The measurement of lift and drag forces on the omithopter model with flapping wings was carried out in the wind tunnel. The wing movement had two degrees of freedom: flapping (around the longitudinal axis of the model) and feathering (around the wing axis). Forces were measured in static case - as averaged values during many cycles of movement, and in dynamic case - as unsteady forces captured in function of the flapping phase. The magnitudes of the aerodynamic coefficients of lift and drag were calculated.

The helical jet is generated in a tangential pipe nozzle having the tangential and the axial inlets and the axial outlet. The flow directions in free jet spreading in the stationary air was measured by means of a flag type probe. The flow was visualized using the planar scattering technique. It was found that due to asymmetrical distribution of the tangential velocity in the jet leaving the nozzle, the air particles spread in the ambient with various intensity depending on the azimuthal angle. The result is that the jet has a spiral shape with bean-like cross-section.

Turbulent boundary layer separation induced by positive pressure gradient at a plane surface is investigated experimentally. Separation is delayed by means of a jet vortex generator in a form of small jets injected to the boundary layer through orifices distributed across the main flow. The effect of jets intensity on delay of separation is examined. Swirled and non-swirled jets have been used. The energy of the air supplying the generator required to delay boundary layer separation is in the former case up to 40% lower than in the latter one.

Two semi-circular rods set up in V-shape form were used to generate streamwise vortices in a turbulent boundary layer. The vortices, due to induced helical flow, supplement the streamwise momentum of retarded air particles at the body surface with the momentum of the external flow. In this experimental study it was found that vortices are at their most intensity if the Reynolds number of the flow over generator, based on the diameter of rods is within the range I 04-1.5 · I 04 • Several semi-circular rods set up in a tooth line were examined in delaying the separation of the turbulent boundary layer at a convex cylindrical surface. It has been noted that delay of separation is at its most efficient when the height of the generator is equal to at least half of the boundary layer thickness.

The helical flow is generated by a jet from a single nozzle inflowing tangentially into a pipe. The effect of the distance travelled by the air in the pipe from its tangential inlet to its axial outlet on the issuing jet is investigated. The axial and tangential velocity distributions were measured at the outlet cross-section of the pipe using the hot-wire probe. It was observed that for a short pipe the strongest asymmetry of the tlow velocity distributions exists for a part of the pipe crosssection near the pipe wall. Contrary to this, for a long pipe, the largest deviations from axisymmetry appear in the middle part. In this result the total effect of asymmetry expressed by RMS of swirl number considerably decreases.

Helical Jet in moving air was used to simulate the flow downstream of a helicopter blade tip or a wing tip. The jet was generated by means of an opened pipe supplied tangentially (tangential nozzle), and placed in a wind tunnel. Flow properties were investigated in several cross-sections downstream of the nozzle. The flow direction and the total pressure were measured in function of the azimuthal angle and the distance from the axis of the system. The flow was visualized using the planar laser scattering technique. The decay of swirl intensity was measured by means of a probe with a rotating plate fixed to a miniature voltage generator.