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GLASGOW 2003 INTEGRATING CFD AND EXPERIMENT

GLASGOW 2003 INTEGRATING CFD AND EXPERIMENT. A Detailed CFD and Experimental Investigation of a Benchmark Turbulent Backward Facing Step Flow Stephen Hall & Tracie Barber University of New South Wales Sydney, Australia. INTRODUCTION. Turbulent Backward Facing Step - benchmark flow

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GLASGOW 2003 INTEGRATING CFD AND EXPERIMENT

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  1. GLASGOW 2003INTEGRATING CFD AND EXPERIMENT A Detailed CFD and Experimental Investigation of a Benchmark Turbulent Backward Facing Step Flow Stephen Hall & Tracie Barber University of New South Wales Sydney, Australia

  2. INTRODUCTION • Turbulent Backward Facing Step - benchmark flow • Compare Particle Image Velocimetry (PIV) and CFD • Not just to check CFD • Rather to use the best of each • What is the best of each? - first steps

  3. TURBULENT BACKWARD FACING STEP • Mean flow structures • Characteristic lines and points • Wide velocity, turbulence range • Good CFD and PIV test

  4. EXPERIMENTAL TEST RIG • Dimensions and PIV access

  5. EXPERIMENTAL TEST RIG • Clear acrylic – light access • Low reflection base • Full side view

  6. EXPERIMENTAL TEST RIG • High density PIV seeding – critical • Particle – hollow polymer spheres • Venturi jet seeder well upstream

  7. HIGH RESOLUTION PIV • Basic 2D arrangement • Mean flow aligned in light sheet • Camera perpendicular to light sheet

  8. HIGH RESOLUTION PIV

  9. HIGH RESOLUTION PIV • Constant intensity light sheet • Adjustable width and thickness

  10. PIV VERIFICATION USING CFD • Contours From Standard PIV Images of Okamoto and Watanabe (1999) • Contours From a PIV Analysis of the Standard PIV Images

  11. PURPOSE OF CFD • Not only to validate CFD against experiment • But to reveal greater detail about phenomena • And supplement experimental results • Make full use of the reliability of modern CFD

  12. CFD APPROACH • 2D RANS finite volume (Fluent) • RNG k-, RSM turbulence closure (literature) • Second order interpolation • Ambient and boundary conditions – use experimental

  13. CFD VERIFICATION ASSESSMENT • Key functionals Xr, Xs, Ys, Sp, Ss, Lift, Drag • Grid convergence – literature 200 cells vertical • Iterative convergence • 3D vs 2D – same grid resolution • 3% on Xr • Turbulence modeling, is code correct? • commercial code

  14. CFD AND PIV COMPARISON • Many quality CFD and Experimental data sets • Most missing complete boundary conditions • not previously required • Perform both CFD and PIV myself • “exactly equivalent” • Work in raw variables u, v, Vmag • less need to non-dimensionalise • Contours – variation • Streamlines - direction

  15. MEAN VELOCITY MAGNITUDE • Velocity Mag. in CS Plane, (top) PIV, (mid.) RNG k-, (bot.) RSM

  16. STREAMLINES • Streamlines in CS Plane, (top) PIV, (mid.) RNG k-, (bot.) RSM

  17. U HORIZONTAL VELOCITY • Mean Horizontal Velocity in CS Plane, (top) PIV, (mid.) RNG k-, (bot.) RSM

  18. V VERTICAL VELOCITY • Mean Vertical Velocity in CS Plane, (top) PIV, (mid.) RNG k-, (bot.) RSM

  19. VORTICITY • Vorticity Mag. in CS Plane, (top) PIV, (mid.) RNG k-, (bot.) RSM

  20. VELOCITY MAGNITUDE AND STREAMLINES BEHIND STEP • Characteristic Lines in CS Plane, (top) PIV, (mid.) RNG k-, (bot.) RSM

  21. FOCUSED BEHIND STEP • Mean Velocities in CS Plane, (left) PIV, (right) RSM tp=70 s

  22. FOCUSED BEHIND STEP • Streamlines in CS Plane, (left) PIV, (right) RSM, tp=70 s

  23. CONCLUSIONS • CFD and PIV reveal detailed flow structure • “Exactly Equivalent” simultaneous CFD and PIV • Highlights limitations in each • Improves confidence in results • Essential complimentary techniques

  24. FUTURE DIRECTIONS • CFD should be first part of any PIV? • Unsteady 3D CFD PIV (TR PIV, stereoscopic) • Total integration of CFD PIV • PIV modifies turbulence closure model throughout • CFD error checks PIV and fills in error regions • mathematically rigorous

  25. PLANES OF INTEREST

  26. HIGH RESOLUTION PIV • Basic sub-systems • Optimise performance of each

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