Multiphase Flow Experiment Study On LNAPL Pollutes Soil

The Light non-aqueous phase liquid (LNAPL) enter into underground will result in underground entironment system pollution, which poses a serious threat to environment and public health and welfare. In order to control the environmental problems effectively, it is important to understand the underground migration mechanism of LNPAL.Due to the lack of experimental work and data compared to model study on LNAPL pollute underground entironment, This paper is an experimental investigation. This paper presents the experimental methods and results in two major parts: parameter trials and simulating experiments. The parameter trials obtain the functional relationships between saturation and pressure of two-phase immiscible flow in porous medium. The simulating experiments simulate the transport behavior of LNPAL in the unsaturated zone. Selecting medium sand and coarse sand as homogeneous porous medium; Putting medium sand on coarse sand and fine sand in coarse sand as heterosphere porous medium. Selecting diesel oil as LNPAL.In the experiments that obtain the functional relationships between saturation and pressure of two-phase immiscible flow (water-air, water-oil, oil-air) in porous medium, the experiment apparatus was designed according to tensiometer and proved to be successful to obtain a series of functional relationships between saturation and pressure of different two-phase immiscible flow. The experiment results showed that there are many similarities in the process of wetting phase monotonously displaced in different two-phase system, is as same as the water-air system. Saturation-pressure relationship in arbitrary fluid pairs could be expressed by Van formula. Using VGM model, we can obtain three-phase K-S-P curves from the three-phase P-S cures . The three-phase P-S cures were obtiained from two-phase P-S cures by adopting the three scaling methods which was validated by F.F. Fagerlund. The three-phase K-S-P curves can offer parameter for numerical simulation.The movement of LNAPL in un-saturated zone were simulated in a two-dimensional plexiglass tank which was designed by ourselves. The movement of tinct LNAPL in porous medium was successfully traced by digital camera. The phase pressure in the process of LNAPL spill were measured by a pressure collection system. Obtaining the following results:(1) In homogeneous porous medium, the oil front retains a regular, circular shape at the initial stage, the vertical spread is superior to lateral spread; After the oil front reaches the boundary between visibly unsaturated zone and capillary zone, it becomes irregular and spreads with a caky shape. In heterosphere porous medium, the interface between two different sands will influence the movement of LNAPL and the oil shape become irregular.(2) The heterosphere and rock type will influence the distribution and movement of LNAPL. The rock type of the porous medium below the LNAPL spill source strongly influence the movement of LNAPL and will decide the distribution and location of LNAPL front.(3) The tater table variation will change equilibrium in air, oil and water and influence the distribution and movement of LNAPL.(4) The leakage of diesel oil will bring the movement of water in porous medium. The water saturation will influence the movement of LNAPL. The vertical movement of LNAPL was counteracted at the high water saturation. The air pressure has very small change during oil spill and the process of oil spill have little influence on air pressure.(5) The multiphase flow datas from the experiments can be appied by validating the existing multiphase models.