Naslov
Numerical prediction of Airfoil Flow
(Numerical Prediction of Airfoil Flow)

Autori
Milas, Zoran

Vrsta, podvrsta i kategorija rada
Radovi u zbornicima skupova, cjeloviti rad (in extenso), znanstveni

Izvornik
Proceedings of the 4th International Congress of Croatian Society of Mechanics / Franjo Matejiček - Zagreb : Hrvatsko društvo za mehaniku (HDM), 2003, 609-614

Skup
4th International Congress of Croatian Society of Mechanics

Mjesto i datum
Bizovac, Hrvatska, 18.09.2003. - 20.09.2003

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
airfoil; stall; lift/drag; modeling

Sažetak
Aerodynamic characteristics of the axial turbomachines, particularly of those with low rotor “ solidity” , are largely determined by their airfoil characteristics. Airfoil stall controls most of the blade stall smeared by 3D effects at the root and tip area. Turbulent flow around NACA 0012 airfoil in the range of incidence angles from 0.0 up to stall angle at Re=2.8 106 is calculated by applying finite volume method with modified turbulence model. A grid independent solution is achieved on the C-type grid around airfoil with 1664*320 control volumes for the finest grid. Testing of various boundary conditions along open side boundaries at small incidence angles proves that they have negligible effect on calculated pressure and shear stress distribution along airfoil and airfoil lift/drag coefficients as well. Calculation of the flow at incidence angle with inlet boundary conditions along B-C-D ( ) and outlet boundary conditions along A-B diverged. Inclusion of the laminar part by prescibing transition is required in order to bring the calculated data closer to the experimental ones. The computer programme is modified by suppressing turbulence, i.e. turbulent stress in the laminar region. Location of transition on the upper-lower part of airfoil is prescribed on the basisi of experimental data . Zero value of turbulent viscosity and very small value of turbulence kinetic energy are imposed to all nodes in the laminar region in every step of the global iteration procedure. Very good agreement is obtained between the calculated and the experimental values for the lift-drag coefficients and the pressure coefficient distribution at moderate incidence angles. Drag coefficient perfectly matches experimental values for smaller incidence angles. Underprediction of the lift coefficient is reduced. Maximum of the lift is more distinguished and analysis of the flow pattern indicates presence of separation bubble near the trailing edge at . Significant reduction of drag is due to smaller skin friction in the laminar part of the boundary layer that extends almost along entire lower part of the airfoil. Increase of the lift is mainly because of higher (under) pressure along the airfoil suction side. Fig. 5 illustrates that increase in the peak pressure is quite discernible ( for ) and that calculated values no longer fall short of the experimental ones as much as before.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo

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