Parameter-retrieval Of Dry-air Wake Vortices With A Scanning Doppler Lidar

Aircraft wake is an inevitable phenomenon generated by a flying aircraft.It could be very hazardous in aviation since it may cause a following aircraft to jolt,roll,even loss of control.To avoid such hazards,ICAO(International Civil Aviation Organization)released a series of regulations for the minimum spatial intervals between flights.However,these regulations are generally conservative to a certain degree and have limited the capacity of airports.With the rapid increase of air traffic,the dynamic flight interval rule based on real-time detection of aircraft wake can serve as a feasible way to improve the efficiency and capacity of airports.The existing wake vortex detection sensors include radar and Lidar,which are applicable for wet weather condition(such as rainy and foggy)and dry-air condition respectively.This thesis focuses on the Lidar detection of dry-air wake vortices,and proposes two new algorithms to retrieve the characteristic parameters of wake vortices.The first one is an optimization-based parameter-retrieval algorithm.According to the weak inertia of aerosols in the dry air,a governing equation is established to describe the relationship between the measured data and the characteristic parameters(circulation and vortex-core trajectory).From which,the target parameters are well estimated by the optimization theory.In the method,the distortion of Doppler velocity caused by the scanning of Lidar beam has been adjusted,and the effects of complex background wind(crosswind,wind shear and turbulence)and ground effect have also been considered;these give very good applicability of this method to practical detection of wake vortices.The second one is a max-min velocity-based parameter-retrieval algorithm.In this algorithm,the vortex cores are located from the Doppler velocity distribution,and then the circulation is derived from the radial velocity difference between two points across the vortex cores.When the fluctuation of background wind is not very dramatic,this new algorithm can avoid the estimation of background wind and the total calculation cost of it is very small.These two parameter-retrieval algorithms have been applied on the simulated data and field detection data,and good performances(high accuracy and small calculation cost)are observed.Therefore,the algorithms can provide very important support to the development of new regulations on the dynamic-interval of fights in ATM(air traffic management).