Hybrid RANS-LES Versus URANS Simulations of a Simplified Compressor Blades Cascade

DOI: 10.1007/978-3-319-15141-0_2

Comparison of thermodynamic models for ice accretion on airfoils

Purpose This paper aims to assess the strengths and weaknesses of four thermodynamic models used in aircraft icing simulations to orient the development or the choice of an improved thermodynamic model. Design/methodology/approach Four models are compared to assess their capabilities: Messinger, iterative Messinger, extended Messinger and shallow water icing models. They have been implemented in the aero-icing framework, NSCODE-ICE, under development at Polytechnique Montreal since 2012. Comparison is performed over typical rime and glaze ice cases. Furthermore, a manufactured geometry with multiple recirculation zones is proposed as a benchmark test to assess the efficiency in runback water modeling and geometry evolution. Findings The comparison shows that one of the main differences is the runback water modeling. Runback modeling based on the location of the stagnation point fails to capture the water film behavior in the presence of recirculation zones on airfoils. However, runback modeling based on air shear stress is more suitable in this situation and can also handle water accumulation while the other models cannot. Also, accounting for the conduction through the ice layer is found to have a great impact on the final ice shape as it increases the overall freezing fraction. Originality/value This paper helps visualize the effect of different thermodynamic models implemented in the same aero-icing framework. Also, the use of a complex manufactured geometry highlights weaknesses not normally noticeable with classic ice accretion simulations. To help with the visualization, the ice shape is presented with the water layer, which is not shown on typical icing results

DDES and OES Simulations of a Morphing Airbus A320 Wing and Flap in Different Scales at High Reynolds

The present study concerns the use of unsteady numerical simulations by means of Navier Stokes Multi Block (NSMB) solver including both high order schemes and turbulence resolving methods. Firstly, this work attempts to highlight the role of the morphing applied to the supercritical Airbus A320 wing and flap in the trailing-edge for a Reduced Scale (RS) prototype at the clean position, this morphing includes a slight deformation of the trailing edge with a selected frequency and amplitude, which has an impact on the flow near the trailing edge and specially in the wake structures. This solution can transform the 3-dimensional chaotic flow into a 2-dimensional one by enhancing coherence of 2D structures rows of von Kármán vortices. In Addition, the highlift A320 wing-flap at the take-off position in Large-Scale (LS) configuration have been studied using advanced hybrid models DDES, the Organised Eddy Simulation OES and SST for the RANS regions as well as LES Smagorinsky model

MORPHING FOR SMART WING DESIGN THROUGH RANS/LES METHODS

This article presents numerical simulation results obtained in the context of the H2020 European research project SMS, “Smart Morphing and Sensing for Aeronautical configurations” by using among other, hybrid RANS-LES methods, able to accompany the design of the wings of the future. The morphing concepts studied are partly bio-inspired and are able to act in multiple time and length scales. They are proven efficient for the increase of the aerodynamic performances of A320 wings in reduced scale and near scale one, in synergy with the prototypes built within this project. The simulations have shown the ability of novel electroactive actuators performing slight deformation of the trailing edge region and optimal vibrations, to create suitable vortex breakdown of specific coherent structures and to enhance beneficial vortices, leading to thinning of the shear layers and the wake’s width. The simulations quantified the optimal actuation ranges and the gains in lift increase, drag reduction and simultaneous attenuation of the noise sources past the trailing edge

Coil Flow Inversion as a Route To Control Polymerization in Microreactors

Linear and branched polymers of 2-(dimethylamino)ethyl methacrylate (PDMAEMA) were synthesized in flow by atom transfer radical polymerization (ATRP) and self-condensing vinyl copolymerization adapted to ATRP, respectively, in capillary type stainless steel coiled tube (CT) microreactors. Coil flow inversion (CFI) was introduced to achieve better mixing and narrower residence time distributions during polymerization. This strategy was adopted to improve control over macromolecular characteristics and polymer architecture. Polydispersity index (PDI), as an overall indicator of control over polymerization, was significantly lower for CFI in the case of linear PDMAEMA, 1.39 compared to 1.53 for CT. For branched polymers containing up to 10 mol % of inimer, a reduced PDI was also obtained for CFI microreactor. As for the branching efficiency, it was found to follow the following trend CFI > CT > batch reactor

Improved size-tunable preparation of polymeric nanoparticles by microfluidic nanoprecipitation

International audienceSize-tunable polymeric nanoparticles have been successfully produced by a microfluidic-assisted nanoprecipitation process. A multilamination micromixer has been chosen to fabricate continuously nanoparticles of methacrylic polymers. Various operating conditions, such as the polymer concentration, the amount of non-solvent and the characteristics of the raw polymer (molecular weight and architecture: linear vs. branched) have been investigated. Their influences on the final particle size, ranging from 76 to 217 nm, have been correlated to the mechanisms leading to the formation of nanoparticles. In this type of microfluidic device, mixing mainly operates by diffusion mass transfer, helped by hydrodynamic focusing. The effect of micromixing on the size of particles has also been shown experimentally and supported by a computational fluid dynamics (CFD) study. A mixing criterion has been defined and numerically calculated to corroborate the effect of the flow rate of polymer solution on the particles size. An increase in the polymer solution flow rate increases the value of this mixing criterion, resulting in smaller nanoparticles