Aerodynamik Astrid Herbst (Bombardier), Tomas Muld & Gunilla Efraimsson ( KTH)
Future demands Higher speeds and high capacity Wide body trains with max speed > 250 km/h Aerodynamic challenges specific for wide body trains: head pressure pulse & slipstream 2
Slipstream Safety issue for passengers on platform and trackside workers Measures on operation & train design 3
More value for environment and performance: Aerodynamic optimisation Reduction of drag saves energy and traction power Drag and Cross-Wind Optimisation
More value for environment and performance: Aerodynamic optimisation starting section of the nose tangent between nose and car body Parameterized model defines the variables and boundary conditions Computer optimisation by using the parameterized model Goal function is reduce drag while keeping the cross wind safety height and length of the nose height and length of the nose starting section of the nose size of the bogie fairing size of the bogie fairing upper curvature of the carbody upper curvature of the carbody spoiler geometry spoiler geometry tangent between nose and car body chamfering chamfering upper curvature of the nose tip lateral tangent at the nose tip upper part of the nose tip lower part of the nose tip upper curvature of the nose tip lateral tangent at the nose tip upper part of the nose tip lower part of the nose tip
Low drag More value for environment and performance: Aerodynamic optimization Thousands of virtual wind tunnel tests in the computer used to find the very best shape Main result shows 20 30 % lower drag and 10 15 % lower energy consumption Installed power can be reduced with lower cost Lower energy cost for operators Design Space Pareto front Increasing stability
Slipstream Test Setup Down Track Västerås Up Track Catenary Pole 1 USA 1 USA 2 HPP USA 3 LS 1 LS 2 30.58 m 20 m 20 m 6 m 5 m Enköping 9m 9.42 m 60 m Car 13m Catenary Pole 2 Västerås Road T-junction Legend USA : Ultra Sonic Anemometer HPP : Head Pressure Pulse Rake LS : Light Switch Reference Pressure Enköping Measurements with fast 3D-ultrasonic anemometers (USA) Train speed and positions measured with light switch Light switch mounted to detect single rail passages 7
10 7,5 5 Head Passage Measurement results Impact of Bogie Skirts 0,144 0,108 0,072 u Wind [m/s] 2,5 0-2,5-5 Intercar Gap Tail Passage -50 0 50 100 150 200 x [m] Ensemble average overall Ensemble average Skirt leading Ensemble average Skirt trailing Maximum Axles 0,036 0-0,036-0,072 c u,wind [ ] 8
Numerical simulations of slipstream performed at KTH
Slipstream Slipstream= Induced velocity by the train Regions 1) Head pressure pulse 2) Boundary Layer (Freight Trains) 3) Near wake (High-speed Train) 4) Far Wake
Train models Aerodynamic Train Model (ATM) Regina (CRH1)
Decomposition models Full flow field = = + + + Mode 1 Mode 2,3 Mode 4,5 Mode 6+
Connection between modes Phase portrait Spiraling circles when the modes are connected Random patterns when not
Isosurface of V-velocity Mode 1+4+5 Example of flow structure
Decomposition models Challenges - Long computation times - Accurate results Understanding of dominant energetic structures Two methods - Proper Orthogonal Decomposition (POD) - Dynamic Mode Decomposition (DMD)
Comparing with Experiments CFD by KTH Water Towing Tank from Bombardier performed at DLR
Grid study Small cells Medium cells Large cells
TSI-measurements 1.2 m 3 m Velocity for an observer standing on platform 0.07s (1s) time averaged velocity
Achievements Showed that POD and DMD can be used with Detached Eddy Simulation flow fields. Identified dominant flow structures for two different trains. Used advanced models on applied geometries. Cooperation and exchange of knowledge with Bombardier. Fundament for efficient prediction to connect train geometry and slipstream.
Publications Muld, T.W, Analysis of Flow Structures in Wake Flows for Train Aerodynamics, Licentiate Thesis in Mechanics, KTH Stockholm, ISBN 978-91-7415-651-5, 2010 Muld T.W, Efraimsson G., Henningson D. S, Flow structures around a high-speed train extracted using Proper Orthogonal Decomposition and Dynamic Mode Decomposition, Computer & Fluids, DOI: 10.1016/j.compfluid.2011.12.012, 2012 Muld T.W, Efraimsson G., Henningson D. S, Mode decomposition on surface mounted cube, Flow, Turbulence and Combustion, DOI: 10.1007/s10494-011-9355-y, 2011 Muld T.W, Efraimsson G., Henningson D. S, Mode Decomposition of Flow Structures in the wake of Two High-Speed Trains, The First International Conference on Railway Technology: Research, Development and Maintaince, April 16-18, Gran Canaria, Spain, 2012 Muld T. W., Efraimsson G., Henningson D. S., Herbst A. H. and Orellano A., Analysis of Flow Structures in the Wake of a High-Speed Train, Aerodynamics of Heavy Vehicles III: Trucks, Buses and Trains, September 12-17, 2010, Potsdam, Germany Muld T. W., Efraimsson G., Henningson D. S., Herbst A. H., Orellano A., Detached Eddy Simulation and Validation on the Aerodynamic Train Model, Euromech Colloquim 509, Vehicle Aerodynamics, Berlin Germany, March 24-25 2009 Muld T. W., Efraimsson G., Henningson D. S., Proper Orthogonal Decomposition of Flow Structures around a Surfacemounted Cube Computed with Detached-Eddy Simulation, SAE paper 09B-0170, 200915