Experimental Investigation and control of turbulent flow structures in mixed convection in a small-scale model experiment

• Applicant: Dr. Christian Resagk
• Subject Area: Fluid Mechanics ; Chemical and Thermal Process Engineering ; Technical Thermodynamics
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 442083214

• Final Report Year: 2025

Final Report Abstract

Air conditioning of passenger cabins in aircraft or trains aims always to generate a comfortable and safe environment with the appropriate temperature. Due to the heat load of the passenger’s natural convection is superimposed to the forced convection by the ventilation system. Thus, very complex and often unstable flow structures occur (mixed convection), local regions with too high or too low air velocity lead to a significant impairment of the passenger’s comfort or to insufficient air exchange, which should be avoided in terms of safety (risk of infection from diseases transmitted by aerosols) and air conditioning. To understand the flow physics the project aims to optically measure the complex velocity field in a simplified and down scaled model cabin under elevated pressures in the unique SCALEX-facility. In detail, the following project objectives were achieved: Design and construction of the model cell with heating, ventilation and temperature measurement technique. - Separate control and measurement of the inflow velocity. - Development of a LabView software code for controlling of the experimental facility and long-term stability of the boundary conditions. - Particle Image Velocimetry with high resolution for the velocity field measurement. - Flow velocity measurement in air and SF6 at pressures of 5 bar (air) and 4 bar (SF6). - Measurement of time-resolved velocity fields for scaling factors 2.25 (air) and 10 (SF6). - Characterization of coherent flow structures at mixed convection with small, medium and large Richardson number using pressurized air and SF6. The results of the project are intended to further improve future ventilation concepts for safe and comfortable traveling.

Publications

• “Automatisierung eines Versuchsaufbaus zur Untersuchung von Strömungsstrukturen in Mischkonvektion“, Forschungsbericht, TU Ilmenau
  C. Naumann et al.
  
• “Measurements of large-scale circulations in mixed convection in a pressurized model room”, In: 20th Int. Symp. On Applications of Laser Techniques to Fluid Mechanics, 11.-14. July, Lisbon
  M. Herzberg
  
• Experimental Investigation of Indoor Air Ventilation in a Small-Scale Aircraft Cabin Model. Environmental Science and Engineering, 1935-1941. Springer Nature Singapore.
  Herzberg, Martin; Otto, Henning; Resagk, Christian & Cierpka, Christian
  
• The SCALEX facility – an apparatus for scaled fluid dynamical experiments. tm - Technisches Messen, 90(5), 296-309.
  Sharifi Ghazijahani, Mohammad; Kästner, Christian; Valori, Valentina; Thieme, Alexander; Täschner, Kerstin; Schumacher, Jörg & Cierpka, Christian
  
• “Charakterisierung der Zuluftströmung in einem Passagierkabinenmodell“, In: Fachtagung Experimentelle Strömungsmechanik, 07.-09. September, München
  M. Herzberg