Computational Fluid Dynamics Drag Prediction

Computational Fluid Dynamics Drag Prediction
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Total Pages: 30
Release: 2018-08-16
Genre:
ISBN: 9781725583115

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Results from the Viscous Transonic Airfoil Workshop are compared with each other and with experimental data. Test cases used include attached and separated transonic flows for the NACA 0012 airfoil. A total of 23 sets of numerical results from 15 different author groups are included. The numerical method used vary widely and include: 16 Navier-Stokes methods, 2 Euler boundary layer methods, and 5 potential boundary layer methods. The results indicate a high degree of sophistication among the numerical methods with generally good agreement between the various computed and experimental results for attached or moderately separated cases. The agreement for cases with larger separation is only fair and suggests additional work is required in this area. Holst, Terry L. Ames Research Center NASA-TM-100095, A-88142, NAS 1.15:100095 ...

Transonic Drag Prediction Using an Unstructured Multigrid Solver

Transonic Drag Prediction Using an Unstructured Multigrid Solver
Author: Dimitri J. Mavriplis
Publisher:
Total Pages: 22
Release: 2002
Genre: Aerodynamics, Transonic
ISBN:

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This paper summarizes the results obtained with the NSU3D unstructured multigrid solver for the AIAA Drag Prediction Workshop held in Anaheim, CA, June 2001. The test case for the workshop consists of a wing-body configuration at transonic flow conditions. Flow analyses for a complete test matrix of lift coefficient values and Mach numbers at a constant Reynolds number are performed, thus producing a set of drag polars and drag rise curves which are compared with experimental data. Results were obtained independently by both authors using an identical baseline grid, and different refined grids. Most cases were run in parallel on commodity cluster-type machines while the largest cases were run on an SGI Origin machine using 128 processors. The objective of this paper is to study the accuracy of the subject unstructured grid solver for predicting drag in the transonic cruise regime, to assess the efficiency of the method in terms of convergence, cpu time and memory, and to determine the effects of grid resolution on this predictive ability and its computational efficiency. A good predictive ability is demonstrated over a wide range of conditions, although accuracy was found to degrade for cases at higher Mach numbers and lift values where increasing amounts of flow separation occur. The ability to rapidly compute large numbers of cases at varying flow conditions using an unstructured solver on inexpensive clusters of commodity computers is also demonstrated.

An Investigation of the Transonic Viscous Drag Coefficient for Axi-symmetric Bodies

An Investigation of the Transonic Viscous Drag Coefficient for Axi-symmetric Bodies
Author: Yue Sang Fan
Publisher:
Total Pages: 0
Release: 1995
Genre:
ISBN:

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Viscous drag in the transonic regime over an axi-symmetric body with a unique aft contour surface is investigated. The forebody is composed of an arbitrary ellipsoid. The unique aft contour surface has been obtained by an exact solution of the small perturbation transonic equation, using guidelines and tools developed at the Naval Postgraduate School. This unique contour allows the delay of shock formation in the aft portion, hence delaying the onset of wave drag which results in a reduction of the overall transonic pressure drag on the body. The drag coefficient thus computed is compared with another axisymmetric body with the same ellipsoid forebody but a simple boat-tailed conical afterbody. Computational Fluid Dynamics (CFD) has been used to compute the viscous flow over the two bodies at zero incidence using a Navier-Stokes flow-solver. Results obtained confirm the advantage of the special shaped afterbody over the conical afterbody by showing the delayed formation of shock waves at the aft portion in transonic flow, consequently achieving a lower maximum drag coefficient of approximately 5.5%. These results can be used in the design low pressure-drag surfaces for shapes such as missiles, projectiles, aircraft external ferry tanks and aircraft engine nacelles for improved performance within the transonic flight regime.

NASA Tech Briefs

NASA Tech Briefs
Author:
Publisher:
Total Pages: 466
Release: 1990
Genre: Technology
ISBN:

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An Investigation of the Transonic Viscous Drag Coefficient for Axi-symmetric Bodies

An Investigation of the Transonic Viscous Drag Coefficient for Axi-symmetric Bodies
Author: Yue Sang Fan
Publisher:
Total Pages: 53
Release: 1995
Genre:
ISBN:

Download An Investigation of the Transonic Viscous Drag Coefficient for Axi-symmetric Bodies Book in PDF, Epub and Kindle

Viscous drag in the transonic regime over an axi-symmetric body with a unique aft contour surface is investigated. The forebody is composed of an arbitrary ellipsoid. The unique aft contour surface has been obtained by an exact solution of the small perturbation transonic equation, using guidelines and tools developed at the Naval Postgraduate School. This unique contour allows the delay of shock formation in the aft portion, hence delaying the onset of wave drag which results in a reduction of the overall transonic pressure drag on the body. The drag coefficient thus computed is compared with another axisymmetric body with the same ellipsoid forebody but a simple boat-tailed conical afterbody. Computational Fluid Dynamics (CFD) has been used to compute the viscous flow over the two bodies at zero incidence using a Navier-Stokes flow-solver. Results obtained confirm the advantage of the special shaped afterbody over the conical afterbody by showing the delayed formation of shock waves at the aft portion in transonic flow, consequently achieving a lower maximum drag coefficient of approximately 5.5%. These results can be used in the design low pressure-drag surfaces for shapes such as missiles, projectiles, aircraft external ferry tanks and aircraft engine nacelles for improved performance within the transonic flight regime.