9 Analytical wall-functions of turbulence for complex surface flow phenomena

2010 ◽  
pp. 331-380 ◽  
Author(s):  
K. Suga
Keyword(s):  
Complex Surface ◽  
Surface Flow ◽  
Wall Functions ◽  
Flow Phenomena

scholarly journals Experimental Research and Numerical Analysis of Flow Phenomena in Discharge Object with Siphon

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3330
Author(s):  
Milan Sedlář ◽  
Pavel Procházka ◽  
Martin Komárek ◽  
Václav Uruba ◽  
Vladislav Skála
Keyword(s):  
Experimental Research ◽  
Turbulence Models ◽  
Free Surface Flow ◽  
Stationary Flow ◽  
Surface Flow ◽  
Flow Structures ◽  
Complex Flow ◽  
Flow Topology ◽  
Image Velocimetry ◽  
Flow Phenomena

This article presents results of the experimental research and numerical simulations of the flow in a pumping system’s discharge object with the welded siphon. The laboratory simplified model was used in the study. Two stationary flow regimes characterized by different volume flow rates and water level heights have been chosen. The study concentrates mainly on the regions below and behind the siphon outlet. The mathematical modelling using advanced turbulence models has been performed. The free-surface flow has been carried out by means of the volume-of-fluid method. The experimental results obtained by the particle image velocimetry method have been used for the mathematical model validation. The evolution and interactions of main flow structures are analyzed using visualizations and the spectral analysis. The presented results show a good agreement of the measured and calculated complex flow topology and give a deep insight into the flow structures below and behind the siphon outlet. The presented methodology and results can increase the applicability and reliability of the numerical tools used for the design of the pump and turbine stations and their optimization with respect to the efficiency, lifetime and environmental demands.

scholarly journals Thermal structure and basal sliding parametrisation at Pine Island Glacier – a 3-D full-Stokes model study

2014 ◽  
Vol 8 (5) ◽  
pp. 4913-4957
Author(s):  
N. Wilkens ◽  
J. Behrens ◽  
T. Kleiner ◽  
D. Rippin ◽  
M. Rückamp ◽  
...  
Keyword(s):  
Flow Structure ◽  
Thermal Structure ◽  
Complex Surface ◽  
Surface Flow ◽  
Surface Velocity ◽  
Model Study ◽  
Basal Sliding ◽  
Modelling Studies ◽  
Global Sea Level ◽  
The Antarctic

Abstract. Pine Island Glacier is one of the fastest changing glaciers in the Antarctic Ice Sheet and therefore in scientific focus. The glacier holds enough ice to raise global sea level significantly (∼0.5 m), when fully melted. The question addressed by numerous modelling studies of the glacier focuses on whether the observed changes are a start for an uncontrolled and accelerating retreat. The movement of the glacier is, in the fast flowing areas, dominated by basal motion. In modelling studies the parametrisation of the basal motion is therefore crucial. Inversion methods are commonly applied to reproduce the complex surface flow structure at Pine Island Glacier, which use information of the observed surface velocity field, to constrain basal sliding. We introduce two different approaches of combining a physical parameter, the basal roughness, with basal sliding parametrisations. This way basal sliding is connected again to its original formulation. We show that the basal roughness is an important and helpful parameter to consider and that many features of the flow structure could be reproduced with these approaches.

scholarly journals Thermal structure and basal sliding parametrisation at Pine Island Glacier – a 3-D full-Stokes model study

2015 ◽  
Vol 9 (2) ◽  
pp. 675-690 ◽  
Author(s):  
N. Wilkens ◽  
J. Behrens ◽  
T. Kleiner ◽  
D. Rippin ◽  
M. Rückamp ◽  
...  
Keyword(s):  
Flow Structure ◽  
Thermal Structure ◽  
Complex Surface ◽  
Surface Flow ◽  
Surface Velocity ◽  
Model Study ◽  
Basal Sliding ◽  
Modelling Studies ◽  
Global Sea Level ◽  
The Antarctic

Abstract. Pine Island Glacier is one of the fastest changing glaciers of the Antarctic Ice Sheet and therefore of scientific interest. The glacier holds enough ice to raise the global sea level significantly (~ 0.5 m) when fully melted. The question addressed by numerous modelling studies of the glacier focuses on whether the observed changes are a start of an uncontrolled and accelerating retreat. The movement of the glacier is, in the fast-flowing areas, dominated by basal motion. In modelling studies the parametrisation of the basal motion is therefore crucial. Inversion methods are commonly applied to reproduce the complex surface flow structure of Pine Island Glacier by using information of the observed surface velocity field to constrain, among other things, basal sliding. We introduce two different approaches of combining a physical parameter, the basal roughness, with basal sliding parametrisations. This way basal sliding is again connected closer to its original formulation. We show that the basal roughness is an important and helpful parameter to consider and that many features of the flow structure can be reproduced with these approaches.

A Numerical Analysis of a Mixed Flow Pump

2002 ◽  
Author(s):  
J. Ferna´ndez ◽  
E. Blanco ◽  
C. Santolaria ◽  
T. J. Scanlon ◽  
M. T. Stickland
Keyword(s):  
Flow Rate ◽  
Three Dimensional ◽  
Axial Direction ◽  
Second Order ◽  
Mixed Flow ◽  
Wall Functions ◽  
Flow Phenomena ◽  
Numerical Grid ◽  
Flow Through ◽  
Flow Pump

The rotating passages of turbomachinery contain some very interesting and complex fluid flow phenomena. This paper presents the three-dimensional turbulent flow through the impeller passages and surroundings of a mixed-flow pump. The model has five impeller blades mounted on a conical hub and nine stator blades in a diffuser which brings the diagonally outward flow back to the axial direction. This pump was tested with air, giving a nominal flow-rate of 1.01 m3/s and 250 Pa at 1200 rpm. Temporal discretization has second order accuracy and this is in line with the discretization of convection which is also second order. For turbulence closure the standard k-e model has been applied with conventional wall functions employed at solid surfaces. For this transient, three-dimensional computation, the numerical grid has been decomposed into five separate regions in order to process these in a parallel cluster of five individual PC’s. The results show entirely reasonable correlations with published experimental data as detailed in the flow rate-head comparisons and the numerical / experimental flow fields. These outcomes allow us to confirm that such a complex transient phenomenon may be reasonably captured by employing a commercial CFD code.

Effects of surface flow control on fluid flow phenomena and mixing time in a bottom blown bath

1999 ◽  
Vol 30 (4) ◽  
pp. 631-637 ◽  
Author(s):  
Manabu Iguchi ◽  
Ryoji Tsujino ◽  
Kei-Ichi Nakamura ◽  
Mitsuhiro Sano
Keyword(s):  
Fluid Flow ◽  
Flow Control ◽  
Mixing Time ◽  
Surface Flow ◽  
Flow Phenomena

Multidimensional Predictions of In-Cylinder Turbulent Flows: Contribution to the Assessment of k-ε Turbulence Model Variants for Bowl-in-Piston Engines

2005 ◽  
Vol 127 (4) ◽  
pp. 883-896 ◽  
Author(s):  
Mirko Baratta ◽  
Andrea E. Catania ◽  
Ezio Spessa ◽  
Rui L. Liu
Keyword(s):  
Turbulent Flows ◽  
Turbulence Model ◽  
Internal Combustion Engines ◽  
Flow Analysis ◽  
Combustion Process ◽  
Turbulence Models ◽  
Wall Functions ◽  
Spacing Effects ◽  
Flow Phenomena ◽  
Cylinder Flow

Multidimensional computational fluid dynamics (CFD) codes with reliable turbulence models are useful investigation and design tools for internal combustion engines, in-cylinder flow phenomena being critical to the combustion process and related emission sources. Although a variety of turbulence models has long been proposed, the assessment of even the most widely used k-ε model is still lacking, especially for bowl-in-piston engines. This paper provides a survey of k-ε turbulence model variants and their numerical implementation for in-cylinder flow analysis. Mean motion and turbulence quantities were simulated in the axisymmetric combustion chamber of a motored model engine featuring one centrally located valve and each of a flat-piston and cylindrical bowl-in-piston arrangements. A noncommercial CFD code developed by the authors was applied for calculation, using a finite-volume conservative implicit method and applying various order-of-accuracy numerical schemes. Simulation results are presented at the engine speed of 200 rpm throughout the whole engine cycle. These were obtained using three k-ε turbulence model versions, standard, renormalization group (RNG) and two scale, each of which focuses on one main engine flow feature, i.e., compressibility, anisotropy, and high unsteadiness, respectively. Modified boundary conditions with respect to conventional logarithmic wall functions were applied. Effects of equation-differencing scheme and computational-grid spacing effects on flow predictions were tested. The numerical results were compared to those of laser Doppler velocimetry measurements and the influence of the k-ε model variants on the flow-field features was examined during the induction stroke and around compression top dead center. For the flat-piston case, a comparison between the homemade and commercial STAR-CD® code results was also made.

Measurements and Computations of Compressible Flow Through a Turbine Cascade With Surface Roughness

2006 ◽  
Author(s):  
Lan Qin Yuan ◽  
Richard J. Kind
Keyword(s):  
Surface Roughness ◽  
Compressible Flow ◽  
Rough Surfaces ◽  
Surface Flow ◽  
Turbine Cascade ◽  
Roughness Effects ◽  
Near Surface ◽  
Wall Functions ◽  
Flow Through ◽  
Viscous Flow Field

Experiments and computations have been carried out for a high-pressure turbine cascade having bands of roughness on the blade surfaces, for cascade-exit Mach numbers ranging from 0.4 to 1.13 Tests were carried out with three different relative roughness heights as well as with smooth surfaces. The results comprise profile-loss coefficients and deviation angle. Corresponding flow computations were done using the Fluent 6.0 CFD code with the Spalart-Almaras turbulence model and wall functions to model the near-surface flow. Good agreement was found between the experimental and computational results, especially with regard to trends with Mach number, roughness height and roughness-band configuration. This indicates that current computational methods, which use essentially the same approach to model surface-roughness effects as validated for incompressible flow, can give good predictions of compressible flow over rough surfaces, including details of the viscous flow field. The experimental data constitutes a valuable resource for future efforts to improve prediction capabilities for flows involving rough surfaces.

Sign in / Sign up

Export Citation Format

Share Document