NPARC Alliance Validation Archive
Validation Home   >   Archive   >   Annular Duct

Annular Duct

Figure 1 is described in the surrounding text
Figure 1. The flow domain and Mach contours
for a subsonic flow through an annular duct.

Introduction

This check case involves a subsonic, turbulent flow through a straight annular duct with a boundary layer profile specified at the inflow boundary. The case examines the ability to specify the total pressure, total temperature, and local flow angles of a boundary layer at an arbitrary inflow boundary.

Download tar File

All of the files of this validation case are available in the Unix compressed tar file anduct.tar.Z. The files can then be accessed by the commands

uncompress anduct.tar.Z
tar -xvof anduct.tar

Flow Domain and Grid

The flow domain is an annular duct with a hub radius of 2.69 inches and a case radius of 5.083 inches. The duct is 24.0 inches long with inflow at x = 0.0 inches and outflow at x = 24.0 inches.

Two grids are examined as listed in Table 1. Grid A is for an axisymmetric flow analysis, whereas grid B is for a three-dimensional flow analysis. Both use uniform grid spacing in the I (axial) direction and the same grid stretching in the J (radial) direction. Both analyses conider a 10 degree wedge of the duct. Grid B models the geometry of the section and uses 5 uniformly-space grid points (circumferently). Both grid files are in PLOT3D format and are whole, unformatted (SGI), and multi-zone.

Table 1. Annular duct grids.
Grid Grid File Grid Density
A anduct.A.x 49 x 41 x 1
B anduct.B.x 49 x 41 x 5

The CFCNVT utility is used to convert the PLOT3D grid files (3D, multi-zone, whole, unformatted) to the common grid file format (*.cgd) for WIND. This is done using the commands

cfcnvt < cfcnvt.A.x.com
cfcnvt < cfcnvt.B.x.com

Boundary Conditions

Table 1 lists the boundary condition types used for this case.

Table 1. Boundary Conditions.
I1 ARBITRARY INFLOW
IMAX CONFINED OUTFLOW
J1 VISCOUS WALL
JMAX VISCOUS WALL
K1 REFLECTION
KMAX REFLECTION

GMAN is used to set the boundary conditions using the command input files,

gman < gman.A.com
gman < gman.B.com

Flow and Initial Conditions

The primary flow conditions are specified in Table 3.

Table 2. Primary flow conditions.
Mach number Total Pressure (psia) Total Temperature(R) Angle-of-Attack (deg) Angle-of-Sideslip (deg)
0.3 14.0 500.0 0.0 0.0

The flow domain is initialized by WIND using the values from the ijk_range keyword in the arbitraray inflow section of the input data file. Thus, the ijk_range has a range of I1 to I49. This essentially initializes the boundary layer along the hub and case.

Computation Strategy

The computation is performed using the time-marching capabilities of WIND to approach the steady-state flow starting from the initial conditions generated by WIND.

Input Parameters and Files

The input data files for WIND are anduct.A.dat and anduct.B.dat. The freestream keyword indicates that the total freestream flow conditions are specified as Mach number, pressure (psia), temperature (R), angle-of-attack (degrees), and angle-of-sideslip (degrees). The turbulence keyword indicates that the Baldwin-Lomax turbulence model is used. For anduct.A.dat, the axisymmetric keyword indicates that an axisymmetric flow should be modeled assuming a 10 degree segment of the duct. The implicit boundary keyword indicates that implicit boundary conditions are to be used at the viscoud walls. The compressor face keyword indicates that the Boeing model should be used in which the average Mach number at the CONFINED OUTFLOW boundary is specified. The cfl keyword indicates that a CFL number of 5.0 was used for run A, while a CFL number of 2.5 was used for run B. By default, WIND uses local maximum allowable time-step based on the specified CFL number. The arbitrary inflow section defines the conditions on the ARBITRARY INFLOW boundary (I1). The total keyword indicates that pressure and temperatures are total values. The hold_totals keyword indicates that the total temperature and flow angles are to be held fixed along with the total pressure. The ijk_range keyword indicates that grid range for which the specified conditions apply.

Computation

The WIND solver is run by entering

wind -runinplace -dat anduct.A
or
wind -runinplace -dat anduct.B

This runs the wind script which sets up the problem for solver. The runinplace option indicates that WIND is to be run in the current directory. The computation creates output list files named anduct.A.lis and anduct.B.lis.

Convergence

RESPLT reads a output list file and creates a GENPLOT file containing the L2 residual to examine the convergence of the computation,

resplt < resplt.A.nsl2.com
resplt < resplt.B.nsl2.com

The GENPLOT files are named nsl2.A.gen and nsl2.B.gen, respectively. They can be plotted by CFPOST,

cfpost < cfpost.A.nsl2.com
cfpost < cfpost.B.nsl2.com

Figure 2 shows compares the convergence properties of each run.

Figure 2 is described in the surrounding text
Figure 2. The convergence properties of each run.

Post-Processing

CFPOST is used to create the PLOT3D solution files for visualization in FAST,

cfpost < cfpost.A.plot3d.q.com
fast fast.A.com
cfpost < cfpost.B.plot3d.q.com
fast fast.B.com

The PLOT3D solution files are named anduct.A.q and anduct.B.q. They are unformatted, whole, 3D, and multi-zone.

CFPOST can list out the conditions at the inflow boundary to examine whether the total conditions and flow angles were held fixed,

cfpost < cfpost.A.inflow.com
cfpost < cfpost.B.inflow.com

GENPLOT files named inflow.A.gen and inflow.B.gen, respectively, are created and plotted. The GENPLOT file lists the Mach number, total pressure, total temperature, local alpha, local beta, u-velocity, v-velocity, w-velocity, and the total velocity at each grid point on the inflow boundary.

CFPOST can list out the conditions at the outflow boundary,

cfpost < cfpost.A.outflow.com
cfpost < cfpost.B.outflow.com

GENPLOT files named outflow.A.gen and outflow.B.gen, respectively, are created and plotted. The GENPLOT file lists the Mach number, static pressure, static temperature, density, and u-velocity at each grid point on the outflow boundary.

CFPOST can list out the average total pressure recovery and average Mach number at the outflow boundary,

cfpost < cfpost.A.cf.com
cfpost < cfpost.B.cf.com

List files named cf.A.lis and cf.B.lis, respectively, are created.

Results

Upon examing the conditions at the inflow boundary from run A (inflow.A.gen) and B (inflow.B.gen), one can see that the total pressure, total temperature, and local flow angles are held fixed as prescribed.

Contact Information

This case was created on November 10, 1998 by John W. Slater. John Slater may be contacted at:
NASA Glenn Research Center, MS 86-7
21000 Brookpark Road
Cleveland, Ohio 44111
Phone: (216) 433-8513
e-mail: John.W.Slater@grc.nasa.gov

Last Updated: Wednesday, 16-Jul-2008 10:03:53 EDT