Assessment and calibration of the γ equation transition model for a wide range of Reynolds numbers at low Mach

The numerical simulation of flows over large-scale wind turbine blades without considering the transition from laminar to fully turbulent flow may result in incorrect estimates of the blade loads and performance. Thanks to its relative simplicity and promising results, the Local-Correlation based Transition Modelling concept represents a valid way to include transitional effects into practical CFD simulations. However, the model involves coefficients to be tuned to match the required application. In this paper, the γ-equation transition model is assessed and calibrated, for a wide range of Reynolds numbers at low Mach, as needed for wind turbine applications. Different airfoils are used to evaluate the original model and calibrate it, whereas a large-scale wind turbine blade is employed to show that the calibrated model can lead to reliable solution for complex three-dimensional flows. The calibrated model shows promising results for both two-dimensional and three-dimensional flows, even if cross-flow instabilities are neglected

Accurate Predictions of Hovering Rotor Flows Using CFD

With work on the S-76 rotor providing encouraging results regarding the prediction of integral loads with CFD in hover, the XV-15 rotor is now analysed. Fully turbulent and transitional results are obtained showing the capability of modern CFD methods. The transition onset and distribution of skin friction are well predicted and were found to have a mild effect on the overall figure of merit. This work also shows the potential of transport-based models for transition prediction in complex 3D flows. Finally, hover simulations for the PSP blade are also shown in terms of surface pressure coefficient and wake visualisation

Aerodynamic effects of surface deformities on aerofoils for low-speed stratospheric flight

© IMechE 2022. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1177/09544100221093210High-altitude pseudo-satellites are an expanding focal area of the aerospace industry which require new technologies and manufacturing processes to reduce weight and increase efficiency with the aim of increasing endurance. One such process has resulted in the occurrence of small deformities along the leading edge of a lightweight unmanned aerial vehicle structure with the application of its skin, which may have a detrimental impact on its performance and efficiency. This paper focuses on the effects of these manufacturing deformities on the aerodynamic performance of the vehicle’s aerofoil when operating in low Reynolds number flow with the intention of identifying any detrimental flow variation. This analysis is achieved by comparing the lift curve, drag polar and pressure coefficient of both the deformed and undeformed cases of two aerofoils: a SG6042 and a GOE 523. This is accompanied with an examination of the local flow conditions scrutinising the near-wall y+ and turbulent kinetic energy calculations. The investigation finds that in two-dimensional flow, the deformities replicate the effects of transition trips in the shrinking or elimination of laminar separation bubbles. At Reynolds numbers below 250,000, the deformities reduce the net drag while leaving the lift largely unaffected. However, as a result, there is a slight shift in the minimum power condition in the order of 8% which would produce some performance loss for power efficiency and endurance.Peer reviewe

Coupling of particle-based and grid-based methods within object-oriented multi-physics CFD framework

A novel multi-physics approach involving mesh-based methods for kinetic-Boltzmann equations coupled with molecular dynamics (MD) simulations of thermal relaxation is introduced. The particle method, its parallel performance and the implemen- tation in MΦC are discussed, including the unification and re-use of the source code for different methods and models. The hypersonic partially rarefied flow of a diatomic gas around a sphere and a spaceplane configuration are considered as examples, providing de- tails about the thermal non-equilibrium conditions to be modelled using MD simulations. The MD results show that existing empirical models may not provide sufficient accuracy for the gas flow in strong expansions and that the proposed method provides a mechanism for improving the accuracy

Coupling of particle-based and grid-based methods within object-oriented multi-physics CFD framework

A novel multi-physics approach involving mesh-based methods for kinetic-Boltzmann equations coupled with molecular dynamics (MD) simulations of thermal relaxation is introduced. The particle method, its parallel performance and the implemen- tation in MΦC are discussed, including the unification and re-use of the source code for different methods and models. The hypersonic partially rarefied flow of a diatomic gas around a sphere and a spaceplane configuration are considered as examples, providing de- tails about the thermal non-equilibrium conditions to be modelled using MD simulations. The MD results show that existing empirical models may not provide sufficient accuracy for the gas flow in strong expansions and that the proposed method provides a mechanism for improving the accuracy

Compiling an inventory of glacier-bed overdeepenings and potential new lakes in de-glaciating areas of the Peruvian Andes: approach, first results, and perspectives for adaptation to climate change

Global warming causes rapid shrinking of mountain glaciers. New lakes can, thus, form in the future where overdeepenings in the beds of still-existing glaciers are becoming exposed. Such new lakes can be amplifiers of natural hazards to downstream populations, but also constitute tourist attractions, offer new potential for hydropower, and may be of interest for water management. Identification of sites where future lakes will possibly form is, therefore, an essential step to initiate early planning of measures for risk reduction and sustainable use as part of adaptation strategies with respect to impacts from climate change. In order to establish a corresponding knowledge base, a systematic inventory of glacier-bed overdeepenings and possible future lakes was compiled for the still glacierized parts of the Peruvian Andes using the 2003-2010 glacier outlines from the national glacier inventory and the SRTM DEM from the year 2000. The resulting inventory contains 201 sites with overdeepened glacier beds >1 ha (104 m²) where notable future lakes could form, representing a total volume of about 260 million m³. A rough classification was assigned for the most likely formation time of the possible new lakes. Such inventory information sets the stage for analyzing sustainable use and hazard/risk for specific basins or regions