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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Thu, 30 Mar 2023 01:05:42 GMT2023-03-30T01:05:42ZNumerical investigation of three-dimensional partial cavitation in a Venturi geometry
http://hdl.handle.net/10985/20502
Numerical investigation of three-dimensional partial cavitation in a Venturi geometry
GOUIN, Camille; JUNQUEIRA-JUNIOR, Carlos; GONCALVES DA SILVA, Eric; ROBINET, Jean-Christophe
Sheet cavitation appears in many hydraulic applications and can lead to technical issues. Some fundamental outcomes, such as, the complex topology of 3-dimensional cavitation pockets and their associated dynamics need to be carefully visited. In the paper, the dynamics of partial cavitation developing in a 3D Venturi geometry and the interaction with sidewalls are numerically investigated. The simulations are performed using a one-fluid compressible Reynolds-averaged Navier–Stokes solver associated with a nonlinear turbulence model and a void ratio transport equation model. A detailed analysis of this cavitating flow is carried out using innovative tools, such as, spectral proper orthogonal decompositions. Particular attention is paid in the study of 3D effects by comparing the numerical results obtained with sidewalls and periodic conditions. A three-dimensional dynamics of the sheet cavitation, unrelated to the presence of sidewalls, is identified and discussed.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/10985/205022021-01-01T00:00:00ZGOUIN, CamilleJUNQUEIRA-JUNIOR, CarlosGONCALVES DA SILVA, EricROBINET, Jean-ChristopheSheet cavitation appears in many hydraulic applications and can lead to technical issues. Some fundamental outcomes, such as, the complex topology of 3-dimensional cavitation pockets and their associated dynamics need to be carefully visited. In the paper, the dynamics of partial cavitation developing in a 3D Venturi geometry and the interaction with sidewalls are numerically investigated. The simulations are performed using a one-fluid compressible Reynolds-averaged Navier–Stokes solver associated with a nonlinear turbulence model and a void ratio transport equation model. A detailed analysis of this cavitating flow is carried out using innovative tools, such as, spectral proper orthogonal decompositions. Particular attention is paid in the study of 3D effects by comparing the numerical results obtained with sidewalls and periodic conditions. A three-dimensional dynamics of the sheet cavitation, unrelated to the presence of sidewalls, is identified and discussed.Study on the Resolution of Large-Eddy Simulations for Supersonic Jet Flows
http://hdl.handle.net/10985/22736
Study on the Resolution of Large-Eddy Simulations for Supersonic Jet Flows
JUNQUEIRA-JUNIOR, Carlos; F. ABREU, Diego; T. V. DAURICIO, Eron; F. AZEVEDO, João Luiz
The present study is concerned with large-eddy simulations (LES) of supersonic jet flows. The work addresses, in particular, the simulation of a perfectly expanded free jet flow with an exit Mach number of 1.4 and an exit temperature equal to the ambient temperature. Calculations are performed using a nodal discontinuous Galerkin method. The present effort studies the effects of mesh and polynomial refinement on the solution. The present calculations consider computational meshes and polynomial orders such that the number of degrees of freedom (DOFs) in the solution ranges from 50 to 410 million. Mean velocity results and root mean square (RMS) values of velocity fluctuations indicate a better agreement with experimental data as the resolution is increased. The generated data provide a good understanding of the effects of increasing the discretization refinement for LES calculations of jet flows. The present results can guide future simulations of similar flow configurations.
Wed, 01 Jun 2022 00:00:00 GMThttp://hdl.handle.net/10985/227362022-06-01T00:00:00ZJUNQUEIRA-JUNIOR, CarlosF. ABREU, DiegoT. V. DAURICIO, EronF. AZEVEDO, João LuizThe present study is concerned with large-eddy simulations (LES) of supersonic jet flows. The work addresses, in particular, the simulation of a perfectly expanded free jet flow with an exit Mach number of 1.4 and an exit temperature equal to the ambient temperature. Calculations are performed using a nodal discontinuous Galerkin method. The present effort studies the effects of mesh and polynomial refinement on the solution. The present calculations consider computational meshes and polynomial orders such that the number of degrees of freedom (DOFs) in the solution ranges from 50 to 410 million. Mean velocity results and root mean square (RMS) values of velocity fluctuations indicate a better agreement with experimental data as the resolution is increased. The generated data provide a good understanding of the effects of increasing the discretization refinement for LES calculations of jet flows. The present results can guide future simulations of similar flow configurations.A comparison of low and high-order methods for the simulation of supersonic jet flows
http://hdl.handle.net/10985/22656
A comparison of low and high-order methods for the simulation of supersonic jet flows
F. ABREU, Diego; T. V. DAURICIO, Eron; F. AZEVEDO, João Luiz; JUNQUEIRA-JUNIOR, Carlos
The present work compares results for different numerical methods in search of alternatives to improve the quality
of large-eddy simulations for the problem of a supersonic turbulent jet flows. Previous work has analyzed supersonic
jet flows using a second-order, finite difference solver based on structured meshes, and the results indicated a shorter
potential core of the jet and different levels of velocity fluctuations. In the present work, the results of previous simulations
are compared to new results using a high-order, discontinuous Galerkin solver for unstructured meshes. All simulations
are performed, keeping the total number of degrees of freedom constant. The results of the current simulations present very
similar mean velocity distributions and slightly smaller velocity fluctuations, and they seem to correlate better with the
experimental data. The present results indicate that additional studies should focus on the jet inlet boundary conditions
in order to improve the physical representation of the early stages of the jet development.
Mon, 01 Nov 2021 00:00:00 GMThttp://hdl.handle.net/10985/226562021-11-01T00:00:00ZF. ABREU, DiegoT. V. DAURICIO, EronF. AZEVEDO, João LuizJUNQUEIRA-JUNIOR, CarlosThe present work compares results for different numerical methods in search of alternatives to improve the quality
of large-eddy simulations for the problem of a supersonic turbulent jet flows. Previous work has analyzed supersonic
jet flows using a second-order, finite difference solver based on structured meshes, and the results indicated a shorter
potential core of the jet and different levels of velocity fluctuations. In the present work, the results of previous simulations
are compared to new results using a high-order, discontinuous Galerkin solver for unstructured meshes. All simulations
are performed, keeping the total number of degrees of freedom constant. The results of the current simulations present very
similar mean velocity distributions and slightly smaller velocity fluctuations, and they seem to correlate better with the
experimental data. The present results indicate that additional studies should focus on the jet inlet boundary conditions
in order to improve the physical representation of the early stages of the jet development.Comparison of Shock-Boundary Layer Interactions in Adiabatic and Isothermal Supersonic Turbine Cascades
http://hdl.handle.net/10985/22657
Comparison of Shock-Boundary Layer Interactions in Adiabatic and Isothermal Supersonic Turbine Cascades
JUNQUEIRA-JUNIOR, Carlos; R. WOLF, William; F. S. LUI, Hugo; R. RICCIARDI, Tulio
Wall-resolved large eddy simulations are employed to investigate the shock-boundary layer
interactions (SBLIs) in a supersonic turbine cascade. An analysis of the suction side separation
bubbles forming due to the SBLIs is presented for adiabatic and isothermal (cooled) walls. Flow
snapshots indicate that the separation bubble contracts and expands in a similar fashion for
both thermal boundary conditions. However, the skin-friction coefficient distributions reveal a
downstream displacement of the separation region when cooling is applied. The separation
bubble is also smaller for this setup compared to the adiabatic one. A steeper pressure rise is
observed for the isothermal wall downstream of the incident oblique shock, and this occurs
because the incident shock wave gets closer to the blade surface when cooling is applied. The
Reynolds stresses are computed to investigate the effects of wall temperature on the turbulence
activity. While the levels of the tangential stresses are similar for the cases analyzed, those for
the wall-normal component are higher for the cooled wall.
Wed, 01 Jun 2022 00:00:00 GMThttp://hdl.handle.net/10985/226572022-06-01T00:00:00ZJUNQUEIRA-JUNIOR, CarlosR. WOLF, WilliamF. S. LUI, HugoR. RICCIARDI, TulioWall-resolved large eddy simulations are employed to investigate the shock-boundary layer
interactions (SBLIs) in a supersonic turbine cascade. An analysis of the suction side separation
bubbles forming due to the SBLIs is presented for adiabatic and isothermal (cooled) walls. Flow
snapshots indicate that the separation bubble contracts and expands in a similar fashion for
both thermal boundary conditions. However, the skin-friction coefficient distributions reveal a
downstream displacement of the separation region when cooling is applied. The separation
bubble is also smaller for this setup compared to the adiabatic one. A steeper pressure rise is
observed for the isothermal wall downstream of the incident oblique shock, and this occurs
because the incident shock wave gets closer to the blade surface when cooling is applied. The
Reynolds stresses are computed to investigate the effects of wall temperature on the turbulence
activity. While the levels of the tangential stresses are similar for the cases analyzed, those for
the wall-normal component are higher for the cooled wall.On the scalability of CFD tool for supersonic jet flow configurations
http://hdl.handle.net/10985/18277
On the scalability of CFD tool for supersonic jet flow configurations
JUNQUEIRA-JUNIOR, Carlos; AZEVEDO, João Luiz F.; PANETTA, Jairo; WOLF, William R.; YAMOUNI, Sami
New regulations are imposing noise emissions limitations for the aviation industry which are pushing researchers and engineers to invest efforts in studying the aeroacoustics phenomena. Following this trend, an in-house computational fluid dynamics tool is build to reproduce high fidelity results of supersonic jet flows for aeroacoustic analogy applications. The solver is written using the large eddy simulation formulation that is discretized using a finite difference approach and an explicit time integration. Numerical simulations of supersonic jet flows are very expensive and demand efficient high-performance computing. Therefore, non-blocking message passage interface protocols and parallel Input/Output features are implemented into the code in order to perform simulations which demand up to one billion grid points. The present work addresses the evaluation of code improvements along with the computational performance of the solver running on a computer with maximum theoretical peak of 2.727 PFlops. Different mesh configurations, whose size varies from a few hundred thousand to approximately one billion grid points, are evaluated in the present paper. Calculations are performed using different workloads in order to assess the strong and weak scalability of the parallel computational tool. Moreover, validation results of a realistic flow condition are also presented in the current work.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/10985/182772020-01-01T00:00:00ZJUNQUEIRA-JUNIOR, CarlosAZEVEDO, João Luiz F.PANETTA, JairoWOLF, William R.YAMOUNI, SamiNew regulations are imposing noise emissions limitations for the aviation industry which are pushing researchers and engineers to invest efforts in studying the aeroacoustics phenomena. Following this trend, an in-house computational fluid dynamics tool is build to reproduce high fidelity results of supersonic jet flows for aeroacoustic analogy applications. The solver is written using the large eddy simulation formulation that is discretized using a finite difference approach and an explicit time integration. Numerical simulations of supersonic jet flows are very expensive and demand efficient high-performance computing. Therefore, non-blocking message passage interface protocols and parallel Input/Output features are implemented into the code in order to perform simulations which demand up to one billion grid points. The present work addresses the evaluation of code improvements along with the computational performance of the solver running on a computer with maximum theoretical peak of 2.727 PFlops. Different mesh configurations, whose size varies from a few hundred thousand to approximately one billion grid points, are evaluated in the present paper. Calculations are performed using different workloads in order to assess the strong and weak scalability of the parallel computational tool. Moreover, validation results of a realistic flow condition are also presented in the current work.Strong scaling of numerical solver for supersonic jet flow configurations
http://hdl.handle.net/10985/17676
Strong scaling of numerical solver for supersonic jet flow configurations
JUNQUEIRA-JUNIOR, Carlos; AZEVEDO, João Luiz F.; PANETTA, Jairo; WOLF, William R.; YAMOUNI, Sami
Acoustics loads are rocket design constraints which push researches and engineers to invest efforts in the aeroacoustics phenomena which is present on launch vehicles. Therefore, an in-house computational fluid dynamics tool is developed in order to reproduce high-fidelity results of supersonic jet flows for aeroacoustic analogy applications. The solver is written using the large eddy simulation formulation that is discretized using a finite-difference approach and an explicit time integration. Numerical simulations of supersonic jet flows are very expensive and demand efficient high-performance computing. Therefore, non-blocking message passage interface protocols and parallel input/output features are implemented into the code in order to perform simulations which demand up to one billion degrees of freedom. The present work evaluates the parallel efficiency of the solver when running on a supercomputer with a maximum theoretical peak of 127.4 TFLOPS. Speedup curves are generated using nine different workloads. Moreover, the validation results of a realistic flow condition are also presented in the current work.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/176762019-01-01T00:00:00ZJUNQUEIRA-JUNIOR, CarlosAZEVEDO, João Luiz F.PANETTA, JairoWOLF, William R.YAMOUNI, SamiAcoustics loads are rocket design constraints which push researches and engineers to invest efforts in the aeroacoustics phenomena which is present on launch vehicles. Therefore, an in-house computational fluid dynamics tool is developed in order to reproduce high-fidelity results of supersonic jet flows for aeroacoustic analogy applications. The solver is written using the large eddy simulation formulation that is discretized using a finite-difference approach and an explicit time integration. Numerical simulations of supersonic jet flows are very expensive and demand efficient high-performance computing. Therefore, non-blocking message passage interface protocols and parallel input/output features are implemented into the code in order to perform simulations which demand up to one billion degrees of freedom. The present work evaluates the parallel efficiency of the solver when running on a supercomputer with a maximum theoretical peak of 127.4 TFLOPS. Speedup curves are generated using nine different workloads. Moreover, the validation results of a realistic flow condition are also presented in the current work.