Aerodynamic aspects of train shapes suitable for Vacuum Tube Train System are investigated in this paper. Three feasible geometries for the vacuum tube train system have been considered and modelled in three dimensions and have been computationally studied using the commercial software Ansys Fluent. Aerodynamic Drag loads on these geometries have been calculated under different tube pressures and speeds of the train, which provide insight on various operating parameters that need to be considered while designing the vacuum tube train system. The present computational research shows that, the suitable vacuum pressure, and different shapes of head and tail of the train have significantly effects the Drag force of the vacuum train in the tunnel. Overall, the elliptical train shape with a height to base ratio of 2: 1 is more efficient for aerodynamic Drag reduction of the vacuum tube train at the vacuum tube pressure of 1013. 25 Pa.

Decreasing pressure losses in microtubes is an important subject, especially when an increase in the flow capacity is required. In the same pumping power, decreasing the pressure drops coincides with increasing the fluid flow rate passing through a microtube. The current study aims to examine how the water pressure drop across a microtube can be affected by the addition of small concentrations of different Drag-reducing polymeric agents. A kind of the laminarization behaviour was found by the addition of the selected polymer to the turbulent flow. The effect of the concentration of the Drag-reducing agent (DRA) on the observed viscosity and Drag values are reported. Moreover, the effects of different types of Drag-reducing agents on the friction factor are obtained at the best concentration in the range of examined concentrations. Under this condition the percentage of the Drag reduction and increase in the capacity of the flow were respectively 33 % and 36 %. The obtained results show that more Drag reduction occurs at a higher flow rate for 20 ppm of the polyacrylamide with a high molecular weight.

Reducing aerodynamic Drag of heavy trucks is crucially important for the reduction of fuel consumption and hence results in less air pollution. One way to reduce the aerodynamic Drag is the deployment of Drag reduction devices at the rear of trucks and this paper describes a numerical study of flow over a bluff body with rear Drag devices using the Reynolds-Averaged-Navier-Stokes (RANS) approach to investigate the Drag reduction mechanisms and also to assess accuracy of the RANS approach for this kind of flow. Four cases, a baseline case without any Drag reduction devices and three cases with different Drag reduction devices, have been studied and the predicted mean and turbulent quantities agree well with the experimental data. Drag reduction varies hugely from a few percent in one case to more than 40% in another case and detailed analysis of flow fields has been carried out to understand such a difference and to elucidate the Drag reduction mechanism, which ultimately can lead to better design of future Drag reduction devices.

In recent years, marine transportation as well as land and air transportation has become in the centre of attention. There has been an attempt to reduce the Drag exerted on vessels by various methods, such as rough surfaces and base bleed. Study of the high-speed seawater animals like sharks and dolphins has triggered the use of riblets on the hull of marine vessels. The use of riblet is easy among various methods of skin friction Drag reduction. For this reason, there is an interest for construction and optimization of riblet as an efficient and economical way. In this research, the shark’ s skin was modeled for the first time in ANSYS CFX using Computational Fluid Dynamics, through analyzing the effects of riblet on a submerged flat plate. Different types of riblet based on height and space between micro channels were studied, and then a comparison between a riblet-covered plate and a smooth plate in various velocities were performed. It was found that by selecting the most appropriate type of riblet, 11 % Drag reduction can be attained. Then, by comparing different types of riblets, the best type for Drag reduction was selected. Furthermore, the obtained results were compared with the available experimental data.