Glide Ratio Research Articles

Vertical Wind-Tunnel Testing of Steerable Cruciform Parachute System

This paper presents an experimental approach for testing a steerable cruciform parachute system using a vertical wind tunnel. A controller to stabilize the canopy heading is developed and tuned. A model that captures the open-loop heading dynamics is identified, and a rudimentary estimate of the glide ratio (GR) is obtained using inverse dynamics. The heading stabilization controller developed during the vertical wind-tunnel experiments is applicable during outdoor flight testing with only minor modifications, and the open-loop heading model and GR model both produce results that are consistent with data collected during outdoor flight testing. The vertical wind-tunnel testing methodology itself is discussed in terms of the cost and time savings as compared to traditional outdoor flight testing. Additionally, the extensibility of the vertical wind-tunnel testing methodology to other parachute systems is discussed. The vertical wind-tunnel approach to testing a system like the steerable cruciform provides the capability to investigate the viability of an untested parachute system rapidly while still providing realistic performance, thereby creating a repeatable and inexpensive alternative to outdoor flight testing.

A novel algorithm for conceptual design and optimisation of an affordable gliding airdrop platform using TCOMOGA

ABSTRACTUnlike conventional ballistic parachutes, gliding parachutes have been extensively used as guided precision aerial delivery system (GPADS) platforms in recent years. The reasoning may be found in gliding and manoeuvering capabilities, which make this kind of ram-air parachutes superior for precision aerial delivery application. In contrast, wing-shaped configuration along with more design variables create a cumbersome design procedure for this type of parachute. Especially, when an affordable configuration is demanded, the design procedure will be a more important problem. In this respect, an innovative integrated design framework is proposed in which significant design aspects are considered so that the gliding parachute configuration can be optimiseoptimised through a bi-objective optimisation problem to find optimum cost for achievable gliding ranges. To do so, the configuration is defined with minimum required parameters and design space is constrained by performance and stability as significant design requirements to guarantee the feasibility of the solutions in practice. The objective functions are defined in terms of gliding characteristics and amount of materials for fabrication which are representative for maximum reachable stand-off distance and unit cost, respectively. As an effective numerical optimisation method, a niched multi-objective genetic algorithm (MOGA) is used to generate a pareto-optimal set for a specific payload mass whereas constraints are handled through a tournament selection process. Based on results, the provided pareto front can aid the designers in decision-making and trade-off between demanded objectives for a payload weight. The underlying design problem is solved using an all-at-once (AAO) approach and the design loop converges to favourable results in a reasonable time. Finally, as a comparative study, an optimiseoptimised affordable cargo parachute is proposed for the GPADS application in which the material cost is reduced by at least 25% with respect to an available low-cost gliding parachute with the same glide ratio.

Aerodynamic Performance Study of Wind Turbine Blade for Variable Airfoils

We study the variable airfoils (NACA2414, NACA0024, NACA0012 and NACA2424) and compare for aerodynamic performance. XFOIL is used for finding out Lift coefficient, Drag coefficient, Glide ratio (Cl/Cd) and attack angle (α). for finding out the performance of the wind turbine blade we use blade element momentum (BEM) method.

PERANCANGAN AWAL SCALE MODEL GLIDER STTA-25-02_SAILPLANE

The knowledge and experience in aircraft design, especially for glider or sailplane are very important to have. Today, process of designing glider developed so rapidly, especially in America and Europe, one of the significant achievement is the performance aspect of glider. For example, the German-built Eta has a wingspan 30.78 m, aspect ratio 51 and wing loading 50.97 kg/m2, with glide angle of 0.8 degree and 3 km altitude, the glider able to fly 213 km in horizontal direction. Therefore, as the first step to understand the preliminary design of glider, it is important to start with designing a scale model glider STTA-25-02_Sailplane. The goals of this design are to get geometry and configuration of the glider, to obtained stability of glider and to gain performance data that meet with design requirements and objectives data (DR&O). The conclusions from the preliminary design of scale model glider STTA-25-02_Sailplane are the geometry and configuration are good, for example the achivement in performance, the minimum sink rate 0.52 m/s, the glide ratio more than 20 at a cruising speed over 13 m/s, stall speed 11.45 m/s at angle of attack 0 degree. In addition glider STTA-25-02_Sailplane has static and dynamic stability, the static stability condition is indicated by the value of trim angle is positive 1 degree, curve of Cma and Clfi has negative slope, Cnfi curve has positive slope. The dynamic stability condition is indicated by the eigen value for each mode o f movement are negative except on phugoid and spiral mode, eigen value for short period -5.7681 ± 7.0010, phugoid 0.0403 ± 1.1136, rool damping -32.6243, dutch roll -1.0468 ± 3.4891 and spiral 0.1467. Positive eigen value on phugoid and spiral mode can be solved by adding a control parameter of the controlsurfaces.

Tip Loss Factor Effects on Aerodynamic Performances of Horizontal Axis Wind Turbine

Abstract: Tip loss corrections are an important factor in Blade Element Momentum (BEM) theory when determining optimum blade design for maximum power production. This paper presents the optimal tip design using the new tip loss correction. A semi-analytical solution was proposed to find the optimum rotor considering Shen’s new tip loss model. The optimal blade geometry is obtained for which the maximum power coefficient is calculated at different design tip speed and glide ratio. Our simulation is conducted for S809 rotor wind turbine blade type, produced by National Renewable Energy Laboratory (NREL).

Experimental investigation on flow boiling characteristics of zeotropic binary mixtures (R134a/R245fa) in a rectangular micro-channel

In the present study, the flow boiling characteristics of R134a/R245fa zeotropic mixtures with three mass fractions (10/90, 30/70 and 70/30 by wt%) in a single rectangular micro-channel and their pure components were experimentally investigated. The flow boiling in micro-channel was visualized from the top view and heated on three sides with the cross-sectional area of 1mm×1mm and length of 106mm. For each test refrigerant, the visualization results and heat transfer coefficients were obtained under the parametric conditions comprising the heat flux range of 30–120kW/m2 and mass flux range of 60–1100kg/m2s at the same evaporating temperature of 18.5°C. The corresponded outlet vapor quality was in the range of 0–1. Results showed that almost all of the test refrigerants experienced five typical flow patterns. Different bubble coexistence phenomena were observed for the pure and mixed refrigerants, respectively. The hysteresis of flow pattern transition for R134a/R245fa zeotropic mixtures was strongly affected by both of the temperature glide and blending ratio. Based on the comparison with pure components, flow boiling heat transfer characteristics of test zeotropic mixtures were analyzed and discussed in detail by considering the mixture effects. Taking account of capillary and Marangoni effect in confined space, as well as other impact factors, the developed prediction method exhibited satisfactory accuracy in predicting the heat transfer coefficient of zeotropic mixtures.

Design and simulation for large parafoil fix line object homing algorithm

Traditional parafoil homing usually uses a point as object. As the mobility of parafoil is limited by its glide ratio and wind, in some cases when the parafoil scatter area is large, or the glide ratio of parafoil is small, the deviation of its landing point to object point will be arduous to control. Accordingly, during these situations, when parafoil is used in recovery of spacecraft or satellite, the landing area of parafoil can be set as a rectangle, and the object of parafoil can be set as a line segment. The thesis of this work is designing an algorithm for parafoil homing using line segment as object. The algorithm of wind velocity and direction calculation in different flying segments was also investigated. The algorithm designed navigates the parafoil to land into the predestined area and largely reduce the probability of recovery loads falling to unwanted area to damage houses and people.

Development of an Aeroelastic Flap to Increase the Aerodynamic Efficiency of a Wind Turbine’s Rotor Blade

Horizontal-axis wind turbines are sophisticated technical constructions that require modern design methods for further improvement and higher economic output. Thorough understanding of the whole turbine and its components is indispensable for this aim. The technological development in the last decades indicates the progress in this area and shows the potential of optimizations due to the improvement of rotor blade aerodynamics by additional aerodynamic devices. In this project the effect of an aeroelastic flap mounted on the trailing edge of a rotor blade on energy yield was investigated. For this purpose a flexible flap of fiberglass reinforced plastic for the profile at 70% of the rotor blade span has been designed for the trailing edge and analyzed using a 2-way fluid-structure-interaction simulation. In the first step the simulation is reduced to a two-dimensional investigation using the cross-section at 70% diameter of the rotor blade. Compared to an unmodified profile, the aeroelastic flap increases the lift-to-drag-ratio of the profile in an angle of attack range between 3.5° to 9.5°. The aeroelastic flap has a positive effect on the glide ratio, similar to a non-elastic, static flap.

Gliding performance of the red giant gliding squirrel Petaurista petaurista in the tropical rainforest of Indian eastern Himalaya

Gliding squirrels occur globally and many are of conservation concern due to habitat fragmentation and degradation. Information on their ability to cover the distance between two trees by gliding is lacking in many species which might be vital for habitat management and conservation. The aim of the study was to present the field observations on gliding behaviour of the red giant gliding squirrel Petaurista petaurista observed within tropical rain‐forest of Namdapha National Park, Arunachal Pradesh, Indian eastern Himalaya. The data were collected on 71 glides observed at nights. The mean height of launching and landing trees were 28.5 ± 1.0 m and 16.4 ± 0.9 m, respectively. Gliding variables calculated were vertical drop (mean = 13.4 ± 1.0 m), horizontal distance (mean = 36.3 ± 2.7 m), air speed (mean = 8.9 ± 0.2 m s‐1), ground speed (mean = 7.9 ± 0.2 m s‐1), glide ratio (mean = 3.1 ± 0.2), glide angle (mean = 19.0 ± 0.9°), GBH of launching tree (mean = 156.8 ± 8.5 cm) and GBH of landing tree (mean = 195.2 ± 9.5 cm). Gliding distance was categorized in four types. The highest glides in a 26–50 m glide‐class (44% (n = 31)) were the most frequently observed. Gliding squirrels preferred top canopy (56%, n = 40) for distant glides. Forest structure has an influence on the gliding habits of gliding squirrels and thus our data on gliding parameters should be used when planning forest management actions.

Airfoil Selection Methodology for Small Wind Turbines

On wind turbine technology, the aerodynamic performance is fundamental to increase efficiency. Nowadays there are several databases with airfoils designed and simulated for different applications, that is why it is necessary to select those suitable for a specific application. This work presents a new methodology for airfoil selection used in feasibility and optimization of small wind turbines with low cut-in speed. On the first stage airfoils data is tested on XFOIL software to check its compatibility with the simulator; then, arithmetic mean criteria is recursively used to discard underperformed airfoils; the best airfoil data was exported to Matlab for a deeper analysis. In the second part, data points were interpolated using “splines” to calculate glide ratio and stability across multiple angles of attack, those who present a bigger steadiness were conserved. As a result, 3 airfoils, from an initial group of 189, were selected due to its performance above the average as exemplification of the methodology.

An Automated Emergency Landing System for Fixed‐Wing Aircraft: Planning and Control

A number of hurdles must be overcome in order to integrate unmanned aircraft into civilian airspace for routine operations. The ability of the aircraft to land safely in an emergency is essential to reduce the risk to people, infrastructure, and aircraft. To date, few field‐demonstrated systems have been presented that show online replanning and repeatability from failure to touchdown. This paper presents the development of the guidance, navigation, and control (GNC) component of an automated emergency landing system (AELS) intended to address this gap, suited to a variety of fixed‐wing aircraft. Field‐tested on both a fixed‐wing unmanned aerial vehicle (UAV) and Cessna 172R during repeated emergency landing experiments, a trochoid‐based path planner computes feasible trajectories, and a simplified control system executes the required maneuvers to guide the aircraft toward touchdown on a predefined landing site. This is achieved in zero‐thrust conditions with engine forced to idle to simulate failure. During an autonomous landing, the controller uses airspeed, inertial, and GPS data to track motion and maintains essential flight parameters to guarantee flyability, while the planner monitors glide ratio and replans to ensure approach at correct altitude. Simulations show reliability of the system in a variety of wind conditions and its repeated ability to land within the boundary of a predefined landing site. Results from field‐tests for the two aircraft demonstrate the effectiveness of the proposed GNC system in live operation. Results show that the system is capable of guiding the aircraft to close proximity of a predefined keyhole in nearly 100% of cases.

Feather roughness reduces flow separation during low Reynolds number glides of swifts.

Swifts are aerodynamically sophisticated birds with a small arm and large hand wing that provides them with exquisite control over their glide performance. However, their hand wings have a seemingly unsophisticated surface roughness that is poised to disturb flow. This roughness of about 2% chord length is formed by the valleys and ridges of overlapping primary feathers with thick protruding rachides, which make the wing stiffer. An earlier flow study of laminar-turbulent boundary layer transition over prepared swift wings suggested that swifts can attain laminar flow at a low angle of attack. In contrast, aerodynamic design theory suggests that airfoils must be extremely smooth to attain such laminar flow. In hummingbirds, which have similarly rough wings, flow measurements on a 3D printed model suggest that the flow separates at the leading edge and becomes turbulent well above the rachis bumps in a detached shear layer. The aerodynamic function of wing roughness in small birds is, therefore, not fully understood. Here, we performed particle image velocimetry and force measurements to compare smooth versus rough 3D-printed models of the swift hand wing. The high-resolution boundary layer measurements show that the flow over rough wings is indeed laminar at a low angle of attack and a low Reynolds number, but becomes turbulent at higher values. In contrast, the boundary layer over the smooth wing forms open laminar separation bubbles that extend beyond the trailing edge. The boundary layer dynamics of the smooth surface varies non-linearly as a function of angle of attack and Reynolds number, whereas the rough surface boasts more consistent turbulent boundary layer dynamics. Comparison of the corresponding drag values, lift values and glide ratios suggests, however, that glide performance is equivalent. The increased structural performance, boundary layer robustness and equivalent aerodynamic performance of rough wings might have provided small (proto) birds with an evolutionary window to high glide performance.

Research of Trajectory Planning of a High-Altitude Long-Range Gliding Unmanned Underwater Vehicle

The air trajectory planned studied of the high-altitude long-range gliding unmanned underwater vehicle (HALRG-UUV) based on segmented control strategy is proposed. The aim of this research is twofold. On the one hand, specifying an altitude penetration strategy at the end of the gliding stage was presented with the aim of improving the vehicle glide ratio and achieving penetration. On the other hand, a rocket deceleration strategy was applied to adjust the speed and attitude of the vehicle in order to meet the water entry requirement. Besides, six-degrees-of-freedom mathematical model of the HALRG-UUV was developed based on the Newton’s law. Dynamic simulations of the vehicle under various conditions were performed with the aid of the MATLAB/Simulink codes. The result shows that the vehicle has a glide ratio of 1/9 in the air trajectory and meets the water entry requirement above water. This study lays the foundation for the further research of maneuverability and water impact of the vehicle.

Research of Trajectory Planning of a High-Altitude Long-Range Gliding Unmanned Underwater Vehicle

The air trajectory planned studied of the high-altitude long-range gliding unmanned underwater vehicle (HALRG-UUV) based on segmented control strategy is proposed. The aim of this research is twofold. On the one hand, specifying an altitude penetration strategy at the end of the gliding stage was presented with the aim of improving the vehicle glide ratio and achieving penetration. On the other hand, a rocket deceleration strategy was applied to adjust the speed and attitude of the vehicle in order to meet the water entry requirement. Besides, six-degrees-of-freedom mathematical model of the HALRG-UUV was developed based on the Newton’s law. Dynamic simulations of the vehicle under various conditions were performed with the aid of the MATLAB/Simulink codes. The result shows that the vehicle has a glide ratio of 1/9 in the air trajectory and meets the water entry requirement above water. This study lays the foundation for the further research of maneuverability and water impact of the vehicle.

Gliding performance in the yellow-bellied glider in low-canopy forest

Knowledge of the gliding performance of gliding mammals is fundamental to understanding how these species have adapted to their environment and is of increasing relevance to their conservation. I describe aspects of the glide performance of the yellow-bellied glider (Petaurus australis) based on 22 glides of 17 individuals within 20–30-m-high open forest in western Victoria. Gliders launched into a glide from a horizontal branch that was, on average, 2.8 m below the top of a tree, 5.2 m out from the main trunk and 18.5 m above the ground. Gliders landed on the trunks of trees 5.8 m above the ground. The mean horizontal glide distance was 25.2 ± 1.5 m (s.e.) (range = 19–45 m), producing a glide ratio (horizontal distance/height dropped) of 2.0 and a glide angle of 27.3°. These values are similar to those reported for other gliding petaurids in low-canopy forest. This knowledge should be used to guide the management of habitat connectivity for yellow-bellied gliders.

남자 고등부 포환던지기 선수들의 연도 별 기록에 따른 글라이드와 딜리버리 국면의 운동학적 차이

The purpose of this study was to provide high school male shot putters training methods of gliding and delivery motion through comparative analysis of kinematic characteristics. To accomplish this purpose, three dimensional motion analysis was performed for the subjects(PKC, KKH, YDL) who participated in high school male shot putter competition on 92nd (2011), 93rd (2013) National Sports Festival. The subjects were filmed by four Sony HXR-MC2000 video cameras with 60 fields/s. The three-dimen- sional kinematic data of the glide, conversion and delivery phase were obtained by Kwon3d 3.1 version. The data of the shoulder rotational angles and projection angles were calculated with Matlab R2009a. The following conclusions had been made. With the analysis of the gliding and stance length ratio, the gliding length was shorter at the TG than the SG with short-long technique but the gliding and stance length ratio was 46.8:53.2% respectively. The deviation of the shots trajectory from APSS(Athlete-plus- shot-system) revealed that the PKC showed similar to n-a-b-c-I of skilled S-shape type, KKH and YDL showed n-a-d-f-I' of unskilled type. Furthermore, they showed smaller radial distance from the central axis of the APSS and the shots were away from the linear trajectory. From this characteristics, The PKC who performed more TG than SG had shorter glide with S-shape of APSS(skilled type) showed the better record than others with technical skill. But KKH and YDL had bigger glide ratio with n- a-d-f-I' of unskilled type and improved their records with technical factor. The projection factor had an effect on the record directly. Because PKC maintained more lower glide and transition posture with momentum transfer through COG's rapid hor- izontal velocity respectively the subject possessed the characteristics of high horizontal and vertical velocity with large turning radius from shot putter to APSS.

Glide Slope Control Authority for Parafoil Canopies with Variable Incidence Angle

The addition of glide slope control to guided airdrop systems has the potential to provide dramatic improvements in landing accuracy. Dynamic rigging incidence control has been demonstrated in flight tests and shown to provide effective glide slope control. The current work presents flight-test results exploring the range of glide slope control that can be achieved with high-performance parafoil canopies of two different aspect ratios. The low- and medium-aspect-ratio canopies have peak glide ratios of 4.4 and 4.9, respectively. By varying the incidence angle in flight, the glide slope can be reduced from these peak values to a glide slope near two for both canopies. Flight tests investigating the relationship between symmetric brake and incidence control demonstrate that symmetric braking produces effective airspeed control with little effect on glide slope, the incidence angle produces significant effects on both glide slope and airspeed, the rapid variation of the incidence angle in flight can lead to significant long period oscillations in both glide slope and airspeed, and the coupled effect of the control mechanisms of incidence angle and symmetric brake can produce dramatic changes in glide slope in any wind condition.

240 競技用フライングディスクの空力性能と飛翔軌跡(飛翔体の空力特性)

A flying disc can fly through the air because of the combination of the lift and drag forces by the oncoming air flow. Actual fight conditions were confirmed to perform the wind tunnel experiment beforehand. In order to clarify the mechanism of flight of flying discs, the flow field structure and the fluid force were investigated on non-spinning and spinning conditions. In the fluid force measurement, lift and drag forces were taken by varying wind speeds, spin speeds, and angle of attack. Drag and lift forces were found to increase as spin increased. The angle of attack on the maximum range of lift-drag ratio or glide ratio was found to be wide from 6 to 13 degrees which was suitable for a long distance throwing. Using a smoke wind tunnel, flow visualization around the disc was performed in order to understand the effect of disc spin. It was found that spin enhances lift force by attracting the Coanda effect on the trailing edge.

G1104 競技用フライングディスクの空力特性(GS11 物体まわり流)

A flying disc can fly through the air because of the combination of the lift and drag forces by the oncoming air flow. Actual fight conditions were confirmed to perform the wind tunnel experiment beforehand. In order to clarify the mechanism of flight of flying discs, the flow field structure and the fluid force were investigated on non-spinning and spinning conditions. In the fluid force measurement, lift and drag forces were taken by varying wind speeds, spin speeds, and angle of attack. Drag and lift forces were found to increase as spin increased. The angle of attack on the maximum range of lift-drag ratio or glide ratio was found to be wide from 6 to 13 degrees which was suitable for a long distance throwing. Using a smoke wind tunnel, flow visualization around the disc was performed in order to understand the effect of disc spin. It was found that spin enhances lift force by attracting the Coanda effect on the trailing edge.

고등부 남자 포환던지기 선수의 시기 별 글라이드 유형과 딜리버리 국면의 운동학적 분석 - 고등부 이형근 선수를 중심으로 -

The purpose of this study was to provide information about kinematic variables of the gliding and delivery motion of Hyung-Keun Lee, a high school shot putter who was ranked 1st at the 2011 National Sports Festivals. Three-Dimensional motion analysis using a system of 4 video cameras at a sampling frequency of 60 Hz was conducted during shot-putting events at the 2011 National Sports Festivals. During the gliding and delivery phase of the player the results showed following characteristics; 1) The gliding technique types of the player appeared to be the short-long technique as the gliding and stance length ratio were <TEX>$42.3{\pm}3.87$</TEX> % and <TEX>$57.7{\pm}3.87$</TEX> %, respectively. In addition, the trajectory of shots during the gliding and delivery phase showed different trajectory patterns with "S-shaped" type of elite players due to the deviation from a central axis of the APSS (athletic-plus shot system). 2) The horizontal velocity of COG made from gliding should maintain the velocity during transition and release phase, but the player showed a small momentum for a gradual decrease of velocity. 3) Therefore, the player requires to adjust an appropriate ratio between gliding and stance length with a strong muscle power at the trunk, throwing arm, and the lower extremity during gliding and delivery phase.