Modeling and Computation of Flow in a Passage With 360-Degree Turning and Multiple Airfoils

1993 ◽  
Vol 115 (1) ◽  
pp. 103-108 ◽  
Author(s):  
W. Shyy ◽  
T. C. Vu
Keyword(s):  
Porous Medium ◽  
Global Analysis ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Hydraulic Turbine ◽  
Complex Flow ◽  
The Individual ◽  
Spiral Casing

The spiral casing of a hydraulic turbine is a complex flow device which contains a passage of 360-degree turning and multiple elements of airfoils (the so-called distributor). A three-dimensional flow analysis has been made to predict the flow behavior inside the casing and distributor. The physical model employs a two-level approach, comprising of (1) a global model that adequately accounts for the geometry of the spiral casing but smears out the details of the distributor, and represents the multiple airfoils by a porous medium treatment, and (2) a local model that performs detailed analysis of flow in the distributor region. The global analysis supplies the inlet flow condition for the individual cascade of distributor airfoils, while the distributor analysis yields the information needed for modeling the characteristics of the porous medium. Comparisons of pressure and velocity profiles between measurement and prediction have been made to assess the validity of the present approach. Flow characteristics in the spiral casing are also discussed.

scholarly journals Modeling and Computation of Flow in a Passage With 360° Turning and Multiple Airfoils

1991 ◽  
Author(s):  
W. Shyy ◽  
T. C. Vu
Keyword(s):  
Porous Medium ◽  
Numerical Modeling ◽  
Detailed Analysis ◽  
Flow Condition ◽  
Global Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Hydraulic Turbine ◽  
The Individual ◽  
Spiral Casing

Numerical modeling of the three-dimensional flows in a spiral casing of a hydraulic turbine, containing a passage of 360-degree turning and multiple elements of airfoils (the so-called distributor), is made. The physical model is based on a novel two-level approach, comprising of (1) a global model that adequately accounts for the geometry of the spiral casing but smears out the details of the distributor and represents the multiple airfoils by a porous medium treatment, and (2) a local model that performs detailed analysis of flow in the distributor region. The global analysis supplies the inlet flow condition for the individual cascade of distributor airfoils, while the distributor analysis yields the information needed for modeling the characteristics of the porous medium. Comparisons of pressure and velocity profiles between measurement and prediction have been made to assess the validity of the present approach. Flow characteristics in the spiral casing are also discussed.

Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach

2005 ◽  
Vol 127 (1) ◽  
pp. 136-144 ◽  
Author(s):  
Yahya Dogu
Keyword(s):  
Porous Medium ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Force Balance ◽  
Complex Flow ◽  
Blow Down ◽  
Permeability Coefficients ◽  
Backing Plate ◽  
Brush Seal

The flow behavior through a brush seal has been investigated by developing a flow analysis procedure with a porous medium approach. In order to increase the brush seal performance and use at more severe operating conditions, the complex flow in the bristle pack has become the major concern affecting seal features such as blow-down, hang-up, hysteresis, and bristle flutter. In this study, an axisymmetric CFD model is employed to calibrate anisotropic permeability coefficients for the bristle pack based on available experimental data: leakage, axial pressure on the rotor surface, and radial pressure on the backing plate. A simplified form of the force balance equation is introduced for the flow in the porous bristle pack. Different sets of permeability coefficients are defined for the fence height region below the seal backing plate and the upper region of the seal to correlate the different physical structures and behavior of these regions during operation. The upper region is subject to more stiffening due to backing plate support while the fence height region is free to spread and bend in the axial direction. It is found that flow resistance for the upper region should be 20% higher than the fence height region in order to match the experimental pressure within the bristle pack. Analysis results prove that the brush seal is well represented as a porous medium with this approach. Based on the model developed, characteristic flow and pressure fields in the entire bristle pack have been explored.

A High-Order LES Turbulent Model to Study Unsteady Flow Characteristics in a High Pressure Turbine Cascade

2008 ◽  
Author(s):  
Tomohiko Jimbo ◽  
Debasish Biswas ◽  
Yasuyuki Yokono ◽  
Yoshiki Niizeki
Keyword(s):  
Physical Process ◽  
Pressure Loss ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Measured Data ◽  
High Order ◽  
Turbulent Model ◽  
Loss Mechanism

In this work, unsteady viscous flow analysis around turbine blade cascade using a High-Order LES turbulent model is carried out to investigate basic physical process involved in the pressure loss mechanism. This numerical analysis is assessed to the wind tunnel cascade test. Basically, all the physical phenomena occurring in nature are the effect of some cause, and the effect can somehow be measured. However, to understand the cause, detail information regarding the visualization of the phenomena, which are difficult to measure, are necessary. Therefore, in our work, firstly the computed results are compared with the measured data, which are the final outcome of the cause (of the phenomena under investigation), to verify whether our physics-based model could qualitatively predict the measured facts or not. It was found that the present model could well predict measured data. Therefore, the rest of the computed information, which were difficult to measure, were used to visualize the overall flow behavior for acquiring some knowledge of the physical process associated with the pressure loss mechanism. Our study led to an understanding that the interaction of the vortex generated on the suction and pressure surface of the blade and the secondary vortex generated on the end-wall, downstream the trailing edge resulted in the formation of a large vortex structure in this region. This unsteady three-dimensional flow characteristic is expected to play an important role in the pressure loss mechanism.

Studies on Unsteady Flow Characteristics in a High Pressure Turbine Cascade Based on a High-Order Large Eddy Simulation Turbulence Model

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Tomohiko Jimbo ◽  
Debasish Biswas ◽  
Yoshiki Niizeki
Keyword(s):  
Turbulence Model ◽  
Physical Process ◽  
Pressure Loss ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Measured Data ◽  
High Order ◽  
Loss Mechanism

In the present paper, unsteady viscous flow analysis around turbine blade cascade using a high-order LES turbulence model is carried out to investigate the basic physical process involved in the pressure loss mechanism. This numerical analysis is assessed to the wind tunnel cascade test. Basically, all the physical phenomena occurring in nature are the effect of some cause, and the effect can somehow be measured. However, to understand the cause, detail information regarding the visualization of the phenomena, which are difficult to measure, are necessary. Therefore, in the present paper, firstly the computed results are compared with the measured data, which are the final outcome of the cause (of the phenomena under investigation), to verify whether our physics-based model could qualitatively predict the measured facts or not. It was found that the present model could well predict measured data. Therefore, the rest of the computed information, which were difficult to measure, were used to visualize the overall flow behavior for acquiring some knowledge of the physical process associated with the pressure loss mechanism. The present study led to an understanding that the interaction of the vortex generated on the suction and pressure surface of the blade and the secondary vortex generated on the end wall, downstream of the trailing edge, resulted in the formation of a large vortex structure in this region. This unsteady three-dimensional flow characteristic is expected to play an important role in the pressure loss mechanism.

Investigation of Brush Seal Flow Characteristics Using Bulk Porous Medium Approach

2003 ◽  
Author(s):  
Yahya Dogu
Keyword(s):  
Porous Medium ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Force Balance ◽  
Complex Flow ◽  
Blow Down ◽  
Permeability Coefficients ◽  
Backing Plate ◽  
Brush Seal

The flow behavior through a brush seal has been investigated by developing a flow analysis procedure with a porous medium approach. In order to increase the brush seal performance and use at more severe operating conditions, the complex flow in the bristle pack has become the major concern affecting seal features such as blow-down, hang-up, hysteresis and bristle flutter. In this study, an axi-symmetric CFD model is employed to calibrate anisotropic permeability coefficients for the bristle pack based on available experimental data; leakage, axial pressure on the rotor surface and radial pressure on the backing plate. A simplified form of the force balance equation is introduced for the flow in the porous bristle pack. Different sets of permeability coefficients are defined for fence height region below the seal backing plate and the upper region of the seal to correlate the different physical structures and behavior of these regions during operation. The upper region is subject to more stiffening due to backing plate support while fence height region is free to spread and bend in the axial direction. It is found that flow resistance for upper region should be 20% higher than fence height region in order to match the experimental pressure within the bristle pack. Analysis results prove that the brush seal is well represented as a porous medium with this approach. Based on the model developed, characteristic flow and pressure fields in the entire bristle pack have been explored.

Navier-Stokes Flow Analysis for Hydraulic Turbine Draft Tubes

1990 ◽  
Vol 112 (2) ◽  
pp. 199-204 ◽  
Author(s):  
T. C. Vu ◽  
W. Shyy
Keyword(s):  
Stokes Flow ◽  
Stokes Equations ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Hydraulic Turbine ◽  
Navier Stokes ◽  
Numerical Result ◽  
Wide Range ◽  
Draft Tubes

Three-dimensional turbulent viscous flow analyses for hydraulic turbine elbow draft tubes are performed by solving Reynolds averaged Navier-Stokes equations closed with a two-equation turbulence model. The predicted pressure recovery factor and flow behavior in the draft tube with a wide range of swirling flows at the inlet agree well with experimental data. During the validation of the Navier-Stokes flow analysis, particular attention was paid to the effect of grid size on the accuracy of the numerical result and the importance of accurately specifying the inlet flow condition.

Flow Behavior Around Stayvanes and Guidevanes of a Francis Turbine

1996 ◽  
Vol 118 (1) ◽  
pp. 110-115 ◽  
Author(s):  
Toshiaki Suzuki ◽  
Tomotatsu Nagafuji ◽  
Hiroshi Komiya ◽  
Takako Shimada ◽  
Toshio Kobayashi ◽  
...  
Keyword(s):  
Viscous Flow ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Francis Turbine ◽  
Good Prediction ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Pressure Distributions

The three-dimensional computation of steady and incompressible internal flows is of interest in numerical simulations of turbomachinery, and such simulations are currently under investigation, from inviscid to viscous flow analyses. First, surface pressure distributions have been measured for the stayvanes and the guidevanes of a Francis turbine. They are presented to verify the numerical results. Second, both inviscid and viscous three-dimensional flow analyses have been made, so as to predict the flow behavior in the same domain. Comparison of the measured pressure distributions to the predicted pressure distributions has been made to study the usefulness of the present simulations. It can be pointed out that a global analysis which includes a runner flow passage, except runner blades, is necessary to predict the three-dimensional flow characteristics and that inviscid flow analysis has the capability of good prediction for flow without separation. Viscous flow analysis gives similar results, though it is necessary to investigate further the improvement of prediction accuracy. Flow characteristics around the stayvanes and the guidevanes are also discussed.

Numerical study of polymer melt flow in a three-dimensional sudden expansion: viscous dissipation effects

2014 ◽  
Vol 34 (8) ◽  
pp. 755-764
Author(s):  
Mustafa Tutar ◽  
Ali Karakus
Keyword(s):  
Viscous Dissipation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Polymer Melt ◽  
Sudden Expansion ◽  
Melt Flow

Abstract This numerical paper presents the effects of viscous dissipation on both hydrodynamic flow behavior and thermal flow characteristics of fluid included in rheological polymer flow analysis. The shear rate dependence of the viscosity is modeled using a modified form of the Cross constitutive equation, while the density changes are modeled using the modified Tait state of equation. The Navier-Stokes equations are solved in a sequential, decoupled manner with energy conservation equations using a finite volume method based fluid flow solver. Hydrodynamic and thermal boundary layer developments in an asymmetric sudden expansion for different velocity and melt flow injection temperature boundary and geometry conditions are determined under the influence of viscous dissipation effects and the results are compared with each other to measure the relative effects of viscous dissipation on the interactions of these layers for a commercial polymer melt flow, namely polypropylene (PP). The numerical results demonstrate that proposed mathematical and numerical formulations for viscosity and density variations including viscous heating terms lead to more accurate representation of the polymer melt flow and heat transfer phenomena in plane channels or mold cavity associated with a sudden expansion.

Viscous Flow Analysis as a Design Tool for Hydraulic Turbine Components

1990 ◽  
Vol 112 (1) ◽  
pp. 5-11 ◽  
Author(s):  
T. C. Vu ◽  
W. Shyy
Keyword(s):  
Viscous Flow ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Hydraulic Turbine ◽  
Design Tool ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Alternative Designs

Viscous flow analysis based on the full Reynolds-averaged Navier-Stokes equations is being applied to successfully predict turbulent flow characteristics and energy losses in different hydraulic turbine components. It allows the designer to evaluate the hydraulic performance of alternative designs before proceeding with laboratory testing or to perform elaborate parametric study to optimize the hydraulic design. In this paper, the applications of three-dimensional viscous flow analysis as an analytical design tool for elbow draft tube and spiral casing are presented and their impact on engineering design assessed.

Computational and Experimental Study of Enhanced Laminar Flow Heat Transfer in Three-Dimensional Sinusoidal Wavy-Plate-Fin Channels

2003 ◽  
Author(s):  
Jiehai Zhang ◽  
Arun Muley ◽  
Joseph B. Borghese ◽  
Raj M. Manglik
Keyword(s):  
Heat Transfer ◽  
Flow Behavior ◽  
Computational Simulation ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Staggered Grid ◽  
Uniform Heat Flux ◽  
Complex Flow ◽  
Constant Property ◽  
Fin Efficiency

Enhanced heat transfer characteristics of low Reynolds number airflows in three-dimensional sinusoidal wavy plate-fin channels are investigated. For the computational simulation, steady state, constant property, periodically developed, laminar forced convection is considered with the channel surface at the uniform heat flux condition; the wavy-fin is modeled by its two asymptotic limits of 100% and zero fin efficiency. The governing equations are solved numerically using finite-volume techniques for a non-orthogonal, non-staggered grid. Computational results for velocity and temperature distribution, isothermal Fanning friction factor f and Colburn factor j are presented for airflow rates in the range of 10 ≤ Re ≤ 1500. The numerical results are further compared with experimental data, with excellent agreement, for two different wavy-fin geometries. The influence of fin density on the flow behavior and the enhanced convection heat transfer are highlighted. Depending on the flow rate, a complex flow structure is observed, which is characterized by the generation, spatial growth and dissipation of vortices in the trough region of the wavy channel. The thermal boundary layers on the fin surface are periodically disrupted, resulting in high local heat fluxes. The overall heat transfer performance is improved considerably, compared to the straight channel with the same cross-section, with a relatively smaller increase in the associated pressure drop penalty.

Sign in / Sign up

Export Citation Format

Share Document