Wind forces generated by passing vehicles on cyclists and development of a model to determine the necessary width of bicycle lanes

• Applicant: Dr.-Ing. Christof-Bernhard Gromke, since 8/2019
• Subject Area: Fluid Mechanics
• Term: from 2010 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 173545595

• Final Report Year: 2023

Final Report Abstract

The project investigated the aerodynamic loads acting on cyclists transversely to their direction of travel during overtaking maneuvers by vehicles and their influence on their riding behavior. The incentive for the investigations was the qualitative perception of cyclists that they are exposed to a vehicle-induced aerodynamic load sequence during an overtaking maneuver, in which they are first pushed away from the vehicle by a transverse pressure load and then pulled towards the vehicle or the middle of the road by a transverse suction load. The objectives of the project were, on the one hand, the quantitative determination of the transverse aerodynamic loads and, on the other hand, the acquisition of the effect of these loads on the trajectory of a cyclist. The latter included the quantitative determination of the lateral deviation from straight-ahead travel in a pendulum ride caused by a disturbing load effect. If pertinent, i.e. in the case of large deviations relevant to cyclist safety, a design approach for the required bicycle lane width should be establish. Based on an extensive field measurement campaign in which overtaking maneuvers were carried out with various types of vehicles and cyclists (the latter represented by dummies mounted on bicycles), the aerodynamic loads acting on cyclists transverse to their direction of travel were determined. As a result, the essential input quantities that determine the strength of the pressure and suction loads could be identified. These are (i) the vehicle type (e.g. truck or car), (ii) the overtaking speed, (iii) the overtaking distance, and (iv) the cyclist type (e.g. adult on a trekking bike or adolescent on a youth bike). Systematic correlations between the main input quantities and the resulting aerodynamic loads were identified and a mathematical model for their determination was established. Due to its simplicity and the easily accessible input quantities, this model is also suitable for use in the non-scientific field, e.g. in the practice of traffic planning or road safety. To understand and acquire the effect of vehicle-induced loads on the trajectory of a cyclist, test drives were carried out under controlled aerodynamic lateral load conditions. For this purpose, test persons on bicycles rode between two offset fans facing each other, which applied simulated vehicle-induced pressure and suction loads. The rides took place in an indoor environment and were recorded with cameras from above and the trajectories of cyclists were determined by tracking marker points. The analysis of the trajectories showed that the vehicleinduced lateral loads occurring during overtaking lead to increased maximum lateral deviations, but that the extreme maximum lateral deviations remain unaffected.

Publications

• Bestimmung des Widerstandsbeiwerts von Fahrradfahrern bei seitlicher Anströmung. Proc. 26. GALA Fachtagung "Experimentelle Strömungsmechanik", Rostock, Germany, Sep. 2018, pp. 50.1-8
  Gromke, C., Florencio, A.L., Ruck, B.
  
• Aerodynamic loads on a cyclist passed by a passenger car. Proc. 15th Int. Conf. Wind Engineering (ICWE15,) Beijing, China, Sep. 2019, 4 p.
  Gromke, C. & Ruck, B.
  
• Aerodynamic loads on a cyclist while overtaking by a vehicle. Proc. 27. GALA Fachtagung "Experimentelle Strömungsmechanik", Erlangen, Germany, Sep. 2019, pp. 7.1-8
  Gromke, C. & Ruck, B.
  
• A model for the determination of vehicle-induced aerodynamic lateral loads on cyclist during overtaking maneuvers. Proc. 28. GALA Fachtagung "Experimentelle Strömungsmechanik", Bremen, Germany, Sep. 2021, pp. 37.1-9
  Gromke, C. & Ruck, B.
  
• Full-scale laboratory simulation of lateral loads exerted by overtaking vehicles on cyclists. Proc. AEROVEHICLES 4, Berlin, Germany, Aug. 2021, pp. 182-185
  Cardenas, C.; Gromke; C. & Ruck, B.
  
• Passenger car-induced lateral aerodynamic loads on cyclists during overtaking. Journal of Wind Engineering and Industrial Aerodynamics, 209(2021, 2), 104489.
  Gromke, Christof & Ruck, Bodo
  
• Roll moment acting on a cyclist induced by an overtaking station. Proc. AEROVEHICLES 4, Berlin, Germany, Aug. 2021, pp. 178-181
  Gromke, C. & Ruck, B.
  
• A Model for the Estimation of the lateral aerodynamic Peak Pressure Load on Cyclists induced by overtaking Vehicles. Proc. 16th Int. Conf. Wind Engineering (ICWE16), Florence, Italy, Aug. 2023, 4 p.
  Gromke, C. & Ruck, B.
  
• Aerodynamic Side Loads on Cyclists induced by Vehicles in Overtaking Maneuvers. Proc. AEROVEHICLES 5, Poitiers, France, June 2023, 4 p.
  Gromke, C. & Ruck, B.
  
• On-Site Measurements and Model for Gust Loads on Cyclists induced by Vehicles in Overtaking Manoeuvres. Proc. 11th International Cycling Safety Conference ICSC11, The Hague, The Netherlands, Nov. 2023, pp. 88-90
  Gromke, C. & Ruck, B.
  
• Vehicle-induced aerodynamic lateral loads on cyclists in overtaking maneuvers - Field measurements and universal model description. Journal of Wind Engineering and Industrial Aerodynamics, 243(2023, 12), 105594.
  Gromke, Christof & Ruck, Bodo