Presentation on theme: "Aerodynamic analysis of a two-man bobsleigh Centro Interdipartimentale di Fluidodinamica e Idraulica Università di Udine Sport Aerodynamics- CISM course."— Presentation transcript:
Aerodynamic analysis of a two-man bobsleigh Centro Interdipartimentale di Fluidodinamica e Idraulica Università di Udine Sport Aerodynamics- CISM course – Udine, 3-7 September 2007 A.Soldati, S. Filippi, G. Miclet, M. Campolo, M. Andreoli, G. Moretti
A typical bobsleigh race … from inside!
…the track… Torino, Italy, Cesana Pariol track, 2006 Winter Olympics Course length: 1,435 m Difference in height : 114 m Bends: 19 Push off stretch Starting area Main track Decelerating area Finish line
…the importance of men & bob aerodynamics… From 0 to 40 km/h Average speed: km/h Top speed: 140 km/h
…and typical performances What can we do to go faster?
1.Evaluate aerodynamic performances (drag and lift forces) of italian team two-man bobsleigh using numerical analysis 2.Identify and test design modifications which may improve aerodynamic performances Motivation and Objectives
Reverse engineering CFD model CFD optimization & Virtual testing Model 1, …, Model n Steps of work Meshing technique CAD model CFD solver Performance index Scaled Prototype & Wind tunnel testing Full scale Prototype & field testing
Technical partners University of Udine Multidisciplinary team Fluid dynamic analysis/optimization (A. Soldati) Reverse engineering/fast prototyping (S. Filippi) Coordination (G. Miclet) Research cooperation Aerodynamical optimization (M.V. Salvetti, UNIPI) Wind tunnel tests (G. Gibertini, PoliMi) Reverse engineering/Prototyping (MarMax, UD) Technical consultancy Design Rule/Constraint (I. Ferriani, Nazionale Italiana Bob) RANS CFD solver (CD Adapco, TO) Carbon/Kevlar shells (CS Canoe, PN)
1. From real object to design: reverse engineering
Virtual Italian 2-men bobsleigh Wings Chute PilotBrakeman Nose Bumpers
2. Virtual model: check of allowed dimensions (FIBT rules) Shape optimization of shell will be constrained by external vincula!
1.simulate the flow around the bobsleigh 2.evaluate the forces (drag/lift) acting on the solid surface 3. Discretization for CFD analysis 1.Steady state 2.Ideal gas 3.Turbulent flow (k-epsilon model + wall treatment) TARGET: ASSUMPTIONS:
Simulation data Box dimensions (4.5m x 2.5m x 1.5m) Height from bottom: 50 mm Air relative velocity: 39 m/s (140 Km/h) Wall velocity: 39 m/s (140 Km/h) Inlet Free shear/wall outlet 4. Computational domain & boundaries Straight track Bends
5. Results: velocity field & streamlines
From qualitative analysis of flow…
Drag: 121 N (pressure) N (shear) (Lift : N) … to quantitative evaluation of forces! Pressure/shear distribution over surface Identification of critical regions
World championship 07 (Cortina dAmpezzo, Italy) Need ideas to improve design? Look at competitors!
Can we exploit any ground effect to improve performances? High h (70 mm) USA GERMANYRUSSIA Airfoil Bobsleight International rules: h 100 mm Observation 1: bobsleights have variable distances from bottom wall Low h (50 mm)
Speed140 km/h draglift H=50 mm H=70 mm %- 5% h=50 mm h=70 mm Simulation results: Higher distance smaller drag …but drag reduction is not significant!
*Ref.: Advanced bobsleigh design: Part 2, aerodynamic modifications to a two-man bobsleigh, by F Motallebi, P Dabnichki* and D Luck, Department of Engineering, Queen Mary, University of London, London, UK Observation 2: bobsleights have variable nose shapes USA GERMANY ITALIA Rounded noseTriangular nose Pentagonal nose Best performing!*
Restart from good design to make it better: evaluation of German bobsleigh Reverse engineering from sequence of photos
Italian vs German bobsleigh GERMANY ITALIA Nose shapeBumpers and wingsShell curvature & Men position
Simulation data Box dimensions (4.5m x 2.5m x 1.5m) Height from bottom: 70 mm Air relative velocity: 39 m/s (140 Km/h) Wall velocity: 39 m/s (140 Km/h) Inlet Free shear/wall outlet Computational domain & boundaries Straight track GER ITA Bends
Results: velocity field & streamlines
H=70 mm, v=140km/h Streamline comparison GER ITA
Drag: 113 N (pressure) N (shear) (Lift : N) … and quantitative evaluation of forces! Pressure/shear distribution over surface Identification of critical regions
Speed140 km/h draglift H=50 mm H=70 mm H=70 mm h=50 mm h=70 mm Comparison of performances …but we know we can do better! h=70 mm
Aerodynamic profile of shell Rounded boumpers Flat bottom Better shape Shape of wings Chute … other design modifications implemented Rounded boumpers
… and final result! Still to be tested in lab to confirm results of CFD simulations in the field … to win next bob championship