Figure 1. The flow domain and Mach contours
for a subsonic flow through an annular duct.
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.
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
tar -xvof anduct.tar
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.
|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
Table 1 lists the boundary condition types used for this case.
GMAN is used to set the boundary conditions using the command input files,
gman < gman.A.com
gman < gman.B.com
The primary flow conditions are specified in Table 3.
|Mach number||Total Pressure (psia)||Total Temperature(R)||Angle-of-Attack (deg)||Angle-of-Sideslip (deg)|
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.
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.
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.
The WIND solver is run by entering
wind -runinplace -dat anduct.Aor
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.
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. The convergence properties of each run.
CFPOST is used to create the PLOT3D solution files for visualization in FAST,
cfpost < cfpost.A.plot3d.q.com
cfpost < cfpost.B.plot3d.q.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.
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.
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