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\overrightarrow t - P\overrightarrow n } \right)dA The value of aerodynamic drag force can also be calculated according to the following equation [ 5 ]: F a drag = 1 2 ρ Sc x v 2 {F_{{a_{drag}}}} = {1 \over 2}\rho S{c_x}{v^2} where: ρ – fluid density, S – frontal area, c x – drag coefficient, v – velocity. The transformation of the above equation allows easy determination of the drag coefficient value knowing the rest of the variables. 2 Researched models The research includes comparison of four Eagle Two vehicle concepts. The dimensions of the models are 4.95 m × 1

Abstract

A numerical study is performed to analyze steady state forced convection fluid flow through a confined porous square cylinder. The Darcy-Brinkman-Forchheimer model is adopted for the porous region. The finite volume method and the iterative SIMPLE algorithm are used to solve the governing equations. The results obtained are presented for the streamlines, variation of Nusselt number and drag coefficient for the range of conditions as 5 ≤ Re ≤ 40 and 10−2Da ≤ 10−6.

Abstract

This article presents a two-dimensional steady viscous flow simulation past circular and square cylinders at low Reynolds numbers (based on the diameter) by the finite volume method with a non-orthogonal body-fitted grid. Diffusive fluxes are discretized using central differencing scheme, and for convective fluxes upwind and central differencing schemes are blended using a ‘deferred correction’ approach. A simplified pressure correction equation is derived, and proper under-relaxation factors are used so that computational cost is reduced without adversely affecting the convergence rate. The governing equations are expressed in Cartesian velocity components and solution is carried out using the SIMPLE algorithm for collocated arrangement of variables. The mesh yielding grid-independent solution is then utilized to study, for the very first time, the effect of the Reynolds number on the separation bubble length, separation angle, and drag coefficients for both circular and square cylinders. Finally, functional relationships between the computed quantities and Reynolds number (Re) are proposed up to Re = 40. It is found that circular cylinder separation commences between Re= 6.5-6.6, and the bubble length, separation angle, total drag vary as Re, Re−0.5, Re−0.5 respectively. Extrapolated results obtained from the empirical relations for the circular cylinder show an excellent agreement with established data from the literature. For a square cylinder, the bubble length and total drag are found to vary as Re and Re−0.666, and are greater than these for a circular cylinder at a given Reynolds number. The numerical results substantiate that a square shaped cylinder is more bluff than a circular one.

Abstract

The paper focuses on the verification of the suitability of the SST k - ω model on the flow past a circular cylinder in 2D for a high Reynolds number. The study compares the results of drag and lifts coefficients with respect to different types of meshes and time steps. The mean velocity field in the wake region behind the cylinder is evaluated and compared to experimental data available from literature. The numerical simulations are solved using CFD codes in the ANSYS Fluent software and use the finite volume method.

Abstract

The paper presents application of Particle Image Velocimetry for determination of an airfoil’s drag coefficient in wind tunnel tests. The purpose of the study was to investigate the feasibility of using PIV as an alternative to pressure rake measurements, especially at high angles of attack. The integral momentum concept was applied for determination of fluid drag from experimental low speed wind tunnel data. The drag coefficient was calculated from velocity and pressure rake data for intermediate angles of attack from 5° to 10°. Additionally, the experimental results were compared to panel method results. After validating the procedures at low angles of attack, the drag coefficient was calculated at close to critical angles of attack. The presented study proved that PIV technique can be considered as an attractive alternative for drag coefficient determination of an airfoil.

Abstract

The main purpose of this article was to study flaps application influence on airfoil, which flies in the wing in ground effect with lift, and drag coefficients changes. Wing in ground effect occurs in the direct proximity of ground, it makes lift coefficient higher than in free stream flight, also decreases drag coefficient. WIG effect craft can be an alternative for traditional aircraft, but also for marine transportation. The article presents wing in ground effect creation mechanism description with height coefficient explanation, also presents experimental analysis of lift coefficient with reference to height coefficient. Airfoil with flaps simulation and for free stream flight. Application of flaps makes the wing in ground effect more efficient by lift coefficient rise, what provides also to drag coefficient rise. Flaps provide to absolute pressure rise under the airfoil. It allows to fly slower without lift force change or to make aircraft start shorter without risk of stall. The article shows also conditions and results of Ansys Fluent software simulation for NACA M8 airfoil for angles of attack equal to: 0°, 6°, 10° for three different cases: free stream flight, wing in ground flight with the clear wing, wing in ground flight with flaps, and conditions of analysis convergence.

Abstract

The main purpose of this article was to select airfoil, which generates the biggest lift coefficient, with possibly smallest drag coefficient when the airfoil flies in the wing in ground effect. Wing in ground effect occurs in the direct proximity of ground, the article presents wing in ground effect creation mechanism description with automotive and aerospace examples.

The article shows also wing in ground conditions of Ansys Fluent software simulation for all cases with conditions of analysis convergence. The article contains results of the numerical analysis for ten airfoils in three different positive angles of attack in the wing in ground flight; ten airfoils for free stream flight in the same angles of attack as in wing in ground effect, results contains lift and drag coefficients with NACA M8 airfoil presentation as authors choice for wing in ground effect crafts airfoil with full simulation results for angles of attack from –5° to 15°, with profile characteristics.

The article shows physics of stall in the wing in ground effect, and a description why stall in WIG effect flight occurs only with drag coefficient rise without lift coefficient drop, and safety measures for aircraft landing with wing in ground effect influence.

Abstract

In order to evaluate the impacts of a motor vessel after installing wind sails, the aerodynamics of the sail should be accurately calculated. However most of the research on sails are based on stable wind instead of natural wind which is changing horizontally and vertically. In this paper wind tunnel tests are carried out based on stable wind field and simulated natural wind field, the results shown that there are 16–44% decrease in natural wind in terms of lifting coefficient and 11–42% decrease for drag coefficient. This would provide a valuable reference to the effectiveness evaluation of the impact of sails for sail assisted ships.

Abstract

This paper presents simulation studies on the aerodynamics of vehicles moving in an organized column. The object of research is a column that consist of three vehicles of the same type (homogeneous column). In this research geometry of Ford Transit was used. As a part of the studies, the air drag forces acting on individual vehicles were calculated. The results are presented in dimensionless drag coefficient. The influence of the distance between cars on the generated force was also determined. In the first stage of the work, a numerical model was developed based on the Ahmed body reference structure. The calculations were carried out for 9 different velocities. The obtained results of the drag coefficient were compared with the work of other authors. The applied turbulence model and parameters of the boundary layer were used to create a numerical model of a moving column of vehicles. Mesh independence for numerical model of van was verified. The Finite Volume Method was implemented in the ANSYS Fluent program and used for the calculations. The use of supercomputers was necessary due to the large size of the grid.

Abstract

This paper reports the results of experimental investigations of flow-induced loading on perforated and solid flat plates at zero incidence with respect to the incoming flow. The plates had a streamwise length to transverse thickness ratio of 23.5. The effect of the perforations was investigated for three different perforation diameters. The results corresponding to the perforated plates were compared with the reference case of the solid plate (no perforations) at five inflow velocities. We quantified the effect of the perforations on the unsteady fluid loading on the plate in terms of the variations of the corresponding Strouhal number, the mean drag coefficient and the fluctuating lift coefficient as functions of the Reynolds number and the perforation diameter. The results indicate that the loading was dominated by the dynamics of the wake. In particular, increasing the perforation diameter resulted in a wider wake, corresponding to the increase in mean drag coefficient and the decrease in the Strouhal number. Onset of coupling between the vortex shedding and the transverse oscillations of the plate was manifested as a rapid increase in the fluctuating lift coefficient, as the perforation diameter exceeds the plate thickness.