scholarly journals Computational fluid dynamics for turbomachinery internal air systems

2007 ◽  
Vol 365 (1859) ◽  
pp. 2587-2611 ◽  
Author(s):  
John W Chew ◽  
Nicholas J Hills
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Internal Flow ◽  
Eddy Simulation ◽  
Cfd Models ◽  
Geometrical Features ◽  
Air System ◽  
Buoyancy Driven Flows ◽  
Flow Phenomena

Considerable progress in development and application of computational fluid dynamics (CFD) for aeroengine internal flow systems has been made in recent years. CFD is regularly used in industry for assessment of air systems, and the performance of CFD for basic axisymmetric rotor/rotor and stator/rotor disc cavities with radial throughflow is largely understood and documented. Incorporation of three-dimensional geometrical features and calculation of unsteady flows are becoming commonplace. Automation of CFD, coupling with thermal models of the solid components, and extension of CFD models to include both air system and main gas path flows are current areas of development. CFD is also being used as a research tool to investigate a number of flow phenomena that are not yet fully understood. These include buoyancy-affected flows in rotating cavities, rim seal flows and mixed air/oil flows. Large eddy simulation has shown considerable promise for the buoyancy-driven flows and its use for air system flows is expected to expand in the future.

Detached-Eddy Simulation of Flow Around the NREL Phase-VI Blade

2002 ◽  
Author(s):  
J. Johansen ◽  
N. N. So̸rensen ◽  
J. A. Michelsen ◽  
S. Schreck
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Simulation Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Reynolds Averaged Navier Stokes ◽  
Nrel Phase Vi

The Detached-Eddy Simulation model implemented in the computational fluid dynamics code, EllipSys3D, is applied on the flow around the NREL Phase-VI wind turbine blade. Results are presented for flow around a parked blade at fixed angle of attack and a blade pitching along the blade axis. Computed blade characteristics are compared with experimental data from the NREL/NASA Ames Phase-VI unsteady experiment. The Detached-Eddy Simulation model is a method for predicting turbulence in computational fluid dynamics computations, which combines a Reynolds Averaged Navier-Stokes method in the boundary layer with a Large Eddy Simulation in the free shear flow. The present study focuses on static and dynamic stall regions highly relevant for stall regulated wind turbines. Computations do predict force coefficients and pressure distributions fairly good and results using Detached-Eddy Simulation show considerably more three-dimensional flow structures compared to conventional two-equation Reynolds Averaged Navier-Stokes turbulence models, but no particular improvements are seen on the global blade characteristics.

Development and Validation of Computational Fluid Dynamics Models for Initial Stages of Cavitation

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Cavitating Flows ◽  
Cavitation Inception ◽  
Eddy Simulation ◽  
Cfd Models ◽  
Liquid Flows

Various computational fluid dynamics (CFD) models employed for cavitating flows are substantially based on semi-empirical assumptions about cavitation forms and liquid flows around cavitating bodies. Therefore, the model applicability must be validated with experimental data. The stages of validation of the models are analyzed here with data on cavitating hydrofoils and axisymmetric bodies in water. Results of Reynolds-averaged Navier–Stokes (RANS), large-eddy simulation (LES), detached-eddy simulation (DES), and viscous-inviscid interaction methods are compared. The necessity of simultaneous validation of several flow parameters (as cavitation inception number and location of the appearing cavity) is pointed out. Typical uncertainties in water tunnel model test data (water quality, simplified account of wall effect) and possibilities to take them into account are also discussed. The provided comparison with experimental data manifests the impossibility to describe initial stages of cavitating flows using any single model and importance of employment of a combination of models for both the cavitation zones and the flow outside of cavities.

scholarly journals Investigation of Flow Through Centrifugal Pump Impellers Using Computational Fluid Dynamics

2003 ◽  
Vol 9 (1) ◽  
pp. 49-61 ◽  
Author(s):  
Weidong Zhou ◽  
Zhimei Zhao ◽  
T. S. Lee ◽  
S. H. Winoto
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Internal Flow ◽  
Solution Procedure ◽  
Computational Results ◽  
Centrifugal Pumps ◽  
Straight Blade ◽  
Twisted Blade ◽  
Blade Pump

With the aid of computational fluid dynamics, the complex internal flows in water pump impellers can be well predicted, thus facilitating the design of pumps. This article describes the three-dimensional simulation of internal flow in three different types of centrifugal pumps (one pump has four straight blades and the other two have six twisted blades). A commercial three-dimensional Navier-Stokes code called CFX, with a standardk–εtwo-equation turbulence model was used to simulate the problem under examination. In the calculation, the finite-volume method and an unstructured grid system were used for the solution procedure of the discretized governing equations for this problem.Comparison of computational results for various types of pumps showed good agreement for the twisted-blade pumps. However, for the straight-blade pump, the computational results were somewhat different from widely published experimental results. It was found that the predicted results relating to twisted-blade pumps were better than those relating to the straight-blade pump, which suggests that the efficiency of a twisted-blade pump will be greater than that of a straight-blade pump. The calculation also predicts reasonable results in both the flow pattern and the pressure distribution.

The Influence of Variable Gas Properties on Turbomachinery Computational Fluid Dynamics

2005 ◽  
Vol 128 (4) ◽  
pp. 632-638 ◽  
Author(s):  
John D. Northall
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Current Model ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Large Temperature ◽  
Specific Heats ◽  
Cfd Models ◽  
Radial Profiles ◽  
Gas Properties

This paper describes the inclusion of variable gas properties within a Reynolds average Navier-Stokes solver for turbomachinery and its application to multistage turbines. Most current turbomachinery computational fluid dynamics (CFD) models the gas as perfect with constant specific heats. However, the specific heat at constant pressure CP can vary significantly. This is most marked in the turbine where large variations of temperature are combined with variations in the fuel air ratio. In the current model CP is computed as a function of the local temperature and fuel air ratio using polynomial curve fits to represent the real gas behavior. The importance of variable gas properties is assessed by analyzing a multistage turbine typical of the core stages of a modern aeroengine. This calculation includes large temperature variations due to radial profiles at inlet, the addition of cooling air, and work extraction through the machine. The calculation also includes local variations in fuel air ratio resulting from the inlet profile and the dilution of the mixture by the addition of coolant air. A range of gas models is evaluated. The addition of variable gas properties is shown to have no significant effect on the convergence of the algorithm, and the extra computational costs are modest. The models are compared with emphasis on the parameters of importance in turbine design, such as capacity, work, and efficiency. Overall the effect on turbine performance prediction of including variable gas properties in three-dimensional CFD is found to be small.

Numerical Analysis of Internal Flow in Mufflers with Complex Structures

2010 ◽  
Vol 29-32 ◽  
pp. 89-94
Author(s):  
Zhong Cai Zheng ◽  
Na Liu ◽  
Jian Li ◽  
Yan Gao ◽  
Hai Ou Chen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Analysis ◽  
Velocity Field ◽  
Pressure Field ◽  
Three Dimensional ◽  
Internal Flow ◽  
Complex Structures ◽  
Simulation Results ◽  
Volume Models

This paper builds three-dimensional finite volume models for 4 different mufflers. Internal flow numerical analysis for mufflers is carried out with computational fluid dynamics software. Velocity field and pressure field are obtained to analyze the airflow influences on muffler performances. The corresponding regularities are obtained from simulation results, which provide a method for design optimization of mufflers.

Vortex Induced Vibration Analysis of Twin Box Girders by Means of Computational Fluid Dynamics

2014 ◽  
Vol 638-640 ◽  
pp. 1012-1017
Author(s):  
Qing Liang Zhan ◽  
Zhi Yong Zhou ◽  
Ting Yang ◽  
Yao Jun Ge
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Time History ◽  
Box Girders ◽  
Vibration Displacement ◽  
Vortex Induced Vibration ◽  
Eddy Simulation ◽  
Cfd Models ◽  
History Of ◽  
Lock In

This paper analyzes the vortex induced vibration (VIV) phenomena of twin box bridge girders by means of 2D computational fluid dynamics (CFD) models. The modeling of turbulence follows a methodology known as large eddy simulation (LES) in which the large scales of turbulence are resolved, while the small ones are modeled by means of sub-grid-models. The dynamic response of structure in relation to the fluid is solved by embedding the code of Newmark-β method in user defined functions of Fluent. The time history of girder’s vibration displacement is obtained successfully, which agrees well with the experiment results of wind tunnel tests. “Lock-in”, “beat” phenomena and the displacement “detuning” phenomena in the locked field are also gained.

The Effect of Raised Benches Containing Crops on the Indoor Environment in Greenhouses

2015 ◽  
Author(s):  
Sunita Kruger ◽  
Leon Pretorius
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Velocity Distribution ◽  
Crop Production ◽  
Indoor Environment ◽  
Three Dimensional ◽  
Cfd Models ◽  
Computational Fluid Dynamics Cfd ◽  
Plant Level

The purpose of this paper is to investigate the influence of peninsular arranged perforated benches containing plants on the indoor environment of a naturally ventilated greenhouse. The results are compared to a greenhouse containing peninsular arranged solid benches with no plants. The investigation will be conducted numerically using three-dimensional Computational Fluid Dynamics (CFD) models. The overall temperature and velocity distribution were investigated at different sections of the greenhouse. The temperature and velocity distributions at plant level were of particular interest. Results indicated that the greenhouse containing the perforated benches were in general cooler, but also exhibited higher velocities throughout. The velocities observed were higher than those recommended by ASHRAE [1]. It was concluded that care should be taken when placing plants on the perforated benches especially in the regions adjacent to the walls, as this can lead to non-uniform crop production.

scholarly journals Circumferential vascular deformation after stent implantation alters wall shear stress evaluated with time-dependent 3D computational fluid dynamics models

2005 ◽  
Vol 98 (3) ◽  
pp. 947-957 ◽  
Author(s):  
John F. LaDisa ◽  
Lars E. Olson ◽  
Ismail Guler ◽  
Douglas A. Hettrick ◽  
Judy R. Kersten ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Stent Implantation ◽  
Neointimal Hyperplasia ◽  
Three Dimensional ◽  
Time Dependent ◽  
Cfd Models

The success of vascular stents in the restoration of blood flow is limited by restenosis. Recent data generated from computational fluid dynamics (CFD) models suggest that stent geometry may cause local alterations in wall shear stress (WSS) that have been associated with neointimal hyperplasia and subsequent restenosis. However, previous CFD studies have ignored histological evidence of vascular straightening between circumferential stent struts. We tested the hypothesis that consideration of stent-induced vascular deformation may more accurately predict alterations in indexes of WSS that may subsequently account for histological findings after stenting. We further tested the hypothesis that the severity of these alterations in WSS varies with the degree of vascular deformation after implantation. Steady-state and time-dependent simulations of three-dimensional CFD arteries based on canine coronary artery measurements of diameter and blood flow were conducted, and WSS and WSS gradients were calculated. Circumferential straightening introduced areas of high WSS between stent struts that were absent in stented vessels of circular cross section. The area of vessel exposed to low WSS was dependent on the degree of circumferential vascular deformation and axial location within the stent. Stents with four vs. eight struts increased the intrastrut area of low WSS in vessels, regardless of cross-sectional geometry. Elevated WSS gradients were also observed between struts in vessels with polygonal cross sections. The results obtained using three-dimensional CFD models suggest that changes in vascular geometry after stent implantation are important determinants of WSS distributions that may be associated with subsequent neointimal hyperplasia.

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