Fly low: The ground effect of a barn owl (Tyto alba) in gliding flight

2020 ◽  
pp. 095440622094393
Author(s):  
Jialei Song
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Ground Effect ◽  
Barn Owl ◽  
Wake Vortex ◽  
Tyto Alba ◽  
Ground Clearance ◽  
Weight Support ◽  
Gliding Flight ◽  
Induction Model

Birds take advantage of the ground effect to improve their flight performance by flying low over ground. In this paper, we created a high-fidelity computational fluid dynamics model of a barn owl ( Tyto alba) to study its ground effect in gliding flight. A computational fluid dynamics simulation shows that the ground effect leads to increases in the lift/drag ratio and span efficiency. Interestingly, the span efficiency exceeds one when the bird is below a certain ground clearance ( h/ c = 0.8). Such an estimation is under the condition of different weight supports; hence, there is no fair comparison for many parameters. Therefore, we used a vortex induction model validated by computational fluid dynamics to estimate the aerodynamics at different ground clearances under a constant weight support. As the ground blocks the downwash of the bird, an image wake system can equivalently replace the ground, forming a vortex system with four components: the wake vortex, bound vortex, image wake vortex and image bound vortex. The vortex induction model shows the vertical flows induced by these four vortex components. Such vertical flow can be used to estimate the drag production on the bird. As the ground clearance decreases, the drag due to the wake vortex and its image counterpart as a whole decreases, while that due to the bound vortex and its image counterpart increases slightly and then decreases. The remaining drag, namely, the zero-lift drag, undergoes a shallow “U” shape as a function of the ground clearance. We also analyzed the streamwise flow induction using this model and showed that the streamwise flow is reduced due to the ground effect, which might cause insufficient weight support at low speeds.

scholarly journals From wing shape to fluid dynamics in the barn owl (Tyto alba)

2020 ◽  
Author(s):  
Jorn A Cheney ◽  
Jonathan PJ Stevenson ◽  
Nick E Durston ◽  
Jialei Song ◽  
Masateru Maeda ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Shape Control ◽  
Aerodynamic Force ◽  
Barn Owl ◽  
Wing Shape ◽  
Tyto Alba ◽  
Weight Support ◽  
Gliding Flight ◽  
Wide Range ◽  
Wing Morphing

AbstractBirds morph their wings and tail in order to glide under a wide range of aerodynamic conditions. Gross wing morphing has been described in a multitude of studies, but the finer details of wing morphing are still unknown. Here, we measured the changes in wing shape and pose in a barn owl, Tyto alba, when gliding across a range of fifteen self-selected speeds. We found that T. alba does not use fine-wing shape control to glide at slow speeds in steady conditions, with the measured wing shapes being highly consistent across all flights. Instead, T. alba relied upon wing postural control (gross pitch) and changes in both tail shape and pose to modulate aerodynamic force. A consistent wing shape provides an exceptional aerodynamic tool for understanding gliding flight in birds through postural change and tail morphing. This geometry was used as the basis for computational fluid dynamics simulations which gave very similar wake measurements and weight support to those measured in flight. This geometry is provided here to assist other researchers interested in exploring the fluid dynamics behind gliding flight in birds.

Wind Tunnel Testing and Computational Fluid Dynamics Analysis of a Wing-in-Ground Effect Vehicle

2007 ◽  
Author(s):  
Boonseng Soh ◽  
Andrew Low ◽  
Cees Bil ◽  
Brendon Bobbermien
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Ground Effect ◽  
Wind Tunnel Testing ◽  
Cfd Modelling ◽  
Aerodynamic Analysis ◽  
Computational Fluid Dynamics Analysis ◽  
Wing In Ground Effect ◽  
Tunnel Testing

The Wing-in-Ground Effect Concept Technology Demonstrator (WIGE CTD) project is a joint venture between Advanced Aerosystem Technologies Pty Ltd and RMIT University, aiming to design, validate and build a prototype recreational vehicle to fly two passengers over a distance of 500km at approximately 120km/h. The WIGE vehicle will fly very close to the surface, usually water, taking advantage of ground effect to transport passengers with a greater lift/drag ratio, and thus greater fuel-efficiency than conventional aircraft. Following preliminary design, an aerodynamic analysis of the vehicle was performed using wind tunnel testing and Computational Fluid Dynamics (CFD). This paper describes the methods used for wind tunnel testing and CFD modelling of the WIGE CTD design. Results obtained using the two approaches are compared with the aim of validating the CFD model and the techniques used in both wind tunnel and CFD modelling for use in future analyses. In addition to the aerodynamic analysis, a basic CFD prediction of the maximum hydrodynamic drag experienced during take off was attempted using a simple model of the WIGE vehicle hull. This result is required in order to ensure that the aquatic take off required by WIGE vehicles was possible for the design. Concurrently, the feasibility of using a general-purpose CFD solver like Fluent to analyse hull performance was also evaluated through this aspect of the investigation.

Numerical Investigation of the Ground Effect for a Small Bird

2013 ◽  
Vol 29 (3) ◽  
pp. 433-441 ◽  
Author(s):  
J.-H. Tang ◽  
J.-Y. Su ◽  
C.-H. Wang ◽  
J.-T. Yang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Investigation ◽  
Ground Effect ◽  
Lower Surface ◽  
Experimental Models ◽  
Simplified Model ◽  
Wing Model ◽  
Aerodynamic Effect ◽  
Small Bird

AbstractAn investigation with computational fluid dynamics of the ground effect on a small bird revealed quantitatively the obstruction of the vortex expansion resulting from the presence of the ground at varied distance. Preceding authors focused mainly on the bird's wings, generally neglecting the bird's body; we discuss specifically the distinction of the aerodynamic effect between cases with and without the presence of the bird's body. The results of simulation show that, considering only two wings, for a distance between the wing model and the ground smaller than a semi-span, the smaller is the ground clearance, the more significant is the ground effect. At clearance 0.37 times a semi-span, the drag is decreased 11%, and the lift is increased 5.6%. The ground effect for an intact bird model composed of both wings and body is less effective than that for a simplified model with body omitted, because a suction was observed on the lower surface of the intact bird's trunk at clearance 0.37 times a semi-span; for this reason the intact bird model benefits less from the ground effect than the model with body excluded, but increased lift and decreased drag remain observable. This research treating the ground effect on a gliding bird reveals the importance of the presence of the bird's body in both computational and experimental models.

scholarly journals Synergistic integration of computational fluid dynamics and experimental fluid dynamics for ground effect aerodynamics studies

2012 ◽  
Vol 226 (6) ◽  
pp. 602-619 ◽  
Author(s):  
T J Barber ◽  
G Doig ◽  
C Beves ◽  
I Watson ◽  
S Diasinos
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Ground Effect ◽  
Large Datasets ◽  
Data Types ◽  
Complementary Information ◽  
Experimental Fluid Dynamics ◽  
Computational Fluid Dynamics Cfd ◽  
Disparate Data ◽  
Experimental Fluid

This article highlights the ‘synergistic’ use of experimental fluid dynamics (EFD) and computational fluid dynamics (CFD), where the two sets of simulations are performed concurrently and by the same researcher. In particular, examples from the area of ground effect aerodynamics are discussed, where the major facility used was also designed through a combination of CFD and EFD. Three examples are than outlined, to demonstrate the insight that can be obtained from the integration of CFD and EFD studies. The case studies are the study of dimple flow (to enhance aerodynamic performance), the analysis of a Formula-style front wing and wheel, and the study of compressible flow ground effect aerodynamics. In many instances, CFD has been used to not only provide complementary information to an experimental study, but to design the experiments. Laser-based, non-intrusive experimental techniques were used to provide an excellent complement to CFD. The large datasets found from both experimental and numerical simulations have required a new methodology to correlate the information; a new post-processing method has been developed, making use of the kriging and co-kriging estimators, to develop correlations between the often disparate data types.

scholarly journals Modeling and Simulation of Wake Safety Interval for Paired Approach Based on CFD

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xin He ◽  
Yilong Ma ◽  
Hong Yang ◽  
Yaqing Chen
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Modeling And Simulation ◽  
Visual Analysis ◽  
Calculation Model ◽  
Wake Vortex ◽  
Optimization Modeling ◽  
Operation Efficiency ◽  
Vortex Field

In order to relieve the stress caused by the surge of flight flow, Closely Spaced Parallel Runways (CSPRs) have been built in many hub airports, and a paired approach mode has been applied to CSPRs in some countries. This paper proposes a method for optimizing the wake separation between aircrafts which utilizes a paired approach, aiming at reducing longitudinal separation by using computational fluid dynamics technology. Firstly, the model of the wake vortex field of the paired lead aircraft is constructed. Secondly, the numerical simulation preparation for the characteristics of the wake vortex field is completed through the computational pretreatment of the model. Thirdly, a calculation model of wake safety interval based on paired approach operation is established. Finally, the proposed method shows its superiority comparing with other methods. This method realized visual analysis of wake vortex through optimization modeling based on computational fluid dynamics, contributing to increasing the capacity of the runway and improving the operation efficiency of an aerodrome.

scholarly journals Применение CFD для проектирования системы управления движением экраноплана

2020 ◽  
Author(s):  
A.V. Nebylov ◽  
S.A. Brodsky ◽  
A.I. Panferov ◽  
V.A. Nebylov
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Control System ◽  
Motion Control ◽  
Numerical Study ◽  
Ground Effect ◽  
Comsol Multiphysics ◽  
Motion Control System ◽  
Control Laws ◽  
Interactive Control

В статье рассматриваются возможности применения программного пакета Comsol Multiphysics на стадии предварительного проектирования системы автоматического управления движением экраноплана. Разработка новых методов синтеза алгоритмов управления движением в зоне действия экранного эффекта базируется на результатах численного исследования аэродинамики летательного аппарата и расчета аэродинамических сил и моментов с использованием модуля вычислительной гидродинамики CFD ( computational fluid dynamics , позднее переименованный в colorful fluid dynamics или разноцветная гидродинамика ), расширяющего возможности среды численного моделирования COMSOL Multiphysics. Мелкие и непринципиальные для интегральной аэродинамики элементы конструкции не учитывались. Конструкция создавалась непосредственно в графическом редакторе COMSOL с целью избежать непредсказуемых ошибок конвертации. Многосеточные методы были использованы для повышения точности и сокращения времени решения. Полученные модели и законы управления позволяют создать симулятор управляемого движения экраноплана с функциями симулятора полета. На основе симулятора планируется создание системы краткосрочного прогнозирующего интерактивного управления в ускоренное время. Аппаратная реализация этой системы как части автоматической системы управления движением включает в себя также систему отображения информации, подразумевающую допустимое сокращение сложности модели системы и законов управления.The article discusses the possibilities of using the Comsol Multiphysics software package at the stage of preliminary design of a motion control system for a promising big ekranoplane (WIG-craft). The development of new methods for synthesizing automatic motion control algorithms in the area of ground effect is based on the results of a numerical study of the vehicle aerodynamics and the calculation of aerodynamic forces and torques using the CFD ( computational fluid dynamics , later recalled in colorful fluid dynamics ) module, which expands the capabilities of the COMSOL Multiphysics numerical simulation environment. Small and unprincipled structural elements slightly influenced integral aerodynamics were not taken into account. The design was created directly in the COMSOL graphics editor in order to avoid unpredictable conversion errors. Multigrid methods have been used to reduce the solution time. The resulting model and the control laws allow to create a simulation of the controlled motion of airplane with flight simulator. Based on this simulator, it is planned to create a system of short-term predictive interactive control in accelerated time. The hardware implementation of this system as a part of an automatic motion control system also includes an information display system that implies an acceptable reduction in the complexity of the system model and control laws.

scholarly journals Brownout Simulations of Model-Rotors In Ground Effect

2020 ◽  
Vol 314 ◽  
pp. 01006
Author(s):  
F. Rovere ◽  
G.N. Barakos ◽  
R. Steijl
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Particle Tracking ◽  
Ground Effect ◽  
Experimental Results ◽  
Safety Studies ◽  
Effect Time ◽  
Particle Paths ◽  
Simulated Flow

In this work computational fluid dynamics is used to validate experimental results for a two-bladed small rotor In Ground Effect conditions. The paper focuses on the evaluation and prediction of the rotor outwash generated in ground effect. Time-averaged outflow velocities are compared with experimental results, and the simulated flow field is used for safety studies using the PAXman model and particle tracking methods. The aircraft weights have been studied, evaluating scaling factors to define how helicopter weight can affect the outflow forces and the particle paths. Results show how the wake generated by heavier helicopters can lead to stronger forces on ground personnel and push the particles farther away from the rotor.

Numerical Study of Dynamic Ground Effect of a Carrier-Based UAV

2015 ◽  
Vol 733 ◽  
pp. 522-525
Author(s):  
Mu Qing Yang ◽  
Dong Li Ma
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Aerodynamic Force ◽  
Numerical Study ◽  
Ground Effect ◽  
Pitching Moment ◽  
Aerodynamic Forces ◽  
Sliding Mesh ◽  
The Stability

The paper uses computational fluid dynamics combined with sliding mesh and dynamic layering methods to study the dynamic ground effect of a UVA during the phase of takeoff. The research focused on longitude characteristics, such as lift, drag and pitching moment. Results showed that the aerodynamic force would vibrate acutely, which affected the stability of the UAV and the safety of takeoff. Pitching angle is the most important factor influencing the aerodynamic forces. Increase the pitching angle properly is benefit to the safety of takeoff operation.

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