Description The use of geologic storage reservoirs for CO2 and hydrogen are all part of the current concepts in achieving net zero energy use, free of CO2 emissions. One of the key issues is the charging of the reservoirs which initially needs to clear the existing fluid and replace it with the desired fluid. This is complex and depends on a micro flow process in the reservoir rock pores. There is evidence that transient processes are more efficient at this but are not well understood. This project will investigate the clearing processes by looking at transient flows in very simple geometries to understand the process and then move to more complex ones more representative of a rock pore. The project is a Fluid Dynamic study , will be CFD based and will use ansys fluent. Key Objectives The objectives would be specific to the project but could involve some or all of the following (i) Review of rock pore fluid flow (ii) Development of a series of models using ansys fluent (iii) assessment of clear out processes (iv) characterisation of processes with geometry