THERMAL SCIENCE

International Scientific Journal

Thermal Science - Online First

online first only

Investigation of vortex shedding from an airfoil by CFD simulation and computer-aided flow visualization

ABSTRACT
The article presents an experimental and numerical study of vortex generation and shedding from a NACA 4421 airfoil at low Reynolds number. The experiment was conducted in a low-speed wind tunnel by flow visualization. A high-speed camera was used to record flow structures at the airfoil trailing edge. The recorded images were processed with an in-house developed software based on the advection-diffusion equation to compute instantaneous 2D velocity fields. These results were compared with results of the CFD simulation which employed the scale-adaptive simulation (SAS) turbulence modelling. The SST-SAS model produced finer and less stable turbulent structures compared to an URANS simulation with the SST model. Time-averaged velocities and frequency spectra for the both models are in good agreement, but variability of flow in both time and frequency domain is higher in case of the SST-SAS model. Velocity fields computed on the basis of visualization show generally acceptable agreement with the CFD results. Higher errors occur in areas of unperturbed smoke trails and areas of high velocity gradients, however, the vortex shedding frequency is captured with excellent agreement to the experiment.
KEYWORDS
PAPER SUBMITTED: 2017-11-14
PAPER REVISED: 2017-11-25
PAPER ACCEPTED: 2017-11-26
PUBLISHED ONLINE: 2018-02-18
DOI REFERENCE: https://doi.org/10.2298/TSCI170615002N
REFERENCES
  1. Carmichael, B. H., Low Reynolds Number Airfoil Survey, vol 1, NASA CR 165803, 1981
  2. Yarusevych, S., et al., On vortex shedding from an airfoil in low-Reynolds-number flows, J. Fluid. Mech., 632 (2009), pp. 245-271
  3. Bajcar, T., et al., Quantification of flow kinematics using computer-aided visualization, Strojniški vestnik - Journal of Mechanical Engineering, 55 (2009), pp. 215-223
  4. Bizjan, B., et al., Flow Image Velocimetry Method Based on Advection-Diffusion Equation, Strojniški vestnik - Journal of Mechanical Engineering, 60 (2014), pp. 483-494
  5. Bizjan, B., et al., A computer-aided visualization method for flow analysis, Flow Measurement and Instrumentation, 38 (2014), pp. 1-8
  6. Spalart, P. R., et al., Comments on the Feasibility of LES for Wings and on the Hybrid RANS/LES Approach, Proceedings, The First AFOSR International Conference on DNS/LES, Columbus, Louisiana, USA, 1997, pp. 137-147
  7. Menter, F. R., Egorov Y., The scale-adaptive simulation method for unsteady turbulent flow predictions Part 1: Theory and Model Description, Flow Turbulence Combustion, 85 (2010), pp. 113-138
  8. Menter, F. R., et al., Steady and unsteady flow modelling using the k − √kL model, Proceedings, The Int. Symp. on Turbulence, Heat and Mass Transfer, Dubrovnik, Croatia, 2006, Vol. 5, pp. 403-406
  9. Younsi, M., et al., Application of the SAS turbulence model to predict the unsteady flow field behaviour in a forward centrifugal fan, Int. J. of Computational Fluid Dynamics, 22 (2008), pp. 639-648
  10. Lucius, A., Brenner G., Unsteady CFD simulations of a pump in part load conditions using scale-adaptive simulation, Int. J. of Heat and Fluid Flow 31 (2010), pp. 1113-1118
  11. Škerlavaj, A., et al., Choice of a Turbulence Model for Pump Intakes, Proceedings of the Institution of Mech. Engineers, Part A: Journal of Power and Energy, 225 (2011), pp. 764-778
  12. Jošt, D., et al., Improvement of efficiency prediction for a Kaplan turbine with advanced turbulence models, Strojniški vestnik - Journal of Mech. Engineering, 60 (2014), pp. 124-134
  13. Derakhshandeh, J. F., et al., The effect of arrangement of two circular cylinders on the maximum efficiency of Vortex-Induced Vibration power using a Scale-Adaptive Simulation model, Journal of Fluids and Structures, 49 (2014), pp. 654-666
  14. Elkhoury, M., Assessment of turbulence models for the simulation of turbulent flows past bluff bodies, Journal of Wind Engineering and Industrial Aerodynamics, 154 (2016), pp. 10-20
  15. Eberlinc, M., et al., Experimental investigation of the interaction of two flows on the axial fan hollow blades by flow visualization and hot-wire anemometry, Experimental Thermal and Fluid Science, 33 (2009), pp. 929-937
  16. Leschziner, M. A., Modelling turbulent separated flow in the context of aerodynamic applications, Fluid Dynamics Research, 38 (2006), pp. 175-210
  17. Sekavčnik M., et al., Heat transfer evaluation method in complex rotating environments employing IR thermography and CFD, Experimental heat transfer, 21 (2008), pp. 155-168
  18. ANSYS Inc., ANSYS Fluent Release 13.0 User's Guide, 2010
  19. Berger, E., Wille R., Periodic Flow Phenomena, Annual Reviews of Fluid Mechanics, 4 (1972), pp. 313-34