Purpose

This paper aims to present the novel methodology of computational simulation of a helicopter flight, developed especially to investigate the vortex ring state (VRS) – a dangerous phenomenon that may occur in helicopter vertical or steep descent. Therefore, the methodology has to enable modelling of fast manoeuvres of a helicopter such as the entrance in and safe escape from the VRS. The additional purpose of the paper is to discuss the results of conducted simulations of such manoeuvres.

Design/methodology/approach

The developed methodology joins several methods of computational fluid dynamics and flight dynamic. The approach consists of calculation of aerodynamic forces acting on rotorcraft, by solution of the unsteady Reynold-averaged Navier–Stokes (URANS) equations using the finite volume method. In parallel, the equations of motion of the helicopter and the fluid–structure-interaction equations are solved. To reduce computational costs, the flow effects caused by rotating blades are modelled using a simplified approach based on the virtual blade model.

Findings

The developed methodology of computational simulation of fast manoeuvres of a helicopter may be a valuable and reliable tool, useful when investigating the VRS. The presented results of conducted simulations of helicopter manoeuvres qualitatively comply with both the results of known experimental studies and flight tests.

Research limitations/implications

The continuation of the presented research will primarily include quantitative validation of the developed methodology, with respect to well-documented flight tests of real helicopters.

Practical implications

The VRS is a very dangerous phenomenon that usually causes a sudden decrease of rotor thrust, an increase of the descent rate, deterioration of manoeuvrability and deficit of power. Because of this, it is difficult and risky to test the VRS during the real flight tests. Therefore, the reliable computer simulations performed using the developed methodology can significantly contribute to increase helicopter flight safety.

Originality/value

The paper presents the innovative and original methodology for simulating fast helicopter manoeuvres, distinguished by the original approach to flight control as well as the fact that the aerodynamic forces acting on the rotorcraft are calculated during the simulation based on the solution of URANS equations.

中文翻译：

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使用URANS求解器研究直升机主旋翼上的涡流环状态

目的

本文旨在介绍一种新型的直升机飞行计算仿真方法，特别是为了研究旋涡环状态（VRS）而开发的-这种现象是在直升机垂直或陡降时可能发生的危险现象。因此，该方法必须能够对直升机的快速机动进行建模，例如进入VRS并从中安全逃生。本文的另一个目的是讨论这种动作进行的仿真结果。

设计/方法/方法

所开发的方法学结合了多种计算流体动力学和飞行动力学方法。该方法包括通过使用有限体积方法求解不稳定的雷诺平均Navier–Stokes（URANS）方程来计算作用在旋翼飞机上的空气动力。同时，求解了直升机的运动方程和流固耦合方程。为了减少计算成本，使用基于虚拟叶片模型的简化方法对由旋转叶片引起的流动效应进行建模。

发现

研制的直升机快速机动计算仿真方法论可能是一种有价值且可靠的工具，在调查VRS时很有用。所呈现的直升机操纵模拟结果在质量上与已知实验研究和飞行试验的结果一致。

研究局限/意义

提出的研究的继续将主要包括相对于有据可查的真实直升机飞行测试，对开发的方法进行定量验证。

实际影响

VRS是一种非常危险的现象，通常会导致转子推力突然下降，下降率增加，机动性下降和动力不足。因此，在实际飞行测试中测试VRS既困难又冒险。因此，使用开发的方法进行的可靠的计算机仿真可以显着提高直升机的飞行安全性。

创意/价值

本文介绍了一种新颖且新颖的方法，用于模拟快速直升机的动作，其独特之处在于飞行控制的原始方法，以及基于URANS方程的求解在仿真过程中计算作用在旋翼飞机上的空气动力的事实。