Figure:1 Plot of the preasue coefficients on the M6 ONERA wing surface.

This study is an example demonstrating the use of PAB3D to compute three-dimensional, transonic, turbulent flow over the ONERA M6 wing.

Most of the files for this example study are available in the Unix compressed tar file Onera.tar . The files can then be accessed by the commands

This study uses the grid lines from the Plot3d grid file (SGI unformatted, 3D, multi-zone) m6wing.x, which is from the original NPARC validation ONERA M6 Wing example case.

It consists of four zones wrapped as a C-grid about the wing leading edge.

The boundaries at the surface of the wing are specified as no slip wall boundary conditions. The inflow boundary is specified with a constant total pressure, total temperature and flow angle. The farfield boundaries are specified as characteristic boundaries. The outflow boundary is specified as an extrapolation boundary. The boundary conditions are set within the control file tpab3d.cont. Procedure for setting the case, USER can refer to Tutorial.

The initial flow conditions are simply the freestream flow values as presented in Table 2. These corresond to a Reynolds number of 11.72 million based on the mean aerodynamic chord length.

Table 2. Freestream conditions.

These conditions correspond match the Mach number, Reynolds number, and angle-of-attack of test 2308 from the paper by Schmitt and Charpin in AGARD Report AR-138.

The computation is performed using the time-marching with mesh sequencing capabilities of PAB3D to march to a steady-state (time asymptotic) solution. Local time stepping is used at each iteration. The time-marching is performed until a convergence criterion is achieved.

Step 1: Preprocessing of grid file can be done two ways; either by running autog3d program or using graphical user interface (UPMS).

If user prefers to use autog3d, he must change the values in control files as needed by user modeling requirements.

If user prefers UPMS graphical user interface, after completing the all needed steps (Ref: Tutorial), he/she must save the project and export this project. This prompts user to choose the solver from three codes (TLNS3D, PAB3D, CFL3D) available. Once user selects PAB3D and clicks OK, it presents user with interface as shown below

User should enter names of control files. The User filename must be user.cont. User can give name to G3D filename. For this case, we name the file: g3d.cont

Step 2: Run Pre2 to generate the database information and tpab3d.cont control file. This can be done by issuing the following command as shown below

Pre2 g3d.cont

Step 3: Keep all the generated control files and grid file in one subdirectory. Now run PAB3D code by issuing the following command.

On single processor: Pab2

or

On multi processor: mpirun –p4pg hostfile Pab2

hostfile should contain the information about the cluster information. For example, if some one wants to run the code on a cluster machine with machine names e2, e3, e4, user should create a hostfile with the information as shown below.

E.g.: hostfile

Here, executable Pab2 is located in sub-directory bin of hamid home directory.

Step 4: Once results are obtained, output files can be processed by using POST and tecplot. Refer POST tutorial for post processing.

The pressure coefficients at the several sections on the wing are examined and compared to experimental values. Comparisons were made at seven sections: 0.2, 0.44, 0.65, 0.8, 0.9, 0.95, 0.99.

The corresponding experimental profile data for these sections were taken from the file ONERAb114.tec.

The computations are performed on Pentium 3 with 800MHz clock speed and two-processor capability. Convergence of solution can be examined from residual history plots (Fig. 10 and 11).

The design of this web page and the grid for this test case were based on the ONERA M6 Wing validation Study # 1 or the Wind code by John W. Slater of NASA LeRC

Schmitt, V. and F. Charpin, "Pressure Distributions on the ONERA-M6-Wing at Transonic Mach Numbers," Experimental Data Base for Computer Program Assessment. Report of the Fluid Dynamics Panel Working Group 04, AGARD AR 138, May 1979.

John W. Slater, M6 ONERA Wing Study for Wind Validation WWW site.