scholarly journals Analysis of fan-stage gap-flow data to inform simulation of fan broadband noise

2019 ◽  
Vol 377 (2159) ◽  
pp. 20190080 ◽  
Author(s):  
Sheryl Grace ◽  
Ignacio Gonzalez-Martino ◽  
Damiano Casalino
Keyword(s):  
Flow Simulation ◽  
Simulated Data ◽  
Potential Effect ◽  
Broadband Noise ◽  
Navier Stokes ◽  
Time Resolved ◽  
Eddy Simulation ◽  
Flow Parameters ◽  
Gap Flow ◽  
Depth Study

Time-resolved simulations present a new opportunity for studying the disturbances responsible for the broadband interaction noise created by the fan stage. In this paper, two vane configurations from the source diagnostic test at the approach rotor speed were computed with PowerFLOW's very large-eddy simulation (VLES) method using two solution strategies: a coarser mesh near the rotor and a trip to trigger turbulent transition on the rotor; and a much finer mesh near the rotor with no trip. The simulated data allow for an investigation of the potential effect from the vane configuration and an in-depth study of the mean and turbulent flow in the interstage gap. A challenge related to post-processing of high-resolution simulations is discussed. Comparison of the flow quantities with previously obtained Reynolds Averaged Navier–Stokes simulation results indicates that little advantage is gained by running a lattice Boltmann method (LBM)/VLES to simply recover the gap flow parameters for use with a lower-order fan broadband interaction noise calculation method. The true benefit of the LBM/VLES is that the noise calculation can be directly and simultaneously completed with the flow simulation. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.

scholarly journals Zonal Detached Eddy Simulation of the Fan-OGV Stage of a Modern Turbofan Engine

2020 ◽  
Author(s):  
Benjamin François ◽  
Raphaël Barrier ◽  
Cyril Polacsek
Keyword(s):  
Statistical Convergence ◽  
Hybrid Approach ◽  
Broadband Noise ◽  
Detached Eddy Simulation ◽  
Turbofan Engine ◽  
The Core ◽  
Eddy Simulation ◽  
Gap Flow ◽  
Radial Profiles ◽  
Radial Evolution

Abstract The present article deals with the Zonal Detached Eddy Simulation of the fan module of a modern turbofan engine. The fan module, tested at the AneCom facility, is equipped with rotating fan blades and stationary outlet guide vanes (OGV). The simulation was performed to capture the interaction of the turbulent fan wakes with the OGV walls. The final goal of this simulation is the prediction of the associated broadband noise, not adressed here. In this paper, only the aerodynamic aspects are treated. The simulation relies on a hybrid RANS/LES approach with a zonal strategy: the core airflow is treated in RANS while the bypass airflow is solved with the hybrid approach. Mesh criteria meeting both RANS/LES and acoustic requirements were fulfilled, leading to a mesh of 380 million cells. The simulation was performed during five revolutions and statistical convergence was reached. Inspections of the flow-fields highlight a consistent behaviour of the shielding function (border between RANS and LES solving areas) around the blade walls, at the trailing-edge and in the tip gap flow areas. Comparisons with performance and hot-wire measurements are also presented. Aerodynamic performance and radial evolution of averaged velocities on a plane in-between the fan and the OGV are well retrieved, both in shape and levels. For the turbulent quantities, the shape of the radial profiles are close to the measurements, with much better accuracy in the upper region compared to the RANS solution.

scholarly journals Effect of uniform and non-uniform mesh on the development of turbulent boundary layer

2021 ◽  
Author(s):  
Lokesh Kalyan Gutti ◽  
◽  
Bhupendra Singh Chauhan ◽  
Hee-Chang Lim ◽  
◽  
...  
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Stokes Equations ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Uniform Mesh ◽  
Navier Stokes Equations ◽  
Eddy Simulation ◽  
Grid Points ◽  
Long Channel

For incompressible flow simulation, it is commonly accepted to use uniform meshes to solve the governing equation of turbulent boundary layer. It follows the laws of conservation stabilizing the flow field in the domain and preventing odd-even decoupling in the pressure field. In this study, Large Eddy Simulation (LES) has been conducted in a long channel. In order to calculate the turbulent boundary layer in the channel, the unsteady Navier-Stokes equations has been adopted at a Reynolds number =180, which is based on mean centerline velocity and the half-width of the channel. The mesh used in this study was based on both stretch and uniform mesh having grid points, which is corresponding to . Turbulence statistics were also calculated to compare to the existing results. In the results, the turbu lent boundary layer was fully developed at around . In addition, fully developed channel flow was achieved at the non-dimensional time of .

Assessment of Free Surface Treatment Techniques and Turbulence Models Influence Using the Slightly Compressible Flow Simulation

2007 ◽  
Author(s):  
C. Ciortan ◽  
C. Guedes Soares ◽  
J. Wanderley
Keyword(s):  
Free Surface ◽  
Surface Treatment ◽  
Compressible Flow ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Slightly Compressible ◽  
Eddy Simulation ◽  
Treatment Techniques ◽  
Flow Parameters ◽  
Wigley Hull

A free surface, finite-difference code on collocated grids, using the Slightly Compressible Flow formulation, is used for simulating turbulent flow around a Wigley hull. Two free-surface treatment techniques are compared in terms of accuracy and influence on the flow parameters. The runs were performed in standard conditions of Froude numbers and the results were compared against experimental and numerical results. The initial version of the code used an interface-tracking technique and two turbulence models (Large Eddy Simulation and Baldwin-Lomax). The numerical scheme was marched in time using the factorized Beam and Warming implicit method. The second version of the code uses an interface-capturing technique. For the time being, the code uses a fixed grid on which the kinematic free surface equation is solved. The grid is identical to the initial grid used in the first set of formulations. Other changes in the code were necessary, the most important being the switch of the time-marching method to a 2nd order, explicit Runge-Kutta. The results show good agreement with the experimental results.

Study of 3D Mixing Processes by Numerical and Experimental Approaches

2002 ◽  
Author(s):  
Y. Zhao ◽  
R. S. Brodkey ◽  
S. Nakamura
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Mixing Processes ◽  
Time Resolved ◽  
Simplified Approach ◽  
Eddy Simulation ◽  
Flow Mixing ◽  
Mixing Vessels ◽  
Simulation And Validation

Mixing vessels are widely used for blending and chemical reactions. Although much has been done on mixing processes, the complex, three-dimensional flow phenomena are still not well understood. The purpose of our first step in this research is the simulation and validation of time-resolved, three-dimensional velocity vector data. Such results are an essential part of the design of mixing systems, but are generally not available to the engineers. The computational work involves direct numerical simulation (DNS) and large eddy simulation (LES) of the Navier-Stokes equations. Later, modeling of the Reynolds averaged Navier-Stokes (RANS) equations will be undertaken as a simplified approach. Simulations and modeling are being validated by experiments. Two flow mixing systems are under investigation. First and most important for validation is an opposed jet flow system that offers some unique characteristics that can be used for validation of DNS/LES simulations. It also has applications in the injection molding of plastics. Second, simulations of impeller driven mixing vessels that are more commonly used in processing are under development. Here the moving mesh system adds complexity. In addition, visualization of both numerical and experimental results, 3-D particle tracking velocimetry (PTV) techniques have been developed. The proposed paper will address the problems in the modeling of chemical mixing and discuss the results of simulation and validation.

Large eddy simulation for aerodynamics: status and perspectives

2009 ◽  
Vol 367 (1899) ◽  
pp. 2849-2860 ◽  
Author(s):  
Pierre Sagaut ◽  
Sébastien Deck
Keyword(s):  
Large Eddy Simulation ◽  
Computational Cost ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Error Quantification ◽  
Geometrical Complexity ◽  
First Case ◽  
Large Eddy ◽  
First Results

The present paper provides an up-to-date survey of the use of large eddy simulation (LES) and sequels for engineering applications related to aerodynamics. Most recent landmark achievements are presented. Two categories of problem may be distinguished whether the location of separation is triggered by the geometry or not. In the first case, LES can be considered as a mature technique and recent hybrid Reynolds-averaged Navier–Stokes (RANS)–LES methods do not allow for a significant increase in terms of geometrical complexity and/or Reynolds number with respect to classical LES. When attached boundary layers have a significant impact on the global flow dynamics, the use of hybrid RANS–LES remains the principal strategy to reduce computational cost compared to LES. Another striking observation is that the level of validation is most of the time restricted to time-averaged global quantities, a detailed analysis of the flow unsteadiness being missing. Therefore, a clear need for detailed validation in the near future is identified. To this end, new issues, such as uncertainty and error quantification and modelling, will be of major importance. First results dealing with uncertainty modelling in unsteady turbulent flow simulation are presented.

scholarly journals Large eddy simulation of flow around semi-conical piers vertically mounted on the bed

2021 ◽  
Author(s):  
Yasin Aghaee-Shalmani ◽  
Habib Hakimzadeh
Keyword(s):  
Large Eddy Simulation ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Flow Structures ◽  
Shear Stresses ◽  
Eddy Simulation ◽  
Large Eddy

Abstract In this paper, details, and results of three-dimensional numerical modeling of flow around the semi-conical piers vertically mounted on the bed in a channel, are presented. For flow simulation, 3-D Navier-Stokes equations are solved numerically using the finite volume method and large eddy simulation (LES). In this study, the semi-conical piers with different side slope angles are tested, and the flow around them is compared with the cylindrical reference pier. Flow structures, vortex shedding behind piers, horseshoe vortices, instantaneous and time-averaged flow structures are presented and discussed. Numerical model results show that the semi-conical piers are eventuated remarkable reduction (up to 25%) in downward flow velocity in the upstream side of the piers, and much more reduction (up to 46%) in bed shear stresses in comparison with the cylindrical pier. Moreover, the model results showed some decrease in vortex shedding frequency for the semiconical piers compared to the cylindrical pier.

Validation of Unsteady CFD in a Confined Row of Cylinders

2010 ◽  
Author(s):  
Brandon Wilson ◽  
Jeff Harris ◽  
Barton L. Smith ◽  
Robert Spall
Keyword(s):  
Global Scale ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Time Resolved ◽  
Pressure Losses ◽  
Eddy Simulation ◽  
Cfd Models ◽  
Piv Measurement ◽  
Validation Parameters ◽  
Dominant Frequencies

A validation study for two CFD models of the time-varying flow through a confined bank of cylinders is presented. The facility mimics the lower plenum of a high temperature reactor and is arranged with the cylinders on equilateral triangles with pitch to diameter ratio of 1.7. Time-resolved Particle Image Velocimetry (PIV) measurement coupled with pressure measurements along the facilities walls are compared to both the Unsteady Reynolds Averaged Navier Stokes (URANS) k–ω model and the Detached Eddy Simulation (DES) models. Spatial (i.e. time-averaged bulk velocity and pressure losses and local velocity distributions) and temporal (i.e. dominant frequencies and correlations) validation parameters on both the local and global scale are used for validation. It is found the CFD models accurately predict frequencies present in the pressure along the walls next to the cylinders in the first and the last cylinder, yet predicts other dominant frequencies in the remaining cylinders that are not found in the experiment. The temporal behavior of the DES was generally far superior to that of the URANS model.

NUMERICAL STUDY OF DETONATION PROPAGATION IN VISCOUS TURBULENT FLOW IN A DUCT

2020 ◽  
Author(s):  
V. A. SABELNIKOV ◽  
◽  
V. V. VLASENKO ◽  
S. BAKHNE ◽  
S. S. MOLEV ◽  
...  
Keyword(s):  
Complex Geometry ◽  
Numerical Study ◽  
Navier Stokes ◽  
Detonation Waves ◽  
Detonation Propagation ◽  
Eddy Simulation ◽  
Detonation Structure ◽  
Classical Studies ◽  
Large Eddy ◽  
Physical Effects

Gasdynamics of detonation waves was widely studied within last hundred years - analytically, experimentally, and numerically. The majority of classical studies of the XX century were concentrated on inviscid aspects of detonation structure and propagation. There was a widespread opinion that detonation is such a fast phenomenon that viscous e¨ects should have insigni¦cant in§uence on its propagation. When the era of calculations based on the Reynolds-averaged Navier- Stokes (RANS) and large eddy simulation approaches came into effect, researchers pounced on practical problems with complex geometry and with the interaction of many physical effects. There is only a limited number of works studying the in§uence of viscosity on detonation propagation in supersonic §ows in ducts (i. e., in the presence of boundary layers).

Mathematical modeling of steady stratified flows

2003 ◽  
Vol 3 ◽  
pp. 195-207
Author(s):  
A.M. Ilyasov ◽  
V.N. Kireev ◽  
S.F. Urmancheev ◽  
I.Sh. Akhatov
Keyword(s):  
Stokes Equations ◽  
Approximate Model ◽  
Immiscible Liquid ◽  
Stratified Flows ◽  
Navier Stokes ◽  
Flat Channel ◽  
Navier Stokes Equations ◽  
Two Fluids ◽  
Flow Parameters ◽  
Direct Numerical Solution

The work is devoted to the analysis of the flow of immiscible liquid in a flat channel and the creation of calculation schemes for determining the flow parameters. A critical analysis of the well-known Two Fluids Model was carried out and a new scheme for the determination of wall and interfacial friction, called the hydraulic approximation in the theory of stratified flows, was proposed. Verification of the proposed approximate model was carried out on the basis of a direct numerical solution of the Navier–Stokes equations for each fluid by a finite-difference method with phase-boundary tracking by the VOF (Volume of Fluid) method. The graphical dependencies illustrating the change in the interfase boundaries of liquids and the averaged over the occupied area of the phase velocities along the flat channel are presented. The results of comparative calculations for two-fluid models are also given, according to the developed model in the hydraulic approximation and direct modeling. It is shown that the calculations in accordance with the hydraulic approximation are more consistent with the simulation results. Thus, the model of hydraulic approximation is the most preferred method for calculating stratified flows, especially in cases of variable volumetric content of liquids.

scholarly journals Comparative Study of Different Turbulence Models for Cavitational Flows around NACA0012 Hydrofoil

2021 ◽  
Vol 9 (7) ◽  
pp. 742
Author(s):  
Minsheng Zhao ◽  
Decheng Wan ◽  
Yangyang Gao
Keyword(s):  
Angle Of Attack ◽  
Large Angle ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Specific Information ◽  
Cloud Cavitation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Shedding Frequency ◽  
Reynolds Average

The present work focuses on the comparison of the numerical simulation of sheet/cloud cavitation with the Reynolds Average Navier-Stokes and Large Eddy Simulation(RANS and LES) methods around NACA0012 hydrofoil in water flow. Three kinds of turbulence models—SST k-ω, modified SST k-ω, and Smagorinsky’s model—were used in this paper. The unstable sheet cavity and periodic shedding of the sheet/cloud cavitation were predicted, and the simulation results, namelycavitation shape, shedding frequency, and the lift and the drag coefficients of those three turbulence models, were analyzed and compared with each other. The numerical results above were basically in accordance with experimental ones. It was found that the modified SST k-ω and Smagorinsky turbulence models performed better in the aspects of cavitation shape, shedding frequency, and capturing the unsteady cavitation vortex cluster in the developing and shedding period of the cavitation at the cavitation number σ = 0.8. At a small angle of attack, the modified SST k-ω model was more accurate and practical than the other two models. However, at a large angle of attack, the Smagorinsky model of the LES method was able to give specific information in the cavitation flow field, which RANS method could not give. Further study showed that the vortex structure of the wing is the main cause of cavitation shedding.

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