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Wind Tunnel Modelling in Conservation

Wind Tunnel Modelling in Conservation. Stanislav Pospíšil, Miloš Drdácký, Zuzana Slížková, Jaroslav Lesák , Dagmar Knotko vá Institute of Theoretical and Applied Mechanics, AS CR. 1 Introduction and motivation. 2. 3. 1. 2 Current status.

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Wind Tunnel Modelling in Conservation

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  1. Wind Tunnel Modelling in Conservation Stanislav Pospíšil, Miloš Drdácký, Zuzana Slížková, Jaroslav Lesák, Dagmar Knotková Institute of Theoretical and Applied Mechanics, AS CR 7th European Conference SAUVEUR

  2. 1 Introduction and motivation 2 3 1 7th European Conference SAUVEUR

  3. 2 Current status • Several wind tunnels available but only few combine more effects -> CWT • Mostly designated to automotive industry • For buildings and urban zones -> athmospheric WT • CWT Nantes (CSTB) -1990, aerod. characteristics of full scale supercritical Reynolds numbers– real, large scale physical simulation 7th European Conference SAUVEUR

  4. 2 Current status – CWT, BLWT CLIMATIC WIND TUNNEL • rain-250 mm/h • sand conc. - 10 g/m3 in a 10 m2 section • -25 °C to +50 °C and relative humidity from 30% to 100% • flow speed can be set from 90 km/h to 140 km/h. • snow mantle (15 cm/h) on the 200 m2 floor of the test chamber. BL WIND TUNNEL • flow speed from 0 km/h to 140 km/h. • visualization 7th European Conference SAUVEUR

  5. 3 Gothic sandstone pinnacles subjected to a combined climatic load • Gothic pinnacles from one of the most important late medieval Gothic churches, St. Barbara’s in Kutná Hora (Bohemia), were exposed to accelerated clima for a period of four days in order to test the efficiency of hydrophobic surface coating • Usually individual effects are analysed • CWT based research - unique opportunity for the analyse the behaviour of historic materials subjected to combined climatic loads 7th European Conference SAUVEUR

  6. 3 Gothic sandstone pinnacles subjected to a combined climatic load Real structure Complex shape St. Barbara catedral Influence of the wind direction on the deterioration of valuable architectural detail 7th European Conference SAUVEUR

  7. 3 Gothic sandstone pinnacles subjected to a combined climatic load Weighting of the specimens Loading of the specimen by low and high temperature cycles 7th European Conference SAUVEUR

  8. 3 Gothic sandstone pinnacles subjected to a combined climatic load Thermocamera analysis lower temperature scan higher temperaturescan 7th European Conference SAUVEUR

  9. 3 Gothic sandstone pinnacles subjected to a combined climatic load • Temperature changes are very sensitive to the shape of details of complex architectural forms. • Cooling and evaporation are highly influenced by the wind flow, especially cold wind flow. • Driven rain increases the water penetration into the stone only at the beginning • A hydrophobic surface coating protects the stone very well, if applied compactly on a sufficiently large area of interest. product. • Our technique can be advantageously applied for studying the air flow and eddies around complex shapes and forms. 7th European Conference SAUVEUR

  10. 3 Corrosion due to weather and air pollution CZ National MUSEUM Corrosion due to particles deposition- wind analysis is important Plan view of the building and soiling sensors placement 7th European Conference SAUVEUR

  11. 3 Corrosion due to weather and air pollution Wind tunnel analysis • Dust deposition – • optical determination-big costly effort • 2. fine weighting procedure New adhesive samplers has been used with success. 7th European Conference SAUVEUR

  12. 3 Corrosion due to weather and air pollution • There has been no unambiguous relation between the deposition degree on the samplers at the models with differrent scales • More experiments are needed in order to understand scale factors and similitude between the prototype and models. • The spectrofotometric method has been used with good results 7th European Conference SAUVEUR

  13. 3 Wind and wind driven rain damage to historical objects • use of numerical calculation need to be confronted with experiments • laser sheet fluid visualization Pressure taps on several levels Benchmark objects 7th European Conference SAUVEUR

  14. 3 Wind and wind driven rain damage to historical objects RMS pressures patterns num exp • virtual wind tunnel with appropriate numerical model can give qualitatively reliable results 7th European Conference SAUVEUR

  15. 4 Conclusions • Three examples demonstrating the exposure of HO to wind and combined load were presented • There is evident need of experimental facility for the multidimensional science like heritage conservation • The use of CWT can create the link between individual researches and therefore focus on synergetic effects 7th European Conference SAUVEUR

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