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Investigation of responses of a modular manoeuvring mathematical model to parameters variations
Published in C. Guedes Soares, T.A. Santos, Trends in Maritime Technology and Engineering Volume 1, 2022
The sidewash velocity inside the slipstream is vRPE=kdeflvRE, where kdefl is the factor accounting for the slipstream lateral deflection
Electric Aircraft Propeller Design
Published in Ranjan Vepa, Electric Aircraft Dynamics, 2020
Extending the non-linear actuator disk theory of Conway [7,8], Bontempo and Manna [9] have obtained the exact solution of the flow around a ducted actuator disk. Based on the earlier model of Bontempo and Manna [9], Bontempo [10] and Bontempo et al. [11,12] have presented an extension of the actuator disc theory of propellers to ducted rotors. The method simultaneously accounts for the proper shape of the slipstream, the rotation of the wake, a variable radial distribution of the load and ducts of general shape. Bontempo et al. [11] present a generalized semi-analytical actuator disk model as applied to the analysis of the flow around ducted propellers in different operating conditions. They have shown that power and thrust coefficients for a ducted propeller have two contributions: one from the actuator disc representing the propeller, and the second from the duct. When properly optimized the two add up to maximize the performance of the ducted propeller, and the duct functions as an accelerating duct. Bontempo and Manna [13] have found that an optimized duct with augmentation of both the camber and thickness of the duct leads to an increase in the ideal propulsive efficiency of the ducted propeller.
Interaction of an expansion wave with a shock wave and a shock wave curvature
Published in George Emanuel, Analytical Fluid Dynamics, 2017
The 2-5-7-12 and 6-11 streamlines separate regions of different rotationality and, thus, are C0 characteristics. Another possibility is that these boundaries are actually slipstreams. It is essential for the subsequent MOC discussion to resolve this question. Slipstreams normally start at a triple point, where three shock waves intersect. The magnitude of the velocity is then different on the two sides of a slipstream. For this to be the case, the strength of the shock at points 2 and 6 would have to change discontinuously All primary variables, however, change continuously in the Prandtl-Meyer expansion. In turn, this means the strength of the shock is continuous. In short, the bounding streamlines are not slipstreams, and β is a continuous function of s, including at points 2 and 6.
Effect of bogie fairings on the flow behaviours and aerodynamic performance of a high-speed train
Published in Vehicle System Dynamics, 2020
Jiabin Wang, Guangjun Gao, Xiaobai Li, Xifeng Liang, Jie Zhang
In the present study, the IDDES with Shear-Stress Transport (SST) k–ω turbulence model was used to evaluate the effects of the bogie fairing configurations on the unsteady aerodynamic performance of the HST. As a typical hybrid turbulence model of Reynolds-Averaged Navier–Stokes simulations (RANS) and Large Eddy Simulation (LES), the IDDES applies RANS to simulate the boundary layer and utilizes the LES to capture the large-scale turbulent flow away from near walls. An improved delayed shielding function is used to obtain the accurate numerical results within the RANS-LES blending region. Additionally, due to the great advantage on modelling the near-wall boundary-layer regions, the SST k–ω model is adopted in the RANS part. A more detailed description of the IDDES turbulence model has been given by Spalart [20]. The IDDES technique has been applied successfully in engineering application concerning the train aerodynamics, such as the drag assessment [10,21], slipstream prediction [12,13], underbody flow as well as the wake flow [22,23].
Comparison of different configurations of aerodynamic braking plate on the flow around a high-speed train
Published in Engineering Applications of Computational Fluid Mechanics, 2020
Jiqiang Niu, Yueming Wang, Dan Wu, Feng Liu
For the convenience of comparison and analysis in this study, the aerodynamic drag (Fd), aerodynamic lift force (Fl), pressure (p), and slipstream velocity (u) were nondimensionalised via the following: where Um is the velocity of the incoming flow of 60 m/s. Str is the cross-sectional area of the uniform train body of 0.175 m2 for a 1: 8 scaled model. Cd and Cl are the drag coefficient and lift force coefficient, respectively. Cp and Cu are pressure coefficient and slipstream velocity ratio, respectively. p0 is the reference pressure at infinity of 0 Pa.
Numerical investigation on the crosswind effects on a train running on a bridge
Published in Engineering Applications of Computational Fluid Mechanics, 2020
Simin Zou, Xuhui He, Hanfeng Wang
With the continuous raising of train speed, slipstream becomes a more and more crucial aerodynamic issue. Recently, four different techniques were used for studying the slipstream, e.g. full-scale field test (2014a, 2014b; Baker, 1991), moving model test (Baker et al., 2001; 2015), wind tunnel test (Bell et al., 2014; Xia et al., 2018) and CFD simulation (Wang et al., 2017; Xia et al., 2016, 2017). The investigations have revealed the connection between the vortex motion and the slipstream in the wake of an HST. However, the lateral load on the wind barrier induced by the slipstream has not been widely studied yet.