Papers by Keyword: Flow Velocity

Abstract: Floating Vegetation Islands (FVIs) are commonly found on the shallow surfaces of open channels, such as rivers and canals. These FVIs can significantly alter the flow characteristics, causing changes in flow velocity and turbulence around the canopy zone. This research employs Computational Fluid Dynamics (CFD) modeling to investigate the impact of FVIs on flow velocity in an open channel. The numerical simulations were conducted using ANSYS-FLUENT software, utilizing the Reynolds Stress Model (RSM). Three patches of FVIs with a density of 2.0583/cm² were considered in the simulations. The findings demonstrate a substantial reduction in flow velocity, up to 100%, within the vegetation zone, while a velocity increase of 285% was observed in the free adjacent zone. A shedding behavior with large and turbulent wake structures was observed behind the floating patches, whereas a significant difference in the velocity magnitudes between the upper canopy part and the lower free part (water column) was observed. This study highlights the significant influence of FVIs on flow dynamics in open channels.

Abstract: Bridge Scour is the localized loss of the geomaterials around the foundation of a bridge as a result of the movement of water around it. Scour is a great risk to the stability of a bridge’s foundation, thus leading to collapse, loss of lives and setback in a nation’s socio-economic life. Artificial Neural Networks (ANN) are collections of simple, highly connected processing elements that learn according to sets of input parameters and use that to simulate the networks of nerve cells of humans or animal central nervous system. The Asa Dam Bridge, one of the longest bridges in Ilorin, Kwara State, Nigeria, has five (5) spans of 20m each. The bridge connects Ilorin to the Ogbomosho Express way (leading to the western part of the country) and the Eyenkorin-Jebba road (leading to the north). Thus, the bridge has a high economic value. In this research, factors such as flow depth, average flow velocity of the river and median sediment size were investigated to show how they affect the depth of scour around the bridge pile foundation. Data were taken for a period of 48 weeks and ANN was applied to predict and generate a model that shows how these factors relate to the scour depth of the riverbed. The model revealed that the hydraulic parameters and soil grading around the pile cap of Asa River Bridge bears significant influence on the scour depth of its foundation. The model was compared with five (5) other established scour equations.

Abstract: To ascertain the influence of gases temperature on the viscosity and flow velocity of melt in the gas-assisted extrusion forming of plastic micro-tube, the three phase fluid geometric model was established and the finite element numerical simulation method was used in this paper. In the simulations, four different assisted-gases temperatures were imposed on the inlet boundaries of inner and outer assisted gas layers. Under a certain inlet volume flow rate of melt and assisted gases, as well as the thermal boundaries conditions, the numerical results about the effect of gases temperature on the viscosity and flow velocity of melt for the gas-assisted extrusion forming of the plastic micro-tube were obtained. Results show that with the increase of gases temperature, the viscosity distribution of melt in the radial direction of die channel decreases. However, at the axial direction of die channel, when the gases temperature is less than that of the melt, the viscosity of melt increases first and then decreases finally increases outside of die. When the gases temperature is larger than that of melt, the viscosity of melt decreases first and then increases finally increases outside of die. In addition, the flow velocity of melt increases with the gases temperature.

Abstract: The influence of flow velocity on the protectiveness of calcareous deposits which formed by cathodic protection in seawater was studied. The deposition process and the protectiveness of calcareous deposits were investigated by electrochemical impedance spectrum (EIS) and linear polarization resistance technique (LPR). The EIS results showed that the capacitive loops sizes decreased with increasing flow velocities, indicating that calcareous deposits formed at higher flow velocities provided poorer protectiveness. An exponential decrease of protectiveness with increasing flow velocities was observed, which was quantified by LPR. The results of SEM and XRD showed that aragonite of calcium carbonate deposited at lower flow velocities but magnesium hydroxide deposited at higher velocities.

Abstract: The purpose of this research is to investigate the corrosion rate of low carbon steel in saline environment. The influence of variety of conditions that represent the actual conditions in practice such as the flow velocity and solution composition, particularly Na+, Cl^- and SO₄^-2, content were performed. Weight loss test of low carbon steel in the lab was conducted to determine the corrosion rate data in stagnant and flowing seawater for comparison to investigate the effect of flow velocity of sea water on the corrosion behavior of the low carbon steel. Results show that the corrosion rate of low carbon steel is increased by increasing the flow of seawater, but at very high velocities the corrosion rate was recorded to be decreased. XRD results show that the corrosion products contain both Fe₂O₃ and FeO(OH).

Abstract: Bubble of which diameter ranges 50μm to nanometer-order is called micro-nanobubble (here in after “MNB”), it has properties different from the millimeter-order and centimeter-order naturally generated. In general, the bubble rises rapidly in water and burst at the surface. However, the MNB tends to stay in the water as the diameter of itself becomes small. In addition, MNB has various characteristics unlike general water. A typical characteristic includes water purification effect, and is utilized such as water treatment, agricultural industry and chemical industry. However, there is not much report that was utilized in the construction sector so far. In this study, it paid attention to the feature of MNB that the resistance when flowing in the tube decreases, and the possibility of the workability improvement of the grout material and the filling material by the use of MNB was investigated by the experiment of the cement paste. As the results, when it compared properties of the paste that used both MNB and tap water, no difference was observed in the air content and the flow value. However, plastic viscosity of the paste that used MNB was smaller than control paste. In consequence it was confirmed that the flow speed of the paste when it flows in the pipe was improved. On the other hand there is no difference in the compressive strength.

Abstract: The article investigates the counter-vortex flow, one of the most complex spatial nonuniform liquid and gas flows. Counter-vortex phenomenon implies an interaction of two or more wake coaxial circular-longitudinal lines twisted in opposite directions. The relevance of the research issue has determined the desirability of further research and application of unique hydraulic devices in the new situation based on the effect of the interaction of coaxial oppositely swirling flows of water in a circular pipe.

Abstract: The paper using electrical capacitance tomography to test the flow velocity and flow rate of the mud transporting in the dredging.The testing process based on two 12 electrodes capacitive sensor sets (ie,the upstream and downstream sensors).The computer can gather the capacitance signals from the upstream and downstream sensor,then by the method of cross-correlation method it can calculate the flow velocity and flow rate of the mud in the slurry pipelines.In oader to verify the measurement error,the system measure the flow velocity and flow rate of the mud in the same situation at the different time (including five different time).Comparing the results of related calculations and the actual measurement it can prove that the cross-relation method is feasible and reliable,the tesing result have high accuracy.

Abstract: We studied the effects of flushing on water quality and biofilm biomass in different daily flow patterns of distribution system. After building up steady biofilm layers in two flow velocity (0.25 m/s and 0.65 m/s) distribution systems consisting of PE pipe, then flushed by stepwise increased flow velocity. An increase flow velocity caused an immediate increase in turbidity and heterotrophic bacteria of water as a result of detachment of biofilms in the pipes, especially in low flow patterns distribution system. Three days later after flushing, water quality of two systems were generally lower and more stable than before flushing. Flushing strategies only limited biofilm growth to a certain extent and did not completely eliminate microorganisms from the systems.The low flow velocity distribution system was easily being disturbed by flushing.

Abstract: We have developed new type semi-solid injection process for magnesium alloy. This process does not require to use any cover gases and the special magnesium billet such as thixo-billet. In this study, plate specimens were produced by injecting the semi-solid billet with different fraction solid. The microstructure observation, detection of casting defects by an X-ray computed tomography scanner, and tensile test were carried out. With increasing fraction solid, the size and shape of α-Mg solid particles became smaller and more spherical. In the condition of low fraction solid or forming in liquid state, the casting defects were located in the center of the specimen at the thickness direction. Additionally, the volume fraction of the casting defect decreased with increasing fraction solid. Moreover, the casting defects can be reduced by preventing solidifying and clogging of the top of the nozzle. Then, the specimen which has few casting defects could be obtained by injecting the slurry of fraction solid 0.5. However, the tensile strength and yield strength were highest in fraction solid 0.4. It is contemplated that the composition of the solid solution component element in the matrix was increased in fraction solid of 50%, therefore the matrix became brittle.