NGC

The NGC project is a continuation of at least one other project sponsored by Northrup Grumman Corporation studying active flow control in ducts with various geometries that tend to induce large adverse pressure gradients and massive separation in the flow. The present project concerns high subsonic flow in a square channel which is subjected to a aggressive diffuser. Flow control is performed with unsteady tangential blowing near the upstream side of the diffuser. The previous project was an aggressive S-duct which used similar tangential blowing to keep the flow attached.

The CFD at CU has been conducted in conjunction with experiments at RPI for several years. In that time, the primary student working on the CFD has changed from Yi Chen to Kyle Woolwine to Nicholas Mati. It is the intent of this page to provide some continuity for future transitions with brief documentation of present work. It is also hoped that maintaining this page will increase communication with Prof. Jansen, and help keep track of simulation cases as they proliferate.

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S-Duct

This page was created after Yi stopped working on the project. For more information, read Yi Chen's thesis.

Diffuser

Series 10

Series 10.3

The only difference between series 10.2 and 10.3 is the splitting of a surface in the blower near the lip into three separate surfaces. This allowed the mesh height on the lower blower wall to be manually cut down near the lip. This fixed an issue from 10.2 where the mesher was not trimming the boundary layer correctly in a refinement box for some reason.

-Interpolating from the 10.1 solution to the M3 mesh, high z-velocity oscillations clipping at +-250 m/s continued in the blower. This solution was abandoned.

-Interpolating from the 11.2 solution to the M3 mesh, the blower started off with nearly zero velocity. Some inflow was initially observed in the blower, but no substantial z-oscillations were observed. However, backflow was present in the 11.2 solution which resulted in temperature clipping high at the bottom of the diffuser with at most 2 orders of magnitude of convergence in the nonlinear residual. Dropping the upper limit from 400 K to 340 K to 320 K resulted in only minor benefit and the solution was abandoned.

-Starting from near zero velocity initial conditions on the M3 mesh broke phasta. There was a version compatibility issue with the smd which resulted in all flow fields being zero. While debugging, the geometry was remeshed.

-Starting from near zero velocity initial conditions on the M4 mesh resulted in similar flow separation and temperature clipping. Elevated viscosity of 10 nu, 100 nu, and 1000 nu was tried in the diffuser, but this resulted in only minor improvement.