X ray and visible light transmission for laboratory measurement of two‐dimensional saturation fields in thin‐slab systems

Two independent techniques, X ray absorption and light transmission, are developed and demonstrated for imaging transient saturation fields in thin‐slab porous systems. The techniques yield full two‐dimensional saturation fields with high spatial and temporal resolution. In the time required to make a single measurement by one of the traditional methods (e.g., gravimetric or gamma densitometry) an entire image consisting of hundreds of thousands of points is acquired by either the X ray or light technique. These methods are also very sensitive, capable of resolving a hundred or more levels of saturation at each of these points. Evaluation of these techniques is accomplished by direct comparison of X ray and light data as well as comparison with gravimetric and gamma densitometry data. Results of the comparison show very close agreement between the four techniques (on average within 5% saturation). These techniques represent useful tools for investigating processes governing unsaturated flow and transport through porous media.