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There are significant variations in the fuel consumption of aircraft during the descent phase of a flight. This paper uses aircraft flight data measurements to develop an improved understanding of these variations. A model of the aircraft engines is developed that is matched to flight data and shown to reproduce the time history of engine parameters. This model is used to determine the overall engine efficiency at each point during a descent. This enables an energy breakdown to be completed, in terms of mechanical energy from fuel, gravitational potential energy and kinetic energy. During descent, the aircraft engines operate at low overall pressure ratios corresponding to low fuel flow rates and low overall efficiencies. On average, the engine overall efficiency during descent is one-third of cruise efficiency. The airframe aerodynamic performance is deteriorated during descent with an average lift-to-drag ratio that is 87% of the average value at cruise. There are also large variations in air-track efficiency, and for the flights analysed the great circle descent distance was found to be 85% of the average descent air distance. To minimise fuel burn, flights should cruise as far as possible before starting descent and follow a trajectory with the shortest possible air distance. The descent air speed should be set to maximise the aircraft lift-to-drag ratio. Such descents could save up to 0.5% of the total aircraft mass in fuel.

The newly proposed ground test technique for aeroelastic flutter emulation is applied to examine the effectiveness of passive flutter suppression. The technique is to substitute wind-tunnel flutter test by emulating unsteady aerodynamic force using several point-loading actuators. Besides the simplicity of the technique, the essential advantage of applying it to the flutter test is that it has unlimited airspeed range, provided that the proper aerodynamic model and actuators are available. Since all the previous works on the emulated flutter test has been performed for the rectangular plate wings, an example of passive flutter suppression design for the swept-back plate structure model is studied, in this paper. The delay of the flutter onset due to the structural modification is analytically and experimentally observed using typical methods, namely root-locus and wind-tunnel test. The flutter emulation test technique is also applied to the same structure. The results show that the flutter emulation technique is capable of validating the flutter suppression effect. The close correlation of the flutter test results obtained by the emulated flutter test and the other two conventional methods suggests an alternative experimental validation of flutter suppression design.

Purpose The purpose of this study is to detect and reconstruct a fault in pitot probe and static ports, which are components of the air data system in commercial aircrafts, without false alarm and no need for pitot-static measurements. In this way, flight crew will be prevented from flying according to incorrect data and aircraft accidents that may occur will be prevented. Design/methodology/approach Real flight data collected from a local airline was used to design the relevant system. Correlation analysis was performed to select the data related to the airspeed and altitude. Fault detection and reconstruction were carried out by using adaptive neural fuzzy inference system and artificial neural networks, which are machine learning methods. MATLAB software was used for all the calculations. Findings No false alarm was detected when the fault test following the fault modeling was carried out at 0–2 s range by filtering the residual signal. When the fault was detected, fault reconstruction process was initiated so that system output could be achieved according to estimated sensor data. Practical implications The presented alternative analytical redundant airspeed and altitude calculation scheme could be used when the pitot-static system contains any fault condition. Originality/value Instead of using the methods based on hardware redundancy, the authors designed a new system within the scope of this study. Fault situations that may occur in pitot probes and static ports are modeled and different fault scenarios that can be encountered in all flight phases have been examined.

This letter proposes a novel method for model-aided synthetic airspeed estimation of UAVs. The major contribution of the proposed algorithm is that the synthetic airspeed measurement is newly formulated for analytical redundancy. This filter only requires inertial measurement unit (IMU), airflow angles, and elevator control input along with a simple aircraft model containing only three lift coefficient parameters; no GPS or complex aircraft dynamic model are required. Particularly, two novel filters (unscented Kalman filter and complementary filter) are proposed and evaluated without direct airspeed and GPS measurements. Flight test results of a UAV demonstrated that the proposed algorithm yields accurate estimated airspeed, demonstrating its effectiveness for analytical redundancy.

Flying animals exploit highly nonlinear dynamics to achieve efficient and robust flight control. It appears that the distributed flow and force sensor arrays found in flying animals are instrumental in enabling this performance. Using a wind-tunnel wing model instrumented with distributed arrays of strain and pressure sensors, we characterized the relationship between the distributed sensor signals and aerodynamic and load-related variables. Estimation approaches based on nonlinear artificial neural networks (ANNs) and linear partial least squares were tested with different combinations of sensor signals. The ANN estimators were accurate and robust, giving good estimates for all variables, even in the stall region when the distributed array pressure and strain signals became unsteady. The linear estimator performed well for load estimates but was less accurate for aerodynamic variables such as angle of attack and airspeed. Future applications based on distributed sensing could include enhanced flight control systems that directly use measurements of aerodynamic states and loads, allowing for increase maneuverability and improved control of unmanned aerial vehicles with high degrees of freedom such as highly flexible or morphing wings.

The problem of determining feasible maneuver envelope in multi-unmanned aerial vehicle (multi-UAV) formations is considered. In the leader–follower framework, an analysis is carried out relating th...

In this article, a numerical investigation was performed on a quadrotor UAV propeller with the aim of examining effects of airspeed and rotational speed on thrust coefficient, which is one of the most important parameters on propeller aerodynamic performance. In that purpose, Computational Fluid Dynamics (CFD) analyses of an 11-inch propeller were carried out at different airspeeds and rotational speeds in vertical climbing flight condition. In order to have optimum number of mesh elements in computational domain, mesh independence analyses were also conducted. In conclusion, results of the analyses with k-ω SST turbulence model were shown that, increase in rotational speed was leaded to higher turbulent kinetic energy. Furthermore, higher rotational speeds also resulted in higher differences between numerical estimations and experimental data, but found to become more independent from airspeed.

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).

An electric propulsion model for propeller-driven aircraft is developed with the aim of minimising the power consumption for a given airspeed and thrust. Blade Element Momentum Theory (BEMT) is employed for propeller performance predictions fed with aerodynamic aerofoil data obtained from a proposed combined Computational Fluid Dynamics (CFD)–Montgomerie method, which is also validated. The Two-Dimensional (2D) aerofoil data are corrected to consider compressibility, three-dimensional, viscous and Reynolds-number effects. The BEMT model showed adequate fitting with experimental data from the University of Illinois Urbana Champaign (UIUC) database. Additionally, Goldstein optimisation via vortex theory is employed to design pitch and chord distributions minimising the induced losses of the propeller. Particle swarm optimisation is employed to find the optimal value for a wide range of geometrical and operational parameters considering some constraints. The optimisation algorithm is validated through a study case where an existing optimisation problem is approached, leading to very similar results. Some trends and insights are obtained from the study case and discussed regarding the design of an optimal propulsion system. Finally, CFD simulations of the study case are carried out, showing a slight relative error of BEMT.

Stratospheric airships are lighter-than-air vehicles that work at an altitude of 20km in the lower calm portion of the stratosphere. They can be used as real-time surveillance platforms for environment monitoring and civil communication. Solar energy is the ideal power choice for long-endurance stratospheric airships. Attitude control is important for airships so that they can point at a target for observation or adjust the attitude to improve the output performance of solar panels. Stratospheric airships have a large volume and semi-flexible structure. The typical actuators used are aerodynamic surfaces, vectored thrust and ballonets. However, not all these actuators can work well under special working conditions, such as low density and low speed. In this study, moving-mass control is introduced to stratospheric airships because its control efficiency is independent of airspeed and atmospheric density. A nonlinear feedback controller based on generalised inverse with a nonlinear mapping module is designed to implement moving-mass control. Such a new station keeping scheme with moving masses is proposed for airships with different working situations.

This paper investigates robustness and finite-time stability issues for the phase separation problem in standoff target tracking. First, via a new angle, existing results concerning the stability o...

Flutter and limit cycle oscillation (LCO) are important phenomena that need to be considered in aircraft design. Previous harmonic-balance-based flutter and LCO prediction methods either have low l...

In turbulent flows as in HVAC applications, the fluctuation of air speed can affect the sensation of thermal comfort. This study is a part of a larger experimental and numerical campaign intended t...

The Energy Saving Car Contest (KMHE) is a contest organized by the Ministry of Research, Technology and Higher Education (Kemenristekdikti). This is a contest among students to make a national level fuel efficient vehicle. The purpose of designing this design is to produce an energy-efficient car body design "Mataram Proto" and to produce a vehicle that has a good aerodynamic level. This design of the car body is designed elegantly but still has good aerodynamics and does not reduce the safety aspects of the driver. The process of making a car body design uses Autodesk Inventor and the process of aerodynamic analysis of the Mataram Proto car body uses Ansys Mechanical software. Aerodynamic testing was carried out at an air speed of 45 km / h or 12.5 m / s. From the previous Mataram Proto body test results, the drag coefficient was 0.233 and the lift coefficient was 0.1887 and from the Mataram Proto V5 car body test, the drag coefficient was 0.47 and the lift coefficient was 9.95. From the results of this test, it shows that the previous Mataram Proto car body had a better aerodynamic level due to the difference in the input of different airspeed variables, where the air velocity on the previous Mataram Proto car body was 40 (km / h) and the air speed on the Mataram Proto V5 body. amounting to 45 (km / hour).

Age‐related changes in survival and reproduction are common in seabirds; however, the underlying causes remain elusive. A lack of experience for young individuals, and a decline in foraging performance for old birds, could underlie age‐related variation in reproduction because reproductive success is connected closely to provisioning offspring. For seabirds, flapping flight during foraging trips is physiologically costly; inexperience or senescent decline in performance of this demanding activity might cap delivery of food to the nest, providing a proximate explanation for poor breeding success in young and old age, respectively. We evaluated the hypothesis that young and old Nazca boobies (Sula granti), a Galápagos seabird, demonstrate deficits in foraging outcomes and flight performance. We tagged incubating male and female adults across the life span with both accelerometer and GPS loggers during the incubation periods of two breeding seasons (years), during the 2015 El Niño and the following weak La Niña. We tested the ability of age, sex, and environment to explain variation in foraging outcomes (e.g., mass gained) and flight variables (e.g., wingbeat frequency). Consistent with senescence, old birds gained less mass while foraging than middle‐aged individuals, a marginal effect, and achieved a slower airspeed late in a foraging trip. Contrary to expectations, young birds showed no deficit in foraging outcomes or flight performance, except for airspeed (contingent on environment). Young birds flew slower than middle‐aged birds in 2015, but faster than middle‐aged birds in 2016. Wingbeat frequency, flap–glide ratio, and body displacement (approximating wingbeat strength) failed to predict airspeed and were unaffected by age. Sex influenced nearly all aspects of performance. Environment affected flight performance and foraging outcomes. Boobies' foraging outcomes were better during the extreme 2015 El Niño than during the 2016 weak La Niña, a surprising result given the negative effects tropical seabirds often experience during extreme El Niños., For seabirds, flapping flight during foraging trips is physiologically costly; inexperience or senescent decline in performance of this demanding activity might cap delivery of food to the nest, providing a proximate explanation for poor breeding success in young and old age, respectively. In this study, we evaluated age‐related variation in the foraging outcomes and flight performance of Nazca boobies (Sula granti), a long‐lived seabird breeding in Galápagos, during the 2015 El Niño and the following weak La Niña.

This paper focuses on the prediction of disturbance effects of the vertical acceleration of an aircraft flying in atmospheric turbulence. To this end, 5-hole probes with high-dynamic differential pressure sensors are installed in front of a fixed-wing unmanned aircraft system (UAS) and a manned experimental aircraft to measure the local airspeed and angle of attack of the airflow. Test flights are performed in light, moderate and severe turbulence to assess the anticipating character and the accuracy of the predicted acceleration. Thereby, depending on the flown airspeed, anticipation times up to 0.1 s are observed. For the UAS the prediction accuracy is assessed to be 71.19% for moderate turbulence and 71.05% for severe turbulence, where vertical acceleration disturbances higher than 30 m/s2are measured. The first manned test flight revealed a prediction accuracy of 61.97%.

During the current SARS‐CoV‐2 and tuberculosis global pandemics, public health and infection prevention and control professionals wrestle with cost‐effective means to control airborne transmission. One technology recommended by Centers for Disease Control and Prevention and the World Health Organization for lowering indoor concentration of these and other microorganisms and viruses is upper‐room ultraviolet 254 nm (UVC254) systems. Applying both a material balance as well as some nondimensional parameters developed by Rudnick and First, the impact of several critical parameters and their effect on the fraction of microorganisms surviving UVC254 exposure was evaluated. Vertical airspeed showed a large impact at velocities 0.05 m s−1. In addition, the efficacy of any upper‐room UVC system is influenced greatly by the mean room fluence rate as opposed to a simple volume‐ or area‐based dosing criteria. An alternative UVC254 dosing strategy was developed based on the fluence rate as a function of the UVC254 luminaire output (W) and the square root of the product of the room volume and the ceiling height., During the current SARS‐CoV‐2 and tuberculosis global pandemics, public health and infection prevention and control professionals wrestle with cost‐effective means to control airborne transmission. One technology recommended by CDC and WHO for lowering the indoor concentration of these and other microorganisms and viruses is upper‐room ultraviolet 254 nm systems. The design cycle for implementation of UVC systems starts with UVC dosing in the space and moves through many other steps before installation. This paper describes an alternative dosing strategy to the recently proposed volumetric dosing criterion.

Maintaining optimal parameters of the microclimate in the car along the route is the most important requirement for the passenger’s travel. In the 1st class passenger cars, maintaining optimal microclimate parameters is achieved through the operation of the air conditioning system, which provides individual regulation of the air temperature in each compartment. Individual air temperature control systems used in air conditioning systems are divided into two groups: active and passive.The article proposes for consideration a combined active-passive system with a separate air supply with a lower and higher temperature compared to the temperature maintained in the compartment and the installation of individual induction terminals, which makes it possible to increase the efficiency of individual regulation of air parameters in the compartment.To assess the uniformity of temperature distribution and air flow rate over the car volume with the proposed control scheme, a three-dimensional modeling of the distribution of these parameters in the compartment was carried out on the basis of Autodesk CFD software.The given simulation results indicate the uniformity of temperature and air flow rate distribution over the compartment volume, which makes it possible to characterize the proposed system as sufficiently energy efficient, easy to operate and reliable in operation.

A new method to estimate the aircraft heading angle, wind velocity, and airspeed bias error is proposed without relying on the magnetometer. A GPS, rate-gyro, pitot-static tube, and sideslip angle sensor are combined through a design of an extended Kalman filter based on a vectorial geometric relation among the ground, air, and wind velocity. The feasibility of the method is validated through a desktop simulation. The flight test is conducted utilizing the estimated yaw angle as a guidance variable to evaluate the performance of the method. The estimated wind information is compared to the automatic weather system nearby.

Evaporation pads and tunnel ventilation are commonly adopted in hen houses. To ensure the cooling efficiency of pads and airflow in the building, inlets with pads are often placed in sidewalls. Flaps are often fitted behind inlets to alleviate the sudden temperature drops that can be caused by pads. However, the airflows change their direction after entering from sidewalls with flaps, which affects the environment in the caged-hen occupied zone (OZ). This work explored the effect of inlet position and flap on airflow and temperature in laying hen house using computational fluid dynamics (CFD). The CFD model was validated by field experiments. Results showed that the inlet position and flap significantly affected the airflow and temperature near the inlet. An increased inlet area in the gable wall and a longer distance between cages and sidewall inlets increased air speed, decreased temperature, and improved airflow distribution uniformity in OZ. The maximum increase in air speed, decrease range in temperature, and reduction in the coefficient of air speed variation (CASV) was 0.37 m s−1, 0.19 °C and 11%, respectively. The flap also increased the air speed and decreased the temperature, but it reduced the airflow distribution uniformity. The maximum increase in air speed, decrease range in temperature, and increase of CASV was 0.15 m s−1, 0.07 °C and 6%, respectively. The increase in CASV reduced with the increased distance between the sidewall inlet and cages. Therefore, reducing the overlapping area between sidewall inlets and cages should be considered in practice.

Drying allows water to be removed and food to be preserved, however, this operation can degrade color. Punamuña leaves are aromatic and used for medicinal purposes in the Peruvian Andes. This research aimed to determine and model the drying kinetics, the diffusivity coefficient (Def), the activation energy (Ea), and the color of punamuña leaves. A horizontal dryer was used at 40, 50, and 60 °C and airspeed of 1.0 and 0.5 m / s; drying kinetics was modeled with 10 models. Def was determined with the Fick equation, Ea with the Arrhenius equation; the color was determined in the L* a* b* space. It was found that the triple exponential model with six parameters better represented the drying kinetics (R2> 99.73 and E

Wind data collection in the atmospheric boundary layer benefits from short-term wind speed measurements using unmanned aerial vehicles. Fixed-wing and rotary-wing devices with diverse anemometer technology have been used in the past to provide such data, but the accuracy still has the potential to be increased. A lightweight drone for carrying an industry-standard precision sonic anemometer was developed. Accuracy tests have been performed with the isolated anemometer at high tilt angles in a calibration wind tunnel, with the drone flying in a large wind tunnel and with the full system flying at different heights next to a bistatic lidar reference. The propeller-induced flow deflects the air to some extent, but this effect is compensated effectively. The data fusion shows a substantial reduction of crosstalk (factor of 13) between ground speed and wind speed. When compared with the bistatic lidar in very turbulent conditions, with a 10 s averaging interval and with the unmanned aerial vehicle (UAV) constantly circling around the measurement volume of the lidar reference, wind speed measurements have a bias between −2.0 % and 4.2 % (root-mean-square error (RMSE) of 4.3 % to 15.5 %), vertical wind speed bias is between −0.05 and 0.07 m s−1 (RMSE of 0.15 to 0.4 m s−1), elevation bias is between −1 and 0.7∘ (RMSE of 1.2 to 6.3∘), and azimuth bias is between −2.6 and 7.2∘ (RMSE of 2.6 to 8.0∘). Key requirements for good accuracy under challenging and dynamic conditions are the use of a full-size sonic anemometer, a large distance between anemometer and propellers, and a suitable algorithm for reducing the effect of propeller-induced flow. The system was finally flown in the wake of a wind turbine, successfully measuring the spatial velocity deficit and downwash distribution during forward flight, yielding results that are in very close agreement to lidar measurements and the theoretical distribution. We believe that the results presented in this paper can provide important information for designing flying systems for precise air speed measurements either for short duration at multiple locations (battery powered) or for long duration at a single location (power supplied via cable). UAVs that are able to accurately measure three-dimensional wind might be used as a cost-effective and flexible addition to measurement masts and lidar scans.

This paper considers a collaborative tracking control problem using a group of fixed-wing unmanned aerial vehicles (UAVs) with constant and nonidentical speeds. The dynamics of fixed-wing UAVs are modeled by unicycletype equations with nonholonomic constraints, assuming that UAVs fly at constant altitudes in the nominal operation mode. The controller is designed such that all fixed-wing UAVs as a group can collaboratively track a desired target’s position and velocity. This paper first presents conditions on the relative speeds of tracking UAVs and the target to ensure that the tracking objective can be achieved when UAVs are subject to constant-speed constraints. A reference velocity is constructed that includes both the target’s velocity and position as feedback, which is to be tracked by the group centroid. In this way, all vehicles’ headings are controlled such that the group centroid follows a reference trajectory that successfully tracks the target’s trajectory. A spacing controller is further devised to ensure that all vehicles stay close to the group centroid trajectory. Tradeoffs in the controller design and performance limitations of the target tracking control due to the constant-speed constraint are also discussed in detail. Experimental results with three fixed-wing UAVs tracking a target rotorcraft are provided.

HighlightsThe placement and operation of exhaust fans was assessed using CFD simulation.The effective temperature was used to evaluate the indoor thermal environment.The placement and operation of the exhaust fans mainly affected the airflow patterns in the part of the layer house closest to the fans.Abstract. The thermal environment inside a layer house significantly affects the growth, production, and health of the hens. Tunnel ventilation systems have been widely applied to control the indoor climate and air quality for large-scale poultry facilities around the world. Generally, only a few of the exhaust fans operate during mild seasons (spring and fall) in a tunnel-ventilated layer house depending on the outside air temperature. The decision about which exhaust fans to turn on affects the indoor airflow pattern and temperature distribution. However, little research has been reported that investigated the effects of the locations of exhaust fans on ventilation performance. In this study, a computational fluid dynamics (CFD) model was built and validated using field-measured data. The CFD model was then used to evaluate different ventilation strategies (combinations of exhaust fans) in a typical tunnel-ventilated layer house during the fall. The effective temperature was used to assess the performance of different ventilation strategies. Results showed that the locations of the exhaust fans significantly affected the indoor thermal environment, especially in the part of the house closest to the fans, because different locations of operating fans can generate different airflow patterns and affect the airflow through the animal-occupied zone. Based on the simulations, we conclude that the placement and operation of the exhaust fans can be optimized. Turning on the fans that are lower to the ground or near the sidewalls will result in more air bypassing the animal-occupied zones. Our results can help select the best ventilation strategy during the spring and fall in layer houses with tunnel ventilation systems. Keywords: Airflow distribution, Effective temperature distribution, Indoor thermal environments, Ventilation strategy.

Recently, the station-keeping of the stratospheric airship is an attractive topic due to its application to provide long-endurance communication and surveillance services. The motion of the stratospheric airship is sensitive to the wind because of the characteristics of large volume and low airspeed. When the wind speed exceeds the maximum airspeed, the airship may float out of the given station-keeping region. In such a case, how to recover to the station-keeping site is a necessary problem to consider. In this paper, the recovery trajectory optimization of the stratospheric airship is discussed and the purpose is to find the economical recovery flight trajectory to the station-keeping site. The trajectory optimization model is established by considering the motion model of the stratospheric airship, the atmospheric model, the wind field model, the solar radiation model, and the thermal model. To represent the exploitation of solar energy during the flight, the solar radiation collection problem is modeled for the airship whose hull is approximated by the double-ellipsoid geometry. Then the recovery trajectory optimization problem is formulated with constraints consideration and three recovery flight scenarios are put forward. The trajectory optimization problem is transformed into the nonlinear programming problem (NLP) by the orthogonal collocation and can be solved by the off-the-shelf NLP solver. The accuracy of the solution is improved by a modified ph-adaptive mesh refinement method. Two study cases are carried out to make a profound study of the recovery flight problem. In the first case, the basic characteristics of the flight trajectories using different recovery flight scenarios are compared and analyzed. Then the influence of the solar position on the recovery trajectory is discussed in the second case, which also gives some insights on the flight characteristics of the solar-powered stratospheric airship. The results of this paper may provide some important references for the station-keeping application of the stratospheric airship.

Effective ventilation reduces heat stress in sows. A numerical study was carried out to investigate the effects of airspeed and direction on the convective heat transfer around a sow having different postures and body mass. The convection characteristics of a sow were analysed in a virtual wind tunnel using computational fluid dynamics (CFD) tools. The four postures of the standing, sitting, reclining and lateral lying were included. The investigated sow masses ranged from 130 kg to 340 kg. The results show that: 1) The general convective heat transfer was higher when the sow was standing or sitting postures rather than in a reclining or lateral lying posture; 2) Wind direction affects the sow convective heat transfer coefficient. The convective heat transfer coefficient of a sow was largest when it was standing or sitting with the body axis 60° to wind direction. When reclining or lateral lying sow axis at 45° to wind direction, the convective heat transfer coefficient was the largest; 3) The convective heat transfer coefficient of a single sow can be used to predict the convective heat transfer coefficient of a sow amidst rows of multiple sows; 4) Sow body mass negatively affects the convective heat transfer coefficient; 5) The convective heat transfer coefficient of the sow's trunk is relatively low compared with other parts such as the legs, head etc. Based on these results, when a sow needs to be cooled during hot conditions, an oblique airflow is recommended, and airflow speed around the sow's trunk should be increased as much as possible.

This article proposes a novel dynamic model-aided navigation filter to estimate the safety-critical states of an aircraft including the effect of wind. Aerodynamic coefficients and control signals are used to predict the angular rates. Experimental flight results of a high-altitude long-endurance unmanned aerial vehicle (UAV) demonstrated improvement in attitude estimation compared to a model-based navigation algorithm that does not consider wind, as well as accurate attitude estimation without using gyroscope signals, demonstrating its effectiveness for analytical redundancy.

This paper presents a runtime assurance (RTA) framework for an unmanned aerospace application. RTA systems hold the promise of protecting feedback systems that contain advanced or experimental elem...

The use of natural ventilation strategy in a building is currently encouraged by the emergence of a pandemic Covid-19. In addition to its advantages in minimizing the use of electrical energy, the natural ventilation system is believed could reduce the possibility of spreading the virus. One design approach to this system is by using the window's design properly. Air movement inside a building should be utilized well to allow the movement from inlet to outlet. The position of the window was one of the variables examined in this study besides the types of the window. This study found that the use of a combination of 300 awnings produced the highest airspeed in the living room (R1), while a combination of horizontal sliding windows resulted in the highest air velocity in the bedroom (R2). Still, the airspeed generated from the two combinations less than the minimum level of it is generally required, 0.75 – 0.9 m/s.

This paper presents a thorough evaluation of three flutter prediction techniques based on the well-understood autoregressive moving-average (ARMA) parametric model. Other than the original stabilit...

Crushing feed grain involves hammer crushers, which are characterized by high specific energy consumption and its uneven fractional composition. It is possible to obtain high-quality shredded grain with less energy when using a centrifugal-impact crusher of the new design with a hole in the loading neck to supply the chopping chamber with additional air at a rate of up to 4.8m/s. An additional hole provides a 1.8...13-time increase in the airspeed through the unloading neck when the rotor’s rotation frequency changes from 3,750 to 2,250min–1, thereby enabling thetimely evacuation of the shredded material from the crusher. The regression equations have been derived to determine the structural and regime parameters of the shredder, which ensure the maximal performance andminimal unit energy costs. The greatest impact on crusher productivity is exerted by the diameter of the sieve holes and the area of the bunker’s unloading window. The greatest effect on the specific energy intensity of the grinding process is exerted by the diameter of the sieve holes. The maximal performance of the crusher, 1,440kg/h, and theminimal energy capacity, taking into consideration the achieved grinding degree, of 2.1W∙s/(kg∙grinding degree unit), are observed when using a sieve with the holes’ diameter of 7mm, the rotor’s rotation frequency of 3,500min–1, and the maximally open unloading window of the bunker, at F=1.458m2·10–3. The specific energy consumption for chopping barley is less by 1.22...1.89times than that of the hammer crushers RVO 35, DB-5, KD-2A. The dust-like fraction is less than 5.74%, which is half the amount of the hammer crusher DM-6. The rational crusher operation modes have been determined in order to prepare feed grain for feeding farm animals of different species and ages

Four candidate detect-and-avoid well clear definitions for unmanned aircraft systems encountering noncooperative aircraft are evaluated using safety and operational suitability metrics. These candi...

In recent years, the Active Flutter Suppression (AFS) employing Linear Parameter-Varying (LPV) framework has become a hot spot in the research field. Nevertheless, the flutter suppression technique is facing two severe challenges. On the one hand, due to the fatal risk of flight test near critical airspeed, it is hard to obtain the accurate mathematical model of the aeroelastic system from the testing data. On the other hand, saturation of the actuator may degrade the closed-loop performance, which was often neglected in the past work. To tackle these two problems, a new active controller design procedure is proposed to suppress flutter in this paper. Firstly, with the aid of LPV model order reduction method and State-space Model Interpolation of Local Estimates (SMILE) technique, a set of high-fidelity Linear Time-Invariant (LTI) models which are usually derived from flight tests at different subcritical airspeeds are reduced and interpolated to construct an LPV model of an aeroelastic system. And then, the unstable aeroelastic dynamics beyond critical airspeed are ‘predicted’ by extrapolating the resulting LPV model. Secondly, based on the control-oriented LPV model, an AFS controller in LPV framework which is composed of a nominal LPV controller and an LPV anti-windup compensator is designed to suppress the aeroelastic vibration and overcome the performance degradation caused by actuator saturation. Although the nominal LPV controller may have superior performance in linear simulation in which the saturation effect is ignored, the results of the numerical simulations show that the nominal LPV controller fails to suppress the Body Freedom Flutter (BFF) when encountering the actuator saturation. However, the LPV anti-windup compensator not only enhances the nominal controller’s performance but also helps the nominal controller to stabilize the unstable aeroelastic system when encountering serious actuator saturation.

This work presents the design, construction, instrumentation and thermal evaluation of a single-channel solar chimney under a warm-humid climate. A solar chimney (0.8 m width and 2 m length) with a capacity for varying the air gap (0–0.28 m), the inclination angle (0 − 90°), and the amount of energy absorbed by the absorber plate. A parametric study was performed with a total of 60 tests under laboratory conditions. A maximum temperature difference of 16.7 °C was obtained for an angle of 15° and a 0.075 m air gap, and when the air gap was varied, the highest air speed was 0.38 m s−1. The results show that a solar chimney can be used as a passive ventilation system, where up to 5 times more air flow can be removed in an enclosure, with a maximum air change rate (ACH) of 27.11 h−1, and a maximum efficiency of 88.9%. The data obtained can be used not only to select the configuration of a chimney but also for other applications where heating or the removal of air is required, such as for drying or in ventilated roofs.

The enhanced complexity and weight of conventional air data systems based on aerometric, aerodynamic, and vane sensor methods in using them on ultralight and small aircraft, is justified. The study reveals the theoretical foundations of the vortex method for measuring the incident air flow parameters and its implementation in the original system based on the vortex method using the original vortex sensor of the aerodynamic angle and true air speed. The algorithms of formation and processing of primary informative signals in the measuring channels of the aircraft air data system based on the vortex method are presented. The models are obtained and the quantitative estimation of instrumental errors of measuring channels is carried out.

The evolution of aircraft is closely linked to the study and improvement of propulsion systems. Determining the propulsion performance is a real challenge in aircraft modelling and design. In addition to theory-based approaches, experimental procedures are used to obtain a good estimation of propulsion performance. To evaluate piston-propeller propulsion, several experimental tests are required that can be very demanding in terms of time and money. This paper presents a procedure to estimate the performance of a propeller from a numerical approach using an improved blade element momentum theory. The methodology used rotation effect model and a high angle of attack lift coefficient correction model to increase the accuracy of the results. A computational fluid dynamics (CFD) analysis was also implemented. Polyhedral meshing and the realisable k–e turbulence model were applied to accurately describe the flow pattern around the propeller. Thus, the Reynolds Averaged Navier–Stokes equations were solved using ANSYS FLUENT software. These methods were applied on the UAS-S45 propeller designed and manufactured by Hydra Technologies in Mexico. An extensive investigation was performed for several flight conditions in terms of altitude and airspeed with the objective of determining the thrust coefficient, power coefficient and efficiency of the propeller. The CFD and blade element momentum theory results were compared with experimental data acquired from wind tunnel tests performed at the LARCASE Price-Paidoussis wind tunnel. The results of this comparison demonstrated that our approach is highly accurate.

Large-amplitude limit cycle oscillations (LCOs) in one degree of freedom (1DOF) in pitch and 2DOFs in pitch–heave induced by stall flutter are explored experimentally on a NACA0012 wing. Because st...

This paper proposes a novel dynamic model-aided navigation filter to estimate the safety-critical states of a high-altitude long-endurance (HALE) UAV without measurement of angle of attack (AOA) and sideslip angle (SSA). The major contribution of the proposed algorithm is that the synthetic AOA and SSA measurements are newly formulated for analytical redundancy. In the proposed filter, aerodynamic coefficients and control signals are utilized along with inertial measurement unit (IMU), Global Positioning System (GPS), and pitot tube measurements to estimate the navigation states as well as the steady and turbulent effects of 3D wind using random walk (RW) and Dryden wind models, respectively. Flight test results of a HALE UAV demonstrated that the proposed algorithm yields accurate estimated airspeed, AOA, SSA, attitude, angular rates, and 3D wind states, demonstrating its effectiveness for analytical redundancy.

Designing a stable and robust flight control system for an Unmanned Aerial Vehicle (UAV) is an arduous task. This paper addresses the trajectory tracking control problem of a Ducted Fan UAV (DFUAV) using offset-free Model Predictive Control (MPC) technique in the presence of various uncertainties and external disturbances. The designed strategy aims to ensure adequate flight robustness and stability while overcoming the effects of time delays, parametric uncertainties, and disturbances. The six degrees of freedom DFUAV model is divided into three flight modes based on its airspeed, namely the hover, transition, and cruise mode. The Dryden wind turbulence is applied to the DFUAV in the linear and angular velocity component. Moreover, different uncertainties such as parametric, time delays in state and input, are introduced in translational and rotational components. From the previous work, the Linear Quadratic Tracker with Integrator (LQTI) is used for comparison to corroborate the performance of the designed controller. Simulations are computed to investigate the control performance for the aforementioned modes and different flight phases including the autonomous flight to validate the performance of the designed strategy. Finally, discussions are provided to demonstrate the effectiveness of the given methodology.

LIFTING-LINE theory [1,2] is the foundation for much of our understanding of finite-wing aerodynamics. Solutions based on lifting-line theory are widely accepted and have been shown to be in good agreement with CFD [3-10]. From Prandtl’s analytic solution to the classical lifting-line equation [1,2], the wing section-lift distribution can be expressed as a Fourier series of the form [11] bL~ (θ)/L = (4/π)[sin(θ) + Σ∞n-2 Bnsin(nθ)]; θ = cos-1(-2z/b) (1) where b is the wingspan, L~ is the local wing section lift, L is the total wing lift, z is the spanwise coordinate, and Bn are the Fourier coefficients. For any given planform, the twist distribution required to produce this lift distribution can also be obtained using Prandtl’s lifting-line equation [12]. In steady level flight, L is equal to the weight, W, and the induced drag can be written as [11] Di = (2(W/b)2/πρV∞2)[1+ Σ∞n-2 Bn2] (2) where ρ is the air density and V∞ is the freestream airspeed.

The article is devoted to the development and research of the method of predicting the events on the trajectory of takeoff, climb and overcome highrise obstacles on the course. The prediction method is based on the energy approach to flight control, created by us in previous works. The mathematical formulation of the method is the energy balance equation describing the mutual influence of all acting forces in the aircraft-engine-environment" system. In this article, the equation is extended to ground modes of movement along the runway. For this, a term is added to the equation that takes into account the action of braking forces from the chassis. The balance equation allows us to directly obtain an algorithm for calculating the length of the forward trajectory required for the accumulation of the required amount of terminal energy. Takeoff trajectory includes ground and air segments. Therefore, the possibility of overcoming the obstacle is fixed by the algorithm at the point of a possible decision to takeoff, taking into account the next air segment. This point is reached before the decision-making airspeed prescribed by the flight manual is reached. This advance warning of the possibility of takeoff improves situational awareness of the pilot, which reduces stress and reduces the risk of erroneous actions. A computer stand was developed for the research. Single launches and series of statistical tests are possible. Takeoff scenarios are generated in the stand operator window, as well as initial runway conditions, atmospheric disturbances, aircraft configuration, and obstacle coordinates are specified. The parameters of random errors in the takeoff weight and centering are assigned, as well as the noise of longitudinal overload measurements are set. A large volume of deterministic and statistical tests of algorithms for predicting events on the takeoff trajectory was performed at the stand. Using the statistical analysis module, the characteristics of the range prediction errors to the take-off decision point and the nose wheel separation point were calculated. Probability densities and histograms of error distribution over five characteristic zones of deviations from the mean are constructed. The confidence intervals for calculating the mathematical expectation are obtained. A prototype of an electronic indicator of the takeoff trajectory with marks of predictive characteristic coordinates has been developed.

For an unmanned aerial vehicle (UAV) carrying out a maritime radar surveillance mission, there is a tradeoff between maximizing information obtained from the search area and minimizing fuel consumption. This article presents an approach for the optimization of a UAV's trajectory for maritime radar wide area persistent surveillance to simultaneously minimize fuel consumption, maximize mean probability of detection, and minimize mean revisit time. Quintic polynomials are used to generate UAV trajectories due to their ability to provide complete and complex solutions while requiring few inputs. Furthermore, the UAV dynamics and surveillance mission requirements are used to ensure that a trajectory is realistic and mission compatible. A wide area search radar model is used within this article in conjunction with a discretized grid in order to determine the search area's mean probability of detection and mean revisit time. The trajectory generation method is then used in conjunction with a multiobjective particle swarm optimization algorithm to obtain a global optimum in terms of path, airspeed (and thus time), and altitude. The performance of the approach is then tested over two common maritime surveillance scenarios and compared to an industry recommended baseline.