Identification of a degradation of aerodynamic characteristics of a paraglider due to its flexibility from flight test

2019 ◽  
Vol 91 (6) ◽  
pp. 873-879 ◽  
Author(s):  
Robert Kulhánek
Keyword(s):  
High Speed ◽  
Aerodynamic Drag ◽  
Leading Edge ◽  
Flight Test ◽  
Aerodynamic Characteristics ◽  
Full Scale ◽  
Content Type ◽  
Specific Geometry ◽  
Lift And Drag ◽  
Scaled Models

Purpose Aerodynamics of paragliders is very complicated aeroelastic phenomena. The purpose of this work is to quantify the amount of aerodynamic drag related to the flexible nature of a paraglider wing. Design/methodology/approach The laboratory testing on scaled models can be very difficult because of problems in the elastic similitude of such a structure. Testing of full-scale models in a large facility with a large full-scale test section is very expensive. The degradation of aerodynamic characteristics is evaluated from flight tests of the paraglider speed polar. All aspects of the identification such as pilot and suspension lines drag and aerodynamics of spanwise chambered wings are discussed. The drag of a pilot in a harness was estimated by means of wind tunnel testing, computational fluid dynamics (CFD) solver was used to estimating smooth wing lift and drag characteristics. Findings The drag related to the flexible nature of the modern paraglider wing is within the range of 4-30 per cent of the total aerodynamic drag depending on the flight speed. From the results, it is evident that considering only the cell opening effect is sufficient at a low-speed flight. The stagnation point moves forwards towards the nose during the high speed flight. This causes more pronounced deformation of the leading edge and thus increased drag. Practical implications This paper deals with a detailed analysis of specific paraglider wing. Although the results are limited to the specific geometry, the findings help in the better understanding of the paraglider aerodynamics generally. Originality/value The data obtained in this paper are not affected by any scaling problems. There are only few experimental results in the field of paragliders on scaled models. Those results were made on simplified models at very low Reynolds number. The aerodynamic drag characteristics of the pilot in the harness with variable angles of incidence and Reynolds numbers have not yet been published.

Research on transient aerodynamic characteristics of windshield wipers of vehicles

2019 ◽  
Vol 29 (8) ◽  
pp. 2870-2884
Author(s):  
Zhen Chen ◽  
Zhenqqi Gu ◽  
Tao Jiang
Keyword(s):  
Drag Force ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Dynamic Mesh ◽  
Research Association ◽  
Content Type ◽  
Dynamic Mesh Technique ◽  
Lift And Drag ◽  
Mesh Technique ◽  
Aerodynamic Lift

Purpose The main purpose of this paper is to gain a better understanding of the transient aerodynamic characteristics of moving windshield wipers. In addition, this paper also strives to illustrate and clarify how the wiper motion impacts the airflow structure; the aerodynamic interaction of two wipers is also discussed. Design/methodology/approach A standard vehicle model proposed by the Motor Industry Research Association and a pair of simplified bone wipers are introduced, and a dynamic mesh technique and user-defined functions are used to achieve the wiper motion. Finite volume methods and large eddy simulation (LES) are used to simulate the transient airflow field. The simulation results are validated through the wind tunnel test. Findings The results obtained from the study are presented graphically, and pressure, velocity distributions, airflow structures, aerodynamic drag and lift force are shown. Significant influences of wiper motion on airflow structures are achieved. The maximum value of aerodynamic lift and drag force exists when wipers are rotating and there is a certain change rule. The aerodynamic lift and drag force when wipers are rotating downward is greater than when wipers are rotating upward, and the force when rotating upward is greater than that when steady. The aerodynamic lift and drag forces of the driver-side wiper is greater than those of the passenger-side wiper. Originality/value The LES method in combination with dynamic mesh technique to study the transient aerodynamic characteristics of windshield wipers is relatively new.

An Analysis of the Aerodynamic Characteristics of Split Flaps

1940 ◽  
Vol 44 (352) ◽  
pp. 338-349
Author(s):  
A. P. West
Keyword(s):  
Experimental Data ◽  
Aerodynamic Characteristics ◽  
Full Scale ◽  
The Other ◽  
Aircraft Industry ◽  
The Past ◽  
The Many ◽  
Lift And Drag ◽  
Scale Data

During the past few years an extensive amount of experimental data on split flaps has been made available to the aircraft industry, through the publications of aeronautical research laboratories, both in this country and abroad. In general, each publication deals with one particular aspect of the problem, and when the effect of wing flaps on the performance of an aircraft is being estimated a certain amount of difficulty may be experienced in deciding which of the many reports available gives results most readily applicable to the case being considered ; and what allowances, if any, should be made for wing taper, flap cut-out, fuselage, etc.In this report the available data has been analysed with a view to answering these questions, and presented in such a form that it may be readily applied to determine the most probable change in the aerodynamic characteristics of a wing that may be expected from the use of this type of flap.From the appendix an estimate of the accuracy of the method can be obtained, as a comparison with full-scale data is given for lift and drag, and for the other flap characteristics the original curves have been reproduced.

Cavity for Flow Control and Performance Improvement of Airfoil

2021 ◽  
Author(s):  
Anand Verma ◽  
Bastav Borah ◽  
Vinayak Kulkarni
Keyword(s):  
Moving Boundary ◽  
Flow Analysis ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Suction Surface ◽  
Confined Spaces ◽  
Steady Simulation ◽  
And Performance ◽  
Lift And Drag ◽  
Fluid Flow Analysis

Abstract The fluid flow analysis over a cambered airfoil having three different cavity locations on the suction surface is reported in this paper. The Elliptical cavity is created at LE, MC, and TE along chordwise locations from the leading to trailing edge. In this regard, the steady simulation is carried out in the Fluent at Reynolds number of 105 based on their chord length. The lift and drag characteristics for clean and cavities airfoil are investigated at different angles of attack. For the clean airfoil, the stall point is observed at 18°. The presence of a cavity improves the stall and aerodynamic characteristics of airfoil. It has been seen that the lift and drag coefficients for pre-stalled or lower angles are nearly similar to clean and cavity at MC or TE positions. For the post-stall point, the improvement in the aerodynamic performance is seen for the cavity at MC or TE. The cavity placed at LE produces lower lift and higher drag characteristics against other configuration models. The overall cavity effect for the flow around the airfoil is that it creates vortices, thereby re-energizes the slower moving boundary layer and delays the flow separation in the downstream direction. The outcomes of this analysis are suggested that the cavity at a position before the mid chord from the leading edge does not improve the performance of the airfoil. Though vortex is formed in the confined spaces but it is unable to reattach the flow towards the downstream direction of an airfoil.

Prediction of drag and lift forces of a high-speed vessel at full scale by CFD-based GEOSIM method

2022 ◽  
pp. 147509022110707
Author(s):  
Ugur Can ◽  
Sakir Bal
Keyword(s):  
High Speed ◽  
Full Scale ◽  
Navier Stokes ◽  
Drag Forces ◽  
Fluid Body ◽  
Unsteady Rans ◽  
Lift Forces ◽  
Drag And Lift ◽  
Lift And Drag ◽  
Model Family

In this study, it was aimed to obtain an accurate extrapolation method to compute lift and drag forces of high-speed vessels at full-scale by using CFD (Computational Fluid Dynamics) based GEOSIM (GEOmetrically SIMilar) method which is valid for both fully planing and semi-planing regimes. Athena R/V 5365 bare hull form with a skeg which is a semi-displacement type of high-speed vessel was selected with a model family for hydrodynamic analyses under captive and free to sinkage/trim conditions. Total drag and lift forces have been computed for a generated GEOSIM family of this form at three different model scales and full-scale for Fr = 0.8 by an unsteady RANS (Reynolds Averaged Navier–Stokes) solver. k–ε turbulence model was used to simulate the turbulent flow around the hulls, and both DFBI (Dynamic Fluid Body Interaction) and overset mesh technique were carried out to model the heave and pitch motions under free to sinkage/trim condition. The computational results of the model family were used to get “drag-lift ratio curve” for Athena hull at a fixed Fr number and so the corresponding results at full scale were predicted by extrapolating those of model scales in the form of a non-dimensional ratios of drag-lift forces. Then the extrapolated full-scale results calculated by modified GEOSIM method were compared with those of full-scale CFD and obtained by Froude extrapolation technique. The modified GEOSIM method has been found to be successful to compute the main forces (lift and drag) acting on high-speed vessels as a single coefficient at full scale. The method also works accurately both under fully and semi-planing conditions.

A new moving model test method for the measurement of aerodynamic drag coefficient of high-speed trains based on machine vision

2017 ◽  
Vol 232 (5) ◽  
pp. 1425-1436 ◽  
Author(s):  
Zhiwei Li ◽  
Mingzhi Yang ◽  
Sha Huang ◽  
Dan Zhou
Keyword(s):  
Machine Vision ◽  
Drag Coefficient ◽  
Model Test ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Full Scale ◽  
Test Method ◽  
Test Accuracy ◽  
Friction Resistance ◽  
Aerodynamic Drag Coefficient

A moving model test method has been proposed to measure the aerodynamic drag coefficient of a high-speed train based on machine vision technology. The total resistance can be expressed as the track friction resistance and the aerodynamic drag according to Davis equation. Cameras are set on one side of the track to capture the pictures of the train, from which the line marks on the side surface of the train are extracted and analyzed to calculate the speed and acceleration of the train. According to Newton’s second law, the aerodynamic drag coefficient can be resolved through multiple tests at different train speeds. Comparisons are carried out with the full-scale coasting test, wind tunnel test, and numerical simulation; good agreement is obtained between the moving model test and the full-scale field coasting test with difference within 1.51%, which verifies that the method proposed in this paper is feasible and reliable. This method can accurately simulate the relative movement between the train, air, and ground. The non-contact measurement characteristic will increase the test accuracy, providing a new experimental method for the aerodynamic measurement.

Experimental Studies on Aerodynamic Characteristics of Pantograph System According to the Pantograph Cover Configurations for High Speed Train

2011 ◽  
Author(s):  
Yeongbin Lee ◽  
Minho Kwak ◽  
Kyu Hong Kim ◽  
Dong-Ho Lee
Keyword(s):  
Wind Tunnel ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Aerodynamic Force ◽  
Experimental Studies ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Experimental Models ◽  
High Speed Train ◽  
Drag And Lift

In this study, the aerodynamic characteristics of pantograph system according to the pantograph cover configurations for high speed train were investigated by wind tunnel test. Wind tunnel tests were conducted in the velocity range of 20∼70m/s with scaled experimental pantograph models. The experimental models were 1/4 scaled simplified pantograph system which consists of a double upper arm and a single lower arm with a square cylinder shaped panhead. The experimental model of the pantograph cover is also 1/4 scaled and were made as 4 different configurations. It is laid on the ground plate which modeled on the real roof shape of the Korean high speed train. Using a load cell, the aerodynamic force such as a lift and a drag which were acting on pantograph system were measured and the aerodynamic effects according to the various configurations of pantograph covers were investigated. In addition, the total pressure distributions of the wake regions behind the panhead of the pantograph system were measured to investigate the variations of flow pattern. From the experimental test results, we checked that the flow patterns and the aerodynamic characteristics around the pantograph systems are varied as the pantograph cover configurations. In addition, it is also found that pantograph cover induced to decrease the aerodynamic drag and lift forces. Finally, we proposed the aerodynamic improvement of pantograph cover and pantograph system for high speed train.

Numerical Simulation on Aerodynamic Characteristics of Heavy-Duty Commercial Vehicle

2011 ◽  
Vol 346 ◽  
pp. 477-482 ◽  
Author(s):  
Zhe Zhang ◽  
Ying Chao Zhang ◽  
Jie Li ◽  
Jia Wang
Keyword(s):  
Numerical Simulation ◽  
Fuel Economy ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
National Standards ◽  
Heavy Duty ◽  
Commercial Vehicles ◽  
Automotive Technology ◽  
New Research

With the development of automotive technology and high-speed highway construction, the speed of the vehicles increase which cause the significant increase in the aerodynamic drag when road vehicles are moving. Thereby the power of the vehicles, fuel economy, operational stability and other properties are affected very seriously. Heavy-duty commercial vehicles as the most efficient way to transport goods on the highway are widely used, and the speed of the vehicles increases faster. Especially the demands for heavy-duty commercial vehicles are increasing in recent years. Reducing the aerodynamic drag by the analysis of external aerodynamic characteristics, improving the fuel economy and reducing energy consumption have become new research topics of heavy-duty commercial vehicles. To make the heavy-duty commercial vehicles meet the national standards of energy saving, a simplified heavy-duty commercial truck model was built in this paper. The numerical simulation of the vehicle was completed based on the theory of the aerodynamics. The aerodynamic characteristics were analyzed, according to the graphs of the pressure distribution, velocity distribution and flow visualization. To improve the aerodynamic characteristics of heavy-duty commercial vehicles, the main drag reduction measures are reducing the vortex of the cab and the container, the end of the container and the bottom of the container.

scholarly journals Effect of Leading-Edge Bulges on Aerodynamic Characteristics of Bionic Wingsail

2021 ◽  
Author(s):  
Chen Li ◽  
Peiting Sun ◽  
Hongming Wang
Keyword(s):  
Stokes Equations ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Suction Surface ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Extension Direction ◽  
Lift And Drag

The leading-edge bulges along the extension direction are designed on the marine wingsail. The height and the spanwise wavelength of the protuberances are 0.1c and 0.25c, respectively. At Reynolds number Re=5×105, the Reynolds Averaged Navier-Stokes equations are applied to the simulation of the wingsail with the bulges thanks to ANSYS Fluent finite-volume solver based on the SST K-ω models. The grid independence analysis is carried out with the lift and drag coefficients of the wingsail at AOA = 8° and AOA=20°. The results show that while the efficiency of the wingsail is reduced by devising the leading-edge bulges before stall, the bulges help to improve the lift coefficient of the wingsail when stalling. At AOA=22° under the action of the leading-edge tubercles, a convective vortex is formed on the suction surface of the modified wingsail, which reduces the flow loss. So the bulges of the wingsail can delay the stall.

An experimental parametric study on planar sheared wings tip devices for low-to-moderate aspect ratio wings

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Lourelay Moreira dos Santos ◽  
Guilherme Ferreira Gomes ◽  
Rogerio F. Coimbra
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Parametric Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Sweep Angle ◽  
Wind Tunnel Tests ◽  
Content Type ◽  
Wing Tips ◽  
Wing Tip

Purpose The purpose of this study is to investigate the aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips. Design/methodology/approach In this work, wind tunnel tests were made to study the influence in aerodynamic characteristics over a typical low-to-moderate-aspect-ratio wing of a general aviation aircraft, equipped with sheared – swept and tapered planar – wing tips. An experimental parametric study of different wing tips was tested. Variations in its leading and trailing edge sweep angle as well as variations in wing tip taper ratio were considered. Sheared wing tips modify the flow pattern in the outboard region of the wing producing a vortex flow at the wing tip leading edge, enhancing lift at high angles of attack. Findings The induced drag is responsible for nearly 50% of aircraft total drag and can be reduced through modifications to the wing tip. Some wing tip models present complex geometries and many of them present benefits in particular flight conditions. Results have demonstrated that sweeping the wing tip leading edge between 60 and 65 degrees offers an increment in wing aerodynamic efficiency, especially at high lift conditions. However, results have demonstrated that moderate wing tip taper ratio (0.50) has better aerodynamic benefits than highly tapered wing tips (from 0.25 to 0.15), even with little less wing tip leading edge sweep angle (from 57 to 62 degrees). The moderate wing tip taper ratio (0.50) offers more wing area and wing span than the wings with highly tapered wing tips, for the same aspect ratio wing. Originality/value Although many studies have been reported on the aerodynamics of wing tips, most of them presented complex non-planar geometries and were developed for cruise flight in high subsonic regime (low lift coefficient). In this work, an exploration and parametric study through wind tunnel tests were made, to evaluate the influence in aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips (wing tips highly swept and tapered).

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