a solid body. This technique is usually selected for simulations in which the solid body displacements are small or those simulations in which a single degree of freedom displacements occur. Grid connectivity is maintained as the solid body displaces. This means that the cell edges connecting the grid nodes remain unchanged. If the displacement of the solid body is excessive the grid may distort excessively resulting in a low-quality mesh with high aspect ratio cells or highly skewed grid cells that will reduce the accuracy of the solution or in extreme cases cause the simulation to fail. This method is seldom used in the simulation of WECs due to the relatively high amplitude, multi-degree of freedom motions to which due to their relatively high amplitude, multi-degree of freedom motions. In the OpenFOAM software, a sixDoFRigidBodyMotion solver is included which can manipulate the mesh according to the dynamic mesh morphing method. Using this technique, an inner region must be around the solid displacement body and an outer region some distance away from the body must be defined. These regions are usually defined by a radial distance away from the body. The mesh in both the inner and outer regions does not distort as the solid body displaces, but the mesh in the inner region will deform. In OpenFOAM the mesh displacement in the intermediate region is controlled by the spherical linear interpolation (SLERP) algorithm, based on the distance from the intermediate region cell to the moving body. This algorithm allows the mesh quality to be strictly controlled. The body displacement is diffused into the domain according to the Laplace equation: ∇·(k∇u)=0,
Hybrid rendering of exploded views for medical image atlas visualization
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2018
Tim McGraw, Alejandro Guayaquil-Sosa
Transformations are represented at each node, i, of the hierarchy by a unit quaternion, , a rotation axis position, and a translation vector, . As transformation parameters are updated we do not change them discontinuously, but instead change them smoothly by linearly interpolating the translation and position, and using spherical linear interpolation (slerp) on unit quaternions (Shoemake 1985) to improve visual coherence. We also permit the user to undo and redo the transformation at each node with a button press by interpolating to an identity transformation and back again. We compute the displayed centrelines of explosions using this same transformation interpolation function.