scholarly journals Stability Analysis and Augmentation Design of a Bionic Multi-Section Variable-Sweep-Wing UAV Based on the Centroid Self-Trim Compensation Morphing

2021 ◽  
Vol 11 (19) ◽  
pp. 8859
Author(s):  
Hang Ma ◽  
Yuxue Ge ◽  
Bifeng Song ◽  
Yang Pei
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Speed ◽  
Stability Margin ◽  
Static Stability ◽  
Sweep Angle ◽  
Stability Performance ◽  
Angle Change ◽  
Stability Change ◽  
The Impact

In this study, a design scheme for a high-aspect-ratio bionic multi-section variable-sweep wing unmanned aerial vehicle (UAV) that utilizes the reverse coordinated change in the sweep angle of the inner and outer wing sections is proposed, which improves the aerodynamic performance and realizes the self-trim compensation of the wing’s centroid. According to the layout characteristics of this type of UAV, a reasonable distribution design of the wingspan ratio of the inner and outer sections is explored, to reduce the impact of aerodynamic center movement and moment of inertia change. The calculation and analysis results show that the coordinated variable-sweep scheme can significantly improve the influence of sweep angle change on the longitudinal static stability margin of UAVs with a high aspect ratio. The coordinated sweep angle change in the inner and outer wing sections can not only reduce the drag during high-speed flight, but also play a significant role in improving the performance of the aircraft at different stages in the mission profile. Appropriately increasing the wingspan proportion of the inner section can reduce the trim resistance of the V-tail, reduce the thrust of the engine, and increase the range and duration of the UAV. From the perspective of stability change, the multi-section variable-sweep wing UAV with a wingspan ratio of the inner and outer sections that is between 1.41 and 1.78 has better dynamic stability performance. Among them, the UAV with a wingspan ratio of the inner and outer sections that is equal to 1.41 has better longitudinal stability performance, while the UAV with a wingspan ratio of the inner and outer sections that is equal to 1.78 has better lateral/directional stability performance.

scholarly journals Longitudinal Aerodynamic and Stability Characteristics of High-Aspect-Ratio Unmanned Aerial Vehicles in Gust Response

2019 ◽  
Author(s):  
Junli Wang ◽  
Wensheng Zhang ◽  
Bolin Feng ◽  
Zhigui Ren ◽  
Qinghe Zhao
Keyword(s):  
Numerical Simulation ◽  
Aspect Ratio ◽  
Unmanned Aerial Vehicles ◽  
High Aspect Ratio ◽  
Stability Margin ◽  
Simulation Method ◽  
Static Stability ◽  
Aerial Vehicles ◽  
Numerical Simulation Method ◽  
Gust Response

The aim of this work is to propose an accurate and reliable numerical simulation method of gust response, so as to analyze longitudinal stability characteristics of high-aspect-ratio unmanned aerial vehicles (UAVs) under gust response. Based on the dual-time stepping method, the unsteady Navies-Stokes equation was solved. By introducing grid velocity to study the effects of gust, the numerical simulation of gust response was realized. Moreover, the numerical simulation method was verified to be accurate by using the theoretical value and reference value obtained in previous research. The calculation results of the high-aspect-ratio UAV under the 1-cos gust reveal that longitudinal aerodynamic forces of high-aspect-ratio UAVs changed. In the whole range of gust gradient length, the UAVs were always in the state of static stability. However, with the increase of gust velocity, static stability margin decreased. The numerical simulation method of gusts established in this study preferably overcomes the possible numerical oscillations and divergence problems caused by excessive gust velocity. The analysis on longitudinal static stability and stability margin of high-aspect-ratio UAVs under the effects of gusts can ensure flight quality and safety of UAVs under the effects of gusts.

The Effect of Structural Geometric Nonlinearities on the Flutter of the Straight and Swept Wing Configurations

2012 ◽  
Vol 189 ◽  
pp. 306-311 ◽  
Author(s):  
Qing Guo ◽  
Bi Feng Song
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Swept Wing ◽  
Geometric Nonlinearities ◽  
Air Vehicle ◽  
Structural Nonlinearity ◽  
Flutter Analysis ◽  
Long Endurance ◽  
The Impact ◽  
Straight Wing

High altitude and long endurance (HALE) vehicle always adopt straight or swept configuration, which leads to the problem that the wings of UAV have high aspect ratio and are very flexible. This kind of flexible wing exhibits large deformation when aerodynamic forces are loaded on them and the structural nonlinearity should be considered. So the dynamic and flutter characteristics will be changed. In the engineering applications, the effects of structural geometric nonlinearities on the air vehicle design are the most concerns of aeroelasticity before a systematic flutter analysis for the air vehicle. because the solution for nonlinear flutter speed based on the CFD-CSD method is complex and time consuming. In this paper, we propose a simple and efficient approach that can analyze the effect of structural geometric nonlinearities on the flutter characteristics of high aspect ratio wing quickly. And a straight wing and a straight-swept wing are analyzed to verify the feasibility and efficiency of the proposed method. It is found that the effect of structural geometric nonlinearities has a strong effect on the flutter characteristic of the straight wing, but is weak on the straight-swept wing. And finally the impact of swept angle on the dynamic and flutter characteristics of straight-swept wing is also discussed.

High-Speed Additive Manufacturing Through High-Aspect-Ratio Nozzles

JOM ◽  
2018 ◽  
Vol 70 (3) ◽  
pp. 284-291 ◽  
Author(s):  
Leon Shaw ◽  
Mashfiqul Islam ◽  
Jie Li ◽  
Ling Li ◽  
S. M. Imran Ayub
Keyword(s):  
Additive Manufacturing ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Speed

Bubble behaviour in a horizontal high-speed solid-body rotating flow

2021 ◽  
Vol 925 ◽  
Author(s):  
Majid Rodgar ◽  
Hélène Scolan ◽  
Jean-Louis Marié ◽  
Delphine Doppler ◽  
Jean-Philippe Matas
Keyword(s):  
Aspect Ratio ◽  
Solid Body ◽  
High Speed ◽  
Lift Coefficient ◽  
Rotating Flow ◽  
Axis Of Rotation ◽  
Large Fluctuations ◽  
The Mean ◽  
Drag And Lift ◽  
The Impact

We study experimentally the behaviour of a bubble injected into a horizontal liquid solid-body rotating flow, in a range of rotational velocities where the bubble is close to the axis of rotation. We first study the stretching of the bubble as a function of its size and of the rotation of the cell. We show that the bubble aspect ratio can be predicted as a function of the bubble Weber number by the model of Rosenthal (J. Fluid Mech., vol. 12, 1962, 358–366) provided an appropriate correction due to the impact of buoyancy is included. We next deduce the drag and lift coefficients from the mean bubble position. For large bubbles straddling the axis of rotation, we show that the drag coefficient $C_D$ is solely dependent on the Rossby number $Ro$, with $C_D \approx 1.5/Ro$. In the same limit of large bubbles, we show that the lift coefficient $C_L$ is controlled by the shear Reynolds number $Re_{shear}$ at the scale of the bubble. For $Re_{shear}$ larger than 3000 we observe a sharp transition, wherein large fluctuations in the bubble aspect ratio and mean position occur, and can lead to the break-up of the bubble. We interpret this regime as a resonance between the periodic forcing of the rotating cell and the eigenmodes of the stretched bubble.

scholarly journals Numerical Investigation into Flutter and Flutter-Buffet Phenomena for a Swept Wing and a Curved Planform Wing

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Mario Rosario Chiarelli ◽  
Salvatore Bonomo
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Speed ◽  
Sensitivity Study ◽  
Fuel Saving ◽  
Swept Wing ◽  
Instability Condition ◽  
Aspect Ratios ◽  
Numerical Studies ◽  
Classical Flutter

The results of numerical studies carried out on high-aspect-ratio wings with different planforms are discussed: the transonic regime is analysed for a swept wing and a curved planform wing. The wings have similar aspect ratios and similar aerodynamic profiles. The analyses were carried out by CFD and FE techniques, and the reliability of the numerical aerodynamic results was proven by a sensitivity study. Analysing the performances of the two wings demonstrated that in transonic flight conditions, a noticeable drag reduction can be obtained by adopting a curved planform wing. In addition, for such a wing, the aeroelastic instability condition, consisting in a classical flutter, is postponed compared to a conventional swept wing, for which a flutter-buffet instability occurs. In a preliminary manner, the study shows that, for a curved planform wing, the high speed buffet is not an issue and at the same time notable fuel saving can be achieved.

scholarly journals The Capabilities of Electrodischarge Microdrilling of High Aspect Ratio Holes in Ceramic Materials

2015 ◽  
Vol 6 (3) ◽  
pp. 61-69 ◽  
Author(s):  
Sebastian Skoczypiec ◽  
Magdalena Machno ◽  
Wojciech Bizoń
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Efficiency ◽  
Ceramic Materials ◽  
Good Alternative ◽  
Discharge Voltage ◽  
Drilling Speed ◽  
Electrically Conductive ◽  
Side Gap ◽  
The Impact

Abstract In the first part of the article the review of ceramic materials drilling possibilities was presented. Among the described methods special attention is paid to electrodischarge drilling. This process have especially been predicted for machining difficult-to-cut electrically conductive materials. The second part consist of the results analysis of electrodischarge microdrilling of siliconized silicon carbide. The experiment involves the impact of current amplitude, discharge voltage and pulse time on the hole depth, side gap, linear tool wear and mean drilling speed. The results shows that electrodischarge drilling is a good alternative when machining inhomogeneous ceramic materials and gives possibility to drill high aspect ratio holes with relatively high efficiency (the drilling speed >2 mm/min).

A Study on the Characteristics of Micro Deep Hole Machining Processes

2007 ◽  
Vol 364-366 ◽  
pp. 566-571
Author(s):  
Tae Il Seo ◽  
Dong Woo Kim ◽  
Myeong Woo Cho ◽  
Eung Sug Lee
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Speed ◽  
Printed Circuit Boards ◽  
Hole Drilling ◽  
Deep Hole ◽  
Machining Processes ◽  
Deep Hole Drilling ◽  
Micro Drilling ◽  
Hole Machining

Recently, the trends of industrial products move towards more miniaturization, variety and mass production. Micro drilling which take high precision in cutting work is required to perform more micro hole and high speed working. Especially, Micro deep hole drilling is becoming more important in a wide spectrum of precision production industries, ranging from the production of automotive fuel injection nozzle, watch and camera parts, medical needles, and thick multilayered Printed Circuit Boards(PCB) that are demanded for very high density electric circuitry. The industries of precision production require smaller holes, high aspect ratio and high speed working for micro deep hole drilling. However the undesirable characteristics of micro drilling is the small signal to noise ratios, wandering motion of drill, high aspect ratio and the increase of cutting force as cutting depth increases. In order to optimize cutting conditions, an experimental study on the characteristics of micro deep hole machining processes using a tool dynamometer was carried out. And additionally, microscope with built-in an inspection monitor showed the relationship between burr in workpieces and chip form of micro drill machining.

Through-Silicon-Via Copper Deposition for Vertical Chip Integration

2006 ◽  
Vol 970 ◽  
Author(s):  
Bioh Kim
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Seed Layer ◽  
Copper Deposition ◽  
Process Conditions ◽  
Through Silicon Via ◽  
3D Packaging ◽  
Wafer Thinning ◽  
The Impact ◽  
Deposition Conditions

ABSTRACTConsumers are demanding smaller, lighter electronic devices with higher performance and more features. The continuous pressure to reduce size, weight, and cost, while increasing the functionality of portable products, has created innovative, cost-effective 3D packaging concepts. Among all kinds of 3D packaging techniques, through-silicon-via (TSV) electrodes can provide vertical connections that are the shortest and most plentiful with several benefits (1). Connection lengths can be as short as the thickness of a chip. High density, high aspect ratio connections are available. TSV interconnections also overcome the RC delays and reduce power consumption by bringing out-of-plane logic blocks much closer electrically.The technologies engaged with TSV chip connection include TSV formation, insulator/barrier/seed deposition, via filling, surface copper removal, wafer thinning, bonding/stacking, inspection, test, etc. Process robustness and speed of copper deposition are among the most important technologies to realize TSV chip integration. There are generally three types of via filling processes; lining along the sidewall of vias, full filling within vias, and full filling with stud formation above the via. Here, the stud works as a mini-bump for solder bonding. Two methodologies have been generally adopted for via filling process; (a) via-first approach : blind-via filling with 3-dimensional seed layer, followed by wafer thinning and (b) thinning-first approach : through-via filling with 2-dimensional seed layer at the wafer bottom after wafer thinning. Currently, the first approach is more popular than the second approach due to difficulty in handling and plating thinned wafers (2).We examined the impact of varying deposition conditions on the overall filling capability within high aspect ratio, deep, blind vias. We tested the impacts of seed layer conformality, surface wettablity, bath composition (organic and inorganic components), waveform (direct current, pulse current, and pulse reverse current), current density, flow conditions, etc. Most deposition conditions affected the filling capability and profile to some extent. We found that reducing current crowding at the via mouth and mass transfer limitation at the via bottom is critical in achieving a super-conformal filling profile. This condition can be only achieved with a proper combination of aforementioned process conditions. With optimized conditions, we can repeatedly achieve void-free, bottom-up filling with various via sizes (5-40μm in width and 25-150μm in depth).

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