Computational model is developed to analyze aerodynamic loads and flow characteristics for an automobile, when the rear wing is placed above the trunk of the vehicle. The focus is on effects of the rear wing height that is investigated in four different positions. The relative wind incidence angle of the rear wing is equal in all configurations. Hence, the discrepancies in the results are only due to an influence of the rear wing position. Computations are performed by using the Reynolds-averaged Navier-Stokes equations along with the standard k-ε turbulence model and standard wall functions assuming the steady viscous fluid flow. While the lift force is positive (upforce) for the automobile without the rear wing, negative lift force (downforce) is obtained for all configurations with the rear wing in place. At the same time, the rear wing increases the automobile drag that is not favorable with respect to the automobile fuel consumption. However, this drawback is not that significant, as the rear wing considerably benefits the automobile traction and stability. An optimal automobile downforce-to-drag ratio is obtained for the rear wing placed at 39 % of the height between the upper surface of the automobile trunk and the automobile roof. Two characteristic large vortices develop in the automobile wake in configuration without the rear wing. They vanish with the rear wing placed close to the trunk, while they gradually restore with an increase in the wing mounting height.

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The current fixed-point calibration practice relies on furnaces that provide best achievable uniform temperature distribution, limiting the temperature gradients to about 10 mK to 20 mK along the ingot length. This paper outlines a numerical study conducted to further reveal the influences of the temperature gradients on the physical process involved and to bring some estimates for their influence on the plateau behavior. The mathematical model of the physical process is presented, along with the numerical models used through the FLUENT software package: the transient conductive heat transfer model, the discrete ordinates radiative heat transfer model, and the solidification model. The final model is reduced to axial symmetry for the sake of feasibility with the available computational resources. The convective heat transfer is neglected as it was considered to be of minor importance for the process itself. The geometrical model covers the entire fixed-point cell assembly and distinguishes each of its elements. The paper presents six cases, varying the temperature gradients in the boundary conditions and the cold-rodding. Their influence on the physical process is explained through the temperature fields presented. The study shows that a gradient of ±1 K · m −1 influences the plateau solely in its duration by either prolonging or shortening it by approximately 20 min.

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For the purpose of optimization of the whole arterial tree, a fast method for solving of one-dimensional model of blood flow is required. A semi-analytic transmission line method for solving a linearized one-dimensional model of blood flow in an arterial tree with viscoelastic walls is proposed. The transmission line method that solves the linearized model in the frequency domain and the method of characteristics that solves either linearized or non-linear one-dimensional models in the time domain are compared regarding accuracy and computational time. For this purpose, the benchmark problem of a 37-artery network with available experimental data is used. In the case of the linearized model, the results from the transmission line method and the method of characteristics are practically the same. The difference between the transmission line method solution of the linearized model and the method of characteristics solution of the non-linear model is much smaller than the error of either method of characteristics or transmission line method numerical solutions with respect to the experimental data. For typical applications, the transmission line method is at least two orders of magnitude faster than the method of characteristics.