Validation of RANS Turbulence Models for Labyrinth Seal Flows by Means of Particle Image Velocimetry

2020 ◽  
Author(s):  
Lars Wein ◽  
Tim Kluge ◽  
Joerg R. Seume ◽  
Rainer Hain ◽  
Thomas Fuchs ◽  
...  
Keyword(s):  
Velocity Field ◽  
Numerical Models ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Labyrinth Seal ◽  
Viscous Effects ◽  
Local Pressure ◽  
Wrong Prediction ◽  
Rans Turbulence Models ◽  
Rate Of Dissipation

Abstract Accurate prediction of labyrinth seal flows is important for the design and optimisation of turbomachinery. However, the prediction of such flows with RANS turbulence models is still lacking. The identification of modelling deficits and the development of improved turbulence models requires detailed experimental data. Consequently, a new test rig for straight labyrinth seals was built at the Institute for Turbomachinery and Fluid Dynamics which allows for non-intrusive measurements of the three dimensional velocity field in the cavities. Two linear eddy viscosity models and one algebraic Reynolds stress turbulence model have been tested and validated against global parameters, local pressure measurements, and non-intrusive measurements of the velocity field. While some models accurately predict the discharge coefficient, large local errors occurred in the prediction of the wall static pressure in the seal. Although improved predictions were possible by using model extensions, significant errors in the prediction of vortex systems remained in the solution. These were identified with the help of PIV results. All turbulence models struggled to accurately predict the size of separations and the swirl imposed by viscous effects at the rotor surface. Additionally, the expansion of the leakage jet in the outlet cavity is not modelled correctly by the numerical models. This is caused by a wrong prediction of turbulent kinetic energy and, presumably, its rate of dissipation.

Partially Cavitating Hydrofoils: Experimental and Numerical Analysis*

2000 ◽  
Vol 44 (01) ◽  
pp. 40-58
Author(s):  
Christian Pellone ◽  
Thierry Maître ◽  
Laurence Briançon-Marjollet
Keyword(s):  
Numerical Models ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Navier Stokes ◽  
Viscous Effects ◽  
Local Pressure ◽  
Two Phase ◽  
Complete Study ◽  
Flow Configurations ◽  
Potential Methods

The numerical modeling of partially cavitating foils under a confined flow configuration is described. A complete study of previous numerical models highlights that the presence of a turbulent and two-phase wake, at the rear of the cavity, has a nonnegligible effect on the local pressure coefficient, the cavitation number, the cavity length and the lift coefficient; hence viscous effects must be included. Two potential methods are used, each being coupled with a calculation of the boundary layer developed downstream of the cavity. So, an "open cavity" numerical model, as it is called, was developed and tested with two types of foil: a NACA classic foil and a foil of which the profile is obtained performing an inverse calculation on a propeller blade test section. On the other hand, under noncavitating conditions, for each method, the results are compared with the results obtained by the Navier-Stokes solver "FLUENT." The cavitating flow configurations presented herein were carried out using the small hydrodynamic tunnel at Bassin d'Essais des Carènes [Val de Reuil, France]. The results obtained by the two methods are compared with experimental measurements.

New Insight Into the Flow Around a Wind Turbine Airfoil Section1

2005 ◽  
Vol 127 (2) ◽  
pp. 214-222 ◽  
Author(s):  
F. Bertagnolio ◽  
N. N. Sørensen ◽  
F. Rasmussen
Keyword(s):  
Wind Turbine ◽  
Numerical Models ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Pitching Airfoil ◽  
Wind Turbine Airfoil

The objective of this paper is an improved understanding of the physics of the aeroelastic motion of wind turbine blades in order to improve the numerical models used for their design. Two- and three-dimensional Navier–Stokes calculations of the flow around a wind turbine airfoil using the k−ω SST and Detached Eddy Simulation (DES) turbulence models, as well as an engineering semiempirical dynamic stall model, are conducted. The computational results are compared to the experimental results that are available for both the static airfoil and the pitching airfoil. It is shown that the Navier–Stokes simulations can reproduce the main characteristic features of the flow. The DES model seems to be able to reproduce most of the details of the unsteady aerodynamics. Aerodynamic work computations indicate that a plunging motion of the airfoil can become unstable.

Leakage and rotordynamic characteristics of labyrinth seal and hole-pattern damping seal with special-shaped 3D cavity

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xuan Zhang ◽  
Jin-Bo Jiang ◽  
Xudong Peng ◽  
Jiyun Li
Keyword(s):  
Peer Review ◽  
Numerical Models ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Angular Speed ◽  
Damping Coefficient ◽  
Geometrical Structures ◽  
Content Type ◽  
Shaped Hole ◽  
Inclined Angle

Purpose The purpose of this paper is to enhance sealing and rotordynamic performance of hole-pattern damping seal (HPDS) and labyrinth seal (LS) by structural innovation and geometrical optimization of special-shaped hole or annular-groove cavity. Design/methodology/approach The unsteady flow was transformed into steady one using moving reference frame method. The full period numerical models of LS and HPDS were established. The influence of special-shaped hole or annular-groove cavity at axial inclined angle on leakage rate and rotordynamic coefficient of these two seals at different whirl angular speed were investigated. Findings The results show that dynamic characteristics of straight-tooth LS are better than that of slanted-tooth LS. Compared to typical straight-hole damping seal, HPDS with windward oblique-hole when axial inclined angle ranges from 50 to 60° has superiority in both leakage and rotordynamic characteristics by considering smaller cross-coupled stiffness coefficient and whirl frequency ratio, larger direct damping coefficient and effective damping coefficient. Originality/value A novel HPDS with special-shaped three-dimensional hole cavity was proposed to enhance leakage and rotordynamic performance. The optimized geometrical structures of HPDS for excellent sealing and rotordynamic characteristics were obtained. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0262/

Prediction of Developing Turbulent Flow in a 90° Curved Duct Using Linear and Nonlinear Low-Re k-ε Models

Volume 1 ◽  
2004 ◽  
Author(s):  
M. Raisee ◽  
H. Alemi ◽  
H. Iacovides
Keyword(s):  
Turbulent Flow ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Main Stream ◽  
Local Pressure ◽  
Flow Measurements ◽  
Numerical Predictions ◽  
Flow Development ◽  
Curved Section

This paper reports the outcome of applying two different low-Re number eddy-viscosity models to resolve the complex three-dimensional motion that arises in turbulent flow in a square cross-section duct passing around a 90° bend. Flow computations have been obtained using a three-dimensional, non-orthogonal flow solver. For modeling of turbulence, the Launder and Sharma low-Re k–ε model and a recently modified version of nonlinear low-Re k–ε model that have been shown to be suitable for flow and thermal predictions in re-circulating and impinging jet flows, have been employed. A bounded version of the QUICK scheme was used for the approximation of convection in all transport equations. The numerical predictions are validated through comparisons with the reported flow measurements and are used to explain how the curvature influences the flow development. The results of the present investigation indicate that the curvature induces a strong secondary flow in the curved section of the duct. The secondary motion also persists downstream of the bend, although it slowly disappears with the main stream development. At the entrance of the curved section, the curvature alters the flow development by displacing the fluid towards the convex (inner) wall. Comparisons of the predicted stream-wise and cross-stream velocity components with the measured data indicate that both turbulence models employed in the present study can produce reasonable predictions, although the non-linear model predictions are generally closer to the measurements. Both turbulence models successfully reproduce the distribution as well as the levels of the local pressure coefficient in the curved section of the duct.

Thermal Mixing Length Determination by RANS Models in T-Junction

2010 ◽  
Author(s):  
M. Aounallah ◽  
M. Belkadi ◽  
L. Adjlout ◽  
O. Imine
Keyword(s):  
Turbulent Mixing ◽  
Thermal Field ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Numerical Results ◽  
Test Case ◽  
Thermal Mixing ◽  
Rans Turbulence Models ◽  
Rans Models ◽  
Length Determination

In the present study, a numerical simulation is carried out in order to optimize the length of the mixing part of a T-junction to obtain a homogenous temperature distribution at the outlet. Different RANS turbulence models are tested: the Realizable k-ε the k-ω standard and the k-ω SST. The behavior of turbulent mixing flow in the mixing part of the pipe has helped in understanding the causes of discrepancy between the models used. The test case analysed in this paper is an unsteady state three-dimensional turbulent flow. The numerical results obtained show that there is a difference in the prediction of the thermal field when different models are used. The results obtained for both k-ω standard and SST models are closer compared with those given by the Realizable k-ε model. The numerical results show that a distance of x/L = 0.625 from the branch is enough to supply devices with a constant temperature.

Validation of RANS Turbulence Models for Labyrinth Seal Flows by Means of Particle Image Velocimetry

2021 ◽  
Author(s):  
Lars Wein ◽  
Tim Kluge ◽  
Joerg R. Seume ◽  
Rainer Hain ◽  
Thomas Fuchs ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Turbulence Models ◽  
Labyrinth Seal ◽  
Image Velocimetry ◽  
Rans Turbulence Models

Using Viscous Calculations in Pump Design

1990 ◽  
Vol 112 (3) ◽  
pp. 272-280 ◽  
Author(s):  
F. Martelli ◽  
V. Michelassi
Keyword(s):  
High Performance ◽  
Incompressible Flows ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Computer Code ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Viscous Effects ◽  
Complex Flow ◽  
Pump Design

A viscous computer code for designing the meridional channels of high-performance pumps is presented. An averaging technique is used to reduce the three-dimensional flow to a two-dimensional model. The code, based upon an implicit finite difference method for steady two-dimensional incompressible flows, was validated in complex flow geometries prior to application in the design analysis of an actual pump. Viscous effects are taken into account by two different turbulence models. The Navier-Stokes solver is used in conjunction with a standard blade-to-blade calculation by means of an automatic graphic procedure that exchanges geometric and flowfield data. Various meridional shape solutions are presented and discussed in relation to physical evidence.

scholarly journals Using internal layers from the Greenland ice sheet, identified from radio-echo sounding data, with numerical models

2003 ◽  
Vol 37 ◽  
pp. 325-330 ◽  
Author(s):  
Duncan J. Baldwin ◽  
Jonathan L. Bamber ◽  
Antony J. Payne ◽  
Russel L. Layberry
Keyword(s):  
Velocity Field ◽  
Numerical Models ◽  
Accumulation Rate ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Internal Layers ◽  
Accumulation Rates ◽  
Radio Echo Sounding ◽  
North Greenland ◽  
Echo Sounding

AbstractSpatially extensive internal layers have been traced in airborne radio-echo sounding (RES) data collected over Greenland during the late 1990s. By linking internal layers within individual flight-lines at crossover points, it is possible to identify spatially continuous layers that are interpreted as isochronous surfaces. Several of the survey lines pass over the GRIP core site, and this allows us to use the published GRIP age–depth relationship to accurately date these surfaces. Two layers, with ages of 3891 and 6956 years BP, have been traced over a large part of North Greenland. Accurately dated and spatially continuous isochrones are valuable for both assimilation within, and verification of, numerical models. For example, comparison of isochronous surfaces from a numerical simulation with those layers observed in RES data can be used to inform the choice of parameters (e.g. rheology) and climate history used to force a numerical model. To demonstrate the potential of the RES data, two layers for North Greenland were used to determine palaeo-accumulation rates. The inversion from layer depth to accumulation rate requires a three-dimensional velocity field. This velocity field is constructed by combining a two-dimensional balance-velocity field with an assumed vertical structure for the horizontal velocity. The isochronous-layer derived accumulation rates were compared with the Bales and others (2001) rates. A larger east–west gradient was found across the central ice divide for the derived accumulation rate, suggesting a trend in the Holocene accumulation rates for this region. The layers were also compared with isochronous surfaces derived from simulations of a three-dimensional thermodynamic ice-sheet model. Using the isochronous-layer derived accumulation rates to force the model improved the match between modelled and observed layers.

Development of Local Heat Transfer and Pressure Drop Models for Pebble Bed High Temperature Gas-Cooled Reactor Cores

2008 ◽  
Author(s):  
Brian McLaughlin ◽  
Matthew Worsley ◽  
Richard Stainsby ◽  
Andrew Grief ◽  
Ana Dennier ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Pebble Bed ◽  
Ansys Fluent ◽  
Pebble Bed Reactor ◽  
Rans Turbulence Models

This paper describes pressure drop and heat transfer coefficient predictions for a typical coolant flow within the core of a pebble bed reactor (PBR) by examining a representative group of pebbles remote from the reflector region. The three-dimensional steady state flow and heat transfer predictions utilized in this work are obtained from a computational fluid dynamics (CFD) model created in the commercial software ANSYS FLUENT™. This work utilizes three RANS turbulence models and the Chilton-Colburn analogy for heat transfer. A methodology is included in this paper for creating a quality unstructured mesh with prismatic surface layers on a random arrangement of touching pebbles. The results of the model are validated by comparing them with the correlations of the German KTA rules for a PBR.

scholarly journals Review and Comparison of Numerical Simulations of Secondary Flow in River Confluences

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1917
Author(s):  
Rawaa Shaheed ◽  
Xiaohui Yan ◽  
Abdolmajid Mohammadian
Keyword(s):  
Secondary Flow ◽  
Numerical Models ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Pollutant Dispersion ◽  
Field Studies ◽  
Secondary Flows ◽  
Suitable Model ◽  
River Confluences

River confluences are a common feature in natural water resources. The flow characteristics in confluences are complicated, especially at junction areas between tributaries and the main river. One of the typical characteristics of confluences is secondary flow, which plays an important role in mixing, velocity, sediment transport, and pollutant dispersion. In addition to the experimental and field studies that have been conducted in this area, the development of computational fluid dynamics has allowed researchers in this field to use different numerical models to simulate turbulence properties in rivers, especially secondary flows. Nowadays, the hydrodynamics of flows in confluences are widely simulated by using three-dimensional models in order to fully capture the flow structures, as the flow characteristics are considered to be turbulent and three-dimensional at river junctions. Several numerical models have been recommended for this purpose, and various turbulence models have been used to simulate the flows at confluences. To assess the accuracy of turbulence models, flows have been predicted by applying different turbulence models in the numerical model and the results have been compared with other data, such as field, laboratory, and experimental data. The purpose behind these investigations was to find the suitable model for each case of turbulent flow and for different types of confluences. In this study, the performances of turbulence models for confluences are reviewed for different numerical simulation strategies.

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