The second case, the Apache AH-64 helicopter, investigates the interaction effects between the main and tail rotor. Pressure distributions on the airframe are compared with experimental data and good agreement is found. As validation example, a well-studied single rotor airframe interaction case in forward flight is discussed. Trimming is performed in an automatic and robust fashion using an iterative method to account for the non-linear relation between blade pitch and rotor performance.

Accurate aerodynamic predictions are possible only if the rotors operate at desired thrust and zero moment about the hub. The non-linear, aerodynamic interaction between the rotor wakes with each other and with other structural components is solved by coupling the VBM with the governing flow field equations computed by Fluent's Navier-Stokes solvers. The model allows for an unstructured mesh in the rotor disks yielding easy meshing of multiple rotor geometries in close proximity and convenient local mesh clustering. Thus the effects of the blades are accounted for without them being present in the computational mesh, giving the model its name 'Virtual Blade Model' or VBM. This technique models the rotors implicitly through source terms in the momentum equations. 1 and Yang et al.2 has been implemented into the general purpose solver Fluent. Local mesh refinement controls can resolve geometry details appropriately, and poor CAD models can be improved in SpaceClaim/Discovery, or you can use Fluent's Fault Tolerant meshing workflow, which is robust to CAD faults.A method for analyzing the mutual aerodynamic interaction between multiple rotors and airframes in the spirit of Zori et al. Poor mesh quality can also be caused by insufficient mesh resolution of geometry details or by poor underlying CAD. When selected, you will then enter the percentage of the total cells to be improved, and the number of iterations of smoothing sweeps performed.

If you are in Fluent Solution mode, you can improve the mesh quality by selecting the improve the mesh option on the Quality button under the Domain tab. To improve the surface mesh, you will have to enter a face quality limit to target, and when improving the volume mesh, you will have to enter a cell quality limit value to target. If you are still in the process of generating your mesh in Fluent Meshing mode, you can insert a task after both the 'Generate the Surface Mesh' task and 'Generate the Volume Mesh' task by right-clicking on either one and inserting a new 'Improve Mesh' task. Mesh quality can be improved in a variety of places in Ansys Fluent.

Ansys fluent vbm