[Kummi]

Hello everyone,

I am currently working with my gas turbine combustor model. I need some suggestions for meshing the current model. I am hereby going to explain, what I have tried until now.
1) To do an internal mesh using snappyHexMesh, I created a box around my actual geometry. (Fig. 1. Computational domain inside the box)
2) Then, based on fixing appropriate coordinates in locationInMesh, I could able to create an internal mesh (Fig. 2. Internal mesh in the combustor). The mesh is not fine in center of combustor regime with still little distortion in domain shape.
3) One of my friends recommend me to use STAR CCM+ for good mesh with quick adaptability that saves time (Fig. 3. Mesh in STAR CCM+). However, I prefer using snappyHexMesh or any other open-source tools in order to understand the art of meshing. I would like to learn things perfectly, even though it can take a while at times.


I would like to know the following:
1) May I ask if the above steps I am following step-by-step are correct? I need to play with as many parameters that are present in snappyHexMeshDict file to get my expected mesh.
2) Can someone suggest me snappyHexMesh learning tutorials ?
3) Or should I need to adopt other opensource tools like GMSH (or) Salome ?
Thank you
Kindly correct me and give some valuable suggestions.

[Kummi]

I played with snappyHexMesh parameters and got a reasonable mesh.

castellatedMesh true;
snap true;
addLayers false; // no need to add layers in the present problem

geometry
{
Combustor_15thApril.stl
{
type closedTriSurfaceMesh; //closedTriSurfaceMesh;
name Combustor;
}
cylinder_cone_and_swirler
{
type searchableCylinder;
point1 (0 0 50);
point2 (0 0 85);
radius 12.85;
}
cylinder_fuel_injection
{
type searchableCylinder;
point1 (0 0 65); //(-1.5 -1.5 65)
point2 (0 0 90); //(1.5 1.5 90);
radius 2; //1.5; 1.375; //0.5; //0.89
}
box_combustor
{
type searchableBox;
min (-25 -25 85); //(-20 -35 85); //(-35 -35 85);//(-15 0 90);
max (25 25 120); //(20 35 110); //(35 35 120); //(15 0 110);
}
};

castellatedMeshControls
{
castellatedMesh true;
snap true;
addLayers false;
refinementSurfaces // Global refinement
{
Combustor
{
level (1 1); //this is necessary to patch the internal (flow) patch
}
}
refinementRegions // LOCAL refinement
{
cylinder_cone_and_swirler
{
mode inside;
levels ((2 2)); //((2 2));
}

cylinder_fuel_injection
{
mode inside;
levels ((2 2));
}

box_combustor
{
mode inside; //2 million
levels ((2 2));
}
}
locationInMesh (1e-5 1e-5 200);
allowFreeStandingZoneFaces false;
features ( ); // EDGE refinement
resolveFeatureAngle 30;
}

snapControls
{
nSmoothPatch 1; //5 - Aspect ratio increased to 10 // 3 was kept default (AS - 7.8, Skew = 3.17) // 1 --> (AS - 5.72, Skew = 2.89)
tolerance 2.0;
nSolveIter 30; //50 - no changes, 30 is better
nRelaxIter 20 //10; //5; // recommended
//nRelaxIter 10; 20; - improved
nFeatureSnapIter 10; // recommended
//nFeatureSnapIter 20; 50; 100; //improved
implicitFeatureSnap false;
explicitFeatureSnap true;
multiRegionFeatureSnap true;
}

Hope this helps someone.

Thank you