Severe Turbulence Research Articles

Severe Convection at Burgas Airport: Case Study 17 September 2022

Convection monitoring and forecasting are crucial for air traffic management as they can lead to the development of intense thunderstorms and hazards such as severe turbulence and icing, lightning activity, microbursts and hail that affect aviation safety. The airport of Burgas is located in southeast Bulgaria on the Black Sea coast and occurrences of intense thunderstorms are mainly observed in the warm season between May and September. This work presents an analysis of severe convection over southeast Bulgaria on 17 September 2022. In the late afternoon, a gust front was formed that reached the Burgas airport with a wind speed exceeding 45 m/s, the record for the past 50 years, damaging the instrument landing system of the airport. To analyse the severe weather conditions, we combine state-of-the-art observations from satellite and radar with the upper-air sounding and surface. The studied period was dominated by the presence of a very unstable air mass over southeast Bulgaria ahead of the atmospheric front. As convection developed and moved east towards Burgas, it had four characteristics of severe deep convection, including gravitational waves at the overshooting cloud top, a cold U-shape, a flanking line and a cloud top temperature below −70 °C. The positive integrated water vapour (IWV) rate of change preceded the lightning activity peak by 30 min. Analysis of integrated vapour transport (IVT) gives higher values by a factor of two compared to climatology associated with the atmospheric river covering the eastern Mediterranean sea.

Tropical Aviation Turbulence Induced by the Interaction Between a Jet Stream and Deep Convection

AbstractOn 18 December 2022, Hawaiian Airlines flight HA35 encountered severe turbulence without warning in a cloud‐free height. We reproduced this incident using the Weather Research and Forecasting Model (WRF) at a convection‐permitting resolution. We found that this case of tropical upper‐level turbulence occurred primarily due to the fast‐growing convective tower in the unstable layer created by gravity wave breaking. At lower altitudes, a mesoscale convective system (MCS) caused a decrease in wind speed in both upstream and downstream regions. At upper levels, a large‐scale jet descended and accelerated after flowing over the top of the MCS, which acted like a barrier and produced a situation similar to a downslope windstorm due to mountain terrain. Upper‐level turbulence is 2–3 km higher than the top of the MCS. The critical level above the jet and the locally self‐induced critical level created the locally enhanced descending jet stream, which destabilized the flow through Kelvin–Helmholtz instabilities. The convective tower existed near the flight route and played an important role in triggering turbulence in the unstable environment through its convective gravity waves.

Physical quantity characteristics of severe aircraft turbulence near convective clouds over Australia

Using FY–2G satellite data, Aircraft Meteorological Data Relay (AMDAR) downlink data, and the fifth generation European Centre for Medium–Range Weather Forecasts (ECMWF) atmospheric reanalysis of the global climate (ERA5) dataset, we analyzed the circulation, thermal, and dynamic characteristics of the convective aircraft turbulence over Australia in the Southern Hemisphere. The results show that the near-convective clouds turbulence (NCCT) in the Southern Hemisphere mostly occurred in front of deep warm high–pressure ridges in mid–latitude regions and on the left side of the axis of the subtropical westerly jet stream. The isotherms in this area were relatively dense (i.e., large gradients), and the wind speed was high, with strong horizontal and/or vertical cyclonic wind shear. In addition, the NCCT usually occurred near the zero–divergence or zero–vorticity line and in areas with large vertical wind speed gradients. There were also strong vertical and horizontal wind shears in this area, which could easily trigger severe turbulence. Furthermore, the NCCT in the Southern Hemisphere mostly occurred at the intersection of cold and warm temperature advections (i.e., near the zero–temperature advection line), and the turbulence point was located near the high–altitude frontal zone where there was a strong gradient of cold and warm advections. There was temperature inversion with pseudo–equivalent potential temperatures in the middle and lower troposphere on the warmer side of the turbulence point. The unstable stratification of cold air at the top and warm air at the bottom was conducive to triggering convection from the ground, forming strong convective clouds, and causing severe turbulence.

Research on the spiral case and external concrete structural response under limit operation state

Abstract As the key component of hydroelectric generating units, the spiral case is primarily responsible to make the fluid flow out in a uniform and axisymmetric way. The structural response of the spiral case and external concrete under hydraulic pressure will have an effect on the operational security and power generation efficiency of the whole unit. In this paper, a three-dimensional fluid-structure coupling model of the spiral case and concrete under limit operation state is established. Based on the computational fluid mechanics theory, the flow domain inside the spiral case is simulated to study the stress and deformation structural response of the spiral case and external concrete under the action of maximum inner hydraulic pressure. The value and position of the maximum stress and deformation are determined. The fluid-structure coupling simulation shows that severe turbulence occurs in the middle of the flow channel. The maximum equivalent stress of the spiral case is located near its tongue and there would possibly be a risk of local structural damage. The external concrete can effectively share part of the load from the spiral case, so as to keep the strength and stiffness of the overall structure being within safe levels under the limit state. The results can provide support to the structural optimization and construction of the spiral case, which is helpful for the safety and stability of station operation.

A Numerical Study of Clear-Air Turbulence over North China on 6 June 2017

On 6 June 2017, four severe clear-air turbulence (CAT) events were observed over northern China within 3 h. These events mainly occurred at altitudes between 8.1 and 9.5 km. The characteristics and possible mechanisms of the CAT events in the different regions are investigated here using the weather research and forecasting (WRF) model. The simulated wind and temperature fields in a 27 km coarse domain were found to be in good agreement with those of the ERA5 (European Centre for Medium-Range Weather Forecasts Reanalysis v5) and the observed soundings of operational radiosondes over northern China. In terms of synoptic features, the region where the turbulence occurred is characterized by a southwest–northeast upper-level jet stream. The upper-level jet stream observed at an altitude of 10.4 km consistently moved eastwards, with a maximum wind speed of 61.7 m/s. Simultaneously, the upper-level front–jet system on the cyclonic shear side of the upper-level jet stream also exhibited an eastward motion. The developed upper-level front–jet system induced significant vertical wind shear (VWS) and tropopause folding in the vicinity of these CAT events. Despite the high stability resulting from tropopause folding, the presence of strong VWS (1.90 × 10−2 s−1–2.55 × 10−2 s−1) led to a low Richardson number (Ri) (0.24–0.88) and caused Kelvin–Helmholtz instability (KHI), which ultimately induced CAT. Although a standard numerical weather forecast resolution of tens of kilometers is adequate to capture turbulence for most CAT events, it is still necessary to use high-resolution numerical simulations (such as 3 km) to calculate more accurate CAT indices (such as Ri) for CAT prediction in some specific cases.

Research and Optimization on the Exhaust Flow Characteristics Based on Energy-Splitting Method of the Low-Speed Marine Diesel Engine

Abstract In this study, an optimization scheme for exhaust flow characteristics based on the energy-splitting method is proposed. The low-speed marine diesel engine adopts the exhaust energy-splitting method during the exhaust process. Based on this, a one-dimensional calculation model, a three-dimensional calculation model, and a three-dimensional model of the gas collection box are established. After splitting, the vortex structure in the same phase of the gas collection box has a larger scale, higher flowrate, more significant entropy increase, and more severe turbulence dissipation. The length and diameter of the high-grade gas collection box are optimized. The results show that after optimization, the flow energy dissipation brought by the vortex structure is reduced, and the outlet pressure and flow velocity of the gas collection box are increased.

Severity assessment of sudden plunging motion for jet transport aircraft in response to severe atmospheric turbulence

PurposeThe purpose of this paper is to present a comparative study of flight circumstances, dynamic stability characteristics and controllability for two transport aircraft in severe atmospheric turbulence at transonic cruise flight for the purpose to obtain the prevention concepts of injuries to passengers and crew members for pilot training in International Air Transport Association (IATA) – Loss of Control In-flight (LOC-I) program.Design/methodology/approachA twin-jet and a four-jet transport aircraft encountering severe atmospheric turbulence are the study cases for this paper. The nonlinear unsteady aerodynamic models are established through flight data mining and the fuzzy-logic modeling technique based on the flight data of flight data recorder. This method can be adopted to examine the influence of horizontal wind shear and crosswind on loss of control, dynamic stability characteristics and controllability for transport aircraft in different weights and different sizes in tracking aviation safety of existing different types of aircraft.FindingsThe horizontal wind shear or crosswind before the turbulence encounter will easily induce rolling motion and then initiate the sudden plunging motion during the turbulence encounter. The roll rate will increase the oscillatory rolling motion during plunging motion, if the rolling damping is insufficient. The drop-off altitude will be enlarged by the oscillatory rolling motion during the sudden plunging motion.Research limitations/implicationsA lack of the measurement data of vertical wind speed sensor on board to verify the estimated values of damping term is one of the research limitations for this study. The fact or condition of being severe in sudden plunging motion can be judged through the analysis of oscillatory derivatives with both dynamic stability and damping terms.Practical implicationsThe roll rate will increase the oscillatory rolling motion during plunging motion, if the rolling damping is insufficient. The drop-off altitude will be enlarged by the oscillatory rolling motion during the sudden plunging motion. The horizontal wind shear or crosswind before the turbulence encounter will easily induce rolling motion and then initiated the sudden plunging motion during the turbulence encounter. If the drift angle is large, to turn off the autopilot of yaw control first and stabilize the rudder by the pedal. When passing through the atmosphere turbulence area, the pilots do not need to amend the heading angle urgently.Social implicationsThe flight safety prevention in avoidance of injuries for passengers and cabin crews is essential for the airlines. The horizontal wind shear or crosswind before the turbulence encounter will easily induce rolling motion and then initiated the sudden plunging motion during the turbulence encounter.Originality/valueThe flight safety prevention in avoidance of injuries for passengers and cabin crews is essential. The present assessment method is an innovation to examine the loss of control problems of aviation safety and promote the understanding of aerodynamic responses of the jet transport aircraft. It is expected to provide a valuable lecture for the international training courses for IATA – LOC-I program after this paper is being published.

Coupled motion characteristic of standard flag and inverted flag in tandem arrangement

In this paper, the dynamics of the flow-induced flutter of standard flag and inverted flag in tandem arrangement were experimentally studied in wind tunnel. The kinematics of the flapping flags was investigated using high-speed camera and the flow field around the flags were examined using particle image velocimetry technique. The experimental results show that the critical velocity of inverted flag and standard flag in tandem were both decreased due to the flow perturbation between two flags. In particular, the hysteresis loop of the tandem standard flag was decreased significantly compared with single standard flag. Hence, the flow velocity range for flag flapping is broadened widely as compared to that of a single flag. By the action of the flapping flags, flow around the tandem flags exhibited severe turbulence. Small-scale vortices and Kelvin–Helmholtz instabilities could be observed. These findings will provide theoretical support for the mechanism design based on flag fluttering and overcoming the inherent limitations of the single flag in practical application.

Multifunctional difluoroboron β-diketonate-based luminescent receiver for a high-speed underwater wireless optical communication system.

The last decade has witnessed considerable progress in underwater wireless optical communication in complex environments, particularly in exploring the deep sea. However, it is difficult to maintain a precise point-to-point reception at all times due to severe turbulence in actual situations. To facilitate efficient data transmission, the color-conversion technique offers a paradigm shift in large-area and omnidirectional light detection, which can effectively alleviate the étendue limit by decoupling the field of view and optical gain. In this work, we investigated a series of difluoroboron β-diketonate fluorophores by measuring their photophysical properties and optical wireless communication performances. The emission colors were tuned from blue to green, and >0.5 Gb/s data transmission was achieved with individual color channel in free space by implementing an orthogonal frequency-division multiplexing (OFDM) modulation scheme. In the underwater experiment, the fluorophore with the highest transmission speed was fabricated into a 4×4 cm2 luminescent concentrator, with the concentrated emission from the edges coupled with an optical fiber array, for large-area photodetection and optical beam tracking. The net data rates of 130 Mb/s and 217 Mb/s were achieved based on nonreturn- to-zero on-off keying and OFDM modulation schemes, respectively. Further, the same device was used to demonstrate the linear light beam tracking function with high accuracy, which is beneficial for sustaining a reliable and stable connection in a dynamic, turbulent underwater environment.

The effects of a spur dike location in a 90° sharp channel bend on flow field: Focus on anisotropy degree and anisotropy nature

In this research, the flow features around a spur dike located in a 90˚ sharp channel bend have been studied experimentally in detail. Results showed that the effects of the spur dike on upstream sections increased by increasing α (spur dike location from the beginning of the bend). In addition, by increasing α, the horseshoe vortex (C3) and secondary flow in the channel bend (C1) strengthened. The energy and the Reynolds shear stress in the C3 region decreased by increasing α. It is recommended to use a Barycenteric Map (BM) instead of the normal Reynolds stresses to find the anisotropy nature accurately. A strong anisotropic condition was detected at the border of the recirculation flow region and the main flow. However, in the C3 and the interaction regions, the isotropy condition improved. In the main flow region, by increasing α, the isotropy degree improved. However, by increasing α, an increase in the development of the region with a high anisotropy degree towards the recirculation region was observed. The anisotropy degree in the near-bed layer region and the shear layer region is comparable. However, the anisotropy nature is different. The maximum error of the numerical simulation based on isotropic turbulence occurred at the shear layer region where the severe cigar-shaped turbulence occurred.

An Investigation of Sudden Plunging Motion Mechanisms for Transport Aircraft during Severe Clear-Air Turbulence Encounter

An Investigation of Sudden Plunging Motion Mechanisms for Transport Aircraft during Severe Clear-Air Turbulence Encounter

Free-Space Optical Communications for 6G Wireless Networks: Challenges, Opportunities, and Prototype Validation

Numerous researchers have studied innovations in future sixth-generation (6G) wireless communications. Indeed, a critical issue that has emerged is to contend with society's insatiable demand for high data rates and massive 6G connectivity. Some scholars consider one innovation to be a break-through-the application of free-space optical (FSO) communication. Owing to its exceedingly high carrier frequency/bandwidth and the potential of the unlicensed spectrum domain, FSO communication provides an excellent opportunity to develop ultrafast data links that can be applied in a variety of 6G applications, including heterogeneous networks with enormous connectivity and wireless backhauls for cellular systems. In this study, we perform video signal transmissions via an FPGA-based FSO communication prototype to investigate the feasibility of an FSO link with a distance of up to 20 km. We use a channel emulator to reliably model turbulence, scintillation, and power attenuation of the long-range FSO channel. We use the FPGA-based real-time SDR prototype to process the transmitted and received video signals. Our study also presents the channel-generation process of a given long-distance FSO link. To enhance the link quality, we apply spatial selective filtering to suppress the background noise generated by sun-light. To measure the misalignment of the transceiver, we use sampling-based pointing, acquisition, and tracking to compensate for it by improving the signal-to-noise ratio. For the main video signal transmission testbed, we consider various environments by changing the amount of turbulence and wind speed. We demonstrate that the testbed even permits the successful transmission of ultra-high-definition (UHD: 3840 × 2160 resolution) 60 fps videos under severe turbulence and high wind speeds.

Статистический анализ конвективных процессов над Апшеронским полуостровом

This paper is focuses on to determine the air masses observed during convective processes in Baku and the Absheron Peninsula in 2011-2020. As well as to identify the frequency of air masses and atmospheric phenomena by seasons and years. The purpose of this study is to determine weather phenomena that is significantly influence the safety and the operational activity of air traffic, particularly, in the areas of the aerodrome and route. The formation of thunderstorms is a particularly important meteorological event that has major relevance to aviation safety. Despite all the safety improvements, the weather is still today a major cause of aviation accidents and incidents. According to the International Civil Aviation Organization (ICAO) statistics, 15-20 % of plane crashes are caused by severe weather conditions. Hazards associated with convective weather include thunderstorms with severe turbulence, intense up- and downdrafts, lightning, hail, heavy precipitation, icing, wind shear, microbursts and strong low-level winds. As a source of the information regular observations of Heydar Aliyev International Airport, also soundings, satellite images, surface and upper air maps were used.

Structure health inspection for aging transport aircraft

Purpose This study aims to present a diagnosis method to inspect the structure health for aging transport aircraft based on the postflight data in severe clear-air turbulence at transonic flight. The purpose of this method development is to assist certificate holder of aircraft maintenance factory as a complementary tool for the structural maintenance program to ensure that the transport aircraft fits airworthiness standards. Design/methodology/approach In this study, the numerical approach to analyze the characteristics of flight dynamic and static aeroelasticity for two four-jet transport aircraft will be presented. One of these two four-jet transport aircraft is an aging one. Another one is used to demonstrate the order of magnitude of the static aeroelastic behaviors. The nonlinear unsteady aerodynamic models are established through flight data mining and the fuzzy-logic modeling technique based on postflight data. The first and second derivatives of flight dynamic and static aeroelastic behaviors, respectively, are then estimated by using these aerodynamic models. Findings Although the highest dynamic pressure of aging aircraft is lower, the highest absolute value of static aeroelastic effects response to the wing of aging aircraft is about 3.05 times larger than normal one; the magnitude variations of angles of attack are similar for both aircrafts; the highest absolute value of the static aeroelastic effects response to the empennage of aging aircraft is about 29.67 times larger than normal one in severe clear-air turbulence. The stabilizer of aging aircraft has irregular deviations with obvious jackscrew assembly problems, as found in this study. Research limitations/implications A lack of the measurement data of vertical wind speed sensor on board to verify the estimated values of damping term is one of the research limitations of this study. This research involved potential problem monitoring of structure health for transport aircraft in different weights, different sizes and different service years. In the future research, one can consider more structural integrity issues for other types of aircraft. Practical implications It can be realized from this study that the structure of aging transport aircraft may have potential safety threat. Therefore, when the airline managed aging transport aircraft, it ought to be conducted comprehensive and in-depth inspections to reduce such safety risks and establish a complete set of safety early warning measures to deal with the potential problem of aircraft aging. Social implications It can be realized that the structure of aging transport aircraft has potential safety threat. The airline managed aging transport aircraft; it should conduct comprehensive and in-depth inspections to reduce safety risks and establish a complete set of safety early warning measures. Originality/value This method can be used to assist airlines to monitor aging transport aircraft as a complementary tool of structural maintenance program to improve aviation safety, operation and operational efficiency.

WindPACT 1.5 MW Wind Turbine Rotor Dynamic Loads Under the Effect of Atmospheric Turbulence

The increasing demand for energy in the modern world, and the environmental effects of conventional energy sources, necessitate the need for renewable energy. Among the renewable energy sources, wind energy provides a clean and sustainable source of energy. Since the wind is of turbulent nature, the dynamic behaviour of wind turbines is highly affected by the turbulence intensity value. The study of dynamic loads and behaviour of wind turbine components is of crucial importance to making decisions regarding a wind turbine’s operation. In this work, the rotor dynamics of the WindPACT 1.5 MW wind turbine are studied under the influence of atmospheric turbulence. Four different wind fields with a mean wind speed value of 12 m/s, and turbulence intensities of 1%, 10%, 25% and 50% are simulated for the study. Rotor thrust force and torque are evaluated for each turbulence intensity. It was found that as the turbulence intensity increased, the fluctuations of the load around the mean value increased severely. For the rotor thrust, although the mean value is nearly unchanged, the standard deviation increases by 325% for the 50% turbulence intensity compared to the 1% intensity. An enormous increase in the rotor torque’s standard deviation occurs as well, for the 50% intensity compared to the 1% intensity, a 1300% increase occurs. The extremely high difference implies complications not only in the tower dynamics but also in the added cost of variable speed control continuously in operation. Continuous monitoring of wind speeds is highly recommended for the decision of putting the turbine into brake in such cases of severe turbulence.

Направления и тенденции развития процесса цифровой трансформации в агропродовольственной сфере

The article considers the relevance of the problem of digital transformation development in the context of global economic changes. The issues of the agro-food sector of development are investigated, the factors hindering the digitalizations of process development of the agro-industrial complex are identified. The research uses process, structural, institutional and integrated approaches. Their advantages are shown, limitations of their use are revealed. The directions of the process of digital transformation of development in the agro-food sector are determined, in particular, the creation of a digital education system for training and retraining of personnel, the development of new digital products, innovative technologies, infrastructure, an adaptive mechanism for managing digital processes, etc. The assessment of process development in Germany, Singapore, Israel is given. The necessity of using the experience of foreign countries, taking into account the peculiarities of the development of the digitalization process in Russia, is shown. In modern conditions, ensuring technological independence, national and food security is carried out under the influence of severe turbulence of foreign policy and economic sanctions from unfriendly countries. Therefore, new digital innovative technologies of development is becoming a driver of economic growth and improving the level and quality of life of the population of many countries. The creation and implementation of new digital innovative technologies of the future will contribute to a large-scale transformation in the production and management process in the agro-food sector. The use of new opportunities of digital transformation will significantly strengthen competitive advantages in the development of the economy of enterprises, industries, regions and the country as a whole. At the same time, structural problems in the agro-food sector of the country hinder the development of the digitalization process. In solving these problems, it is advisable to use digital innovative technologies, design the development of new digital products taking into account the peculiarities of the development of the agro-food sector. This will significantly increase the volume of food production and strengthen Russia’s food independence.

Movement mechanisms for transport aircraft during severe clear-air turbulence encounter

AbstractThe objective of this paper is to present the movement mechanisms of transport aircraft response to severe clear-air turbulence to obtain the loss of control prevention for pilot training in IATA – Loss of Control In-flight (LOC-I) program. The transport aircraft in transonic flight is subjected to severe clear-air turbulence, resulting in a sudden plunging motion with the abrupt change in flight attitude and gravitational acceleration. The comparative analyses of the flight environment and aircraft response to severe clear-air turbulence for two four-jet aircraft are studied. The one with a larger dropped-off altitude during the plunging motion will be chosen to construct the movement mechanism. The nonlinear unsteady aerodynamic model of the chosen transport is established through flight data mining and the fuzzy-logic modeling of artificial intelligence technique based on post-flight data. The crosswind before the turbulence encounter will easily induce a rolling motion and then the sudden plunging motion during the turbulence encounter. The influences of the varying vertical wind and crosswind on loss of control are presented. To formulate preventive actions, the situation awareness of varying crosswind encountering for the operational pilot will be studied further in the future. The present study is initiated to examine the possible mitigation concepts of accident prevention for the pilot training course of IATA – Loss of Control In-flight (LOC-I) program.

Wind Turbine Blade Dynamics Simulation under the Effect of Atmospheric Turbulence

Wind energy is one of the fastest growing sources of renewable energy because of its cleanliness and sustainability. Due to the turbulent nature of wind, a wind turbine experiences severe dynamic loading and faces the danger of fatigue failure. In addition, severe blade deflections imply failure by tower strikes. For this reason, the study of blade deflections under different turbulence conditions is of high importance. In this work, a wind turbine’s blade is simulated under different turbulent conditions. Four different wind fields are generated with a mean wind velocity of 12 m/s and turbulence intensities of 1, 10, 25, and 50%. The blade deflections are calculated in the out-of-plane and in-plane directions as a time-marching series with different blade azimuth positions. The higher the turbulence intensity, the severer the fluctuations of the deflections around its mean value. For the 50% turbulence intensity, the standard deviation of the out-of-plane deflection is 600% larger than that of the 1% turbulence intensity case. The maximum deflections increase significantly as well. A maximum of 3.78 m of out-of-plane tip deflection leads to the danger of a tower strike. And a positive tip deflection of 0.07 m in the in-plane direction indicates that the blade goes against its natural behavior and against the inertial loads while rotating. Continuous monitoring of wind conditions is a must, to put the turbine on brake in cases of gusts and severe turbulence. In areas of high turbulence, downwind turbines can provide a better alternative to allow blade deflections without the danger of tower strikes. Doi: 10.28991/ESJ-2023-07-01-012 Full Text: PDF

Quantitative Assessment of Dynamic Stability Characteristics for Jet Transport in Sudden Plunging Motion

In this paper, we present a monitoring program of loss control prevention for airlines to enhance aviation safety and operational efficiency. The assessments of dynamic stability characteristics based on the approaches of oscillatory motion and eigenvalue motion modes for jet transport aircraft response to sudden plunging motions are demonstrated. A twin-jet transport aircraft encountering severe clear-air turbulence in transonic flight during the descending phase was examined as the study case. The flight results in sudden plunging motions with abrupt changes in attitude and gravitational acceleration (i.e., the normal load factor) are provided. Development of the required thrust and aerodynamic models with the flight data mining and the fuzzy logic modeling techniques was carried out. The oscillatory derivatives extracted from these aerodynamic models were then used in the study of variations in stability characteristics during the sudden plunging motion. The fuzzy logic aerodynamic models were utilized to estimate the nonlinear unsteady aerodynamics while performing numerical integration of flight dynamic equations. The eigenvalues of all motion modes were obtained during time integration. The positive real part of the eigenvalues is to indicate unstable motion. The dynamic stability characteristics during sudden plunging motion are easily judged by the values in positive or negative. The present quantitative assessment method is an innovation to examine possible mitigation concepts of accident prevention and promote the understanding of aerodynamic responses of the jet transport aircraft.

Energy dissipation in violent three-dimensional sloshing flows induced by high-frequency vertical accelerations

The European H2020 project SLOWD is aimed to investigate the fuel sloshing damping effect to reduce the design loads on aircraft wings. Wings house the fuel tanks and are highly flexible structures that can significantly deform under gust loads. In the recent experiment by Martinez-Carrascal and González-Gutiérrez [“Experimental study of the liquid damping effects on a SDOF vertical sloshing tank,” J. Fluids Struct. 100, 103172 (2021)], the complex problem of the fuel sloshing inside a flexible wing structure was significantly simplified by considering a partially filled vertically heaving tank attached to a system of springs. In the present research, a smoothed particle hydrodynamic model was adopted to evaluate the energy dissipated in the three-dimensional sloshing flow obtained using the same tank motions. From a numerical point of view, the simulation of such a violent flow is rather challenging, the involved vertical accelerations being as large as 10 g. The resulting flow is extremely complex because of the severe turbulence developed, the violent impacts, and the considerable fragmentation of the air–liquid interface. The role of the viscosity is investigated by taking into account two different liquids. Finally, some comparisons between three-dimensional results and previous two-dimensional studies are also discussed.