Simulation of Lattice Wings with the Actuator Disc Concept

Kurzfassung

During the 1980s lattice wings have been introduced in the Soviet Union in air-to-air as well as in ground-to-ground missile configurations. Lattice wings represent alternative means for keeping aerodynamic control and stability of highly manoeurable supersonic and hypersonic configurations, replacing or complementing planar fins. A lattice wing consists of an outer frame with an internal grid framework, as schematically shown along with the main geometric parametres in Fig. 1. Recently, such configurations have been studied experimentally in wind tunnel testing in the DLR [5], [6]; additional experiments on isolated lattice wings are planned. On the other hand the numerical prediction of the lattice wing behaviour is decisive for the aerodynamic design process, in order to achieve short development times. In the present report a method is developed to effectively perform numerical simulations of configurations including lattice wings using the DLR Euler and Navier-Stokes solver FLOWer [1]. Since the computation of isolated lattice wings is a time consuming process even on a supercomputer, certain simplifications are necessary. One possibility is to represent the lattice wing by an actuator disk. Respective new boundary conditions have been added to FLOWer for both the inflow and outflow boundaries. When passing the actuator disk, the momentum of the fluid is changed due to the impact of the lattice wing. Dependent on the local velocity vector, this impact is interpolated from a data base and is accounted for in the flux balance. The procedure allows to approximately determine the resulting forces and moments caused by the lattice wing as well as interference effects with the fuselage in nonuniform flow. The data base is obtained from wind tunnel testings using isolated grid fins. The data base may further be used to verify the extended code by comparison with qualified numerical solutions for isolated lattice wings. The implementation of the lattice wing boundary conditions consists of two major blocks. First, the required input-data and data from the data base are read in, the latter stored in corresponding arrays. The second block embodies the inflow and outflow boundary conditions for the actuator disk including the necessary data exchange procedures and the interpolation routines for the data base. In this report, the relevant lattice wing parametres are figured out and a method is presented to store the necessary experimental data in a database, which is readable to FLOWer. The theory for the lattice wing actuator disk is given and operativeness is shown for isolated wings.