A numerical strategy to combine high-order schemes, complex geometry and parallel computing for high resolution DNS of fractal generated turbulence

Impressive advances in parallel platform architectures over the past decade have made Direct Numerical Simulation (DNS) a powerful tool which can provide full access to the spatial structure of turbulent flows with complex geometries. An innovative approach which combines high-order schemes and a dual domain decomposition method is presented in this paper and is applied to DNS of multiscale-generated turbulent flows by a fractal grid. These DNS illustrate the applicability of our approach to the simulation of complex turbulent flows and provide results which are compared with recent laboratory experiments thus providing new insights for the interpretation of the experimental measurements.     

Influence of sulfation and structure of zirconia on catalytic isomerization of n‐hexane

Two series of sulfated zirconia have been prepared by immersing amorphous or crystalline zirconia in an H₂SO₄ solution (0.25–2.5 M). They were compared with a commercial sulfated zirconium hydroxide. Activation temperature was varied between 300 and 725°C. Sulfate density varied so that the mean surface area of an individual sulfate ranged from 0.14 to 0.54 nm². Three limiting sulfate states are evidenced and characterized by TPRMS. Catalysts are tested for isomerization of nhexane at 150°C and 3 MPa. Factors influencing the activity are discussed. The data show that a highly active and selective catalyst for producing hexane isomers requires tetragonal zirconia with a sulfate occupancy of about 0.40 nm². Preparation parameters must therefore be adapted to match these constraints.     

WInc3D: A novel framework for turbulence‐resolving simulations of wind farm wake interactions

A fast and efficient turbulence‐resolving computational framework, dubbed as WInc3D (Wind Incompressible 3‐Dimensional solver), is presented and validated in this paper. WInc3D offers a unified, highly scalable, high‐fidelity framework for the study of the flow structures and turbulence of wind farm wakes and their impact on the individual turbines' power and loads. Its unique properties lie on the use of higher‐order numerical schemes with “spectral‐like” accuracy, a highly efficient parallelisation strategy which allows the code to scale up to O(10⁴) computing processors and software compactness (use of only native solvers/models) with virtually no dependence to external libraries. The work presents an overview of the current modelling capabilities along with model validation. The presented applications demonstrate the ability of WInc3D to be used for testing farm‐level optimal control strategies using turbine wakes under yawed conditions. Examples are provided for two turbines operating in‐line as well as a small array of 16 turbines operating under “Greedy” and “Co‐operative” yaw angle settings. These large‐scale simulations were performed with up to 8192 computational cores for under 24 hours, for a computational domain discretised with O(10⁹) mesh nodes.