A Refined Study of Atmospheric Wind Properties in the Beijing Urban Area Based on a 325 m Meteorological Tower

The urban atmospheric boundary layer (UABL) is complex due to the heterogeneous underlying city surface. The nine anemometers installed at different heights along the 325 m meteorological tower provide an opportunity to carry out a refined study of wind properties in the UABL in central Beijing, China. Based on the recent 5-year high-resolution measured data, in total, 229,488 10-min length segments of wind records related to each anemometer are reliable for further analyses. Accordingly, the statistical properties of the wind speed and direction are first analyzed to present the local wind climate in a comprehensive way. Moreover, the pattern of the wind profiles related to two typical synoptic intense events are illustrated in order to give a preliminary perspective, then the statistical properties corresponding to a series of intense windstorms are described. Here, the deviations in the wind direction occur between 200 m and 280 m of the atmosphere, which might be due to the existence of an Ekman spiral; besides this, the laws of wind profiles based on open terrain are not suitable for the UABL, and the aerodynamic characteristic parameters of the UABL based on vertical stratified structures have to be considered. The results contribute to the establishment of revised models for the wind profile and are useful for the further understanding of the structure of UABL wind.

DETERMINING THE AERODYNAMIC CHARACTERISTIC OF A MINE AXIAL FAN WHEN OPERATING IN REVERSIBLE MODE

This paper describes the procedure for determining the approximate aerodynamic characteristics of a fan operating in a reversible mode with the reverse direction of impeller rotation and deployed position of the straightener blades. To calculate the aerodynamic characteristic, the results of computational modeling of the flow around a flat cascade of airfoil blades were used. To check the adequacy of the applied design models, the comparison of flow deflection angles and total pressure losses when flowing around flat cascades composed of NACA65 airfoils in the direct mode and the known experimental data was made. Using the example of a OV-103 fan made according to the design of Central Institute of Aerohydrodynamics, with the known experimentally obtained aerodynamic characteristic of the reversible mode, the angles of reverse flow deflection in a cascade at the middle radius and total pressure loss in it were calculated. The obtained data were used to calculate the values of the coefficient of total fan pressure depending on the flow rate of air flowing through the fan. The obtained characteristics showed the value of maximum air flow rate higher than in the experimental characteristics. But in this case, it is closer to experimentally obtained data than the value calculated from the known theoretical characteristics of flat cascades.

Design And Analysis of CFD Geometry Configuration Canted Winglet Toward Aerodynamic Characteristic on Wing Profil of The UAV LSU-05

The wing is part of an aircraft or UAV which has a function as a major component of producing lift, therefore if a problem occurs such as a vortex at the end of the wing it will affect its performance capability. This study aims to determine the condition of the airflow, the value of induced drag, and the selection of the design of the wingtip devices on the wing profile of the UAV LSU-05. The method used is numerical or computational methods with CFD-based software to predict the aerodynamic characteristics and phenomenon of airflow around the wing with wingtip devices and without it. The model used in this study is a half-wing LSU-05 with NACA 4415 made with CATIA V5R20 software and the simulation uses ANSYS CFX 17.1. Based on the previous simulation results, it was found that the application of the canted winglet geometry to the wing profile of the UAV LSU-05 affects the coefficient lift (CL)/coefficient drag (CD) value and induced drag. Whereas the coefficient lift (CL)/coefficient drag (CD) value before using the canted winglet was 18.904 after application, increased to 21.616, this causes the induced drag value to change inversely with the coefficient lift (CL)/coefficient drag (CD) value where the value before the application was 30.4181 N to 29.0566 N.Keywords: Canted Winglet, CFD, Wing

The dynamics of a laden skip of the shaft pneumatic winding plant during acceleration

Introduction. Ratios for calculating the laden skip acceleration and speed at the motion start are required to calculate skip pneumatic winding plant cycle components. The ratios are the solution to the skip dynamics equation which takes into account the relationship between the flow generated by a power unit and air pressure. Research methodology. The dynamics equation including the dependence of the pressure on the flow rate (aerodynamic characteristic) in a general form is compiled. In a special case of the unit’s physical model, a discharge unit with a linear aerodynamic characteristic is used. Research result. For a particular case, equations are obtained that allow to theoretically describe the kinematic parameters of a skip in the period of unsteady motion. It is established that the skip acceleration, velocity and displacement are asymptotic functions. The obtained expressions for kinematic parameters make it possible to theoretically determine the duration of the acceleration period and the path that the ISSN 0536-1028 «Известия вузов. Горный журнал», № 1, 2021 121 skip takes during this period. A method for calculating skip dynamics during acceleration is proposed, which contains approximating formula conclusion for the power unit aerodynamic characteristics, its substitution into the dynamics equation, and obtaining skip kinematic parameters by solving the dynamics equation. Conclusion. The obtained relations allow to calculate skip dynamics during acceleration taking into account power unit aerodynamic characteristics, which is necessary to determine the working cycle time of the pneumatic winding plant.

On the aerodynamic interactions analysis between the main rotor and the helicopter fuselage

This paper develops a numerical method that is capable of analyzing the aerodynamic characteristic of the helicopter main rotor in consider the influence of fuselage. The method is based on an unsteady nonlinear vortex-lattice method that can be used to simulate the interactions among the helicopter components efficiently. To clarify the effect of the main rotor-fuselage interaction, the aerodynamic characteristics of the main rotor in consider the influence of fuselage is determined along with those of the combined main rotor-fuselage system. The paper also shows the velocity field and free wake model in several flight regimes. The fuselage is modeled as a streamlined object, which is discretized into the system of quadrilateral vortex panels. The no-penetration boundary condition is satisfied on the fuselage surface, and no vorticity is shed from the fuselage. The results obtained in this paper are validated against experimental data and some from previous numerical methods.