Roughness Effect on the Flow Past Axisymmetric Bodies at High Incidence

Jiménez‐Varona, José; Liaño, Gabriel; Castillo, José L.; García‐Ybarra, P.L.

doi:10.3390/aerospace9110668

Cited by 3 publications

(1 citation statement)

References 21 publications

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“…The results of the different grids-ranging in angle of attack-compared well with the experimental data ( [6,14,18]). These comparisons and the conclusions about the influence of the grid in capturing both global instability and convective instability are shown in another paper by the authors [19].…”

Section: Influence Of Roughness: Structured Vs Unstructured Gridsmentioning

confidence: 57%

Fineness Ratio Effects on the Flow Past an Axisymmetric Body at High Incidence

Jiménez‐Varona

Liaño

2023

Aerospace

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The flow past an axisymmetric body at a sufficiently high angle of attack becomes asymmetric and unsteady. Several authors identified three different flow regions for bodies of large fineness ratio at low subsonic flow and high incidence: a steady region in the forebody and two unsteady regions in the rear body. Unsteady Reynolds Averaged Navier–Stokes (URANS) codes with eddy viscosity turbulence models or Reynolds stress turbulence models fail to capture the unsteady flow region. These methods are overly dissipative and resolve only frequencies far lower than turbulent fluctuations. Scale-Adaptive-Simulation (SAS) provides an alternative method to afford the problem of these massively separated flows at high Reynolds numbers without addressing the problem to Large Eddy Simulation (LES). This paper applies SAS to study the effect of slenderness on the flow. The numerical solutions show that the flow becomes more unstable as the fineness ratio increases, and the three flow regions are clearly recognizable. For low fineness ratios, only one of the two unsteady regions is visible. The good agreement between the sectional forces and pressure coefficients with their corresponding experimental data for an ogive-cylinder configuration allows an analysis of the flow structure with a fair degree of confidence.

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Section: Influence Of Roughness: Structured Vs Unstructured Gridsmentioning

confidence: 57%

Fineness Ratio Effects on the Flow Past an Axisymmetric Body at High Incidence

Jiménez‐Varona

Liaño

2023

Aerospace

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Numerical Analysis of the Magnus Effect on the Forces Past an Axisymmetric Body at High Incidence

Jiménez‐Varona

2023

Aerospace

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Rolling motion is the motion where a body flies at a constant pitch angle α with respect to the freestream velocity vector, while undergoing a constant angular rotation p about its longitudinal axis. An effect of this motion is the appearance of a Magnus force and moment, which add to the static forces and moments. One problem that arises at high angles of attack is that the flow is not symmetric in these conditions, leading to a non-zero side force at a zero spin rate. Additionally, the roughness induces a roll angle effect on the side and normal forces, and therefore on the moments. Then, at low roll rates, the prediction is difficult to assess due to the complex interactions due to the moving walls, roughness and shedding vortices that appear at the leeside. Computational fluid dynamics (CFD) is an appropriate tool for investigating these non-linear effects, particularly at high angles of attack. It can help provide a more accurate model of the forces and moments and provide insight into the complex flow field. It is necessary to use high-level turbulence models, transient calculations and fine grids in order to capture the flow field and obtain accurate forces, moments and their derivatives. The calculations have shown that the flow is not symmetrical with the roll rate. There are differences depending on the sign of the spin velocity. The Magnus forces are difficult to determine from the total forces, as there are significant non-linear effects.

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Roughness Effect on the Flow Past Axisymmetric Bodies at High Incidence

et al. 2022

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The flow at low Mach numbers and high angles of attack over axisymmetric configurations is not symmetric. The mechanism that triggers the asymmetry is a combination of a global (temporal) instability and a convective (spatial) instability. This latter instability is caused by roughness and other geometrical imperfections, which lead to roll angle dependent forces. The flow at these conditions has a complex vortex sheet structure, with two or three different flow regions. An accurate simulation by means of Computational Flow Dynamics (CFD) is thus very challenging, and many researchers have therefore employed Large Eddy Simulation (LES) codes. This study demonstrates that Unsteady Reynolds Averaged Navier-Stokes (URANS) methods are a suitable alternative, if Scale Adaptive Simulation (SAS) is used. This method is capable of capturing the main flow features, provided that fine meshes, which achieve geometrical similarity between the meshed geometry and the real object, and small-time steps are used. It is also demonstrated that, by using URANS methods in combination with SAS, strong differences in the global and local forces depending on the surface roughness of the model are obtained, a result which coincides with several wind tunnel tests.

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Roughness Effect on the Flow Past Axisymmetric Bodies at High Incidence

Cited by 3 publications

References 21 publications

Fineness Ratio Effects on the Flow Past an Axisymmetric Body at High Incidence

Fineness Ratio Effects on the Flow Past an Axisymmetric Body at High Incidence

Numerical Analysis of the Magnus Effect on the Forces Past an Axisymmetric Body at High Incidence

Roughness Effect on the Flow Past Axisymmetric Bodies at High Incidence

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