Special Issue “Gust Influences on Aerospace”

An important prerequisite for the design, assessment, and certification of aircraft, their propulsion systems, and associated control systems is a quantitative specification of the environment in which the aircraft are intended to operate. Gust is one of the most common environmental factors that can impose adverse effects on aircraft and has played a critical role in many catastrophic flight accidents in the past decades [1,2,3,4,5]. Investigations into aircraft aerodynamic responses to gusts have demonstrated the importance of gust research in aerospace engineering, because gusts are usually unexpected and leave the aircraft control system less time to respond. Taking aircraft lifting surfaces as example, the unsteady loads imposed by gusts can induce detrimental influences such as fluctuating aerodynamic and structural loads, leading to reduced structural fatigue lifetime, flight dynamic performance, and passenger comfort [6,7]. Strong gusts can seriously affect the flight path of aircraft and the performance of aircraft propulsion systems [8,9,10,11]. Therefore, gust response is an indispensable aspect of the load designs of aircraft and their subsystems [12,13,14,15,16,17]. The mainstream aircraft airworthiness regulations, such as the FAR-25 and the CS-25, have provided detailed specifications for gust considerations [6,18].

This Special Issue of Aerospace includes eight peer-reviewed papers presenting recent advances in gust research in aerospace engineering. These articles introduce a broad insight into the influences of gusts on both the external flow of aircraft and the internal flow of aircraft engines. Their implementation will contribute to the design methods of gust generators, the analysis methods of aircraft and propulsion system gust responses, the visualization and measurement techniques of aircraft flow fields, and an enhancement of the flight safety of aircraft encountering gusty environments.

Liu et al. [19] presented a numerical investigation of suction control in an aggressive S-shaped air intake with large boundary ingestion. The results show that the variation in the suction control parameters such as the suction location, suction pipe diameter, and suction angle all have an impact on the effectiveness of the flow control. Wu et al. [20] designed a novel small-scale gust generator research facility and examined its feasibility for generating Sears-type gusts. Although the filtered experimental measurement results agreed well with the numerical data, validating the capability of the developed gust generator to produce sinusoidal gusts, necessary measures are still needed to prevent mechanical noise from interfering with the gusty flow field. Moreira et al. [21] conducted an experimental approach on two different propeller blade geometries and a varying number of blades with the objective of exploring the characteristics at non-axial inflow conditions. Liu et al. [22] reviewed the fundamentals of plenoptic background-oriented schlieren (Plenoptic BOS), an emerging volumetric method in recent years for high-resolution and large-scale three-dimensional (3D) measurements of flow fields, and then discussed the system configuration, typical application of single-view and multi-view plenoptic BOS, and the related challenges and outlook on the potential development of plenoptic BOS in the future. Zhu et al. [23] studied the internal flow characteristics of the inlet during the hover state of a typical tiltrotor aircraft and the effects of head-on gusts on the aerodynamic characteristics of the inlet, using an unsteady numerical simulation method based on the sliding-mesh technique. The results indicated that head-on gusts mainly affect the mechanical energy and non-uniformity of the air sucked into the inlet by influencing the direction of the rotor’s induced slipstream, thereby impacting the performance of the inlet. Singh et al. [24] presented an experimental investigation of a passive–adaptive slat concept, an aerodynamic control mechanism aimed at avoiding separation in the inward region of a horizontal axis wind turbine blade. It was observed that the passive–adaptive slat was able to achieve similar mean lift values as an airfoil with a fixed slat while showing a significant reduction in the lift fluctuations when facing fluctuating inflows. Liu et al. [25] carried out a Reynolds-averaged Navier–Stokes (RANS) simulation of the rotor–building coupled flow field to address the rotor aerodynamic performance under building interferences in natural atmospheric conditions. It was found that during low-altitude hovering over rooftops, the mixing of building shed vortices with forward flow wakes causes the formation of a circulation region on the rotor’s windward side, resulting in a thrust loss of approximately 7.8%. Yang et al. [26] proposed the fitting strip method as a solution to gust aerodynamic forces for real-time flight simulations with gusts. It only requires the current and previous gust information to calculate the aerodynamic forces and is suitable for different configurations of aircraft and different kinds of gusts. Compared with other methods, the fitting strip method requires a shorter computational time and avoids the shortcomings of the rational function approximation method; thus, it is more accurate than gust grouping methods.

We sincerely wish to thank all the authors of the papers published in this Special Issue for their professional contributions, positive cooperation, and hard work with the expansion and revision of the accepted papers. Furthermore, the invited reviewers deserve praise and appreciation for their insightful critique and suggestions, which have contributed directly to improving the theoretical depth and technical breadth of the journal articles.

Finally, we would like to express our sincere gratitude to Mr. August Wang, Mr. Xiaochun Peng, and the editorial team of Aerospace for offering this opportunity for all the contributors to work together and for their continuous support in preparing this Special Issue.