Flow Analyses in a Single-Stage Propulsion Pump

1996 ◽  
Vol 118 (2) ◽  
pp. 240-248 ◽  
Author(s):  
Y. T. Lee ◽  
C. Hah ◽  
J. Loellbach
Keyword(s):  
Boundary Layer ◽  
Numerical Method ◽  
Turbulence Model ◽  
Eddy Viscosity ◽  
Single Stage ◽  
Acoustic Properties ◽  
Turbulent Eddy ◽  
Trailing Edge ◽  
Local Flow ◽  
Blade Row

Steady-state analyses of the incompressible flow past a single-stage stator/rotor propulsion pump are presented and compared to experimental data. The purpose of the current study is to validate a numerical method for the design application of a typical propulsion pump and for the acoustic analysis based on predicted flowfields. A steady multiple-blade-row approach is used to calculate the flowfields of the stator and the rotor. The numerical method is based on a fully conservative control-volume technique. The Reynolds-averaged Navier–Stokes equations are solved along with the standard two-equation k–ε turbulence model. Numerical results for both mean flow and acoustic properties compare well with measurements in the wake of each blade row. The rotor blade has a thick boundary layer in the last quarter of the chord and the flow separates near the trailing edge. These features invalidate many Euler prediction results. Due to the dramatic reduction of the turbulent eddy viscosity in the thick boundary layer, the standard k–ε model cannot predict the correct local flow characteristics near the rotor trailing edge and in its near wake. Thus, a modification of the turbulence length scale in the turbulence model is applied in the thick boundary layer in response to the reduction of the turbulent eddy viscosity.

scholarly journals Flow Analyses in a Single-Stage Propulsion Pump

1994 ◽  
Author(s):  
Yu-Tai Lee ◽  
Chunill Hah ◽  
James Loellbach
Keyword(s):  
Boundary Layer ◽  
Numerical Method ◽  
Turbulence Model ◽  
Eddy Viscosity ◽  
Single Stage ◽  
Acoustic Properties ◽  
Turbulent Eddy ◽  
Trailing Edge ◽  
Local Flow ◽  
Blade Row

Steady-state analyses of the incompressible flow past a single-stage stator/rotor propulsion pump are presented and compared to experimental data. The purpose of the current study is to validate a numerical method for the design application of a typical propulsion pump and for the acoustic analysis based on predicted flowfields. A steady multiple-blade-row approach is used to calculate the flowfields of the stator and the rotor. The numerical method is based on a fully conservative control-volume technique. The Reynolds-averaged Navier-Stokes equations are solved along with the standard two-equation k-ε turbulence model. Numerical results for both mean flow and acoustic properties compare well with measurements in the wake of each blade row. The rotor blade has a thick boundary layer in the last quarter of the chord and the flow separates near the trailing edge. These features invalidate many Euler prediction results. Due to the dramatic reduction of the turbulent eddy viscosity in the thick boundary layer, the standard k-ε model cannot predict the correct local flow characteristics near the rotor trailing edge and in its near wake. Thus, a modification of the turbulence length scale in the turbulence model is applied in the thick boundary layer in response to the reduction of the turbulent eddy viscosity.

Development and Initial Validation of a Two-Equation Transition Sensitive Turbulence Model for CFD Simulations

2006 ◽  
Author(s):  
J. M. Jones ◽  
D. K. Walters
Keyword(s):  
Boundary Layer ◽  
Turbulence Model ◽  
Eddy Viscosity ◽  
Flow Behavior ◽  
Boundary Layer Separation ◽  
Transitional Flow ◽  
Model Framework ◽  
Modeling Framework ◽  
Initial Development ◽  
New Model

This paper presents the initial development and validation of a modified two-equation eddy-viscosity turbulence model for computational fluid dynamics (CFD) prediction of transitional and turbulent flow. The new model is based on a k-ω model framework, making it more easily implemented into existing general-purpose CFD solvers than other recently proposed model forms. The model incorporates inviscid and viscous damping functions for the eddy viscosity, as well as a production damping term, in order to reproduce the appropriate effects of laminar, transitional, and turbulent boundary layer flow. It has been implemented into a commercially available flow solver (FLUENT) and evaluated for simple attached and separated flow conditions, including 2-D flow over a flat plate and a circular cylinder. The results presented show that the new model is able to yield reasonable predictions of transitional flow behavior using a very simple modeling framework, including an appropriate response to freestream turbulence and boundary layer separation.

Shock–boundary layer interaction and energetics in transonic flutter

2017 ◽  
Vol 832 ◽  
pp. 212-240 ◽  
Author(s):  
Pradeepa T. Karnick ◽  
Kartik Venkatraman
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Turbulence Model ◽  
Viscous Effects ◽  
Trailing Edge ◽  
Aeroelastic System ◽  
Number Range ◽  
Shock Reversal ◽  
Transonic Flutter ◽  
Flutter Boundary

We study the influence of shock and boundary layer interactions in transonic flutter of an aeroelastic system using a Reynolds-averaged Navier–Stokes (RANS) solver together with the Spalart–Allmaras turbulence model. We show that the transonic flutter boundary computed using a viscous flow solver can be divided into three distinct regimes: a low transonic Mach number range wherein viscosity mimics increasing airfoil thickness thereby mildly influencing the flutter boundary; an intermediate region of drastic change in the flutter boundary due to shock-induced separation; and a high transonic Mach number zone of no viscous effects when the shock moves close to the trailing edge. Inviscid transonic flutter simulations are a very good approximation of the aeroelastic system in predicting flutter in the first and third regions: that is when the shock is not strong enough to cause separation, and in regions where the shock-induced separated region is confined to a small region near the trailing edge of the airfoil. However, in the second interval of intermediate transonic Mach numbers, the power distribution on the airfoil surface is significantly influenced by shock-induced flow separation on the upper and lower surfaces leading to oscillations about a new equilibrium position. Though power contribution by viscous forces are three orders of magnitude less than the power due to pressure forces, these viscous effects manipulate the flow by influencing the strength and location of the shock such that the power contribution by pressure forces change significantly. Multiple flutter points that were part of the inviscid solution in this regime are now eliminated by viscous effects. Shock motion on the airfoil, shock reversal due to separation, and separation and reattachment of flow on the airfoil upper surface, also lead to multiple aerodynamic forcing frequencies. These flow features make the flutter boundary quantitatively sensitive to the turbulence model and numerical method adopted, but qualitatively they capture the essence of the physical phenomena.

Assessment and Modification of One-Equation Models of Turbulence for Wall-Bounded Flows

2007 ◽  
Vol 129 (7) ◽  
pp. 921-928 ◽  
Author(s):  
M. Elkhoury
Keyword(s):  
Boundary Layer ◽  
Turbulence Model ◽  
Eddy Viscosity ◽  
Single Equation ◽  
Transport Models ◽  
Nonequilibrium Flows ◽  
Wall Bounded Flows

This work assesses the performance of two single-equation eddy viscosity transport models that are based on Menter’s transformation of the k-ε and the k-ω closures. The coefficients of both models are set exactly the same and follow directly from the constants of the standard k-ε closure. This in turn allows a cross-comparison of the effect of two different destruction terms on the performance of single-equation closures. Furthermore, some wall-free modifications to production and destruction terms are proposed and applied to both models. An assessment of the baseline models with and without the proposed modifications against experiments, and the Spalart-Allmaras turbulence model is provided via several boundary-layer computations. Better performance is indicated with the proposed modifications in wall-bounded nonequilibrium flows.

scholarly journals SIMULASI NUMERIK PADA SILINDER DENGAN SUSUNAN SELANG-SELING (STAGGERED) DALAM SALURAN SEGI EMPAT MENGUNAKAN K Ԑ MODEL

2017 ◽  
Vol 17 (2) ◽  
pp. 89-100
Author(s):  
Nuzul Hidayat ◽  
Ahmad Arif ◽  
M Yasep Setiawan
Keyword(s):  
Boundary Layer ◽  
Nusselt Number ◽  
Turbulence Model ◽  
Second Order ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Velocity Contour

Abstrak— Silinder digunakan pada alat penukar kalor untuk meningkatkan luasan perpindahan panas antara permukaan utama dengan fluida di sekitarnya. Idealnya, material untuk membuat silinder harus memiliki konduktivitas termal yang tinggi untuk meminimalkan perbedaan temperatur antara permukaan utama dengan permukaan yang diperluas. Aplikasi silinder sering dijumpai pada system pendinginan ruangan, peralatan elektronik, motor bakar, trailing edge sudu turbin gas, alat penukar kalor, dengan udara sebagai media perpindahan panasnya. Ada berbagai tipe silinder pada alat penukar kalor yang telah digunakan, mulai dari bentuk yang relatif sederhana seperti silinder segiempat, silindris, anular, tirus atau pin sampai dengan kombinasi dari berbagai geometri yang berbeda dengan jarak yang teratur dalam susunan segaris (in-line) ataupun selang-seling (staggered). Dalam penelitian ini bertujuan untuk mengetahui karakteristik boundary layer turbulen pada Cylinder tersusun staggered  untuk kasus dengan cara mendapatkan data secara kualitatif dan kuantitatif pada a) Coefficient of Pressure (Cp)   , Nusselt Number dan (c) Velocity contour  . Parameter tersebut diukur pada daerah mid span dengan, . Penelitian ini menggunakan software Fluent 6.3.26 dimana pada penelitian secara numerik digunakan turbulence model yaitu k  realisable dengan discretization Second Order Upwind mengunakan software Fluent . Analisa pada penelitian numerik dilakukan secara 2 dimensi (2D) Unsteady Reynolds Averages Navier Stokes. Didapat bahwa dengan meningkatkan Re maka hal yang terjadi Cd pada silinder mengalami penurunan apabila aliran tersebut diganggu oleh silinder yang lain pada susunan staggered karena akibat kenaikan turbulensi aliran,  turbuensi aliran meningkat juga mengakibatkan meningkatnya  perpindahan panas ditandai dengan kenaikan Nu.

Compressor Blade Boundary Layers: Part 2 — Measurements With Incident Wakes

1989 ◽  
Author(s):  
Y. Dong ◽  
N. A. Cumpsty
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Transition Process ◽  
Compressor Blade ◽  
Momentum Thickness ◽  
Trailing Edge ◽  
Boundary Layer Development ◽  
Blade Row ◽  
Layer Development

This paper follows directly from Part I** by the same authors and describes measurements of the boundary layer on a supercritical-type compressor blade with wakes from a simulated moving upstream blade row convected through the passage. (The blades and the test facilities togehter with the background are described in Part I.) The results obtained with the wakes are compared to those with none for both low and high levels of inlet turbulence. The transition process and boundary layer development is very different in each case though the overall momentum thickness at the trailing edge is fairly similar. None of the models for transition is satisfactory when this is initiated by moving wakes.

scholarly journals Hybrid RANS/LES Turbulence Model Applied to a Transitional Unsteady Boundary Layer on Wind Turbine Airfoil

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 128
Author(s):  
Di Zhang ◽  
Daniel R. Cadel ◽  
Eric G. Paterson ◽  
K. Todd Lowe
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Wind Turbine ◽  
Boundary Layers ◽  
Turbulence Model ◽  
Model Problem ◽  
Local Flow ◽  
Flow Angle ◽  
Eddy Simulation ◽  
Large Eddy

A hybrid Reynolds-averaged Navier Stokes/large-eddy simulation (RANS/LES) turbulence model integrated with a transition formulation is developed and tested on a surrogate model problem through a joint experimental and computational fluid dynamic approach. The model problem consists of a circular cylinder for generating coherent unsteadiness and a downstream airfoil in the cylinder wake. The cylinder flow is subcritical, with a Reynolds number of 64,000 based upon the cylinder diameter. The quantitative dynamics of vortex shedding and Reynolds stresses in the cylinder near wake are well captured, owing to the turbulence-resolving large eddy simulation mode that was activated in the wake. The hybrid model switched between RANS and LES modes outside the boundary layers, as expected. According to the experimental and simulation results, the airfoil encountered local flow angle variations up to ±50°. Further analysis through a phase-averaging technique found phase lags in the airfoil boundary layer along the chordwise locations, and both the phase-averaged and mean velocity profiles collapsed into the Law-of-the-wall in the range of 0 < y + < 50 . The features of high blade-loading fluctuations due to unsteadiness and transitional boundary layers are of interest in the aerodynamic studies of full-scale wind turbine blades, making the current model problem a comprehensive benchmark case for future model development and validation.

Compressor Blade Boundary Layers: Part 2—Measurements With Incident Wakes

1990 ◽  
Vol 112 (2) ◽  
pp. 231-240 ◽  
Author(s):  
Y. Dong ◽  
N. A. Cumpsty
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Transition Process ◽  
Compressor Blade ◽  
Momentum Thickness ◽  
Trailing Edge ◽  
Boundary Layer Development ◽  
Blade Row ◽  
Layer Development

This paper follows directly from Part 1 by the same authors and describes measurements of the boundary layer on a supercritical-type compressor blade with wakes from a simulated moving upstream blade row convected through the passage. (The blades and the test facilities together with the background are described in Part 1). The results obtained with the wakes are compared to those with none for both low and high levels of inlet turbulence. The transition process and boundary layer development are very different in each case, though the overall momentum thickness at the trailing edge is fairly similar. None of the models for transition is satisfactory when this is initiated by moving wakes.

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