Variances in airflows during different ventilation modes in a dynamic U-shaped cave

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Authors

FAIMON Jiří LANG Marek

Year of publication 2013
Type Article in Periodical
Magazine / Source International Journal of Speleology
MU Faculty or unit

Faculty of Science

Citation
Doi http://dx.doi.org/10.5038/1827-806X.42.2.3
Field Geochemistry
Keywords airflow; air density; cave; temperature difference; temperature profile; ventilation mode; conceptual model
Description Airflow dynamics were studied in Císařská Cave (Moravian Karst, Czech Republic) under different seasonal conditions. The dependence of airflows on the difference between external and cave temperatures is nonlinear and roughly obeys the Darcy-Weisbach equation. The upward airflows were found to be systematically higher than the downward airflows under comparable driving forces. The principle reason is nonlinearity between air temperature and air density. U-shaped cave geometry magnifies this effect by feedback between external temperature and airflow driving forces. Whereas this feedback is positive during the upward airflow ventilation mode, it is negative during the downward airflow mode. To discuss the behavior in detail, a simplified model based on balancing the masses of two equivalent air columns of different temperatures and densities is proposed. The results contribute to a better understanding of cave microclimate evolution, cave CO2 dynamics, and speleothem growth.
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