Multiscale space–time computation techniques

A number of multiscale space–time techniques have been developed recently by the Team for Advanced Flow Simulation and Modeling (T*AFSM) for fluid–structure interaction computations. As part of that, we have introduced a space–time version of the residual-based variational multiscale method. It has been designed in the context of the Deforming-Spatial-Domain/Stabilized Space–Time formulation, which was developed earlier by the T*AFSM for computation of flow problems with moving boundaries and interfaces. We describe this multiscale space–time technique, and present results from test computations

Decentralized Energy Production System by Anaerobic Digestion Using Organic Waste and Exhaust Heat

Oral Presentaion

Computational analysis of performance deterioration of a wind turbine blade strip subjected to environmental erosion

Wind-turbine blade rain and sand erosion, over long periods of time, can degrade the aerodynamic performance and therefore the power production. Computational analysis of the erosion can help engineers have a better understanding of the maintenance and protection requirements. We present an integrated method for this class of computational analysis. The main components of the method are the streamline-upwind/Petrov–Galerkin (SUPG) and pressure-stabilizing/Petrov–Galerkin (PSPG) stabilizations, a finite element particle-cloud tracking method, an erosion model based on two time scales, and the solid-extension mesh moving technique (SEMMT). The turbulent-flow nature of the analysis is handled with a Reynolds-averaged Navier–Stokes model and SUPG/PSPG stabilization, the particle-cloud trajectories are calculated based on the computed flow field and closure models defined for the turbulent dispersion of particles, and one-way dependence is assumed between the flow and particle dynamics. Because the geometry update due to the erosion has a very long time scale compared to the fluid–particle dynamics, the update takes place in a sequence of “evolution steps” representing the impact of the erosion. A scale-up factor, calculated in different ways depending on the update threshold criterion, relates the erosions and particle counts in the evolution steps to those in the fluid–particle simulation. As the blade geometry evolves, the mesh is updated with the SEMMT. We present computational analysis of rain and sand erosion for a wind-turbine blade strip, including a case with actual rainfall data and experimental aerodynamic data for eroded airfoil geometries

Space–time fsi modeling of ringsail parachute clusters

The computational challenges posed by fluid–structure interaction (FSI) modeling of ringsail parachute clusters include the lightness of the membrane and cable structure of the canopy compared to the air masses involved in the parachute dynamics, geometric complexities created by the construction of the canopy from “rings” and “sails” with hundreds of ring gaps and sail slits, and the contact between the parachutes. The Team for Advanced Flow Simulation and Modeling (T*AFSM) has successfully addressed these computational challenges with the Stabilized Space–Time FSI technique (SSTFSI), which was developed and improved over the years by the T*AFSM and serves as the core numerical technology, and a number of special techniques developed in conjunction with the SSTFSI. We present the results obtained with the FSI computation of parachute clusters and the related dynamical analysis

Multiscale sequentially-coupled fsi computation in parachute modeling

We describe how the spatially multiscale Sequentially-Coupled Fluid–Structure Interaction (SCFSI) techniques we have developed, specifically the “SCFSI M2C”, which is spatially multiscale for the structural mechanics part, can be used for increasing the accuracy of the membrane and cable structural mechanics solution in parachute FSI computations. The SCFSI M2C technique is used here in conjunction with the Stabilized Space–Time FSI (SSTFSI) technique, which was developed and improved over the years by the Team for Advanced Flow Simulation and Modeling (T AFSM) and serves as the core numerical technology, and a number of special parachute FSI techniques developed by the T AFSM in conjunction with the SSTFSI technique

Comparative patient-specific fsi modeling of cerebral aneurysms

We consider a total of ten cases, at three different locations, half of which ruptured sometime after the images were taken. We use the stabilized space–time FSI technique developed by the Team for Advanced Flow Simulation and Modeling, together with a number of special techniques targeting arterial FSI modeling. We compare the ten cases based on the wall shear stress, oscillatory shear index, and the arterial-wall stress. We also investigate how simpler approaches to computer modeling of cerebral aneurysms perform compared to FSI modeling

Computational analysis of particle-laden-airflow erosion and experimental verification

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Heart valve isogeometric sequentially-coupled FSI analysis with the space–time topology change method

Heart valve fluid–structure interaction (FSI) analysis is one of the computationally challenging cases in cardiovascular fluid mechanics. The challenges include unsteady flow through a complex geometry, solid surfaces with large motion, and contact between the valve leaflets. We introduce here an isogeometric sequentially-coupled FSI (SCFSI) method that can address the challenges with an outcome of high-fidelity flow solutions. The SCFSI analysis enables dealing with the fluid and structure parts individually at different steps of the solutions sequence, and also enables using different methods or different mesh resolution levels at different steps. In the isogeometric SCFSI analysis here, the first step is a previously computed (fully) coupled Immersogeometric Analysis FSI of the heart valve with a reasonable flow solution. With the valve leaflet and arterial surface motion coming from that, we perform a new, higher-fidelity fluid mechanics computation with the space–time topology change method and isogeometric discretization. Both the immersogeometric and space–time methods are variational multiscale methods. The computation presented for a bioprosthetic heart valve demonstrates the power of the method introduced

Developmental Changes of Prefrontal Activation in Humans: A Near-Infrared Spectroscopy Study of Preschool Children and Adults

Previous morphological studies indicated that development of the human prefrontal cortex (PFC) appears to continue into late adolescence. Although functional brain imaging studies have sought to determine the time course of functional development of the PFC, it is unclear whether the developmental change occurs after adolescence to adulthood and when it achieves a peak because of the narrow or discontinuous range in the participant's age. Moreover, previous functional studies have not focused on the anterior frontal region, that is, the frontopolar regions (BA9/10). Thus, the present study investigated the developmental change in frontopolar PFC activation associated with letter fluency task by using near-infrared spectroscopy (NIRS), in subjects from preschool children to adults. We analyzed the relative concentration of hemoglobin (ΔHb) in the prefrontal cortex measured during the activation task in 48 typically-developing children and adolescents and 22 healthy adults. Consistent with prior morphological studies, we found developmental change with age in the children/adolescents. Moreover, the average Δoxy-Hb in adult males was significantly larger than that in child/adolescent males, but was not true for females. These data suggested that functional development of the PFC continues into late adolescence. Although the developmental change of the frontopolar PFC was independent of gender from childhood to adolescence, in adulthood a gender difference was shown