Natural water movement occurs predominantly with very small pressure gradients. Currently, the water movement is described almost exclusively as a laminar flow with DARCY equation whereby the flux speed is proportionate to the effective pressure gradients.
The usual kf measurements in soil science are conducted with comparatively high gradients which are rarely to be found in the natural water movement in soils. HARTGE therefore advocated the measurement with very small gradients. The hood permeameter according to HARTGE meets these requirements. It serves to determine the kf value of the soil ring samples in the laboratory from the flux rate and the corresponding pressure difference whilst keeping the pressure gradients as small as possible. The saturated sample in the manual soil sample ring is placed in a tub on a filter plate and covered completely with water. A hood filled with water is placed over the soil sample ring beneath which a pressure gradient is generated over the sample height. This hood is suitable for the manual soil sample rings offered by UGT so that the soil sample can be inserted directly. In the test run, the water volume flowing through the sample during a specific measurement time is determined for the stationary flow. The area and length of the flow path are determined by the geometry of the soil sample ring. The pressure gradient is shown as height difference in the standpipes.
Training ku-pF and Hood-Permeameter:
Sampling in the field, saturation, installation and commissioning, determination of saturated and unsaturated hydraulic conductivity
|Resolution pressure differencewith standpipe||1 mm water column|
|Resolution pressure differencepressure sensor||0,1 mm water column|