EXPERIMENTAL STUDIES OF WETTING FRONT INSTABILITY INDUCED BY GRADUAL CHANGE OF PRESSURE GRADIENT AND BY HETEROGENEOUS POROUS MEDIA.

Experimental observations on the onset of instabilities and the wavelengths of disturbances formed in infiltration flows, when the pressure gradient was gradually increased through zero, were compared with the stability analysis of J. R. Philip. For this case and for that of step-increase in conductivity with depth the theory gave a satisfactory account of the onset and development of instability in Hele-Shaw cells.