Numerical Simulation of a Closed Rotor-stator System Using Large Eddy Simulation PDF Download
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Author: Solal Abraham Teva Amouyal
Publisher:
ISBN:
Category :
Languages : en
Pages : 50
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A large eddy simulation of an enclosed annular rotor stator cavity is presented. The geometry is characterized by a large aspect ratio G = (b-a)/h = 18.32 and a small radius ratio a/b = 0.152, where a and b are the inner and outer radii of the rotating disk and h is the interdisk spacing. The rotation rate [omega] under consideration is equivalent to the rotational Reynolds number Re = [omega]b2/v = 9.5x104, where v is the kinematic viscosity. The main objective of this study is to correctly simulate the rotor stator cavity using a low order numerical scheme on unstructured grids. The numerical simulations were run on the software AVBP developed by the Centre Européen de Recherche et de Formation Avancée en Calcul Scientific. The results were compared to the experimental results obtained by Sebastien Poncet of Université Aix-Marseille. Two large eddy simulations techniques were used: the Smagorinsky and Wall-adapting local eddy-viscosity models. The simulations were run on three set of grids, each with a different cell resolution-14, 35 and 50- along the thickness of the system. Results from each mesh show a good qualitative agreement of the mean velocity field with Poncet's experimental results. It was found that the Samgorinsky model to be more appropriate for this configuration.
Author: Solal Abraham Teva Amouyal
Publisher:
ISBN:
Category :
Languages : en
Pages : 50
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Book Description
A large eddy simulation of an enclosed annular rotor stator cavity is presented. The geometry is characterized by a large aspect ratio G = (b-a)/h = 18.32 and a small radius ratio a/b = 0.152, where a and b are the inner and outer radii of the rotating disk and h is the interdisk spacing. The rotation rate [omega] under consideration is equivalent to the rotational Reynolds number Re = [omega]b2/v = 9.5x104, where v is the kinematic viscosity. The main objective of this study is to correctly simulate the rotor stator cavity using a low order numerical scheme on unstructured grids. The numerical simulations were run on the software AVBP developed by the Centre Européen de Recherche et de Formation Avancée en Calcul Scientific. The results were compared to the experimental results obtained by Sebastien Poncet of Université Aix-Marseille. Two large eddy simulations techniques were used: the Smagorinsky and Wall-adapting local eddy-viscosity models. The simulations were run on three set of grids, each with a different cell resolution-14, 35 and 50- along the thickness of the system. Results from each mesh show a good qualitative agreement of the mean velocity field with Poncet's experimental results. It was found that the Samgorinsky model to be more appropriate for this configuration.
Author: Robert Bruce Broberg
Publisher:
ISBN:
Category :
Languages : en
Pages : 178
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Author: Matthieu Queguineur (docteur en mécanique des fluides).)
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Unsteady phenomena in rotor/stator cavity are well known to be the source of dangerous vibrations in space turbopump. Even though many palliative measures have been taken during their design, experimental campaigns often reveal high flow oscillations that can jeopardize turbomachinery components and even the rocket engine. Today, the origin of such flow instabilities usually called 'pressure band phenomenon'(PBP) is not well understood and difficult to predict numerically. The main goal of this thesis is to investigate such phenomenon mechanism to find technical solutions so as to control it. This problematic is addressed here trough two types of configuration: an academic rotor/stator cavity and a space turbopump cavity. When it comes to cavity flows, their rotating boundary layers are known to be three dimensional and receptive to several instabilities taking the form of spirals or annuli. Reynolds Averaged Navier-Stokes Simulations (RANS)failed to predict such unsteady systems. However, Large Eddy Simulation (LES) proved to be a relevant alternative in many similar applications and is therefore chosen for the present work. Using Power Spectral Analysis (PSD) and Dynamic Mode Decomposition (DMD) on LES predictions, one shows that the PBP is retrieved in an annular smooth rotor/stator cavity and it is composed of three modes driving all the system dynamics. To investigate these mode organization and their possible interactions, a new tool called Dynamic Mode Tracking /Control (DMT/DMTC) is introduced. DMT is constructed so as to extract "on-thefly" flow coherent structures with a given frequency on the basis of LES. Furthermore, augmenting the Navier-Stokes equations with a relaxation term coupled to DMT, DMTC allows to control and follow the evolution of a controlled mode as well as non controlled ones and thereby observe interactions. This strategy after validation is applied to the annular rotating cavity and shows that the low frequency mode is generated by the dominant mode of the system. To go further, Global Linear Stability Analysis (GLSA) augmented with adjoint methods is used to shed some light on all mode origins and points out that the low frequency and dominant modes are coming from the stationary boundary layer. In order to set up control strategies, the GLSA framework is further developed introducing the concept of the sensitivity to base flow modifications which gives the location where the flow should be modified if one wants to stabilize or at least shift a frequency mode. Applied to the academic cavity, one shows that contrary to most studies in the literature, controlling the stator boundary layer is the more efficient way to damp the PBP through suction/injection devices. Finally, gathering all the previous understanding of this flow, the LES framework enables to validate the control strategies proposed and to stabilize the PBP for very low suction amplitudes. To finish, the PBP is analyzed in real space turbompump cavities. In particular, the sensitivity of this specific phenomenon to geometry changes is investigated through two configurations: one without and one with the blades of the stator of the turbopump. Even though the introduction of the blades in the LES creates a more complex flow with the presence of shocks, similar pressure fluctuation spectra are retrieved in both configurations but with azimuthal wavenumber modes that are shifted. Following the studies on the academic cavity, an adapted GLSA to the non-linear dynamics of the turbopump enables to point out that even though the PBP modes are particularly marked in the mainstream of the system, the source of these modes is located in the subcavity in the rotor-stator wheel space. In particular, GLSA results indicate that two possible ways to control the phenomenon are possible: modifying the flow around the seal rim and or modifying the leak around the hub.
Author:
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ISBN:
Category : Aeronautics
Languages : en
Pages : 702
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Author: Joseph John McVeigh
Publisher:
ISBN:
Category :
Languages : en
Pages : 220
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Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
ISBN: 9781793919175
Category : Science
Languages : en
Pages : 26
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Book Description
The current paper reports on numerical investigations on the flow characteristics in a transonic axial compressor, NASA Rotor 37. The flow field was used previously as a CFD blind test case conducted by American Society of Mechanical Engineers in 1994. Since the CFD blind-test exercise, many numerical studies on the flow field in the NASA Rotor 37 have been reported. Although steady improvements have been reported in both numerical procedure and turbulence closure, it is believed that all the important aspects of the flow field have not been fully explained with numerical studies based on the Reynolds Averaged Navier-Stokes (RANS) solution. Experimental data show large dip in total pressure distribution near the hub at downstream of the rotor at 100% rotor speed. Most original numerical solutions from the blind test exercise did not predict this total pressure deficit correctly. This total pressure deficit at the rotor exit was attributed to a hub corner flow separation by the author. Several subsequent numerical studies with different turbulence closure model also calculated this dip in total pressure rise. Also, several studies attributed this total pressure deficit to a small leakage flow coming from the hub in the test article. As the experimental study cannot be repeated, either explanation cannot be validated. The primary purpose of the current investigation is to investigate the transonic flow field with both RANS and a Large Eddy Simulation (LES). The RANS approach gives similar results presented at the original blind test exercise. Although the RANS calculates higher overall total pressure rise, the total pressure deficit near the hub is calculated correctly. The numerical solution shows that the total pressure deficit is due to a hub corner flow separation. The calculated pressure rise from the LES agrees better with the measured total pressure rise especially near the casing area where the passage shock interacts with the tip clearance vortex and flow bec
Author:
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ISBN:
Category : Government publications
Languages : en
Pages : 934
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Author:
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ISBN:
Category :
Languages : en
Pages : 112
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This thesis describes a series of numerical experiments dealing with rotor/stator interactions in hydroturbines. The means of analysis was a nonconforming sliding spectral element method for the unsteady, incompressible Navier-Stokes equations in two-dimensional geometry. The variable parameter in the simulation was the rotor advance coefficient. A comparison of lifting forces, flow rate, dissipation and kinetic energy was conducted for the various test cases. Robustness of the numerical discretizations was demonstrated by the consistency of the computed results. The divergence, vorticity and streamlines generated during postprocessing were in strong agreement with hydrodynamic theory. A step-by-step procedure is presented for manipulating the working environment -- the discrete spectral element control volume -- around the rotor- stator pair. The selection criteria for the input parameters and boundary conditions is developed.
Author: Aziz Belmiloudi
Publisher: BoD – Books on Demand
ISBN: 9533072261
Category : Science
Languages : en
Pages : 670
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Over the past few decades there has been a prolific increase in research and development in area of heat transfer, heat exchangers and their associated technologies. This book is a collection of current research in the above mentioned areas and discusses experimental, theoretical and calculation approaches and industrial utilizations with modern ideas and methods to study heat transfer for single and multiphase systems. The topics considered include various basic concepts of heat transfer, the fundamental modes of heat transfer (namely conduction, convection and radiation), thermophysical properties, condensation, boiling, freezing, innovative experiments, measurement analysis, theoretical models and simulations, with many real-world problems and important modern applications. The book is divided in four sections : "Heat Transfer in Micro Systems", "Boiling, Freezing and Condensation Heat Transfer", "Heat Transfer and its Assessment", "Heat Transfer Calculations", and each section discusses a wide variety of techniques, methods and applications in accordance with the subjects. The combination of theoretical and experimental investigations with many important practical applications of current interest will make this book of interest to researchers, scientists, engineers and graduate students, who make use of experimental and theoretical investigations, assessment and enhancement techniques in this multidisciplinary field as well as to researchers in mathematical modelling, computer simulations and information sciences, who make use of experimental and theoretical investigations as a means of critical assessment of models and results derived from advanced numerical simulations and improvement of the developed models and numerical methods.
Author:
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ISBN:
Category : Aeronautics
Languages : en
Pages : 1232
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