Human Computational Fluid Dynamics: Analysis of Nose Flow

Transcription

1 Human Computational Fluid Dynamics: Analysis of Nose Flow Wolfgang Schröder, Andreas Lintermann, Lennart Schneiders, Jerry Grimmen Institute of Aerodynamics RWTH Aachen University JARA High Performance Computing

2 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

3 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

4 Anatomy of the Nasal Cavity Functions Sense of Smell (Regio olfactoria) Isolation (Airfilled Cavities) Resonance Organ (Paranasal Sinuses) Tempering Air (Turbinates) Moistening (Goblet Cells) Cleaning Air (Ciliated Epithelium)

5 Physiological Data Physiological Respiration through Standard Nose (R. Hincliff, D. Harrison) minute ventilation [1/min ] ventilation frequency [1/min ] tidal volume [ml ] medium respiration maximum respiration

6 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

7 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

8 Computer Tomography of the Human Nasal Cavity

9 Human Engineering

10 Surface Extraction by Computer Tomography Marching Cube Algorithm 300 Cuts, 1mm Spacing DICOM Format Bytes per Cut Unstructured Surface Nodes Triangles

11 Silicone Nose Model

12 Grids clean + upper and lower turb.

13 Numerical Method Navier-Stokes equations, 3D, time dependent Approximation: Finite Volume Method second-order accuracy for non-euler terms AUSM (Advective Upstream Splitting Method) for Euler terms time integration via 5-step Runge-Kutta method of second-order accuracy

14 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

15 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

16 Horseshoe Vortex

17 The Horseshoe Vortex

18 Vortex Breakdown vortex free stagnation point

19 Vortex Breakdown (cntd.)

20

21 Inhalation: Streamlines upper and lower turbinate and spurs

22 Comparison Numerics and Experiments Inhalation cross section 1 cross section 2 num. exp. num. exp.

23 Comparison Numerics and Experiments Exhalation cross section 1 cross section 2 num. exp. num. exp.

24 Scheme for Human Respiration Cycle

25 Inhalation/Exhalation Process

26 Pressure Loss vs. Mass Flux

27 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

28 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

29 Engineering Human

30 Human Nasal Cavity via CT-Images

31 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

32 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

33 Grid refinement data structure l 0 (8 0 cells) l 1 (O(8 1 ) cells) l 2 (O(8 2 ) cells) l 3 (O(8 3 ) cells) l 0 (1 cell) l 1 (8 cells) l 2 Octree structure with parent-child relation

34 Boundary refinement l l +2 l +1 l the refined boundary is smoothed by ensuring a level difference of 1

35 Number of offspring reduction l (M) l +1 l +t l +1 (M) l + t Moving subtrees to the upper level

36 Splitting of subtrees level l level l + 1 levels l +2 l +t a copy of the split subtree (n) is introduced to the process

37 Mesh Generation: Sphere

38 Mesh Generation: Dinosaur

39 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

40 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

41 Varying Boundary Cells I Cut cells may become arbitrarily small Result in numerical instability Explicit time integrators require a very small time step to remain stable Small cells must be removed Abrupt changes of the discrete operators result in perturbations Smooth transition of leastsquares stencils required Disappearing cells?

42 Varying Boundary Cells II Cut cells may become arbitrarily small Result in numerical instability Explicit time integrators require a very small time step to remain stable Small cells must be removed Abrupt changes of the discrete operators result in perturbations Smooth transition of leastsquares stencils required Disappearing cells? remain as ghost nodes on the boundary

43 Emerging and Merging Cells n t (n + 1) t n t (n + 1) t

44 Discrete Operator Weighting Functions L. Schneiders et al., JCP 235: (2013)

45 Transversely Oscillating Circular Cylinder I Re = 185, y B = A cos (2 f e t), A = 0.2D, f e = 0.8 f 0, Sr = f 0 D/u = locally refined mesh vorticity contours (cyl. at tdc)

46 Transversely Oscillating Circular Cylinder II cell-merging method vs. weighting-function formulation (, w)

47 Dancing Cylinders Vorticity distribution Folie Schneiders

48 Mesh Generation: Nasal Cavity

49 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

50 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

51 Flow through the Human Nasal Cavity

52 Three Nasal Cavities good poor fair

53 Good Geometry: Streamlines turbinate

54 Fair Geometry: Streamlines

55 Poor Geometry: Streamlines

56 Good Geometry: Wall-Shear Stress

57 Fair Geometry: Wall-Shear Stress

58 Comparison of Three Geometries pressure loss heating good fair poor good fair poor

59 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

60 Coming Up Introduction From the Human Nose to the Engineering Model * laminar or turbulent * steady or unsteady From the Engineering Model to the Human Nose * General Description * Mesh Generation * Accuracy Issues * Results of the Human Nose: Comparison of 3 Geometries Conclusion

61 Conclusion The Good: Massively parallel grid generation on HPC systems; numerical and experimental tools to automatically analyze local and global phenomena are available The Bad: Analysis is costly The Ugly: Uncertainty is high due to too little knowledge on bio-medical structures, mucous membrane, tissues, particles etc.