Vortex profile analysis under different diffuser size for inlet channel of gravitational water vortex power plant

Hydropower is a renewable technology to store the amount of electricity which is the least expensive. Gravitational Water Vortex Power Plant is an ultra-low head micro hydropower system working ranging from 0.7 m to 2m without having the needs of a large reservoir and installation area. Several researches have been conducted on its basin configuration, orifice diameter, blade configuration, the geometry of the basin shape but not onto the addition of the diffuser at the inlet channel. The function of the diffuser is to direct the water into the basin allowing the water vortex to travel towards the tangential direction where this phenomenon will increase the rate of speed flow through the turbine. The simulation results showed that the addition of the diffuser has significantly increased the tangential velocity and the kinetic energy of the vortices. The increase in the velocity of the flow increased the height of the vortex which also led to the increase in the strength of the vortex and affects the vortex uniformity.

Toward a Better Understanding of Sediment Dynamics as a Basis for Maintenance Dredging in Nagan Raya Port, Indonesia

The Port of 2 × 110 MW Nagan Raya Coal Fired Steam Power Plant is one of the facilities constructed by the State Electricity Company in Aceh Province, Indonesia. During its operation, which began in 2013, the port has dealt with large amounts of sedimentation within the port and ship entrances. The goal of this study is to mitigate the sedimentation problem in the Nagan Raya port by evaluating the effect of maintenance dredging. Field measurements, and hydrodynamic and sediment transport modeling analysis, were conducted during this study. Evaluation of the wind data showed that the dominant wind direction is from south to west. Based on the analysis of the wave data, the dominant wave direction is from the south to the west. Therefore, the wave-induced currents in the surf zone were from south to north. Based on the analysis of longshore sediment transport, the supply of sediments to Nagan Raya port was estimated to be around 40,000–60,000 m3 per year. Results from the sediment model showed that sedimentation of up to 1 m was captured in areas of the inlet channel of Nagan Raya port. The use of a passing system for sand is one of the sedimentation management solutions proposed in this study. The dredged sediment material around the navigation channel was dumped in a dumping area in the middle of the sea at a depth of 11 m, with a distance of 1.5 km from the shoreline. To obtain a greater maximum result, the material disposal distance should be dumped further away, at least at a depth of 20 m or a distance of 20 miles from the coastline.

Two-dimensional numerical studies of particle motion and deposition in the channel of diesel particulate filters

A numerical investigation on the soot laden flow of gas in a partial diesel particulate filter (PDPF) is presented based on solving the momentum equations for a continuous phase in the Euler frame and the motion equations for the dispersed phase in the Lagrangian frame. The interaction between the gas phase and the particles is considered as a one-way coupling for dilute particle concentration, while the interaction between particles and porous wall is implemented through user-definedsubroutines. To accurately track motion of nanoscale particles, the Brownian excitation and drag force as well as partial slip are taken into account in the particulate motion equation. Two methods are used to verify the gas flow model and reasonable agreements for both comparisons are observed. The effects of inlet velocity, wall permeability and particle size on the filtration efficiency and deposition distribution of the particles along with wall surface of inlet channel are quantitatively studied. The results show that (i) wall permeability plays the primary role in determining the filtration efficiency of PDPF, (ii) both upstream velocity and particle size have an effect on the initial deposition position of particles and (iii) filtration efficiency of PDPF is not markedly proportional to gas flow into inlet channels at a low wall permeability.

Numerical Investigation of Degasification in an Electrocoagulation Reactor

In order to enhance retention of particulate and colloidal (organic) matter, chemical coagulation (CC) is often used prior to pressure-driven membrane filtration. This combined hybrid membrane system may be a potential solution for environmental problems dealing with drinking water treatment, water reuse, and rational waste management. In this study, an EC reactor with spiral electrodes was investigated numerically, focusing on modeling with a given design/geometry configuration and boundary conditions. Two-phase flow interactions between water and hydrogen were modeled via computational fluid dynamics (CFD). Different flow rates (Q=1−1000 l/h) through two batches of the watering stage (Case 1–3) and the degassing stage (Case 4–6) were simulated. The results provided information about flow characteristics such as sufficient retention time, water circulation, undesirable gas penetration into the water inlet channel, gas holdup during watering and degassing, and finally the optimal period for the degasification. Retention time decreases with increasing water velocity and thirty seconds seemed to be the optimal time with gas holdup of 0.020%, 0.028%, and 0.027%, respectively, for Case 4, Case 5, and Case 6. Another finding is that the consideration for the most abundant gas holdup for the typical BC was the smallest ratio of water to gas flow.

A New Design of a Pinwheel-Shaped High-g Combustor

High-g combustor (HGC) is a significant branch of the ultra-compact combustor, an innovative gas turbine combustor with the ability to shorten the combustor length and improve engine efficiency. To improve the feasibility of the HGC concept, a new HGC was designed to substitute the conventional combustor of a KJ66 small turbine engine. The KJ66 was modified to fit an instrumentation system and test bench to conduct relative experiments. Based on the experiment results, design iterations were conducted relying on simulation methods. The design iteration was comprised of 6 primary configurations, of which the first four configurations focused on establishing an appropriate high centrifugal environment to accelerate primary combustion, while the last two modifications focused on improving overall combustion performance. In Configuration 4, a pinwheel-shaped swirl inlet was designed to successfully create the high-g environment and balance the flow distribution while bringing insignificant total pressure loss. One modification of Configuration 4 was a grid inlet design that divided the inlet channel into several sub-channels to constrain the inlet flow and establish an ideal high-g environment. The other modification was a divergent mainstream channel to encourage the dilution process and improve the exit temperature profile. The final design could save at least 1/3 of combustor length while maintaining the same level of performance as the original combustor. Further, the engine was predicted to save at least 12% of the total engine weight and improve at least 14% of the engine thrust-to-weight ratio.

What mechanisms trigger coastal flow slides?

<p>Some beaches regularly experience a rapid decrease in volume due to ‘coastal flow slides’. These events visually resemble subaerial landslides, but are subaqueous and located along river or tidal channels. Along a steeper shoreface, material eroded from the upper beach can be stored in deep water. In some cases, these events can remove thousands of cubic meters (m<sup>3</sup>) of beach sand in a few hours.<br><br>On several occasions in recent years, a flow slide has formed at Seabrook Island, South Carolina (USA). As of January 2021, there have been five events observed since July 2016. Surveys of a January 2017 event show the slide displaced ~25,000 m<sup>3</sup> into deep water (15–20 m) along North Edisto River Inlet. This volume is comparable to hillside-scale slides observed in mountainous regions like the Blue Ridge, and similar-scale failures have been observed in the Netherlands, France, and Australia (Mastbergen, 2019).<br><br>The Seabrook flow slide is consistently located along a marginal flood channel of a relatively large ebb-dominant inlet, just below a quarrystone revetment protecting an upland development. In this particular location, erosion of the dry beach could cause undermining of the revetment. Historical charts suggest a small inlet was located along this portion of the beach as recently as ~1920. Reviews of available rainfall and water level data suggest exceptional (ie – near-record daily total) rainfall events and spring tide levels may coincide with observed flow slide events.<br><br>This study analyzes available meteorological, water level, geotechnical, and historical shoreline data to identify mechanisms affecting repeat coastal flow slide events at Seabrook Island (SC). A combination of excessive rainfall, spring tidal currents, and sediment characteristics all appear to affect these events. Because of the unpredictability of these events, and the dynamic nature of the inlet channel adjacent to this portion of the island, it is difficult to observe events in situ and identify specific mechanisms triggering flow slides. While a hard structural solution is unlikely to effectively mitigate the hazard in this location, providing an excess of beach sand may help maintain a shallower shoreface slope and mitigate future flow slides.</p>

A Comprehensive Estuarine Hydrodynamics-Salinity Study: Impact of Morphologic Changes on Ria de Aveiro (Atlantic Coast of Portugal)

Shallow coastal lagoons driven by tidal processes are extremely dynamic environments prone to continuous natural and anthropogenic pressures. The hydrodynamics of these systems deeply depends on the effect of local morphology on the tidal propagation, so their permanent evolution constantly changes tidal dependent processes. For this reason, the present work aims to review the main characteristics of Ria de Aveiro hydrodynamics, a shallow lagoon located at the Atlantic Coast of Portugal, evaluating its evolution over the last 30 years (between 1987 and 2020) and investigating the main morphological changes in its origin. For this purpose, a comparative analysis is performed to determine the main process, including the observed hydrodynamic changes: Deepening of the inlet channel or of the main lagoon channels. To achieve these goals, the authors explored a remarkable database including bathymetric, tide gauge, and salinity data from 1987 until the present. This analysis is completed by the exploitation of a hydrodynamical model (Delft3D), validated against field data. Several simulations were performed to analyse changes in tidal propagation along the lagoon channels (considering the main semi-diurnal constituent M2), tidal asymmetry, tidal currents, tidal prism, and salinity patterns. The results show that the general deepening of the lagoon observed between 1987 and 2020 led to important changes in the lagoon hydrodynamics, namely the increase/decrease of the M2 constituent amplitude/phase, as well as the increase of tidal currents and salt intrusion within the entire lagoon, with the changes being amplified towards the head of the main channels. Although the inlet deepening partially contributed to the modifications found, the results revealed that the deepening of the main lagoon channels had the most significant contribution to the changes observed during the last 30 years.

MATAGORDA SHIP CHANNEL AND ITS ENTRANCE'S NAVIGATION EFFICIENCY AND SAFETY IMPROVEMENT VIA ADCIRC AND CMS MODEL SIMULATION

The present study investigated alternatives including deepening/widening of Matagorda Ship Channel in the south central coast of Texas to improve navigation safety through entrance inlet channel by using ADCIRC and CMS numerical models. The alternatives modify bayside channel depths from 38 ft to 50 ft, referenced to Mean Lower Low Water (MLLW), and widths from 200 ft to 600 ft, and deepen the entrance channel from 38 ft to 55 ft MLLW and widen the channel from 300 ft to 600 ft. The alternatives include seven new dredged material placement areas along the ship channel. Model results show the proposed ship channel dimensions will slightly increase flow efficiency and current magnitude in Matagorda Bay. Current velocities in and around ship channel tend to increase with alternatives, large river input and future sea level rise in the region. However, the current effect becomes more pronounced during tropical storms.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/YAugdJe9dIw

Influence of Inlet Charge Swirl on Fuel-Economic and Environmental Indicators of a Gas-Piston Engine

The paper introduces the results of studying the influence of intake ports shape on turbulization and charge swirl in the combustion chamber, combustion rate, ecological and indicator values of the engine. The study was carried out using mathematical simulation of physicochemical processes occurring in the combustion chamber of a piston engine during gas fuel combustion. The turbulent flow of the mixture, spark ignition and combustion of gas fuel are simulated. To simulate the turbulent flow, the RNG (k--ε)-model was used, to simulate the combustion of natural gas in the combustion chamber a model based on the specific surface area of the flame, the so-called G-equation model, was used. When simulating spark ignition, the model of discrete particles of the ignition kernel DPIK (Discrete Particle Ignition Kernel) was applied. As a result of simulation, we found that replacing one inlet channel with a tangential channel allows creating a vortex motion and increasing the turbulence of the mixture in the combustion chamber. An increase in the kinetic energy of the mixture before the spark is applied leads to a decrease in the combustion time. The use of swirling the charge on inlet by replacing one filling channel with a tangential one can significantly improve the environmental performance of the engine while maintaining fuel and economic indicators. The ANSYS Forte program was used to simulate the physicochemical processes in the combustion chamber