The routine solution of multi-scale, physically-complex flows for practical applications in a predictive manner necessitates significant future advances in numerical methods and CFD algorithm design. Toward this end, research is continuing in the CFD and Propulsion Group on the development and application of a range of novel, accurate, efficient, and robust adaptive solution methods for multi-scale physically-complex flows using new and emerging high-performance computing (HPC) architectures. This research includes the development of: (i) high-order spatial (both finite-volume and novel flux reconstruction approaches) and temporal discreatization schemes; (ii) anisotropic body-fitted and hybrid (the latter involves a combination of multi-block body-fitted and more general unstructured grids) adaptive mesh refinement (AMR) meshing strategies with local solution-dependent refinement following from output-based error estimates; and (iii) efficient and highly-scalable parallel algorithm design for effective use of future heterogeneous HPC multi-core systems with floating-point accelerators.

Funding/Partners: Natural Science and Engineering Research Council (NSERC), Digital Research Alliance of Canada

The CFD and Propulsion Group is also investigating the development of novel theoretical and numerical approaches for efficiently predicting non-equilibrium, transition-regime, rarefied flows of gases and anisotropic plasmas using hyperbolic, realizable, maximum-entropy-based, moment closures which follow from kinetic theory. The hyperbolic, maximum-entropy-based, moment closures are particularly promising for the modelling micro-scale nonequilibrium gaseous flows and the treatment of fully and partially ionized anisotropic plasma. Moreover, the purely hyperbolic nature of the resulting moment equations makes the closures particularly appealing from a computational perspective, allowing accurate discretizations on AMR mesh. The development and application of maximum-entropy-inspired moment closures to the predictiion of other complex transport phenomena, such as polydisperse, polykinetic, liquid sprays and aerosols as well as radiative heat transfer, are also being considered.

Funding/Partners: Natural Science and Engineering Research Council (NSERC), Digital Research Alliance of Canada

Contrails are thought to be significant contributors of radiative forcing in climate change. Their formation is due to the presence of soot aerosols in aviation engine exhausts acting as the nuclei to form ice particles. The current understanding is that the soot aerosols, any aqueous aerosols formed in the exhaust, and the ambient aerosols entrained into the plume act as nuclei to form ice crystals when water vapour in the plume becomes supersaturated because of the plume mixing with ambient cold air and cooling rapidly; however, the details of these processes are not well known and there are significant knowledge gaps. Both RANS-based and large-eddy simulation (LES) descriptions of contrail formation are being developed for applications to the near-field prediction of contrails. Quadrature-based moment closures are being formulated for describing the associated soot and ice crystal aerosol dynamics and maximum-entropy-based interpolative moment closures are being considered for describing the radiative heat transfer.

Funding/Partners: Pratt & Whitney Canada, Natural Science and Engineering Research Council (NSERC), Digital Research Alliance of Canada

Today, commercial aviation accounts for about 2.5% of global greenhouse emissionsl; however, the air transport industry has set a goal of achieving net-zero carbon emissions by 2050. Hydrogen is a very attractive sustainable alternative to conventional hydrocarbon-based fuels in many areas, including aviation applications, as carbon dioxide is not a direct product of combustion. However, aside from issues associated with both production and safe storage of hydrogen, there are several significant challenges, knowledge gaps, and major technical impediments related to hydrogen combustion that are currently preventing the adoption of this zero-carbon fuel in practical combustion engines for aviation applications. New RANS-based and large-eddy simulation (LES) descriptions of hydrogen flames are being developed and applied to the prediction of steady-state combustion in attached and lifted partially-premixed and stratified hydrogen flames. Transient phenomena including ignition, propagation, flashback, lean blowout, and detonation are also being studied.

Funding/Partners: Pratt & Whitney Canada, Natural Science and Engineering Research Council (NSERC), Digital Research Alliance of Canada

Gas turbine engines currently operate on liquid hydrocarbon-based fuels and as such can yield a range of undesirable pollutants including gaseous emissions such as nitrogen oxides (NOx), carbon monoxide (CO), green-house gases (GHG, largely CO2, really a combustion product) and unburned hydrocarbons (UHC), as well as nanometer-sized carbonaceous particulate matter (PM) or soot. Due to increasing concerns for the environment and causes of global climate change, the manufacturers of gas turbine engines are today facing increasingly more stringent governmental and/or environmental regulations pertaining to emissions. The CFD and Propulsion Groups is therefore pursuing research related to the development of new mathematical theory, combustion models, and more accurate and efficient numerical methods and tools for enabling improved predictions of PM emission processes in gas turbine engines. The research includes the development of improved moment closure methods for the formation, oxidation, and transport of nanoscale soot particulates as well as the radiative heat transfer in participating media for both laminar and turbulent sooting flames.

Funding/Partners: Pratt & Whitney Canada, Ontario Research Fund (ORF), MITACS

The injection of liquid hydrocarbon-based fuels and the resulting spray atomization and formation have a direct impact on the combustion processes occurring in and the emmissions arising from gas turbine engines. The high-fidelity numerical modeling of the spray formation and atomization associated with liquid fuel injection systems in a computationally efficient manner remains a major challenge for multi-phase combustion applications. Eulerian-based moment closure methods are proving to be very promising techniques for describing the disperse regime of such sprays, as they are well suited to high-performance computations and they provide a natural link with descriptions of the separate-phase flows of dense-spray regimes occurring upstream of primary atomization. The CFD and Propulsion group is conducting research into Eulerian-based moment closure methods for spray applications. Maximum-entropy inspired moment closure strategies for treating droplet size polydispersion, droplet velocity dispersion, and particle trajectory crossings associated with high inertial droplets are being investigated. Additionally, the coupling of the closure methods with spray breakup and atomization processes via empirically-based quasi-multiphase models are also being explored.

Funding/Partners: Pratt & Whitney Canada, Ontario Research Fund (ORF), MITACS

Space Weather is a term that is used to refer to conditions on the Sun and in the solar wind and geospace environment, which includes the lithosphere, hydrosphere, atmosphere, ionosphere, and magnetosphere, that can influence the performance and reliability of both space-borne and ground-based technological systems or can adversely affect human life or health on earth. The Sun and the resulting plasma environment within the heliosphere are the key drivers of space weather. The CFD and Propulsion group is currently involved in the development of an advanced, made-in-Canada, data-driven, global MHD-based simulation model for space weather predictions and the simulation of unsteady transient phenomena such as coronal mass ejections (CMEs) in the heliosphere and solar wind and their impact on the Earth’s magnetosphere, using novel and leading-edge numerical simulation techniques, including anisotropic AMR. Variational-based data assimilation (DA) techniques are also being considered so as to incorporate available ground-based and satellite data and arrive at improved space weather forecasts.

Funding/Partners: Canadian Space Agency (CSA), National Resources Canada (NRCan) Geomagnetic Laboratory

The generation of hydrogen in nuclear power plants arising from a severe accident and its possible combustion is a safety hazard that can present a challenge to the containment integrity of power plants and may lead to the release of nuclear contaminants. The design and implementation of hydrogen mitigation measures can be greatly facilitated by the use of simulation codes describing hydrogen flame ignition and propagation within containment vessels and structures; however, improved modelling is required to increase the confidence of such analyses. To address this shortfall, the CFD and Propulsion Group is pursuing the development of improved combustion CFD modelling and simulation capabilities for predicting hydrogen deflagrations in closed and vented containment systems. In particular, improved large-eddy simulation (LES) techniques and combustion models for the treatment of turbulent/chemistry interactions in premixed hydrogen flames are being investigated as well as effective methods for the efficient numerical solution of the resulting governing equations.

Funding/Partners: Canadian Nuclear Laboratories (CNL)