Hrvoje Gotovac

An improved collocation method for solving the Henry problem

The original Henry problem is characterized with severe (albeit unphysical) sea boundary condition difficult to handle with numerical methods. In this paper, we present an improved numerical solution of the Henry problem. Presented numerical model solves the steady-state dimensionless equations by the collocation method named Fup Fragment Collocation Method (FFCM) and uses R(bf) basis functions of Fup(2) (x, y) type. This method enables application of the classical formulation and high approximation accuracy as proven in comparison with published solutions. Particular difficulty in solving the original Henry problem is in the accurate representation of the seepage face due to the fixed sea concentration at the sea boundary. The results of the original Henry problem formulation and problem with modified boundary conditions indicate the accuracy and robustness of the FFCM in describing the discharge area of the considered problem.

Advective transport in heterogeneous aquifers: Are proxy models predictive?

We examine the prediction capability of two approximate models (Multi-Rate Mass Transfer (MRMT) and Continuous Time Random Walk (CTRW)) of non-Fickian transport, by comparison with accurate 2-D and ...

On the upscaling of chemical transport in fractured rock

The impact of flow heterogeneity on chemical transport from single to multiple fractures is investigated. The emphasis is on the dynamic nature of the specific surface area (SSA) due to heterogenei ...

Risk assessment from the oil waste disposal in the deep wells

In this paper we present the risk assessment analysis of oil waste disposal in deep wells. Oil waste disposal is analyzed in the oil field Žutica (Croatia) at an injection depth of around 2000 m. The risk assessment analysis is based on the flow and transport of injected oil waste using stochastic Monte-Carlo numerical simulations through a heterogeneous injection zone, which consists of low permeable marl and high permeable sandstone zones. The injection zone is bounded by low permeable marl zones, which decrease vertical spreading of the injected oil waste and considerably reduce risk. Risk assessment is defined by exceeding risk, which is the probability that injected oil waste passes through the selected cross section or important surface aquifers. Results show that exceeding risk is a very low or practically negligible, pr=10 for period t=100 year at depth of Z=1850 m and pr=10 for period t=10000 year at depth of Z=500 m (surface aquifers), which confirms the safety and reliability of the presented oil waste disposal methodology.