Airflow instability in dynamic Císařská Cave (Moravian Karst)

Vol.19,No.1-2(2012)

Marek Lang Jiří Faimon

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Abstract
Airflows were studied in two-entranced Císařská Cave (Moravian Karst). Data (airflow and temperature) were measured at the upper cave entrance (UE) at an upward airflow ventilation mode (UAF). The airflow showed high-frequency oscillations with the periods from tens to hundreds seconds. Multiple oscillations and their time-variability indicate that the oscillations are not a cave resonance phenomenon and cannot be described in the terms of Helmholz resonator. The change of external temperature in narrow interval of ~4 °C had only small effect on the airflow. Under given conditions, air residence time in the cave was 2.5 days. If the airflow was constant and ventilation mode was not exchanged during this period, the cave would persist at a period of active ventilation. As result, the cave air would be completely replaced by air from exterior.

Keywords:
Airflow; Císařská Cave; oscillations; spectral analysis; temperature; ventilation mode
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