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Dissertation
Master thesis and internship[BR]- Master's thesis : Impact of operating conditions on the transitional flow in a low-pressure fast turbine cascade[BR]- Integration internship
Authors: --- --- ---
Year: 2021 Publisher: Liège Université de Liège (ULiège)

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Abstract

The transition of boundary layer from laminar to turbulent is more probable to happen across various components of a turbomachine. If narrowed down to a case of low-pressure turbine cascade, the transition of flow in boundary layer is due to separation induction. Due to this, blade losses are observed and it depends on various physical characteristics such as size and the length of the separation bubble. The physical characteristics can vary based on the variation of flow Reynolds number, expansion ration of the flow and the inlet flow turbulence intensity. Such characteristics can be studied using computational techniques, CFD analysis. Various computational techniques can be used for this scope of study, ranging from Reynolds Averaged Navier Stokes to Direct Numerical Simulation modelling, and each technique have its own set of advantages and disadvantages. 

The objective of this thesis is to present and acknowledge on how these separation bubble physical characteristics vary due to the variation of flow expansion ratio and variation of exit isentropic Reynolds number for a SPLEEN blade cascade. Direct Numerical Simulation technique will be adapted for this thesis, due to its ability to accurately predict separation bubble location and size but compromising to relatively high computational power requirement.


Dissertation
Master thesis and internship[BR]- Master's thesis : Improvement of the viscous-inviscid interaction method implemented in DARTFLO[BR]- Integration internship
Authors: --- --- --- ---
Year: 2022 Publisher: Liège Université de Liège (ULiège)

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Abstract

Preliminary aircraft design often relies on solutions of the RANS equations to characterize the flow field in the different conditions of interest. Such a procedure usually comes at the expense of costly computations that can hardly be used routinely in the early stages of the design. To overcome this problematic, inviscid flow models are considered as an alternative since the associated computational time is more interesting. The main drawback of these models is their inability to predict aerodynamic drag or flow separation which is of upmost interest to optimize the aircraft for fuel consumption. Viscous corrections can be used with these flow models and offer a fast tool suited for preliminary design.
This study presents a pseudo-time dependent, two-dimensional interacting boundary layer method for compressible flows in external aerodynamics. An inviscid flow is modeled by an unstructured finite-element, full potential solver suited for transonic flow computations. The flow in the immediate wall vicinity and in the wake is distinguished from the external inviscid flow by its viscosity property and is described by the time-dependent, compressible integral boundary layer equations. Steady-state flow solutions in the boundary layer are obtained on a dedicated mesh through a damped Newton scheme and are interfaced with the inviscid solutions through a quasi-simultaneous coupling method. The eN method is used to capture the laminar to turbulent transition. A pseudo-time marching method is presented with time advancement control and spo- radic numerical information update. Results are presented subsequently for attached and mildly separated flows around a symmetrical airfoil, for high angle of attack and low Reynolds number flows. Transonic capabilities are demonstrated on a supercritical airfoil and compared to RANS solutions which constitute the current reference in the domain. Stable convergence and good agreement with reference results is observed for flows with limited separation regions. Expected limitations are shown when the regime approaches stall. Further possible improvements, such as the use of an inverse method and mesh quality improvements are discussed especially for the transonic regime and results are consequently argued.


Book
Selected Problems in Fluid Flow and Heat Transfer
Author:
ISBN: 3039214284 3039214276 Year: 2019 Publisher: MDPI - Multidisciplinary Digital Publishing Institute

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Abstract

Fluid flow and heat transfer processes play an important role in many areas of science and engineering, from the planetary scale (e.g., influencing weather and climate) to the microscopic scales of enhancing heat transfer by the use of nanofluids; understood in the broadest possible sense, they also underpin the performance of many energy systems. This topical Special Issue of Energies is dedicated to the recent advances in this very broad field. This book will be of interest to readers not only in the fields of mechanical, aerospace, chemical, process and petroleum, energy, earth, civil ,and flow instrumentation engineering but, equally, biological and medical sciences, as well as physics and mathematics; that is, anywhere that “fluid flow and heat transfer” phenomena may play an important role or be a subject of worthy research pursuits.

Keywords

n/a --- thermal performance --- microbubble pump --- particle deposition --- flow oscillation --- orthogonal jet --- flat plate --- gas turbine engine --- air heater --- flow behavior --- transonic compressor --- friction factor --- nonlinear thermal radiation --- oscillators --- porous cavity --- POD --- turbulent flow --- thermosyphon --- turbulence --- mass transfer --- tip leakage flow --- capture efficiency --- pipe flow --- correlation --- decomposition dimensionalities --- heat transfer --- pressure loss --- CANDU-6 --- numerical modeling --- CFD --- magnetic field --- boundary layer --- two-phase flow --- heat transfer performance --- Colebrook-White --- computational burden --- phase change --- surrogate model --- Padé polynomials --- traveling-wave heat engine --- flow regime --- numerical simulation --- energetics --- ( A g ? F e 3 O 4 / H 2 O ) hybrid nanofluid --- pumps --- BEM --- SPIV --- acoustic streaming --- microbubbles --- Aspen® --- push-pull --- Positive Temperature Coefficient (PTC) elements --- iterative procedure --- transient analysis --- spiral fin-tube --- toxic gases --- unsteady heat release rate --- water hammer --- method of moment --- visualization --- superheated steam --- impingement heat transfer enhancement --- X-ray microtomography --- moderator --- wind turbine --- flow rate --- fin-tube --- flue gas --- actuator disc --- temperature distributions --- supercritical LNG --- sharp sections --- moment of inertia --- Colebrook equation --- pump efficiency --- tower --- OpenFOAM --- computational fluid dynamics --- chemical reaction --- pump performance --- logarithms --- numerical results --- downwind --- thermodynamic --- triaxial stress --- flow friction --- energy conversion --- entropy generation --- zigzag type --- inertance-compliance --- section aspect ratios --- laminar separation bubble --- axial piston pumps --- thermogravimetry --- pressure drop --- load resistances --- vortex breakdown --- T-section prism --- flow-induced motion --- centrifugal pump --- load --- vortex identification --- decomposition region --- condensation --- performance characteristics --- pipes --- detached-eddy simulation --- Computational Fluid Dynamics (CFD) simulation --- thermal cracking --- real vehicle experiments --- bubble size --- thermal energy recovery --- hydraulic resistances --- concentration --- tower shadow --- fire-spreading characteristics --- thermoacoustic electricity generator --- bubble generation --- multi-stage --- thermal effect --- ferrofluid --- PHWR --- fluidics --- multiphase flow --- printed circuit heat exchanger --- particle counter --- dew point temperature --- Padé polynomials

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