The purpose of this paper is to design an S‐duct intake for unmanned aerial vehicles (UAVs) applications with good efficiency in a wide range of operating conditions.
A fully‐parametric 3‐D CAD model of the intake was constructed in order to produce different intake configurations, within specific geometric constraints, and to study the influence of geometry variation on efficiency. O‐type blocking methodology was adopted in order to construct the block‐structured mesh of hexahedral elements, used in the simulations. The commercial CFD code ANSYS‐CFX was used to compute the flow field inside the flow domain of each case considered. The Reynolds averaged Navier‐Stokes (RANS) equations are discretized using an implicit, vertex‐based finite volume method, combined with the shear stress transport (SST) two‐equation turbulence model and an automatic wall treatment.
By shortening the axial length the flow separation after the first turning becomes more pronounced and the losses are increasing. For very long ducts the increased internal wall area leads to increased wall friction and, consequently, to increased loss production.
The adoption of Gerlach‐shaped profiles for the design of the S‐duct resulted in a low pressure loss level for the optimal shape, although more uniform distribution of total pressure losses resulted for ducts longer than the optimal one, which should be taken into account in the design process.
