Computational  Modelling  of  Pitching  Airfoil  Flows


Researcher:    M. Schatz,  U. Bunge,  T. Rung 

 
Recent collaborative research efforts ( UNSI,  SFB557: Project A2 ) particularly focus upon the modelling of unsteady turbulent flows based on Reynolds-averaged (RANS) equations. Attention is drawn to the simulation of both natural and forced unsteadiness, with specific emphasis on Vortex Shedding past Bluff Bodies and the prediction of dynamic airfoil/wing behaviour in the context of fluid-structure interaction. The animated example refers to the computation of an oscillating NACA 0015 airfoil featuring dynamic stall, where a large database of experimental results is available from NASA (Piziali, 1994). 
 
  
 Reynolds number  1.95*106
 Mach number  0.29
 mean angle of attack  15o
 pitching angle                        4.2osin(wt)
 reduced frequency   (k=0.5wLref/Uref)  0.1
A.R. Piziali:  An experimental investigation of 2D and 3D oscillating wing aerodynamics for a range of angles of attack including stall, NASA TM 4632, 1994.
  
animated vorticity contours (LLR k-w and SALSA)
LLR k-w: ANIM.GIF(1.26M),  MPEG(280K),  SALSA: ANIM.GIF(560K), MPEG(5.6M), AVI(6.3M)
(the last two SALSA-movies show an animated lift vs. angle of attack graph next to the vorticity contours)		 more information: 
Turbulence Modelling
The below given results display the amount of predictive accuracy obtained from different linear Boussinesq-viscosity models (SA & SALSA: one-equation models;   Wilcox & LLR: two-equation k-w models) for these type of flows. Further details are available on LINK. It is worthwile to mention the difference in the vorticity contours for both turbulence models animated. The leading edge vortex responsible for the suction peak is not nourished by the SALSA model as long as by the LLR k-w model which becomes obvious in the earlier decrease of lift-coefficient before the maximum angle of attack is reached. This can be attributed to an overprediction of trailing edge stall by the SALSA model in the range of angles previous to complete stall.  
 
unsteady lift coefficient, 13k to load enlargement unsteady pitching moment coefficient, 13k to load enlargement unsteady drag coefficient, 13k to load enlargement
 

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Last modified: Wed Feb 9 12:21:06 CET 2000