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.

Computational aerodynamics in architectural siting of the structures of agro-industrial complex

The article presents study of wind effect on silo parks, which was carried out by computer simulation methods. A special modeling technique was created as a software module for the Ansys Workbench platform. A finite element mesh was developed in accordance with two requirements. Through the use of this mesh, which doesn’t contain needless elements which can be used for simplification of calculations and reduction of execution time, it is possible to describe the turbulent airflow in sufficient detail. The dimensions of all mesh elements are determined by special relations as the functions of the silo diameter and the Reynolds number. The major stage in this investigation was modeling of various options for flowing silos and their groups. As a result of the study, we have obtained aerodynamic characteristics of individual silos as part of silo parks and plotted charts of the distribution of pressure coefficients over the cylinder surface, changing the size of the silos, distances between them and local wind regime. Based on these data, we have drawn a conclusion about the optimal space planning locations of silos for different wind directions. Visualizations of turbulent flow around models at different speeds have also been obtained in this study.

METHOD OF DISCRETE FEATURES AS PLANNING MEANS IS AERODYNAMIC OUTLINES OF TRANSPORT VEHICLES

The main stages of the development of the discrete singularities’ method are described. Modern results on the numerical solution of boundary hypersingular integral equations by the methods of collocations and piecewise constant approximations are given. The modern going near planning of aerodynamic design outline of transport vehicles conditionally can be divided into three stages: engineering approaches are close, design on the basis of methods of discrete singularities, approaches that arе based on integration of complete and the Reynolds-averaged of Navier-Stokes equations. On the first stage various engineering approaches are used for forming of aerodynamic outline, going out a requirement specification and requirements of customer. Close geometrical and aerodynamic descriptions are determined in the first. An aerodynamic outline is formed in the first close. On the second stage it follows to use more difficult models of aerodynamics on the basis of various approaches that is built on the model of ideal liquid. Bearing properties are determined, power and moment characteristics for the corresponding outline of aircraft. The third stage is most difficult and expensive cost. On this stage it follows to use methods and models that are based on equations for turbulent flow. The second stage is in-process considered – as means of the previous planning of aerodynamic arrangement with the use of methods of discrete features. A non-stationary chart in that tearing away is designed from all sharp edge of wing is in-process used. This chart has the most general case of forming of process of flowing around of the bearing system of aircraft. However, complication of physical interpretation of forming of such processes in the conditions of ideal liquid remains problematic. The necessities of practice require expansion and deepening of theoretical approaches for the study of non-stationary. Application of model of ideal liquid for the calculation of the bearing system of a perspective transport vehicle allows to set forth aerodynamic task as task of Neumann for Laplace operator. The calculations of the bearing systems of difficult geometrical plane form are conducted. Dependences of carrying capacity and longitudinal moment are got depending on the corner of attack and distance to the ground clearance. A computational experiment confirmed that a method of discrete vorteces was one of important methods of computational aerodynamics. He is effective means for untiing of a number of aerodynamic tasks.

Computational Aerodynamics Analysis of Non-Symmetric Multi-Element Wing in Ground Effect with Humpback Whale Flipper Tubercles

The humpback whale flipper tubercles have been shown to improve the aerodynamic coefficients of a wing, especially in stall conditions, where the flow is almost fully detached. In this work, these tubercles were implemented on a F1 front-wing geometry, very close to a Tyrrell wing. Numerical simulations were carried out employing the k−ω SST turbulence model and the overall effects of the tubercles on the flow behavior were analyzed. The optimal amplitude and number of tubercles was determined in this study for this front wing where an improvement of 22.6% and 9.4% is achieved, respectively, on the lift and the L/D ratio. On the main element, the stall was delayed by 167.7%. On the flap, the flow is either fully detached, in the large circulation zone, or fully attached. Overall, in stall conditions, tubercles improve the downforce generation but at the cost of increased drag. Furthermore, as the tubercles are case-dependent, an optimal configuration for tubercles implementation also exists for any geometry.