Theoretical and Experimental Investigation of Indoor Flying Models

1964 ◽  
Vol 68 (647) ◽  
pp. 728-734
Author(s):  
Max Hacklinger
Keyword(s):  
Flow Characteristics ◽  
Aerodynamic Characteristics ◽  
Light Weight ◽  
Flight Performance ◽  
Wing Loading ◽  
Balsa Wood ◽  
Special Model ◽  
Nichrome Wire ◽  
Horizontal Flight ◽  
Theory And Experiment

SummaryThe development of a special model aeroplane technique is reviewed which renders possible easy and illustrative experimenting In the Reynolds number regime from 1 to 5000. The models are built in extremely light-weight construction; with wing span from 0·1 to 1 metre and all-up weights from 0·01 to 2 grammes, flight velocities between 0·1 and 1 m/ sec are reached. The requirement of extremely low wing loading, together with the special air flow characteristics in this region, leads to rather unconventional construction principles with the materials balsa wood, nichrome wire and cellulose film. These principles are reviewed briefly. The problem of optimum propulsion for such model aeroplanes is treated analytically. Some results are given for flight performance optimisation. By combining theory and experiment there has been evolved, e.g. the Schwebeleistungs method (power required for horizontal flight) for optimising the duration of indoor model aeroplanes without exact knowledge of their aerodynamic characteristics. Flight characteristics with some elasticity of the structure present formidable problems and are reviewed in some examples. Finally, some problems of hangar meteorology are mentioned.

Flow Characteristics of a Powder Lubricant in a Slider Bearing

2001 ◽  
Author(s):  
Manjunath Pappur ◽  
M. M. Khonsari
Keyword(s):  
Slip Velocity ◽  
Thrust Bearing ◽  
Volume Fraction ◽  
Flow Characteristics ◽  
Slider Bearing ◽  
Systematic Development ◽  
Powder Lubrication ◽  
Insight Into ◽  
Theory And Experiment ◽  
Good Agreement

Abstract This paper deals with a systematic development of theory of powder lubrication with the appropriate formalism based on the fundamentals of fluid mechanics. The theory is capable of predicting flow velocity, fluctuation (pseudo-temperature), powder volume fraction, and slip velocity at the boundaries. An extensive set of parametric simulations covering particle size, surface roughness, volumetric flow, load and speed are performed to gain insight into the performance of a powder lubricated thrust bearing. The results of simulations are compared to the published experimental results. Good agreement between the theory and experiment attests to the capability of the model and its potential for design of powder lubricated bearings.

Age Differences in Wing Loading and Other Aerodynamic Characteristics of Red-tailed Hawks

2004 ◽  
Vol 116 (3) ◽  
pp. 272-274 ◽  
Author(s):  
Helmut C. Mueller ◽  
Daniel D. Berger ◽  
Nancy S. Mueller ◽  
William Robichaud ◽  
John L. Kaspar
Keyword(s):  
Age Differences ◽  
Aerodynamic Characteristics ◽  
Wing Loading

scholarly journals Numerical Investigation of Flow around Two Tandem Identical Trapezoidal Cylinders

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yupu Wang ◽  
Wenming Cheng ◽  
Run Du ◽  
Shubiao Wang ◽  
Yong Deng
Keyword(s):  
Flow Instability ◽  
Flow Characteristics ◽  
Simulation Method ◽  
Streamwise Velocity ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Mode Iii ◽  
Extended Body ◽  
Spacing Ratio ◽  
Volume Method

The trapezoidal beam structure is ubiquitous in giant engineering equipment, while their aerodynamic characteristics have not been clearly understood. Numerical simulation method was adopted to investigate the flow around two tandem identical trapezoidal cylinders. The study was conducted using a Reynolds number of 2.2 × 104, and with a spacing ratio varying from 0.5 to 10. The incompressible two-dimensional finite volume method was used for solving Reynolds-Averaged Navier–Stokes (RANS) equations with realizable k−ε model. The effects of cylinder geometry and spacing between the cylinders on aerodynamic characteristics, unsteady flow patterns, time-averaged flow characteristics, and flow instability was studied. The results show that the flow around the two tandem trapezoidal cylinders is highly dependent on the spacing ratio. The flow modes can be classified into: extended-body regime (Mode I, S∗ ≤ 1), reattachment regime (Mode II, 2 ≤ S∗ ≤ 3), and binary regime (Mode III, S∗ ≥ 4). We explored their respective flow characteristics and distinctions through the force/pressure coefficients, time-average streamwise velocity, and the flow field evolution.

scholarly journals Aerodynamic Characteristics of Helicopter with Ducted Fan Tail Rotor in Hover under Low-Speed Crosswind

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Nahyeon Roh ◽  
Sejong Oh ◽  
Donghun Park
Keyword(s):  
Flow Characteristics ◽  
Aerodynamic Characteristics ◽  
Rotor System ◽  
Main Rotor ◽  
Complex Flow ◽  
Open Type ◽  
Low Speed ◽  
Ducted Fan ◽  
Wake Interaction ◽  
Fixed Part

The tail rotor of a helicopter operating under low-speed crosswind undergoes highly complex flow due to the interaction between the main rotor, fuselage, and tail rotor system. In this study, numerical simulations have been conducted on the complete configuration of a helicopter with a ducted fan tail rotor system (comprising a main rotor, ducted fan tail rotor, fuselage, and empennage) to analyze the wake interaction in hovering flight under various crosswind directions. The flow characteristics around the tail rotor, the tail rotor thrust, and the yawing moment of the helicopter are investigated and evaluated. The aerodynamic forces are compared with those of a helicopter with an open-type tail rotor. The results indicate that the aerodynamic performance of the ducted fan tail rotor is highly affected by the wakes of both the main rotor and port wing. Nevertheless, the helicopter with a ducted fan tail rotor is observed to be much more directionally stable under various crosswind directions, than that with an open-type tail rotor. This is because the rotor is protected by the fixed part of the tail rotor system in the former case.

scholarly journals A large-eddy simulation on a deep-stalled aerofoil with a wavy leading edge

2017 ◽  
Vol 813 ◽  
pp. 23-52 ◽  
Author(s):  
Rafael Pérez-Torró ◽  
Jae Wook Kim
Keyword(s):  
Vortex Shedding ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Domain Size ◽  
Aerodynamic Characteristics ◽  
Streamwise Vortices ◽  
Aerodynamic Forces ◽  
Laminar Separation ◽  
Eddy Simulation ◽  
Large Eddy

A numerical investigation on the stalled flow characteristics of a NACA0021 aerofoil with a sinusoidal wavy leading edge (WLE) at chord-based Reynolds number $Re_{\infty }=1.2\times 10^{5}$ and angle of attack $\unicode[STIX]{x1D6FC}=20^{\circ }$ is presented in this paper. It is observed that laminar separation bubbles (LSBs) form at the trough areas of the WLE in a collocated fashion rather than uniformly/periodically distributed over the span. It is found that the distribution of LSBs and their influence on the aerodynamic forces is strongly dependent on the spanwise domain size of the simulation, i.e. the wavenumber of the WLE used. The creation of a pair of counter-rotating streamwise vortices from the WLE and their evolution as an interface/buffer between the LSBs and the adjacent fully separated shear layers are discussed in detail. The current simulation results confirm that an increased lift and a decreased drag are achieved by using the WLEs compared to the straight leading edge (SLE) case, as observed in previous experiments. Additionally, the WLE cases exhibit a significantly reduced level of unsteady fluctuations in aerodynamic forces at the frequency of periodic vortex shedding. The beneficial aerodynamic characteristics of the WLE cases are attributed to the following three major events observed in the current simulations: (i) the appearance of a large low-pressure zone near the leading edge created by the LSBs; (ii) the reattachment of flow behind the LSBs resulting in a decreased volume of the rear wake; and, (iii) the deterioration of von-Kármán (periodic) vortex shedding due to the breakdown of spanwise coherent structures.

Numerical Simulation Research on Aerodynamic Characteristics of the Fixed Transition Airfoil

2013 ◽  
Vol 444-445 ◽  
pp. 385-389 ◽  
Author(s):  
Ji Xiang Shan ◽  
Yong Huang ◽  
Xiao Yong Ma ◽  
Yong Hong Li ◽  
Jie Bai
Keyword(s):  
Lift Coefficient ◽  
Flow Characteristics ◽  
Aerodynamic Characteristics ◽  
Transition Model ◽  
Test Model ◽  
Layer Boundary ◽  
Simulation Research ◽  
Order Of Magnitude ◽  
Important Means ◽  
Flight Model

In wind tunnel tests, the size of the test model is generally much less than the real aircraft, which makes that the Re number during the test is an order of magnitude smaller than the flight Re number. The fixed transition is an important means to improve the test Re number. In the paper, the transition turbulence modelis used to simulate the flow characteristics of the test model (Re=1.5×106), flight model (Re=12×106) and fixed transition model. It is shows that the drag coefficient of the transition model increases and the lift coefficient decreases to compare with the test model and flight model. Compared with the flight model, the turbulent velocity profile of transition model in layer boundary is inadequate, its relative Re number is smaller, so the further amend in the aerodynamic characteristics need to be made.

scholarly journals Aerodynamic Modelling and Analysis of a Novel Mechanism for Chord and Camber Morphing Wing

2018 ◽  
Vol 188 ◽  
pp. 04002 ◽  
Author(s):  
Harun Levent Şahin ◽  
Bora Orçun Çakır ◽  
Yavuz Yaman
Keyword(s):  
Incompressible Flow ◽  
Flow Characteristics ◽  
Aerodynamic Characteristics ◽  
Maximum Speed ◽  
Structural Mechanism ◽  
Speed Range ◽  
Deployable Mechanism ◽  
Aerodynamic Modelling ◽  
Four Bar Linkage ◽  
Transport Theorem

This paper presents the aerodynamic modelling and analysis of surfaces created by a novel deployable mechanism, which is composed of a four-bar linkage and a scissor-structural mechanism (SSM) which contains several scissor-like elements (SLEs). With the help of that mechanism, which is located inside the trailing portion of wing section, continuous adjustment of the airfoil is possible. In order to highlight the advantageous aerodynamic characteristics of newly created airfoil geometries via proposed SSM, several aerodynamic analyses have been performed. The flow characteristics used for the analyses are determined by the flight envelope of an intended generic UAV. Since the maximum speed range of the sample aircraft is well below Mach 0.3, incompressible flow assumption is made throughout the solutions and conservation laws of Reynolds Transport Theorem are employed.

Aerodynamic Simulation of Road Vehicle in Steady Crosswind

2013 ◽  
Vol 376 ◽  
pp. 341-344
Author(s):  
Shan Ling Han ◽  
Ru Xing Yu ◽  
Yu Yue Wang ◽  
Gui Shen Wang
Keyword(s):  
Flow Field ◽  
Wind Direction ◽  
Motor Vehicle ◽  
Aerodynamic Force ◽  
Flow Characteristics ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
External Flow ◽  
Slant Angle ◽  
Ahmed Body

Because crosswind affects drivers to control their vehicles safely, the research on flow characteristics in automotive crosswind has a great significance to improve the crosswind stability of the vehicle. By the steady state numerical simulation method, the aerodynamic characteristics of external flow field of Ahmed body in crosswind was investigated. The Ahmed body with 25° slant angle is built in UG NX. The external flow field of the Ahmed body in the wind direction of 0°, 15º, 30° angle is simulated in XFlow software. According to the map of the pressure and velocity distribution, the flow field both before and after, as well as left and right has significant change as the wind direction angle increased, and the trail turbulence intensity also changes. The changes of aerodynamic force and moment affect the driving stability of a motor vehicle.

scholarly journals The evolution of avian wing shape and previously unrecognized trends in covert feathering

2015 ◽  
Vol 282 (1816) ◽  
pp. 20151935 ◽  
Author(s):  
Xia Wang ◽  
Julia A. Clarke
Keyword(s):  
Foraging Behaviour ◽  
Wing Shape ◽  
Flight Performance ◽  
Wing Morphology ◽  
Wing Loading ◽  
Linear Measurements ◽  
Geometric Morphometric ◽  
Body Sizes ◽  
Wing Tip ◽  
Plastic Character

Avian wing shape has been related to flight performance, migration, foraging behaviour and display. Historically, linear measurements of the feathered aerofoil and skeletal proportions have been used to describe this shape. While the distribution of covert feathers, layered over the anterior wing, has long been assumed to contribute to aerofoil properties, to our knowledge no previous studies of trends in avian wing shape assessed their variation. Here, these trends are explored using a geometric–morphometric approach with landmarks describing the wing outline as well as the extent of dorsal and ventral covert feathers for 105 avian species. We find that most of the observed variation is explained by phylogeny and ecology but shows only a weak relationship with previously described flight style categories, wing loading and an investigated set of aerodynamic variables. Most of the recovered variation is in greater primary covert feather extent, followed by secondary feather length and the shape of the wing tip. Although often considered a plastic character strongly linked to flight style, the estimated ancestral wing morphology is found to be generally conservative among basal parts of most major avian lineages. The radiation of birds is characterized by successive diversification into largely distinct areas of morphospace. However, aquatic taxa show convergence in feathering despite differences in flight style, and songbirds move into a region of morphospace also occupied by basal taxa but at markedly different body sizes. These results have implications for the proposed inference of flight style in extinct taxa.

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