I want to mesh a blade passage domain with inlet and outlet regions very close to the blade leading and trailing edges. The mesh lines bend down near the outlet region on the shroud surface. Movin the closest master control point helps a little, but does not solve the above problem.
Why does the topology line in that small region not follow the trend of topology lines of adjacent region?
The topology line "bends" due to the fact that the blade is so close to the outlet, coupled with the node distribution on the inlet/outlet (which the user has no control over) and the smoothing that takes place.
In order to keep the topology lines consistent with the refined mesh visibility - there is an expert parameter that can help (Step 1 below). There are also a few other things you can do to improve the mesh:
1) Right click on Topology and select Edit in the Command Editor. Set the value of the expert parameter "Smoothing Relaxation on Boundary" to 0.05 and the fine mesh lines will match the topology lines much more closely.
2) In the command editor there are two other parameters "First Block Offset From Blade To Inlet Surface" and "First Block Offset From Blade To Outlet Surface". Change their values to 0.05 - this will bunch the nodes closer to the blade than the inlet and outlet and help with those angles.
3) You can try moving the control points on the periodic boundaries further away from the inlet or outlet to make the aspect ratio of those elements a bit better.
4) Move the trailing edge control point on the low theta side of the blade further away from the trailing edge. This will help out a bit as well.
5) In TurboGrid 10.0, the user also can control the number of nodes in a given block. You can right click on an edge and select "Insert Edge Split Control". Increase the split factor to increase the number of nodes in the blocks. If you do this on the edges just upstream and downstream of the trailing edge, a reasonable mesh refinement in the trailing edge region can be obtained. The only problem here is that you will also be generating elements with poor aspect ratios closer to the periodic boundaries, but this is one of the tradeoffs.
Probably the first suggestion will be sufficient, but the others may also help out.
Also, as a suggestion, remember to freeze the topology once you select your method and are happy with it. It's good practice to do this so that when you start moving control points, etc. the topology isn't compromised.