Abstract
Currently, two-shell paragliders (TSP) find a sufficiently wide application, including the solution of transport problems. A two-shell paraglider is a soft wing, the form of which is supported by the high-speed pressure in the stream and it is a complex aeroelastic system. To determine the aerodynamic characteristics of such system the use of nonlinear aerodynamics and nonlinear theory of elasticity methods is required, it causes the significant computational difficulties. This paper studies the aerodynamic characteristics of various steady-state shapes of gliding parachutes, the calculation-experimental method of their calculation is proposed. It is shown that the replacement of the volumetric profile of TSP median surface allows to receive the results which correctly reflect the qualitative effects of stalled and attached flows. It leads to the assumption that such replacement was possible for obtaining data about the main patterns of parachute finite wings span flow. The aerodynamic characteristics data of TSP steady-state shapes allow to identify the regularities of their changes depending on parachute cutting shape, the deformations of its surface caused by the incoming flow or control actions. To solve the problem of gliding parachute stall, with a stream of air, the discrete vortex method with closed frameworks is used. This method allows to calculate the aerodynamic characteristics of parachutes. The middle surface airflow of TSP steady-state shape with the flow of an ideal incompressible fluid is examined. The parachute fabric permeability is not considered because the upper and lower TSP cloth is either made of low permeable or impermeable fabric. The stalled aerodynamic coefficients are determined by time averaging after calculations up to its larger values. The results of the calculations are given. The possibility of application the proposed methodology for calculation of TSP aerodynamic characteristics in the range of angles of attack to 10° and over 20° for the simplified calculation scheme with accuracy 10% is shown. At the same time, it is revealed that with the increase of soft wing elongation, it is important to consider its main surface curvature for more precise aerodynamic characteristics definition. The proposed methodology can be used for rapid assessments of aerodynamic forces at the design stage and in planning tube experiment. The obtained results can be useful in TSP design during the performance of the tube experiments.
Highlights
A two-shell paraglider is a soft wing, the form of which is supported by the high-speed pressure in the stream and it is a complex aeroelastic system
This paper studies the aerodynamic characteristics of various steady-state shapes of gliding parachutes, the calculation-experimental method of their calculation is proposed
It is shown that the replacement of the volumetric profile of two-shell paragliders (TSP) median surface allows to receive the results which correctly reflect the qualitative effects of stalled and attached flows
Summary
Для определения аэродинамических характеристик такой системы необходимо привлечение методов нелинейной аэродинамики и нелинейной теории упругости, что обусловливает существенные вычислительные затруднения. Для решения задачи об обтекании планирующего парашюта потоком воздуха используется метод дискретных вихрей с замкнутыми рамками, который позволяет вычислять аэродинамические характеристики парашютов. В то же время выявлено, что с увеличением удлинения мягкого крыла важно учитывать его арочность для более точного определения аэродинамических характеристик. В то же время число работ в области расчетного определения аэродинамических характеристик ДПП ограничено, причем в основном решается задача об обтекании парашюта в плоской постановке. Что ДПП представляет собой фактически мягкое крыло, форма которого поддерживается скоростным напором в потоке, и является сложнейшей аэроупругой системой. Одним из авторов статьи был предложен подход к моделированию двухоболочкового парашюта его срединной поверхностью для анализа аэродинамических характеристик [10]. Полученные результаты могут оказаться весьма полезными при проектировании ДПП, при постановке и проведении трубных экспериментов
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