A new axial velocity defect formulation for a far-field drag decomposition method

2012 ◽  
Vol 58 (02) ◽  
pp. 69-82 ◽  
Author(s):  
M. Gariépy ◽  
J. Y. Trépanier
Keyword(s):  
Axial Velocity ◽  
Decomposition Method ◽  
Far Field ◽  
Velocity Defect

scholarly journals Aerodynamic Design and Shape Optimization with the Far-Field Drag Decomposition Approach

2020 ◽  
Vol 38 (3) ◽  
pp. 558-570
Author(s):  
Li Li ◽  
Junqiang Bai ◽  
Xiaolong He
Keyword(s):  
Shape Optimization ◽  
Axial Velocity ◽  
Decomposition Method ◽  
Far Field ◽  
Aerodynamic Shape Optimization ◽  
Decomposition Approach ◽  
Total Drag ◽  
Velocity Defect ◽  
Aerodynamic Shape ◽  
Drag Prediction

In the aerodynamic shape design, the drag prediction has always been an extremely challenging mission for the exploration of a configuration. As for the more complex configurations, it is especially desired to the availability of a highly accurate and reliable aerodynamic numerical solution. For improving the drag prediction accuracy and promoting the aerodynamic shape designs, firstly, the characteristics of drag prediction based on far-field drag method and near-field drag method is analyzed and compared. Also, the merits and demerits of defining axial velocity defect with the current main far-field drag prediction approaches is summarized, which promotes the building of the improved method of axial velocity defect and the improved far-field drag prediction and decomposition approach. Moreover, during the establishment of the drag decomposition method, it is necessary to judge and decide on the selection of the drag region. Therefore, the discussions on the sensitivity of the relevant parameters are fulfilled. Furthermore, based on the far-field drag prediction and decomposition method constructed, the aerodynamic performance research of Common Research Model wing-body configuration is launched. The results show that it can effectively observe and analyze the changes in drag components, their impact on the total drag and the contribution percentage. Finally, combining the far-field drag prediction and decomposition method proposed in this paper with a gradient-based aerodynamic shape optimization design system, the aerodynamic shape optimization designs are studied with CRM wing-body configuration. The results can not only directly analyze the detailed change of the visualized drag region, but also can obtain the more accurate total drag and lift-to-drag ratio of the optimized configuration by removing the spurious drag.

Far-field drag decomposition using hybrid formulas and vorticity based area sensors

2020 ◽  
pp. 095441002097390
Author(s):  
L Qiao ◽  
XL He ◽  
Y Sun ◽  
JQ Bai ◽  
L Li
Keyword(s):  
Flow Field ◽  
Axial Velocity ◽  
Near Field ◽  
Three Dimensional ◽  
Field Method ◽  
Wave Drag ◽  
Viscous Drag ◽  
Far Field ◽  
Velocity Defect ◽  
Detection Failure

Numerical simulation of flow-field has become an indispensable tool for aerodynamic design. Usually, wall surface integration is a tool used to calculate values of pressure drag and skin friction drag, but the aerodynamic mechanism of drag production is still confusing. In present work, in order to decompose the total drag into viscous drag, wave drag, induced drag, and spurious drag, a far-field drag decomposition (FDD) method is developed. This method depends on axial velocity defect and area sensor functions. The present work proposes three hybrid formulas for velocity defect to tackle the negative square root issue by analyzing the existing axial velocity defect formulas. For dealing with the issue of detection failure for near-wall cells, a novel vorticity based viscous area sensor function is proposed. The new area sensor function is also independent of the turbulence model, which ensures easy application to general simulation methods for flow-field. Three tests cases are there to validate the proposed FDD method. The three dimensional transonic CRM test case shows that the present improvement is crucial for accurate drag decomposition. Excellent agreement between total decomposed drags and results from the near-field method or experimental data further confirms the correctness.

Contributions to the theory of sound production by vortex-airfoil interaction, with application to vortices with finite axial velocity defect

1988 ◽  
Vol 420 (1858) ◽  
pp. 157-182 ◽  
Keyword(s):  
Axial Velocity ◽  
Sound Production ◽  
Field Energy ◽  
Small Scale ◽  
Stream Velocity ◽  
Destructive Interference ◽  
Trailing Edge ◽  
Core Diameter ◽  
Velocity Defect ◽  
The Core

An analysis is made of the sound produced when a field of vorticity is cut by an airfoil in low-Mach-number flow. A general formula is given for the acoustic pressure when the airfoil is rigid and the chord is acoustically compact. This expresses the radiation in terms of an integral over the region occupied by the vorticity; the integrand contains factors describing the influence of the thickness, twist and camber of the airfoil. Explicit analytical results are derived for a rectilinear vortex, having small core diameter and finite axial velocity defect, which is ‘chopped’ by a non-lifting airfoil of large aspect ratio. The acoustic signature generally comprises two components, which are associated with the axial and azimuthal vorticity, the latter being determined by the velocity defect distribution within the core. Sound is generated predominantly when the core is in the neighbourhoods of the leading and trailing edges. The contribution from the trailing edge is usually small, however, because of destructive interference between sound produced by edge-diffraction of near-field energy of the vortex and that produced by vorticity shed into the wake of the airfoil to satisfy the unsteady Kutta condition that the pressure and velocity should be bounded at the edge. When the shed vorticity is assumed to convect at the same mean stream velocity as the impinging vortex, the interference is predicted to be complete, and no trailing edge sound is generated. If the shed vorticity is taken to convect at a reduced, ‘near-wake’ velocity, which might be appropriate for small-scale structures comparable in size to the diameter of the vortex core, a small but non-negligible pressure pulse is radiated from the trailing edge. A tentative comparison with experiment appears to confirm the presence of this trailing-edge pulse.

scholarly journals Development and Application of a New Unsteady Far-Field Drag Decomposition Method

AIAA Journal ◽  
2015 ◽  
Vol 53 (11) ◽  
pp. 3414-3429 ◽  
Author(s):  
Hélène Toubin ◽  
Didier Bailly
Keyword(s):  
Decomposition Method ◽  
Far Field

Far-Field Drag Prediction and Decomposition Method for Unsteady Flows

2011 ◽  
Author(s):  
Martin Gariepy ◽  
Jean-yves Trepanier ◽  
Benoit Malonin ◽  
Christian Masson
Keyword(s):  
Decomposition Method ◽  
Unsteady Flows ◽  
Far Field ◽  
Drag Prediction

Convergence Criterion for a Far-Field Drag Prediction and Decomposition Method

AIAA Journal ◽  
2011 ◽  
Vol 49 (12) ◽  
pp. 2814-2818 ◽  
Author(s):  
Martin Gariépy ◽  
Jean-Yves Trépanier ◽  
Christian Masson
Keyword(s):  
Decomposition Method ◽  
Convergence Criterion ◽  
Far Field ◽  
Drag Prediction

scholarly journals Numerical Solution of Riccati Equations by the Adomian and Asymptotic Decomposition Methods over Extended Domains

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Jafar Biazar ◽  
Mohsen Didgar
Keyword(s):  
Decomposition Method ◽  
Near Field ◽  
Adomian Decomposition Method ◽  
Approximate Solutions ◽  
Riccati Equations ◽  
Decomposition Methods ◽  
Field Approximation ◽  
Far Field ◽  
Asymptotic Decomposition ◽  
Adomian Decomposition

We combine the Adomian decomposition method (ADM) and Adomian’s asymptotic decomposition method (AADM) for solving Riccati equations. We investigate the approximate global solution by matching the near-field approximation derived from the Adomian decomposition method with the far-field approximation derived from Adomian’s asymptotic decomposition method for Riccati equations and in such cases when we do not find any region of overlap between the obtained approximate solutions by the two proposed methods, we connect the two approximations by the Padé approximant of the near-field approximation. We illustrate the efficiency of the technique for several specific examples of the Riccati equation for which the exact solution is known in advance.

Far-Field Drag Decomposition Method Applied to the DPW-5 Test Case Results

2013 ◽  
Author(s):  
Martin Gariepy ◽  
Benoit Malouin ◽  
Jean-Yves Trepanier ◽  
Eric Laurendeau
Keyword(s):  
Decomposition Method ◽  
Test Case ◽  
Far Field
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