An Approach for Inclusion of a Nonlocal Transition Model in a Parallel Unstructured Computational Fluid Dynamics Code

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Dragan Kožulović ◽  
B. Leigh Lapworth
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shape Factor ◽  
Nonlocal Boundary ◽  
Reynolds Numbers ◽  
Transition Model ◽  
Low Pressure Turbine ◽  
Computational Overhead ◽  
Transition Modeling ◽  
Good Agreement

The implementation of an integral transition model in a parallel unstructured computational fluid dynamics code is described. In particular, an algorithm for gathering the nonlocal boundary layer values (momentum thickness and shape factor) from parallel distributed computational domains is presented. Transition modeling results are presented for a flat plate and for a low pressure turbine, covering a large variation of Reynolds numbers, Mach numbers, turbulence intensities, and incidence angles. Contrary to fully turbulent simulations, transitional predictions are in very good agreement with measurements. Furthermore, the computational overhead of transitional simulations is only 7% for one multigrid cycle.

An Approach for Inclusion of a Non-Local Transition Model in a Parallel Unstructured CFD Code

2007 ◽  
Author(s):  
Dragan Kozˇulovic´ ◽  
B. L. Lapworth
Keyword(s):  
Shape Factor ◽  
Large Range ◽  
Reynolds Numbers ◽  
Transition Model ◽  
Local Boundary ◽  
Low Pressure Turbine ◽  
Computational Overhead ◽  
Non Local ◽  
Transition Modelling ◽  
Local Transition

The implementation of an integral transition model in a parallel unstructured CFD code is described. In particular, an algorithm for gathering the non-local boundary layer values (momentum thickness, shape factor, etc.) from parallely distributed computational domains is presented. Transition modelling results are presented for a flat plate and for a low pressure turbine, covering a large range of Reynolds numbers, Mach numbers, turbulence intensities and incidence angles. The transitional predictions are in much better agreement with the measurements than fully turbulent simulations. Furthermore, the computational overhead of transitional simulations is only 7% for one multigrid cycle.

Prediction of Separation-Induced Transition on High Lift Low Pressure Turbine Blade

2011 ◽  
Author(s):  
Abdelkader Benyahia ◽  
Lionel Castillon ◽  
Robert Houdeville
Keyword(s):  
Experimental Data ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Transition Model ◽  
Freestream Turbulence ◽  
Low Pressure Turbine ◽  
European Program ◽  
Inlet Conditions ◽  
Development And Validation ◽  
Good Agreement

This paper deals with the development and validation of the Menter and Langtry correlation-based transition model in the RANS code elsA. Two types of experimental linear cascades of low pressure turbine (LPT) airfoils having different loading distributions have been considered for the validation: the T106C and T108 blades. Experimental data have been provided by the Von Karman Institute in the framework of the European program TATMo. Different Reynolds numbers varying from 80 000 to 250 000 and different freestream turbulence intensities have been investigated. The results obtained for the T106C blade are in good agreement with the experimental data: the bubble size and the kinetic energy losses are well predicted. Sensitivity to freestream turbulence is also well demonstrated for the considered Reynolds numbers. However the results for the T108 blade show the limitations of the current version. These limitations are explained and discussed in this paper. The second part of this paper deals with the numerical and physical aspects of periodical unsteady inlet conditions which are introduced in order to take into account the incoming wakes. The original Menter and Langtry transition model has required a modification for performing correct unsteady computations of wake induced transition which is discussed in this paper. The unsteady results obtained with elsA are in quite good agreement with the experimental data.

Study on Manufacturing Tolerances for the Laminar Airfoil

2015 ◽  
Author(s):  
Jaehun Lee ◽  
Kyoung Jin Jung
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Transition Model ◽  
Dynamics Analysis ◽  
Cfd Analysis ◽  
Computational Fluid Dynamics Analysis ◽  
Manufacturing Tolerances ◽  
Forward Facing Step ◽  
Good Agreement

The procedure to determine manufacturing tolerances for the laminar airfoil is explained using the CFD (computational fluid dynamics) analysis. This procedure is applied to a laminar airfoil for the tolerance of the forward-facing step and rearward-facing step. In the CFD analysis the Langtry-Menter SST Transition model is used to simulate a natural transition over the laminar airfoil. The computed tolerances showed good agreement with experimental data.

scholarly journals Thermoelectric Generation with Impinging Nano-Jets

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 492
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Mikhail A. Sheremet
Keyword(s):  
Fluid Dynamics ◽  
Power Generation ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Conversion Efficiency ◽  
Reynolds Numbers ◽  
Thermoelectric Generation ◽  
Volume Fractions ◽  
Water Jets ◽  
Conversion Efficiencies

In this study, thermoelectric generation with impinging hot and cold nanofluid jets is considered with computational fluid dynamics by using the finite element method. Highly conductive CNT particles are used in the water jets. Impacts of the Reynolds number of nanojet stream combinations (between (Re1, Re2) = (250, 250) to (1000, 1000)), horizontal distance of the jet inlet from the thermoelectric device (between (r1, r2) = (−0.25, −0.25) to (1.5, 1.5)), impinging jet inlet to target surfaces (between w2 and 4w2) and solid nanoparticle volume fraction (between 0 and 2%) on the interface temperature variations, thermoelectric output power generation and conversion efficiencies are numerically assessed. Higher powers and efficiencies are achieved when the jet stream Reynolds numbers and nanoparticle volume fractions are increased. Generated power and efficiency enhancements 81.5% and 23.8% when lowest and highest Reynolds number combinations are compared. However, the power enhancement with nanojets using highly conductive CNT particles is 14% at the highest solid volume fractions as compared to pure water jet. Impacts of horizontal location of jet inlets affect the power generation and conversion efficiency and 43% variation in the generated power is achieved. Lower values of distances between the jet inlets to the target surface resulted in higher power generation while an optimum value for the highest efficiency is obtained at location zh = 2.5ws. There is 18% enhancement in the conversion efficiency when distances at zh = ws and zh = 2.5ws are compared. Finally, polynomial type regression models are obtained for estimation of generated power and conversion efficiencies for water-jets and nanojets considering various values of jet Reynolds numbers. Accurate predictions are obtained with this modeling approach and it is helpful in assisting the high fidelity computational fluid dynamics simulations results.

Computational Fluid Dynamics Analysis of a Steam Power Plant Low-Pressure Turbine Downward Exhaust Hood

1996 ◽  
Vol 118 (1) ◽  
pp. 214-224 ◽  
Author(s):  
R. H. Tindell ◽  
T. M. Alston ◽  
C. A. Sarro ◽  
G. C. Stegmann ◽  
L. Gray ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Integrated Approach ◽  
Low Pressure ◽  
Operating Conditions ◽  
Exhaust Hood ◽  
Steam Power ◽  
Low Pressure Turbine ◽  
Computational Fluid Dynamics Analysis ◽  
Turbine Exhaust

Computational fluid dynamics (CFD) methods are applied to the analysis of a low-pressure turbine exhaust hood at a typical steam power generating station. A Navier-Stokes solver, capable of modeling all the viscous terms, in a Reynolds-averaged formulation, was used. The work had two major goals. The first was to develop a comprehensive understanding of the complex three-dimensional flow fields that exist in the exhaust hood at representative operating conditions. The second was to evaluate the relative benefits of a flow guide modification to optimize performance at a selected operating condition. Also, the influence of simulated turbine discharge characteristics, relative to uniform hood entrance conditions, was evaluated. The calculations show several interesting and possibly unique results. They support use of an integrated approach to the design of turbine exhaust stage blading and hood geometry for optimum efficiency.

Manufacturing and Computational Fluid Dynamics Modeling of a Patient-Specific Fistula Model

2017 ◽  
Author(s):  
Yang Liu ◽  
Yihao Zheng ◽  
John Pitre ◽  
William Weitzel ◽  
Joseph Bull ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Patient Specific ◽  
Cfd Model ◽  
Dynamics Modeling ◽  
Computational Fluid Dynamics Modeling ◽  
Computational Fluid Dynamics Cfd ◽  
Particle Imaging ◽  
Venous Wall ◽  
Good Agreement

Arteriovenous fistula is the joining of an artery to a vein to create vascular access for dialysis. The failure or maturation of fistula is affected by the vessel wall shear stress (WSS), which is difficult to measure in clinic. A computational fluid dynamics (CFD) model was built to estimate WSS of a patient-specific fistula model. To validate this model, a silicone phantom was manufactured and used to carry out a particle imaging velocimetry (PIV) experiment. The flow field from the PIV experiment shows a good agreement with the CFD model. From the CFD model, the highest WSS (40 Pa) happens near the anastomosis. WSS in the vein is larger than that in the artery. WSS on the outer venous wall is larger than that on the inner wall. The combined technique of additive manufacturing, silicone molding, and CFD is an effective tool to understand the maturation mechanism of a fistula.

A Numerical and Experimental Investigation of Low-conductivity Unglazed, Transpired Solar Air Heaters

2005 ◽  
Vol 127 (1) ◽  
pp. 153-155 ◽  
Author(s):  
Keith Gawlik ◽  
Craig Christensen ◽  
Charles Kutscher
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Experimental Investigation ◽  
Experimental Work ◽  
Experimental Results ◽  
Flow Conditions ◽  
Numerical Work ◽  
Plate Geometry ◽  
Modeling Flow ◽  
Good Agreement

The performance of low-conductivity unglazed, transpired solar collectors was determined numerically and experimentally. The numerical work consisted of modeling flow conditions, plate geometries, and plate conductivities with modified commercial computational fluid dynamics software, and the experimental work compared the performance of two plate geometries made with high and low conductivity materials under a variety of flow conditions. Good agreement was found between the numerical and experimental results. The results showed that for practical low-conductivity materials, performance differed little from the equivalent plate geometry in high-conductivity material.

Computational Fluid Dynamics Applied on an Autonomous Underwater Vehicle

2004 ◽  
Author(s):  
Arnt-Lennard Fuglestad ◽  
Mads Grahl-Madsen
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Drag Force ◽  
Autonomous Underwater Vehicle ◽  
Reynolds Numbers ◽  
Paper Report ◽  
Computer Aided Analysis ◽  
Present Paper Report ◽  
Defence Research

The present paper report on a comparison between experimental obtained data for the drag force acting on a model prototype of the HUGIN 3000 and data obtained from a Computer Aided Analysis of the drag force carried out by CFD (Computational Fluid Dynamics). The HUGIN 3000 was developed in the nineties, by Kongsberg Maritime and FFI (Norwegian Defence Research Establishment). The experimental results in this paper, origins from a model test carried out by Marintek. The range of Reynolds number for both the experimental data and the computational results is 2.707×106 to 1.146×107. The agreement between the experimental data and the computed results is good. Particularly for the highest Reynolds numbers, the prediction of drag force by CFD seems to be remarkable good.

CFD Simulation on Hydrodynamics of Liquid-Liquid Slug Flow in Microchannel

2014 ◽  
Vol 936 ◽  
pp. 1662-1665
Author(s):  
Yi Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Slug Flow ◽  
Cfd Simulation ◽  
Liquid Slug ◽  
Internal Circulation ◽  
Flow Generation ◽  
Dynamics Method ◽  
Good Agreement

Hydrodynamics in a liquid-liquid slug flow in a T-junction microchannel of 600μm diameter, operated under a squeezing regime, was simulated with the computational fluid dynamics method. The slug flow generation simulated shows very good agreement with experimental snapshots where the clear slug formation takes place in the vicinity of the T-junction. The internal circulation within each slug was also obtained, which could make us better understand the hydrodynamics of liquid-liquid slug flow in microchannel.

Transition Modelling for Vortex Generating Jets on Low-Pressure Turbine Profiles

2011 ◽  
Author(s):  
Florian Herbst ◽  
Dragan Kozˇulovic´ ◽  
Joerg R. Seume
Keyword(s):  
Total Pressure ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Pressure Losses ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Local Transition

Steady blowing vortex generating jets (VGJ) on highly-loaded low-pressure turbine profiles have shown to be a promising way to decrease total pressure losses at low Reynolds-numbers by reducing laminar separation. In the present paper, the state of the art turbomachinery design code TRACE with RANS turbulence closure and coupled γ-ReΘ transition model is applied to the prediction of typical aerodynamic design parameters of various VGJ configurations in steady simulations. High-speed cascade wind tunnel experiments for a wide range of Reynolds-numbers, two VGJ positions, and three jet blowing ratios are used for validation. Since the original transition model overpredicts separation and losses at Re2is ≤ 100·103 an extra mode for VGJ induced transition is introduced. Whereas the criterion for transition is modelled by a filtered Q vortex criterion the transition development itself is modelled by a reduction of the local transition-onset momentum-thickness Reynolds number. The new model significantly improves the quality of the computational results by capturing the corresponding local transition process in a physically reasonable way. This is shown to yield an improved quantitative prediction of surface pressure distributions and total pressure losses.

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