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
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
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
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)
Physiological Data Physiological Respiration through Standard Nose (R. Hincliff, D. Harrison) minute ventilation [1/min ] ventilation frequency [1/min ] tidal volume [ml ] medium respiration 6-8 15 400-500 maximum respiration 50-70 25 2000-2800
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
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
Computer Tomography of the Human Nasal Cavity
Human Engineering
Surface Extraction by Computer Tomography Marching Cube Algorithm 300 Cuts, 1mm Spacing DICOM Format 512 512 2 Bytes per Cut Unstructured Surface 749.681 Nodes 1.499.065 Triangles
Silicone Nose Model
Grids clean + upper and lower turb.
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
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
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
Horseshoe Vortex
The Horseshoe Vortex
Vortex Breakdown vortex free stagnation point
Vortex Breakdown (cntd.)
Inhalation: Streamlines upper and lower turbinate and spurs
Comparison Numerics and Experiments Inhalation cross section 1 cross section 2 num. exp. num. exp.
Comparison Numerics and Experiments Exhalation cross section 1 cross section 2 num. exp. num. exp.
Scheme for Human Respiration Cycle
Inhalation/Exhalation Process
Pressure Loss vs. Mass Flux
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
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
Engineering Human
Human Nasal Cavity via CT-Images
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
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
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
Boundary refinement l l +2 l +1 l the refined boundary is smoothed by ensuring a level difference of 1
Number of offspring reduction l (M) l +1 l +t l +1 (M) l + t Moving subtrees to the upper level
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
Mesh Generation: Sphere
Mesh Generation: Dinosaur
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
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
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?
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
Emerging and Merging Cells n t (n + 1) t n t (n + 1) t
Discrete Operator Weighting Functions L. Schneiders et al., JCP 235: 786-809 (2013)
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 = 0.195 locally refined mesh vorticity contours (cyl. at tdc)
Transversely Oscillating Circular Cylinder II cell-merging method vs. weighting-function formulation (, w)
Dancing Cylinders Vorticity distribution Folie Schneiders
Mesh Generation: Nasal Cavity
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
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
Flow through the Human Nasal Cavity
Three Nasal Cavities good poor fair
Good Geometry: Streamlines turbinate
Fair Geometry: Streamlines
Poor Geometry: Streamlines
Good Geometry: Wall-Shear Stress
Fair Geometry: Wall-Shear Stress
Comparison of Three Geometries pressure loss heating good fair poor good fair poor
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
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
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.