Numerical Prediction of Interference Drag of Strut-Surface Intersection in Transonic Flow

The numerical evaluation of the interference drag produced by a streamlined strut intersecting a e at wall in transonic e ow is presented. The calculations were performed on unstructured grids using the FUN2D and FUN3D codes and the Spalart ‐Allmaras turbulence model (Spalart, P. R., and Allmaras, S. R.,“ A One-Equation Turbulence Model for Aerodynamic Flows,” AIAA Paper 92-0439, Jan. 1992 ). The grids were generated with AFLR2 and VGRIDns. The impact of the thickness-to-chord ratio of the strut, theReynoldsnumber, and theeffect of the dihedral angle made by the strut with the wall are studied for both inviscid and viscous e ows. To better understand the e ow in the region where the strut and the wall intersect, the e owe eld is analyzed in a detailed fashion for the thicker strut with pressure contours and stream traces. When the thickness-to-chord ratio of the strutisreduced, the e owe eld is disturbed only locally at theintersection of thestrut with thewall. Theinterference drag is calculated as the drag increment of the arrangement compared to an equivalent two-dimensional strut of the same cross section. The results show a rapid increase of the interference drag as the angle of the strut deviates from a position perpendicular to the wall. Separation regions appear for low intersection angles, but the viscosity generally provides a positive effect in alleviating the strength of the shock near the junction and, thus, the drag penalty. This study provides an equation to estimate the interference drag of simpleintersections in transonic e ow.

[1]  P. Roe.  Approximate Riemann Solvers, Parameter Vectors, and Difference Schemes , 1997 .

[2]  F. Pierce,et al.  Interference Drag of a Turbulent Junction Vortex , 1990 .

[3]  V. N. Vatsa,et al.  Transonic Navier-Stokes flow computations over wing-fuselage geometries , 1991 .

[4]  F. Gessner,et al.  Numerical investigation of supersonic annular flow about struts of various thicknesses , 1995 .

[5]  Shahyar Pirzadeh,et al.  Three-dimensional unstructured viscous grids by the advancing-layers method , 1996 .

[6]  Patrick J. Roache,et al.  Verification and Validation in Computational Science and Engineering , 1998 .

[7]  S. Pirzadeh.  Structured background grids for generation of unstructured grids by advancing front method , 1991 .

[8]  R. Kulfan,et al.  Application of hypersonic favorable aerodynamic interference concepts to supersonic aircraft , 1978 .

[9]  T. J. Barber,et al.  An Investigation of Strut-Wall Intersection Losses , 1978 .

[10]  Bernard Grossman,et al.  Multidisciplinary design optimization of a strut-braced wing transonic transport , 2000 .

[11]  C. L. Ladson,et al.  Development of a computer program to obtain ordinates for NACA-6 and 6A-series airfoils , 1974 .

[12]  J. T. Turner,et al.  Secondary loss generation by gas turbine support struts , 1985 .

[13]  S. Hoerner.  Fluid Dynamic Drag: Practical Information on Aerodynamic Drag and Hydrodynamic Resistance , 1965 .

[14]  Neal T. Frink,et al.  Tetrahedral Unstructured Navier-Stokes Method for Turbulent Flows , 1998 .

[15]  Paresh Parikh,et al.  Unstructured grid solutions to a wing/pylon/store configuration , 1994 .

[16]  N. Weatherill,et al.  Unstructured grid generation using iterative point insertion and local reconnection , 1995 .

[17]  Werner Pfenninger,et al.  Design aspects of long range supersonic LFC airplanes with highly swept wings , 1988 .

[18]  Philippe-Andre Tetrault,et al.  Numerical Prediction of the Interference Drag of a Streamlined Strut Intersecting a Surface in Transonic Flow , 2000 .

[19]  P. Spalart.  A One-Equation Turbulence Model for Aerodynamic Flows , 1992 .

[20]  R. Lowrie,et al.  Evaluation of Euler solvers for transonic wing-fuselage geometries , 1991 .

[21]  Ramesh K. Agarwal,et al.  COMPUTATIONAL FLUID DYNAMICS OF WHOLE-BODY AIRCRAFT , 1999 .

[22]  David L. Marcum,et al.  Generation of unstructured grids for viscous flow applications , 1995 .

[23]  Raphael T. Haftka,et al.  Multidisciplinary design optimization of a transonic commercial transport with a strut-braced wing , 1999 .

[24]  W. K. Anderson,et al.  An implicit upwind algorithm for computing turbulent flows on unstructured grids , 1994 .

[25]  L. R. Kubendran,et al.  Interference drag in a simulated wing-fuselage juncture , 1984 .

[26]  W. K. Anderson,et al.  Implicit/Multigrid Algorithms for Incompressible Turbulent Flows on Unstructured Grids , 1995 .

[27]  Bernard Grossman,et al.  Conceptual Design Studies of a Strut-Braced Wing Transonic Transport , 2000 .