A Turbine Airfoil Aerodynamic Design Process

2001 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
Design Process ◽  
Splitting Method ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Vortex Method ◽  
Aerodynamic Design ◽  
Discrete Vortex ◽  
Pressure Distributions ◽  
Industry Practice ◽  
Flux Difference

A turbine airfoil aerodynamic design process, similar to the current industry practice, is used to design turbine airfoil sections. The airfoil generator code employs Bezier polynomial curves to produce smooth airfoil shapes. For the calculations of the airfoil pressure distributions a discrete vortex method is used after the airfoil is designed and the novel Navier-Stokes (N-S) solver is developed for further examination of the airfoil performance. The vortex method can provide a fast way to calculate the airfoil pressure distributions. The N-S code is used to obtain the blade-to-blade quasi-three-dimensional, turbulent, and viscous flow characteristics. The time-dependent N-S equations are discretized and integrated in a coupled manner based on a finite-volume formulation as well as a flux-difference splitting. The flux-difference splitting method enables us to compute with a rapid convergence. After the flow solver is validated with experimental data, this new code is further used to obtain an optimal airfoil design by analyzing the cascade flows. The present N-S code can handle computations of both subsonic and supersonic flows and can be connected to an external optimizer code with the airfoil generator.

scholarly journals Bilge-Keel Influence on Free Decay of Roll Motion of a Realistic Hull1

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yichen Jiang ◽  
Ronald W. Yeung
Keyword(s):  
Free Surface ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Vortex Method ◽  
Roll Motion ◽  
Two Dimensional ◽  
Desktop Computer ◽  
Roll Damping ◽  
Discrete Vortex ◽  
Bilge Keel

The prediction of roll motion of a ship with bilge keels is particularly difficult because of the nonlinear characteristics of the viscous roll damping. Flow separation and vortex shedding caused by bilge keels significantly affect the roll damping and hence the magnitude of the roll response. To predict the ship motion, the Slender-Ship Free-Surface Random-Vortex Method (SSFSRVM) was employed. It is a fast discrete-vortex free-surface viscous-flow solver developed to run on a standard desktop computer. It features a quasi-three-dimensional formulation that allows the decomposition of the three-dimensional ship-hull problem into a series of two-dimensional computational planes, in which the two-dimensional free-surface Navier–Stokes solver Free-Surface Random-Vortex Method (FSRVM) can be applied. In this paper, the effectiveness of SSFSRVM modeling is examined by comparing the time histories of free roll-decay motion resulting from simulations and from experimental measurements. Furthermore, the detailed two-dimensional vorticity distribution near a bilge keel obtained from the numerical model will also be compared with the existing experimental Digital Particle Image Velocimetry (DPIV) images. Next, we will report, based on the time-domain simulation of the coupled hull and fluid motion, how the roll-decay coefficients and the flow field are altered by the span of the bilge keels. Plots of vorticity contour and vorticity isosurface along the three-dimensional hull will be presented to reveal the motion of fluid particles and vortex filaments near the keels.

Numerical Investigation of Impeller Tip Tailoring and its Impact on Aerodynamic Design of a Centrifugal Compressor’s Impeller

2014 ◽  
Author(s):  
Ashvin Mahajan ◽  
Lieven Baert ◽  
Michaël Leborgne ◽  
Timothée Lonfils ◽  
I. Gede Parwatha ◽  
...  
Keyword(s):  
Design Optimization ◽  
Significant Contribution ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Aerodynamic Design ◽  
High Pressure Ratio ◽  
Important Improvement ◽  
Geometrical Features ◽  
Isentropic Efficiency

The current research focuses on the aerodynamic design of a centrifugal compressor and the effect of tip tailoring on the aerodynamic impeller efficiency. To this extent a high-fidelity multi-point design optimization process has been developed and exploited on a high pressure ratio transonic impeller. By manipulating the shape of the impeller blades and endwalls and by including advanced geometrical features such as winglets on the impeller blades, the behavior of the impeller flow has been investigated. Here, the results of three-dimensional RANS simulations with the Spalart-Allmaras turbulence model on a structured multi-block mesh is used for the evaluation of the flow characteristics. In the context of radial machines, the results of the aerodynamic design optimization show an important improvement of the impeller isentropic efficiency compared to the reference impeller, with a significant contribution from the presence of the impeller tip winglets. Furthermore, the integration of the impeller winglet has encouraged this study to provide a detailed analysis on the impeller flow structures in order to have a better understanding of the effects of tip tailoring on impeller performance.

Fluid Dynamic Study in a Femoral Artery Branch Casting of Man With Upstream Main Lumen Curvature for Steady Flow

1985 ◽  
Vol 107 (3) ◽  
pp. 240-248 ◽  
Author(s):  
M. R. Back ◽  
Y. I. Cho ◽  
L. H. Back
Keyword(s):  
Steady Flow ◽  
Fluid Transport ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Pressure Distributions ◽  
Flow Investigation ◽  
Measured Pressure

An in-vitro, steady flow investigation was conducted in a hollow, transparent vascular replica of the profunda femoris branch of man for a range of physiological flow conditions. The replica casting tested was obtained from a human cadaver and indicated some plaque formation along the main lumen and branch. The flow visualization observations and measured pressure distributions indicated the highly three-dimensional flow characteristics with arterial curvature and branching, and the important role of centrifugal effects in fluid transport mechanisms.

scholarly journals Analysis of Unsteady Pressure Fluctuation in a Semi-Open Cutting Pump

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3657
Author(s):  
Weidong Cao ◽  
Jiayu Mao ◽  
Wei Li
Keyword(s):  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Lower Plate ◽  
Pressure Distributions ◽  
Axial Forces ◽  
Blade Frequency

In order to understand the pressure fluctuation characteristics of a semi-open cutting pump, the three-dimensional unsteady flow fields were calculated. External and internal flow characteristics of four schemes with different relative angles between the rotary cutter and the impeller were studied. The pressure fluctuations in the lower plate, the upper plate, the clearance between the rotary cutter and the fixed cutter, the first section in volute and nearby parts of the tongue were all analyzed, which are all the places that pressure distributions are greatly affected by the static and dynamic interaction, and at the same time, the force on the impeller was also analyzed. The results show that the fluctuations at different positions change periodically; the main frequency is blade frequency. The amplitude of pressure fluctuation decreases from near the rotating part to far away, from near the tongue to far from the tongue. Due to the influence of both impeller and rotary cutter, the pressure fluctuation on the lower plate is the largest. The pressure fluctuation is affected by flow rate, the larger the flow rate, the greater the pressure fluctuation. The radial and axial forces of the impeller change periodically with time, and the number of wave peaks and wave valleys is the same as the number of blades.

Demonstration of an Aerodynamic Design Process for Turbomachines Using Open Source Software Tools

2010 ◽  
Author(s):  
Oliver Borm ◽  
Balint Balassa ◽  
Sebastian Barthmes ◽  
Julius Fellerhoff ◽  
Andreas Ku¨hrmann ◽  
...  
Keyword(s):  
Open Source ◽  
Design Process ◽  
Open Source Software ◽  
Compressible Flows ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Software Tools ◽  
Two Dimensional ◽  
Aerodynamic Design ◽  
Student Projects

This paper demonstrates an aerodynamic design process for turbomachines for compressible flows, using exclusively open source software tools. Some relevant software already existed and few additional components were required, which have been developed mainly by students and are available at ftp.lfa.mw.tum.de. The geometry of turbomachine blades is described with a newly developed NURBS based blade designer. One-dimensional preliminary analysis is done with OpenOffice.org Calc and an extended mean line program, where loss models are already included. For two-dimensional through-flow computations a compressible streamline curvature method was implemented. Two-dimensional blade-to-blade and three-dimensional simulations are performed with the CFD toolbox OpenFOAM. The two- and three-dimensional results are visualized and analyzed using the open source postprocessing tool ParaView. The presented tools are regularly used in student projects. A generic one stage axial compressor was created with the workflow as a showcase in order to demonstrate the capabilities of the open source software tools.

The Importance of Secondary Shedding in Two-Dimensional Wake Formation at Very High Reynolds Numbers

1982 ◽  
Vol 33 (2) ◽  
pp. 105-123 ◽  
Author(s):  
P.K. Stansby ◽  
A.G. Dixon
Keyword(s):  
Vortex Method ◽  
Reynolds Numbers ◽  
Discrete Vortex ◽  
Pressure Distributions ◽  
Pressure Fields ◽  
High Reynolds Numbers ◽  
First Approximation ◽  
High Reynolds ◽  
Very High ◽  
Good Agreement

SummaryUncertainties in the use of the discrete-vortex method in modelling the time development of the wake of a circular cylinder at very high Reynolds numbers are investigated. It is shown that simply introducing vorticity at generally accepted separation positions at a rate of ½Us2, Us being the velocity at separation, gives wholly unrealistic wake predictions. In the base region pressure fields occur which would promote separation in steady flow and so a first approximation for ‘secondary’ separation is incorporated into the model. This brings pressure distributions and vorticity structures at subcritical and supercritical Reynolds numbers into good agreement with experiment. The convection of the vortices is calculated using the cloud-in-cell technique and comparisons are made with direct summation methods.

Discrete Vortex Simulation of Pulsating Flow Behind a Normal Plate

1994 ◽  
Vol 116 (4) ◽  
pp. 862-869 ◽  
Author(s):  
Hyung Jin Sung ◽  
Young Nam Kim ◽  
Jae Min Hyun
Keyword(s):  
Numerical Study ◽  
Flow Characteristics ◽  
Separated Flow ◽  
Vortex Method ◽  
Threshold Value ◽  
Numerical Results ◽  
Pulsation Frequency ◽  
Discrete Vortex ◽  
Freestream Velocity ◽  
Variable Position

A numerical study is made of the separated flow behind a flat plate. The plate is placed normal to the direction of the approach flow. The oncoming freestream velocity contains a pulsating part, U∞ = U0(1 + A0cosfpt). The temporal behavior of vortex shedding patterns is scrutinized over broad ranges of the two externally specified parameters, i.e., the pulsation amplitude (A0≤ 0.6), and the dimensionless pulsation frequency, (fp≤0.32). A version of the discrete vortex method is utilized. The variable-position nascent vortex technique is applied, and it proves to be adequate for pulsating approach flows. The numerical results clearly capture the existence of lock-on when fp exceeds a threshold value. The modulation of vorticity shedding is also detected when fp is reasonably low. The influence of A0 on the flow characteristics is examined in detail. As A0 increases to a moderate value (e.g., A0≤0.6), an appreciable broadening is seen of the range of fp for which lock-on occurs. Based on the numerical results, three characteristic flow modes in the wakes are identified. These findings are qualitatively consistent with the existing flow-visualization studies for a cylinder.

scholarly journals Conformal Mapping-Based Discrete Vortex Method for Simulating 2-D Flows around Arbitrary Cylinders

2021 ◽  
Vol 9 (12) ◽  
pp. 1409
Author(s):  
Guoqing Jin ◽  
Zhe Sun ◽  
Zhi Zong ◽  
Li Zou ◽  
Yingjie Hu
Keyword(s):  
Conformal Mapping ◽  
Vortex Method ◽  
Reynolds Numbers ◽  
Mapping Method ◽  
Mirror Image ◽  
The Body ◽  
Time Step ◽  
Discrete Vortex ◽  
Fluid Field ◽  
Pressure Distributions

A novel technique based on conformal mapping and the circle theorem has been developed to tackle the boundary penetration issue, in which vortex blobs leak into structures in two-dimensional discrete vortex simulations, as an alternative to the traditional method in which the blobs crossing the boundary are simply removed from the fluid field or reflected back to their mirror-image positions outside the structure. The present algorithm introduces an identical vortex blob outside the body using the mapping method to avoid circulation loss caused by the vortex blob penetrating the body. This can keep the body surface streamlined and guarantees that the total circulation will be constant at any time step. The model was validated using cases of viscous incompressible flow passing elliptic cylinders with various thickness-to-chord ratios at Reynolds numbers greater than Re = 1 × 105. The force and velocity fields revealed that this boundary scheme converged, and the resultant time-averaged surface pressure distributions were all in excellent agreement with wind tunnel tests. Furthermore, a flow around a symmetrical Joukowski foil at Reynolds number Re = 4.62 × 104, without considering the trailing cusp, was investigated, and a close agreement with the experimental data was obtained.

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