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UAV icing: the influence of airspeed and chord length on performance degradation
Aircraft Engineering and Aerospace Technology ( IF 1.5 ) Pub Date : 2021-06-19 , DOI: 10.1108/aeat-06-2020-0127
Richard Hann , Tor Arne Johansen

Purpose

The main purpose of this paper is to investigate the effects of icing on unmanned aerial vehicles (UAVs) at low Reynolds numbers and to highlight the differences to icing on manned aircraft at high Reynolds numbers. This paper follows existing research on low Reynolds number effects on ice accretion. This study extends the focus to how variations of airspeed and chord length affect the ice accretions, and aerodynamic performance degradation is investigated.

Design/methodology/approach

A parametric study with independent variations of airspeed and chord lengths was conducted on a typical UAV airfoil (RG-15) using icing computational fluid dynamic methods. FENSAP-ICE was used to simulate ice shapes and aerodynamic performance penalties. Validation was performed with two experimental ice shapes obtained from a low-speed icing wind tunnel. Three meteorological conditions were chosen to represent the icing typologies of rime, glaze and mixed ice. A parameter study with different chord lengths and airspeeds was then conducted for rime, glaze and mixed icing conditions.

Findings

The simulation results showed that the effect of airspeed variation depended on the ice accretion regime. For rime, it led to a minor increase in ice accretion. For mixed and glaze, the impact on ice geometry and penalties was substantially larger. The variation of chord length had a substantial impact on relative ice thicknesses, ice area, ice limits and performance degradation, independent from the icing regime.

Research limitations/implications

The implications of this manuscript are relevant for highlighting the differences between icing on manned and unmanned aircraft. Unmanned aircraft are typically smaller and fly slower than manned aircraft. Although previous research has documented the influence of this on the ice accretions, this paper investigates the effect on aerodynamic performance degradation. The findings in this work show that UAVs are more sensitive to icing conditions compared to larger and faster manned aircraft. By consequence, icing conditions are more severe for UAVs.

Practical implications

Atmospheric in-flight icing is a severe risk for fixed-wing UAVs and significantly limits their operational envelope. As UAVs are typically smaller and operate at lower airspeeds compared to manned aircraft, it is important to understand how the differences in airspeed and size affect ice accretion and aerodynamic performance penalties.

Originality/value

Earlier work has described the effect of Reynolds number variations on the ice accretion characteristics for UAVs. This work is expanding on those findings by investigating the effect of airspeed and chord length on ice accretion shapes separately. In addition, this study also investigates how these parameters affect aerodynamic performance penalties (lift, drag and stall).



中文翻译:

无人机结冰:空速和弦长对性能下降的影响

目的

本文的主要目的是研究在低雷诺数下结冰对无人驾驶飞行器 (UAV) 的影响,并强调在高雷诺数下对有人驾驶飞机结冰的差异。本文遵循现有关于低雷诺数对积冰影响的研究。这项研究将重点扩展到空速和弦长的变化如何影响积冰,并研究了空气动力学性能退化。

设计/方法/方法

使用结冰计算流体动力学方法对典型的无人机翼型 (RG-15) 进行了空速和弦长独立变化的参数研究。FENSAP-ICE 用于模拟冰的形状和空气动力学性能损失。使用从低速结冰风洞获得的两种实验冰形状进行了验证。选择了三种气象条件来代表霜、釉和混合冰的结冰类型。然后针对霜冻、釉面和混合结冰条件进行了具有不同弦长和空速的参数研究。

发现

模拟结果表明,空速变化的影响取决于积冰情况。对于雾凇,它导致积冰量略有增加。对于混合和釉面,对冰几何形状和惩罚的影响要大得多。弦长的变化对相对冰厚、冰面积、冰限制和性能退化有重大影响,与结冰情况无关。

研究限制/影响

这份手稿的含义与强调有人驾驶飞机和无人驾驶飞机结冰之间的差异有关。无人驾驶飞机通常比有人驾驶飞机更小,飞行速度更慢。虽然之前的研究已经记录了这对积冰的影响,但本文研究了对空气动力学性能下降的影响。这项工作的结果表明,与更大、更快的有人驾驶飞机相比,无人机对结冰条件更敏感。因此,UAV 的结冰条件更为严重。

实际影响

大气飞行中结冰对固定翼无人机来说是一个严重的风险,并极大地限制了它们的运行包线。由于与有人驾驶飞机相比,无人机通常更小且以更低的空速运行,因此了解空速和尺寸的差异如何影响积冰和空气动力学性能损失非常重要。

原创性/价值

早期的工作描述了雷诺数变化对无人机积冰特征的影响。这项工作通过分别研究空速和弦长对积冰形状的影响来扩展这些发现。此外,这项研究还调查了这些参数如何影响空气动力学性能损失(升力、阻力和失速)。

更新日期:2021-06-17
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