Investigation of aerodynamic interaction between the balloon and the ducted wind turbine in airborne configuration

An aerodynamic analysis is presented in the current work, which estimates the separation distance between the balloon and the turbine in an airborne wind energy system (AWES). The stability of the structure of AWES depends on the aerodynamic interaction between the turbine and the balloon. A minimum gap must be maintained between the balloon and the wind turbine to reduce the interaction between the balloon and the turbine assembly. Three cases of AWES have been studied with a separation gap of 5 m, 10 m, and 16 m to estimate the minimum distance of separation between the balloon and the turbine. The aerodynamic interaction details suggest that a minimum distance of 13 m needs to be maintained between the turbine and the balloon to avoid the interaction between the balloon and turbine. Steady-state simulations of the rotor are run for various wind conditions to evaluate the efficiency of the duct-mounted configuration. The ducted turbine configuration saw a 7.4% increase in torque than the inducted turbine for a wind speed of 5 m s−1. A torque increase of 17.85% was observed when the separation distance was increased to 16 m from earlier 10 m.

Determination of the aerodynamic characteristics of the tiltrotor with the wingtip-mounted coaxial rotors

The article describes the study of rotor-to-wing aerodynamic interaction for the wingtip-mounted coaxial rotors configuration of the tiltrotor aircraft. The influence of the rotor slipstreams on lift-to-drag ratio characteristic was determined. Obtained results were compared with similar characteristics of the equivalent in thrust conventional single rotor slipstreams impact. Using the computational aerodynamics methods (panel-vortex method) the flow around the tiltrotor model with the wingtip-mounted single and coaxial rotors has been simulated. A study of the basic model configuration with conventional single rotors, based on the technical characteristics of the AgustaWestland AW609 tiltrotor, was conducted. Further researches were conducted for a modified model where single rotors were replaced with equivalent in thrust coaxial rotors. The influence of the rotor slipstreams on the aerodynamic characteristics of the model for both directions of rotors rotation in coaxial combination is considered. Also, the dependence of the maximum lift-to-drag characteristic due to the coaxial rotor diameters change has been determined. The results show that the coaxial rotor slipstreams-to-wing aerodynamic interaction effect is the similar to the effect of conventional single rotor, but less intensive. Comparison of the results showed that a tiltrotor equipped with wingtip-mounted single rotors has approximately 20% greater maximum lift-to-drag characteristic than one equipped with coaxial rotors with the same thrust. However, the use of coaxial rotors allows getting higher maximum speed, when conventional single rotors lose the efficiency significantly. Therefore, it is advisable to conduct further research for the possibility of using coaxial rotors for tiltrotor aircrafts. The research results are presented in graphical form. The obtained data provides a basis for further studies of the described problem, and also will be useful for new tiltrotor design works.

Experimental Study of the Aerodynamic Interaction between Side-by-Side Propellers in eVTOL Airplane Mode through Stereoscopic Particle Image Velocimetry

Side-by-side propellers characterise the architecture of most new electric aircraft (eVTOLs) designed in recent years for urban air mobility. The aerodynamic interaction between side-by-side propellers represents one of the key phenomena that characterise the flow field and performance of these novel aircraft configurations. The present article describes the main results of a wind tunnel campaign that aimed to investigate the flow features that characterise this aerodynamic interaction, with a particular application to cruise flight conditions in eVTOLs. With this aim, stereo particle image velocimetry (PIV) measurements were performed in the wake of two co-rotating propeller models in a side-by-side configuration. The three-dimensional flow surveys provided detailed insights into the flow physics of the interacting propellers, with a particular focus on the interactional effects on the trajectory of the tip vortices and the wake topology provided at two different advance ratios by reproducing a moderate and a fast cruise speed of eVTOLs in urban areas.

Wind Tunnel Experiment on the Aerodynamic Interaction Between Vertical Axis Wind Turbine Pair

Wind energy has attracted worldwide attention as a pollution-free and widely distributed renewable energy source. Increasing the power density by optimizing the arrangement of wind turbines has been a popular field of research in recent years. In the present work, a systematic study on the influence of array configuration on vertical axis wind turbines is made through wind tunnel experiments. Firstly, the power performance of an isolated vertical axis wind turbine at different tip speed ratios is tested as a benchmark of comparison. Multiple situations of two-turbine configurations are then tested and the results are compared with the isolated wind turbine. The power coefficient of the turbine pair increases by 34% when the turbines are 2.4 rotor diameters apart and rotate in the same direction. In the counter-rotating co-leeward case, it is demonstrated that the turbine pairs will have a positive effect on each other when they are separated by 2.1 rotor diameters to 2.4 rotor diameters. The lateral spacing between the counter-rotating co-windward turbine pair should be greater than 1.5 rotor diameters to avoid turbulence interference between the rotors.