Lai Wai Tan

Flood-Waves Simulation by Classical Method of Consistent Transport

The classical hydrodynamic solver of consistent transport is first-order accurate in capturing the depth-and-velocity discontinuities when the spurious oscillations are managed by a minimal intervention strategy. The computations of two-dimensional flood waves through the meandering channel demonstrate the long-term computational stability of the method.

Lagrangian block hydrodynamics for environmental fluid mechanics simulations

The Lagrangian block hydrodynamics is formulated based on the block advection of fluid. By enforcing the mass and momentum conservations on the Lagrangian mesh, the numerical oscillation problem encountered in the classical Eulerian computational methods is circumvented. A large number of the previously computationally difficult problems in environmental fluid mechanics are successfully simulated using the method. Examples of these simulations are described in this paper.

Hydrology Properties At Sembrong Dam Reservoir in Johor

Water is fresh potable water is not always available at the right time or the right place for human or ecosystem use [1]. According to Straskraba and Tundisi (1999), water impoundments constructed by damming rivers are called dam reservoirs. Under the Malaysian Western Johore Agricultural Development Project, the main function of the Sembrong dam is flood mitigation. The secondary function of the dam is to provide clean water supply to 240,000 consumers in Kluang district area [2]. Water from the Sembrong dam reservoir is treated at the West Sembrong Water Treatment Plant before the distribution. Daily reservoir inflow data were extracted by applying the water balance model to the Sembrong dam reservoir. Developing hydrologic hazard curves for risk assessment uses the length of record and type of data to determine the extrapolation limits for flood frequency analysis [5]. Extrapolation beyond the data is often necessary to provide information needed for dam safety risk assessments [6]. The sources of information used for flood hazard analyses include stream flow and precipitation records and pale flood data.

Characteristics of Air Entrainment in Hydraulic Jump

The characteristics of hydraulic jump, especially the air entrainment within jump is still not properly understood. Therefore, the current work aimed to determine the size and number of air entrainment formed in hydraulic jump at three different Froude numbers and to obtain the relationship between Froude number with the size and number of air entrainment in hydraulic jump. Experiments of hydraulic jump were conducted in a 10 m long and 0.3 m wide Armfield S6MKII glass-sided tilting flume. Hydraulic jumps were produced by flow under sluice gate with varying Froude number. The air entrainment of the hydraulic jump was captured with a Canon Power Shot SX40 HS digital camera in video format at 24 frames per second. Three discharges have been considered, i.e. 0.010 m3/s, 0.011 m3/s, and 0.013 m3/s. For hydraulic jump formed in each discharge, 32 frames were selected for the purpose of analysing the size and number of air entrainment in hydraulic jump. The results revealed that that there is a tendency to have greater range in sizes of air bubbles as Fr1 increases. Experiments with Fr1 = 7.547. 7.707, and 7.924 shown that the number of air bubbles increases exponentially with Fr1 at a relationship of N = 1.3814 e 0.9795Fr1.

Geophysical and Hydrochemical Characteristics of Groundwater at Kerian Irrigation Scheme

.A study was conducted to determine the potential of groundwater uses at the Kerian irrigation scheme, specifically the Selinsing irrigation area. Resistivity image profiling method was employed at four sampling locations within the study area to identify the depth and variation of aquifer layer and the possibility of hard layer presence. Investigations conducted revealed that the thickness of aquifer within the study area varies between 5 m and 10 m, which is located at a depth of 30 m to 70 m below the ground surface. The thickness of clay layer is between 1 m and 80 m which dominates the upper subsurface layer. Seven samples of groundwater were used in determining their hydrochemical and physicochemical characteristics, ionic composition, and the quality suitability for irrigation use. A preliminary characterisation based on the piper diagram provides the hydrofacies classification while Stiff diagram is used to exhibit the ionic relationship. The degree of correlation between cations and anions has been estimated in order to assess their mutual relationships. Strong positive correlation exists for Ca2+-Mg2+, Ca2+-Na+, Na+-Mg2+, Na+-K+, Ca2+-K+, Mg2+-K+, Mg2+-Cl-, K+-HCO3 -, and Na+-Cl-. Profusion of elements also reflects the composition of aquifer and the climatic conditions, which possibly contribute to the genetic relationship.

Flood wave dynamics using Lagrangian block advection

Flood wave dynamics simulations are determined by a robust and accurate Lagrangian block advection (LBA) scheme that can track the dry-and-wet interface and capture the shocks without using any slope limiter to control the numerical oscillations. Two series of challenging numerical problems are considered using the LBA. First, computations are carried out for water waves in a parabolic bowl. The wetting-and-drying interface on the surface of the bowl is tracked by the LBA method with absolute computational stability. The accuracy of the LBA method is verified by the convergent of the numerical solution to an exact solution. Finally, the LBA method is applied to carry out a series of flood wave simulations, which have closely reproduced the data obtained from the laboratory experiments.

Stable Simulation of Shallow-Water Waves by Block Advection

Waves in shallow water are computed using Lagrangian block hydrodynamics. The blocks transfer mass and momentum on a Lagrangian mesh. The computational stability is guaranteed by avoiding any usage of the Eulerian flux. The shock-capture and wave-front-tracking accuracies of the Lagrangian block hydrodynamics as determined from the convergence towards the exact solutions are approximately first order.

Waves Run-Up and Overtopping Simulations Using Lagrangian Blocks

Wave run-up and overtopping of coastal structures are simulated using Lagrangian Blocks on Eulerian Mesh (LBEM). In the LBEM simulations, the blocks carry the mass and momentum. The movement of the blocks is calculated in a Lagrangian reference frame. The water depth defined by the volume blocks is non-negative. The wave fronts across the wet-and-dry interface are simulated by the block method without interruption by the oscillation problem that has limited the applicability of many existing computational methods. To evaluate the accuracy of the LBEM method in this paper, simulations are carried out for (i) the dam-break waves, (ii) the wave run-up on plane beach, and (iii) the overtopping of solitary waves over levee. The simulations of the dam-break wave have produced excellent agreement with the exact solutions by Ritter [1] and Stoker [2], and the semi-analytical solution by Sakkas and Strelkoff [3,4]. The simulations of the wave run-up on plane beach agree with the experimental data and the nonlinear theory of Synolakis [5]. The simulations of wave overtopping trapezoidal dike agree with the finite-volume simulations of Stansby [6]. The results have demonstrated the accuracy of the LBEM method and the versatility of the method for general wave simulations over variable terrain.Copyright

Simulation of Water Advancing over Dry Bed Using Lagrangian Blocks on Eulerian Mesh

Lagrangian Blocks on Eulerian Mesh (LBEM) simulations of water advancing over dry bed are conducted using blocks as the computational elements. The non-negative nature of the blocks have allowed the LBEM simulation to be carried out without the oscillation problem that has limited the applicability of many existing computational schemes. At the leading edge of the water, the velocity is maximum and friction is the dominant effect. The simulation for the dominant friction effect at the wave front is carried out for the release of water from (i) dam-break outflow, (ii) levee overflow, and (iii) sump overflow. Despite the geometric difference, all three flows have the maximum velocity at the wave front following identical asymptotic trend at large time.