ALBERT

Description: The National Combustion Code (NCC) was used to calculate the steady state, nonreacting flow field of a prototype Lean Direct Injection (LDI) swirler. This configuration used nine groups of eight holes drilled at a thirty-five degree angle to induce swirl. These nine groups created swirl in the same direction, or a corotating pattern. The static pressure drop across the holes was fixed at approximately four percent. Computations were performed on one quarter of the geometry, because the geometry is considered rotationally periodic every ninety degrees. The final computational grid used was approximately 2.26 million tetrahedral cells, and a cubic nonlinear k - epsilon model was used to model turbulence. The NCC results were then compared to time averaged Laser Doppler Velocimetry (LDV) data. The LDV measurements were performed on the full geometry, but four ninths of the geometry was measured. One-, two-, and three-dimensional representations of both flow fields are presented. The NCC computations compare both qualitatively and quantitatively well to the LDV data, but differences exist downstream. The comparison is encouraging, and shows that NCC can be used for future injector design studies. To improve the flow prediction accuracy of turbulent, three-dimensional, recirculating flow fields with the NCC, recommendations are given.

Description: Groundwater aquifers are important for the freshwater supply all over the world, especially in dry regions. It occurs that the water bearing rock matrix extends offshore below the sea floor, and as a consequence fresh water is embedded within good conducting seawater-saturated sediments. Whether an aquifer is open to seawater intrusion or closed, depends on the local hydrogeological setting. Prior studies showed that for high demand on fresh water and high exploitation rates, it is necessary to understand the interaction between sea and fresh water to prevent deterioration of the aquifer. Several geophysical surveys have been carried out in the past to investigate a coastal aquifer in the Palmahim region of Israel, which serves as one of the main reservoirs of the national water supply system. Time domain marine LOTEM and DED data have thereby been recorded on similarprofiles. Both results show a resistor at an assumed aquifer depth of roughly 100 m with a comparable offshore extension of 3.5 km from the coastline. However, until now the LOTEM and DED data have only been interpreted separately using 1D inversion and extensive 2D forward modeling. This study presents the first joint 1D and 2D inverse modeling studies of marine LOTEM and DED techniques using synthetic and field data. The synthetic results indicate large benefits of using a joint inversion of both appliedsurvey techniques. However, a joint inversion of the field data is still in progress. Yet, a 2D inversion of the DED data is promising and indicates a brackish transition zone at the expected lateral aquifer boundary. This finding seems consistent with prior studies and suggests an open aquifer scenario with seawater intrusion. This outcome is essential for the groundwater management and supply in Israel.

Description: Various electromagnetic (EM) measuring techniques were developed to fulfil the requirements in diverse earth or resources explorations, such as the long-offset transient electromagnetic (LOTEM) and the semi-airborne EM methods. The novel semi-airborne frequency-domain electromagnetic system takes advantages of both ground and airborne techniques by combining ground-based high power sources with large scale and spatially dense covered data. However, its signal-to-noise ratio is still smaller in comparison with the ground-based method like LOTEM due to the limited stacking time. From the perspective of inversion, the data of different EM methods have distinct resolutions towards the subsurface resistivity structures and therefore they can provide complementary earth information. However, these distinct resolutions could also lead to different inversion results if each dataset is inverted individually, which may introduce confusions to the following interpretations. To reduce the ambiguities and parameter uncertainties, joint inversion algorithms are developed to couple spatially dense sampled semi-airborne data and horizontal electric fields (Ex) measured using LOTEM. Nevertheless, the 1D joint inversion faces convergence problems due to 2D effects in the field data. The synthetic modelling suggests that the 2D effects in different datasets lead to distinct artificial structures in the 1D inversion, which makes the 1D joint inversion unfeasible. Therefore, a 2D joint inversion algorithm was further developed for the frequency-domain semi-airborne EM data and the LOTEM transient electric fields. With its application, the newly developed 2D joint inversion of the semi-airborne and LOTEM Ex field data acquired in eastern Thuringia,Germany, converged successfully and a 2D conductivity model could be derived for the survey area. In the consequent 2D synthetic modelling studies, it is demonstrated that part of the discrepancies between the individual inversion result of each field dataset can be explained by the resolution differences leaded by the different observed quantities and by the measurement configurations, and the 2D joint inversion result of field data is validated to be one effective equivalent model.