Accurate simulation of unsteady turbulent flow is critical for improved design of greener aircraft that are quieter and more fuel-efficient. We demonstrate application of PyFR, a Python based computational fluid dynamics solver, to petascale simulation of such flow problems. Rationale behind algorithmic choices, which offer increased levels of accuracy and enable sustained computation at up to 58% of peak DP-FLOP/s on unstructured grids, will be discussed in the context of modern hardware. A range of software innovations will also be detailed, including use of runtime code generation, which enables PyFR to efficiently target multiple platforms, including heterogeneous systems, via a single implementation. Finally, results will be presented from a full-scale simulation of flow over a low-pressure turbine blade cascade, along with weak/strong scaling statistics from the Piz Daint and Titan supercomputers, and performance data demonstrating sustained computation at up to 13.7 DP-PFLOP/s.

Towards green aviation with python at petascale

Numerical investigation of secondary flows in a high-lift low pressure turbine

Deep learning to replace, improve, or aid CFD analysis in built environment applications: A review

Mathematical programming and meta-heuristics are two types of optimization methods. Meta-heuristic algorithms can identify optimal/near-optimal solutions by mimicking natural behaviours or occurrences and provide benefits such as simplicity of execution, a few parameters, avoidance of local optimization, and flexibility. Many meta-heuristic algorithms have been introduced to solve optimization issues, each of which has advantages and disadvantages. Studies and research on presented meta-heuristic algorithms in prestigious journals showed they had good performance in solving hybrid, improved and mutated problems. This paper reviews the sparrow search algorithm (SSA), one of the new and robust algorithms for solving optimization problems. This paper covers all the SSA literature on variants, improvement, hybridization, and optimization. According to studies, the use of SSA in the mentioned areas has been equal to 32%, 36%, 4%, and 28%, respectively. The highest percentage belongs to Improved, which has been analyzed by three subsections: Meat-Heuristics, artificial neural networks, and Deep Learning. 

https://link.springer.com/content/pdf/10.1007/s11831-022-09804-w.pdf

Advances in Sparrow Search Algorithm: A Comprehensive Survey

https://pureadmin.qub.ac.uk/ws/files/197672195/Tyacke.pdf

Turbomachinery simulation challenges and the future

Using a range of high-fidelity large eddy simulations (LES), the contrasting flow physics on the suction surface, pressure surface, and endwalls of a low-pressure turbine (LPT) blade (T106A) was studied. The current paper attempts to provide an improved understanding of the flow physics over these three zones under the influence of different inflow boundary conditions. These include: (a) the effect of wakes at low and high turbulence intensity on the flow at midspan and (b) the impact of the state of the incoming boundary layer on endwall flow features. On the suction surface, the pressure fluctuations on the aft portion significantly reduced at high freestream turbulence (FST). The instantaneous flow features revealed that this reduction at high FST (HF) is due to the dominance of "streak-based" transition over the "Kelvin-Helmholtz" (KH) based transition. Also, the transition mechanisms observed over the turbine blade were largely similar to those on a flat plate subjected to pressure gradients. On pressure surface, elongated vortices were observed at low FST (LF). The possibility of the coexistence of both the Gortler instability and the severe straining of the wakes in the formation of these elongated vortices was suggested. While this was true for the cases under low turbulence levels, the elongated vortices vanished at higher levels of background turbulence. At endwalls, the effect of the state of the incoming boundary layer on flow features has been demonstrated. The loss cores corresponding to the passage vortex and trailing shed vortex were moved farther from the endwall with a turbulent boundary layer (TBL) when compared to an incoming laminar boundary layer (LBL). Multiple horse-shoe vortices, which constantly moved toward the leading edge due to a low-frequency unstable mechanism, were captured.

Numerical Investigation of Contrasting Flow Physics in Different Zones of a High-Lift Low Pressure Turbine Blade

The secondary flow increases the loss and changes the flow incidence in the downstream blade row. To prevent hot gases from entering disk cavities, purge flows are injected into the mainstream in a real aero-engine. The interaction between purge flows and the mainstream usually induces aerodynamic losses. The endwall loss is also affected by shedding wakes and secondary flow from upstream rows. Using a series of eddy-resolving simulations, this paper aims to improve the understanding of the interaction between purge flows, incoming secondary flows along with shedding wakes, and mainstream flows on the endwall within a stator passage. It is found that for a blade with an aspect ratio of 2.2, a purge flow with a 1% leakage rate increases loss generation within the blade passage by around 10%. The incoming wakes and secondary flows increase the loss generation further by around 20%. The purge flow pushes the passage vortex further away from the endwall and increases the exit flow angle deviation. However, the maximum exit flow angle deviation is reduced after introducing incoming wakes and secondary flows. The loss generation rate is calculated using the mean flow kinetic energy equation. Two regions with high loss generation rate are identified within the blade passage: the corner region and the region where passage vortex interacts with the boundary layer on the suction surface. Loss generation rate increases dramatically after the separated boundary layer transitions. Since the endwall flow energizes the boundary layer and triggers earlier transition on the suction surface, the loss generation rate close to the endwall at the trailing edge (TE) is suppressed.

/pdf/numerical-study-of-purge-and-secondary-flows-in-a-low-3agu2d181o.pdf

Numerical Study of Purge and Secondary Flows in a Low-Pressure Turbine

Aerodynamic performance improvements of a vertical axis wind turbine by leading-edge protuberance

A numerical study was performed to investigate the effects of Microvortex Generators (MVGs) on the aerodynamic performance of the NACA 0018 airfoil and an H-type Darrieus wind turbine. MVGs can delay stall, which may occur for a sustained duration during turbine operation. The flow fields around a single airfoil and the Vertical Axis Wind Turbine (VAWT) rotor are investigated. The purpose of the present work is to determine the best configuration of MVGs. In total, eight different configurations are studied. The results show that MVGs have significantly enhanced the lift of the airfoil near the stall and improve the stall margin. The improved airfoil design with MVGs installed at 20% chord length and 16° to the inlet flow with a rectangle shape has the maximum lift and stall angle. In addition, adding MVGs of the same configuration can significantly improve the power coefficient of the VAWT at a high tip speed ratio, where it typically gives low power production. The flow separation is suppressed in the azimuth angle ranging from 120° to 135°, where the power output increase is observed showing a potential impact for VAWT design.A numerical study was performed to investigate the effects of Microvortex Generators (MVGs) on the aerodynamic performance of the NACA 0018 airfoil and an H-type Darrieus wind turbine. MVGs can delay stall, which may occur for a sustained duration during turbine operation. The flow fields around a single airfoil and the Vertical Axis Wind Turbine (VAWT) rotor are investigated. The purpose of the present work is to determine the best configuration of MVGs. In total, eight different configurations are studied. The results show that MVGs have significantly enhanced the lift of the airfoil near the stall and improve the stall margin. The improved airfoil design with MVGs installed at 20% chord length and 16° to the inlet flow with a rectangle shape has the maximum lift and stall angle. In addition, adding MVGs of the same configuration can significantly improve the power coefficient of the VAWT at a high tip speed ratio, where it typically gives low power production. The flow separation is suppressed in the a...

/pdf/cfd-analysis-for-the-performance-of-micro-vortex-generator-9gmavj73r6.pdf

Jiahuan Cui

Papers

Numerical Investigation of Contrasting Flow Physics in Different Zones of a High-Lift Low Pressure Turbine Blade

Numerical investigation of secondary flows in a high-lift low pressure turbine

Numerical Study of Purge and Secondary Flows in a Low-Pressure Turbine

Aerodynamic performance improvements of a vertical axis wind turbine by leading-edge protuberance

CFD analysis for the performance of micro-vortex generator on aerofoil and vertical axis turbine