Numerical Simulation of Sediment Movement and Deposition in a Meandering Channel

In this research work, predictions have been made for the transport and deposition of incoming sediments in an open channel. Attempt has been made to understand the behavior of sediments flowing in the channel. The geometry consisted of a meandering compound channel with a constant inflow of sediments. For this purpose, 3D version of CFD (Computational Fluid Dynamics) code FLUENT has been used as a research tool. The turbulence closure of Reynolds Averaged Navior-Stokes equation was performed with standard - turbulence model. The Lagrangian particle tracking technique available in the code has been used for modeling sediment movement and deposition. For this purpose, nine different ranges of the particle diameters were released at the inlet of the channel. Initially, the model was validated using point velocities in the downstream direction and discharge values at five cross sections along the meander wavelength. The channel used for simulation purposes had a rectangular section. Once the model validated, it was then used for simulation of sediments. The numerical modeling gave a detailed picture of sediment deposited and transported through the channel. As the model was used with - turbulence model and Lagrangian particle tracking technique and then validated, it showed that when this combination of particle tracking and turbulence closure option will be used, the prediction will be fairly good and trustworthy. A number of numerical experiments were conducted to get the impact of sediment inflow velocity and its diameter on deposition patterns. It showed that boundary shearing stresses and secondary flows had considerable impact on sediment deposition in a river bend. The current study revealed that CFD technique can be used for predicting sediment distribution patterns with reasonable confidence. Such prediction techniques are not only economical but also provide details of complex flow and sediment movement behavior which are difficult to get through experimentation. The results predicted can be utilized in handling the deposition and erosion of the sediments in the meandering channels and design of natural and man-made meandering channels can be improved. It will also be helpful in designing proper flushing arrangements of deposited sediments

Frictional performance of chemically modified cottonseed-based fossil-free biolubricant oil in a sliding tribopair

In this study, the tribological properties of a green lubricant synthesized from cottonseed oil through a two-step transesterification process are investigated, with a specific focus on the maximum throughput of the second step that involves the reaction of cottonseed methyl ester with 2-ethyl-1-hexanol alcohol and a titanium isopropoxide (TIS) catalyst. The research centers on evaluating the physiochemical characteristics of this biolubricant and comparing them with those of commercial oil (5W30) and the ISO VG40 standard. Furthermore, the influence of crucial process variables, such as temperature, pressure, reaction time, and TIS catalyst concentration, is examined by analyzing variance in experimental data. Fourier transform infrared (FTIR) analysis is employed to identify functional groups, particularly emphasizing the impact of temperature and reaction time. By optimizing the second transesterification process under specific conditions (pressure = 19.42 mmHg, temperature = 175°C, catalyst concentration = 0.63%, and reaction time = 4.0 h), a cottonseed oil-based biolubricant is successfully produced, exhibiting properties comparable to those of commercial mineral lubricants. Notably, the findings reveal significant enhancements in the coefficient of friction (CoF) with a 49% reduction and wear resistance with a maximum 19% reduction. This study contributes valuable insights into optimizing biolubricant production derived from cottonseed oil through two-step transesterification, emphasizing its novel potential in improving frictional and wear characteristics.  Validerad;2023;Nivå 2;2023-10-25 (johcin);CC BY 4.0 License</p