Validation of CFD with PIV and other methods Part II

Transcription

1 Validation of CFD with PIV and other methods Part II S.V.Jansen1, M.Behbahani2, M.Laumen1, T.Kaufmann1, M.Hormes1, T.Schmitz-Rode1, M.Behr2, U.Steinseifer1 1: Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University and JARA-SIM, Aachen, Germany 2: Computational Analysis of Technical Systems, RWTH Aachen University and JARA-SIM, Aachen, Germany

2 Overview Introduction Boundary Conditions and Numerical Simulation Realising BCs in Experiment Experimental Setup Results and Comparison Conclusion 2

3 Introduction Validation Case: Steady flow through thoracic aorta Simulation: CATS institute, RWTH Aachen University, solver: XNS Validation: Stereo-PIV measurement Source: Wikipedia 3

4 Overview Introduction Boundary Conditions and Numerical Simulation Realising BCs in Experiment Experimental Setup Results + Comparison Conclusion 4

5 Boundary Conditions and Simulation Boundary Conditions: Geometry (rigid) => MRI-scans (0.44x0.44x3mm) Inlet BC: parabolic velocity Outlet BC: const. pressure Reynoldsnumber: 770 and 2300 (early and late systole) Laminar 5

6 Overview Introduction Boundary Conditions and Numerical Simulation Realising BCs in Experiment Experimental Setup Results and Comparison Conclusion 6

7 Realising BCs in Experiment Geometry (transparent): often used: glas-models How to build a model with identical geometry? => Rapid-prototyping (40x40x16µm) Silicone casting with model as core Matching refractive index: => Water-glycerol mixture (60% glycerol (by mass)) 7

8 Realising BCs in Experiment Inlet BC: parabolic velocity profile Aortic inlet not circular Transition-pipe to adapt circular inlet shape Constriction from circular inlet to aorta (acceleration of fluid => more stable) Included in simulation! Flow needs to be fully developed: Inlet pipe (1400mm due to limited space) L/D = 0.06Re (for laminar flow) Re=770 => sufficient Re=2300 => not sufficient in laminar case 8

9 Realising BCs in Experiment Outlet BC: const. pressure All outlets connected to a reservoir Reynolds numbers: Flow set with a flow meter 9

10 Overview Introduction Boundary Conditions and Numerical Simulation Realising BCs in Experiment Experimental Setup Results and Comparison Conclusion 10

11 Experimental Setup Stereo-PIV: 2 highspeed cameras (up to 2kHz) Measurement plane manipulated by x,z-traverse Fluorescent particles (d 10.5µm) 11

12 Experimental Setup II Measurement: 2D-3C measurement in plane (res: 1.35mm x 1.22mm) Average over 200 images / plane 72 planes (res: 1.35mm x 1.22mm x 2mm) 12

13 Overview Introduction Boundary Conditions and Numerical Simulation Realising BCs in Experiment Experimental Setup Results and Comparison Conclusion 13

14 Results Reynolds:

15 Results II Reynolds:

16 Results III Secondary patterns: Re =

17 Results VI Helicity, Re=770: 17

18 Comparison So far only qualitative comparison: Good agreement of general flow pattern Differences at Re=2300, probably due to incipient turbulence effects 18

19 Comparison II Quantitativ comparison: Data interpolated on same grid => difference by value substraction Mean squared difference Re=770: diff = 11.4% (ref. to max. value) Re=2300: diff = 15.8% Difficult to differentiate between spatial and value errors Reduction of error by manipulating position (section F): 15.5% => 12.5% 19

20 Conclusion Conclusion: Same BCs used Good qualitative agreement Differences due to missing turbulence model at Re=2300 Problems: Defined positioning of measurement data Quantitative comparison: spatial error <=> value error Thank You 20