Open “Aerodium” type wind tunnels with free vertical jet with diameter exceeding 3 m and air velocity in initial section of the jet 60-70 m/s, is being used as a devices for free flight of human and training of sky divers. In a developed and investigated computer model air jet has been created by five propellers with five blades (diameter of 1.8 m). Their horizontal axes are symmetrically located on the circle along its radii. Each propeller is mounted on the profiled ring, which behind the propeller transforms into 3D shaped channel of complex L-type form for smooth and no shedding rotation of the flow at 90 ° along the vertical axis of the device. After turning all five channels are combined into one axis-symmetrical free jet forming nozzle with diameter ~ 3.6 m. The purpose of this work is to develop methods of computer simulation and optimisation of geometric and aerodynamic parameters of the “Aerodium” type devices with low noise level fans for the formation of large diameter free jet. Computer simulation and engineering analysis performed using CAD/CAE software SolidWorks/CFdesign. Geometric modelling enabled solution of complex joining problems of sections of air channels and pairing of multiple channels, taking into account the restrictions for corners narrowing and widening, smooth transitions and turns of channels. Aerodynamic part is described by the unsteady Navies-Stokes equations and numerically solved using adaptive mobile mesh taking into account rotation of the propeller, geometry of air channels, and weak compressibility of the ambient, turbulences of the flow, shedding zones and return flows. On the basis of optimised geometric and aerodynamic results was developed design of the aerodynamic device ”Aerodium“ with five propellers with five blades. Device (“Aerodium”) was manufactured, assembled and experimentally examined in town Jelgava (Latvia). Results of field experiments satisfactorily confirmed data of numerical calculations.