The Hung Nguyen’s research while affiliated with University of Danang and other places

The solute transport equation of one-dimensional (1D) or two-dimensional vertical (2DV) flow is normally constructed by the classic average method. These solute transport equations are integrated from the right to the left river bank; the average values received by this approach therefore do not generalize by means of dual approach. This paper presents the application of a dual approach to establish the 2DV solute transport equation. In particular, the concentration in a 2DV flow is obtained by twice integrals: (i) integration from the right river bank to the intermediate vertical surface layer between the right bank and the left bank, and then (ii) integration from the right bank to the left bank. From the two-dimensional horizontal (2DH) [7] and 2DV flow constructed by a dual approach, the researcher receives the 1D flow equation. The average concentration obtained from the dual approach is better than the classical approach, particularly, in the case of mixed solute transport, stratification, and etc. The basic equation obtained is based on the dual approach that describes the solute transport is more accurate than the classical method. In other words, it provides some flexible parameters to adjust based on the field or experimental data. A case study of solute transport (salinity transport) in Huong river system is illustrated.

The incidents of dam failure occur due to some different reasons, in which the reason for seepage accounts for 35%. The seepage leading to the dam incidents can be divided into piping, internal erosion, solution of soluble rock, excessive internal pressures and/or saturation and excessive uplift, heave, or blowout. Currently, empirical method is commonly used to study the influence of seepage on the dam incidents. This paper presents a research work on the development of the experimental equipment and procedure for evaluating seepage effects on several physical properties of embankment, which include cohesion, friction angle, density and permeability coefficient. The testing results provide important material inputs to the finite element model used for the stability analysis of the main dam of Ta Trach reservoir (Thua Thien Hue Province, Vietnam) caused by the seepage phenomenon.

The two-dimensional horizontal flow model in the classical integration approach is integrated from the three-dimensional Navier-Stokes system of equations. Using the classical theory, the integral is taken directly from the bed to the free water surfaces. Consequently, the effects between the channel bed and free water surface, in the process of integration, was disappeared. However, with the proposed dual-process approach, the integral can be performed locally several times. The receiving equations thus allow to contain many physical phenomena which may be lost in the classical integral process. As a result, the derived model based on the proposed dual approach will be more complex and accurate than the classical one. In this paper, the authors perform twice integrals. The improved two-dimensional horizontal flow model was received from the dual approach which allows the calculation of flow parameters, which, having the unusual phenomena in the channel as solid objects, liquids containing other added ingredients, external forces, reversals, and so on.