Modeling CO2, H2S, COS, and CH3SH Simultaneous Removal Using Aqueous Sulfolane–MDEA Solution

In this study, a rate-based absorption model coupled with an improved thermodynamic model was developed to characterize the removal of acid components (CO2 and H2S) and organic sulfur (COS and CH3SH) from natural gas with an aqueous sulfolane–MDEA solution. First, the accuracy of the thermodynamic model was validated by comparing the calculated partial pressure of CO2, H2S, and CH3SH with those of the experimental data reported in the literature. Then, the industrial test data were employed to validate the absorption model and the simulation results agreed well with the experimental data. The average relative errors of the removal rates of CO2, COS, and CH3SH are 3.3%, 3.0%, 4.1%, respectively. Based on the validated coupled model, the total mass transfer coefficient and mass transfer resistance of each solute component at different column positions were analyzed. The effects of the gas–liquid ratio, overflow weir height, and absorption pressure on the absorption performance of each component were studied, and the influence of the acid component concentration in the feed gas on the removal efficiency of methyl mercaptan (CH3SH) was also discussed. It is found that the improved absorption model can better characterize the absorption performance and be conducive to the optimal design of the absorber column.

STAGE-STORAGE AND FLOOD RISK ASSESSMENTS OF UPGRADED BATU KITANG SUBMERSIBLE WEIR

Batu Kitang Submersible Weir (BKSW) was constructed to secure reliable water yield from the Sarawak Kiri River until 2010. However, ever-increasing water demand had outstretched the weir capacity. Upgrading work has been done to extend the weir height from 1.5 m to 2.5 m using interlocking concrete blocks to increase water storage capacity. However, the storage capacity and flood extend are unknown after the upgrading work. This study aimed to determine the effect of upgrading works on water storage capacity and floodplain coverage in the upper catchment using InfoWorks River Simulation (RS). Results revealed that weir height extension from 1.5 m to 2.5 m at BKSW had increased the water storage capacity from 1012 ML to 1499.62 ML, securing approximately 48% more water. Besides, maximum storage depth was also increased from 6.53 m to 7.53 m, and the distance of storage reservoir coverage from BKSW also increased from 8 Km to 16 Km. However, these increments would not lead to any significant impact on floodplain coverage upstream. It is novel to discover that a 1m weir height increase has extended BKSW service from 2010 to 2030 under a 1:50-year drought scenario. After 2030, various measures such as inter-basin raw water transfer should be implemented to increase the raw water supply and reduce water usage to ensure a sustainable water supply for Kuching City and its surrounding areas.

Apron and Cutoff Wall Scour Protection for Piano Key Weirs

Piano key (PK) weirs are used in a variety of flow control structure applications, including spillway crests and open channel diversion structures. However, to the best of authors’ knowledge, structure-specific design guidance for scour mitigation is still needed. To fill this gap of knowledge, a systematic experimental campaign was conducted by testing different configurations of horizontal aprons with a cutoff wall. Protection structures were located at the toe of the PK weir. Namely, experiments were performed at large-scale to assess the effect of three apron lengths on downstream scour hole geometry under different hydraulic conditions. It was observed that a horizontal apron deflects the plunging jets originating from the PK weir, thus significantly reducing scour. Experimental evidence allowed corroboration that significant scour depth reduction occurs for an apron length 1.5 times the weir height, with longer aprons found to provide marginal benefits. Finally, also provided herein are tools to estimate the main scour characteristics and help practitioners in optimizing apron design.

Development of ANN model for discharge prediction and optimal design of sharp-crested triangular plan form weir for maximum discharge using linked ANN–optimization model

Triangular plan form weirs are advantageous over a normal weir in two ways. Within the limited channel width, use of such a weir increases the crest length and hence for a given head, increases the discharge and for a given discharge, reduces the head in comparison with a normal weir. In a previous study, researchers proposed an empirical equation to compute the discharge coefficient of a triangular plan form weir. The prediction error on the discharge coefficient was ±7% from the line of agreement. In the present study, an ANN model has been utilized to train randomly selected 70% data, with 15% tested and validation made for the remaining 15% data. The model predicts the discharge coefficient with a prediction error in the range of ±2.5% from the line of agreement, thereby decreasing the prediction error in Cd by 64%. Also, the sensitivity analysis of the developed ANN model has been performed for all the parameters (weir height, skew weir length and flow depth) involved in the study and the weir height was found to be the most sensitive parameter. Furthermore, the linked ANN–optimization model has been developed to find the optimal values of design parameters of a triangular plan form weir for maximum discharge.

The Effect of Geometric Parameters of the Antivortex on a Triangular Labyrinth Side Weir

Side weirs are important structural measures extensively used, for instance, for regulating water levels in rivers and canals. If the length of the opening is limited, the amount of water diverted out of the channel and the effective length can be increased by applying a labyrinth side weir. The present study deals with numerical simulations regarding the hydraulic performance of a labyrinth side weir with a triangular plan in single-cycle mode. Specifically, six different types of antivortexes embedded inside it and in various hydraulic conditions at different Froude numbers are analyzed. The antivortexes are studied using two groups, permeable and impermeable, with three different heights: 0.5 P, 0.75 P, and 1 P (P: Weir height). The comparison of the simulated water surface profiles with laboratory results shows that the numerical model is able to capture the flow characteristics on the labyrinth side weir. The use of an antivortex in a triangular labyrinth side weir reduces the secondary flows due to the interaction with the transverse vortexes of the vertical axis and increases the discharge capacity by 11%. Antivortexes in a permeable state outperform those in an impermeable state; the discharge coefficient in the permeable state increases up to 3% with respect to the impermeable state. Finally, based on an examination of the best type of antivortex, taking into account shape, permeability, and height, the discharge coefficient increases to 13.4% compared to a conventional labyrinth side weir.

Modeling of weir height drop on the slope of the open channel hydraulic jump

The model design was developed for the alignment and it was utilized to test for various geometrics and stream conditions searching for a low and incentive for RMSE and the response variable. Also, during the alignment half of the exploratory information was set to their coefficients, and the staying set of information was similarly be utilized for confirmation purposes. Utilizing around thirty out of the fifty informational collections created in the research facility dependent on relapse investigation was applied to the non-direct model to decide the constants. The staying twenty informational collections from research centre analyses were utilized for check of the model. The absence of the fittest was utilized likewise to check the request for the proposed relapse model utilizing the water profundity as the response variable. The Froude numbers from the post-pressure driven hop segment from 0.37 to 0.41 (0.37 < Fr3< 0.41), likewise showing that the streams are subcritical. The Froude numbers from the post-pressure driven hop area inside 0.37 to 0.41 (0.37<Fr3 <0.41), this shows the streams are subcritical. The connection between sequent profundity proportion y3//y2 and speed proportion V2/V3 is around - 5024 +1.485 Fr2 with R2 =0.9957 showing that as the sequent profundity proportion and speed proportion expands the inflow Froude number Fr2 additionally increments, the hydraulic jump extended from - 0.001 to 0.001 which gives some vitality progression with an expansion in the pace of release through the flume. The upstream of the flume, the Froude numbers go from 0.038 to 0.052 (0.038 < Fr1 < 0.52), demonstrating that the streams were subcritical and less harm to the channel.

Discharge coefficient of broad-crested weirs as a function of the relative weir height for different weir lengths

Broad-crested weirs (BCW) are often used in hydraulic engineering and water management. The most complex factor that affects the discharge capacity of BCW is the discharge coefficient. In Ukrainian engineering practice, the flow rate of BCW is defined as a function of the relative height of the spillway wall, while in the most common European methods – as a function of the relative length of the weir. The experimental dependences of the discharge coefficient of rectangular sharp-edged BCW with vertical inlet and outlet walls with the ratio of the weir length and height d/Р = 2; 4 are obtained. A comparison of the obtained results with the values of the discharge coefficient of the same BCW using the methods of Kumin and Hager indicates that this coefficient depends on both the height of the wall and the length of the weir. The corresponding empirical power law dependences are obtained. At the same values of the relative height of the wall, the discharge coefficient for the weir with the ratio d/Р = 4 is significantly lower comparing the weir with d/Р = 2, that can be explained by the more significant effect of friction resistance for the weir with longer threshold.

Effects of weir geometry on scour development in the downstream of Piano Key Weirs

Scouring in the downstream of all weirs, including Piano Key Weirs (PKWs), can have major safety implications. Since the research on downstream scouring of PKWs is very limited, and the weir geometry is also known to have an impact on downstream scouring, this study investigated scouring in the downstream of PKWs with rectangular and trapezoidal geometries and two different heights. The scour hole measurements showed that in both rectangular and trapezoidal models, scour hole parameters increased both with the increase in discharge rate and the increase in weir height. Under similar discharge conditions, the scour depth downstream from the rectangular model was greater than that downstream from the trapezoidal model. The dimensionless maximum scour depth, the distance of maximum scour depth from the weir toe, and the scour hole length for the trapezoidal PKW were, on average, 6, 13, and 11% lower than the corresponding ones for the rectangular PKW, respectively. However, these differences decreased with the increase in falling height. For both weir geometries, the maximum scour depth was aligned with the outlet keys. In addition, the maximum scour depth under the outlet keys was 13% greater than the one under the inlet keys.

Use of bottom slots and submerged vanes for controlling sediment upstream of duckbill weirs

Duckbill weir is one of the water level control structures in irrigation networks, which is of interest to many engineers. Sediments transported in irrigation networks that accumulate upstream of duckbill weirs cause problems in operation, and affect the upstream water level. In this paper, submerged vanes and bottom slots are investigated for flushing the sediment downstream of the said weir. The experiments were conducted in a rectangular flume, 12 m long, and 0.6 m wide. The vanes placed in four sections were perpendicular to the sidewall. Flow-3D software was used for simulation of flow and sedimentation patterns. The results showed that submerged vanes create a secondary flow which is very useful for flushing the sediment, especially in the value of (H is head over the sidewall and P is the weir height). Further, the results showed duckbill weir efficiency (which is defined as the ratio of sediment trap to flow capacity of the weir) is as high as 47% (for values of H/P = 0.1–0.5 and total models). Finally, image processing results showed a maximum relative error of 14.4% for the simulation of the sediment pattern with Flow-3D software.

Energy Dissipation and Hydraulics of Flow over Trapezoidal–Triangular Labyrinth Weirs

In this work experimental and numerical investigations were carried out to study the influence of the geometric parameters of trapezoidal–triangular labyrinth weirs (TTLW) on the discharge coefficient, energy dissipation, and downstream flow regime, considering two different orientations in labyrinth weir position respective to the reservoir discharge channel. To simulate the free flow surface, the volume of fluid (VOF) method, and the Renormalization Group (RNG) k-ε model turbulence were adopted in the FLOW-3D software. The flow over the labyrinth weir (in both orientations) is simulated as a steady-state flow, and the discharge coefficient is validated with experimental data. The results highlighted that the numerical model shows proper coordination with experimental results and also the discharge coefficient decreases by decreasing the sidewall angle due to the collision of the falling jets for the high value of H/P (H: the hydraulic head, P: the weir height). Hydraulics of flow over TTLW has free flow conditions in low discharge and submerged flow conditions in high discharge. TTLW approximately dissipates the maximum amount of energy due to the collision of nappes in the upstream apexes and to the circulating flow in the pool generated behind the nappes; moreover, an increase in sidewall angle and weir height leads to reduced energy. The energy dissipation of TTLW is largest compared to vertical drop and has the least possible value of residual energy as flow increases.