Elastic Simulation of Joints with Particle-Based Fluid

Skinning, which is used in skeletal simulations to express the human body, has been weighted between bones to enable muscle-like motions. Weighting is not a form of calculating the pressure and density of muscle fibers in the human body. Therefore, it is not possible to express physical changes when external forces are applied. To express a similar behavior, an animator arbitrarily customizes the weight values. In this study, we apply the kernel and pressure-dependent density variations used in particle-based fluid simulations to skinning simulations. As a result, surface tension and elasticity between particles are applied to muscles, indicating realistic human motion. We also propose a tension yield condition that reflects Tresca’s yield condition, which can be easily approximated using the difference between the maximum and minimum values of the principal stress to simulate the tension limit of the muscle fiber. The density received by particles in the kernel is assumed to be the principal stress. The difference is calculated by approximating the moment of greatest force to the maximum principal stress and the moment of least force to the minimum principal stress. When the density of a particle increases beyond the yield condition, the object is no longer subjected to force. As a result, one can express realistic muscles.

Coupled Time-Domain Hydro-Elastic Simulation for Submerged Floating Tunnel Under Wave Excitations

We develop a fully-coupled time-domain hydro-elasticity model for the Submerged Floating Tunnel (SFT) based on the Discrete-Module-Beam (DMB) method. Frequency-domain simulation based on 3D potential theory results in multibody’s hydrodynamic coefficients and excitation forces for tunnel sections. Subsequently, we build the time-domain model with the multibody Cummins equation and external stiffness matrix from the Euler-Bernoulli and Saint-Venant torsion theories. We establish the mooring line model with rod theory and couple components with translational springs at their respective connection locations. We then compare the dynamic motions, wave forces, and mooring tensions between the present and Morison-equation-based elastic models under regular wave excitations at different submergence depths. The present model is especially important for the shallowly submerged tunnel in which the Morison model shows exaggerated motions, especially at high-frequency range.

Visco-thermo-elastic Simulation Approach For Prediction of Cure-induced Residual Stresses in Fiber Reinforced Composites

Liquid composite molding (LCM) has established as a high quality manufacturing process for fiber reinforced composite structures. In order to reduce cycle times significantly, novel fast curing matrix resins are being introduced into series production. These put high requirements on process control and part reproducibility. Problems that may be encountered in this context involve process-induced distortion and surface waviness resulting from anisotropic and cure-dependent material properties. Numerical simulations represent a powerful approach to avoid the use of costly trial-and-error methods. For this reason, a simulation approach is being developed which aims at the prediction of residual stresses and accompanying effects on different length scales. Based on a resin characterization comprising reaction kinetics, cure-dependent relaxation modulus as well as thermal expansion and pressure-dependent chemical shrinkage, a generalized MAXWELL model is selected to describe the process-related mechanical behavior of the thermoset. Taking into account the influence of the process parameters on the resin properties enables a detailed analysis of process-property-relationships. By this, the developed simulation approach offers the possibility of a comprehensive analysis of both local and global process-induced phenomena and hence prevention of flaws.

Wind Turbine Controller to Mitigate Structural Loads on a Floating Wind Turbine Platform

This paper summarizes the control design work that was performed to optimize the controller of a wind turbine on the WindFloat structure. The WindFloat is a semisubmersible floating platform designed to be a support structure for a multimegawatt power-generating wind turbine. A controller developed for a bottom-fixed wind turbine configuration was modified for use when the turbine is mounted on the WindFloat platform. This results in an efficient platform heel resonance mitigation scheme. In addition, several control modules, designed with a coupled linear model, were added to the fixed-bottom baseline controller. The approach was tested in a fully coupled nonlinear aero-hydro-elastic simulation tool in which wind and wave disturbances were modeled. This testing yielded significant improvements in platform global performance and tower-base bending loading.

Can fracture orientation and intensity be detected from seismic data? Woodford Formation, Anadarko Basin, Oklahoma investigation

With readily available wide-azimuth, onshore, 3D seismic data, the search for attributes utilizing the azimuthal information is ongoing. Theoretically, in the presence of ordered fracturing, the seismic wavefront shape changes from spherical to nonspherical with the propagation velocity being faster parallel to the fracturing and slower perpendicular to the fracture direction. This concept has been adopted and is used to map fracture direction and density within unconventional reservoirs. More specifically, azimuthal variations in normal moveout velocity or migration velocity are often used to infer natural fracture orientation. Analyses of recent results have called into question whether azimuthal velocity linked to intrinsic azimuthal velocity variations can actually be detected from seismic data. By use of 3D orthorhombic anisotropic elastic simulation, we test whether fracture orientation and intensity can be detected from seismic data. We construct two subsurface models based on interpreted subsurface layer structure of the Anadarko Basin in Oklahoma. For the first model, the material parameters in the layers are constant vertically transverse isotropic (VTI) in all intervals. The second model was constructed the same way as the base model for all layers above the Woodford Shale Formation. For the shale layer, orthorhombic properties were introduced. In addition, a thicker wedge layer was added below the shale layer. Using the constructed model, synthetic seismic data were produced by means of 3D anisotropic elastic simulation resulting in two data sets: VTI and orthorhombic. The simulated data set was depth migrated using the VTI subsurface model. After migration, the residual moveouts on the migrated gathers were analyzed. The analysis of the depth-migrated model data indicates that for the typical layer thicknesses of the Woodford Shale layer in the Anadarko Basin, observed and modeled percentage of anisotropy and target depth, the effect of intrinsic anisotropy is too small to be detected in real seismic data.

Using Multiple Fidelity Numerical Models for Floating Offshore Wind Turbine Advanced Control Design

This paper summarises the tuning process of the Aerodynamic Platform Stabiliser control loop and its performance with Floating Offshore Wind Turbine model. Simplified Low-Order Wind turbine numerical models have been used for the system identification and control tuning process. Denmark Technical University’s 10 MW wind turbine model mounted on the TripleSpar platform concept was used for this study. Time-domain simulations were carried out in a fully coupled non-linear aero-hydro-elastic simulation tool FAST, in which wind and wave disturbances were modelled. This testing yielded significant improvements in the overall Floating Offshore Wind Turbine performance and load reduction, validating the control technique presented in this work.

Elastic Deformations of Floaters for Offshore Wind Turbines: Dynamic Modelling and Sectional Load Calculations

To achieve economically and technically viable floating support structures for large 10MW+ wind turbines, structural flexibility may increase to the extent that becomes relevant to incorporate along with the corresponding physical effects within aero-hydro-servo-elastic simulation tools. Previous work described a method for the inclusion of substructural flexibility of large-volume substructures, including wave-structure interactions through linear radiation-diffraction theory. Through an implementation in the HAWC2 simulation tool, it was shown that one may incorporate the effects of additional modes on substructure and wind turbine response as well as predict the excitation of substructure flexible modes. This work goes one step further and describes a method to calculate internal substructural stresses that includes dynamic effects. In dynamic calculations, the substructure flexibility is considered through a reduced set of modes, selected based on their relevance to the external load frequency range, and represented with a superelement. The implementation of this method in aeroelastic simulation tool HAWC2 and wave-structure analysis program WAMIT is described, highlighting the practical challenges. A case study of the DTU 10MW Reference Wind Turbine installed on the Triple Spar concept is presented to illustrate the method. The results show that the substructure flexible modes, global platform motion and wind turbine loads can influence sectional loads within the substructure.