Javelin Dynamics With Measured Lift, Drag, and Pitching Moment

Optimal release conditions for the javelin are studied using computer simulation. Included are two important and realistic assumptions: (1) initial velocity attainable by the thrower is dependent on the throwing angle, and (2) the aerodynamic center of pressure moves as a function of angle of attack. Aerodynamic forces and moments, previously measured in wind tunnel tests, are incorporated in the simulation. Range contours are presented in the two-space of initial angle of attack–initial flight path angle, assuming zero initial angular velocity.

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Measurement of the Aerodynamic Forces Acting on a Non-Spinning Javelin Using an MSBS

Proceedings ◽

10.3390/proceedings2020049144 ◽

2020 ◽

Vol 49 (1) ◽

pp. 144

Author(s):

Takuto Kobayashi ◽

Kazuya Seo ◽

Shoya Kaneda ◽

Kasumi Sasaki ◽

Kento Shinji ◽

...

Keyword(s):

Wind Tunnel ◽

Angle Of Attack ◽

Magnetic Suspension ◽

Pitching Moment ◽

Aerodynamic Forces ◽

Balance System

Using the world’s largest magnetic suspension and balance system (MSBS) and a low-turbulence wind tunnel, we successfully measured the aerodynamic forces acting on a non-spinning women’s javelin. It was found that the drag and the lift increased as the angle of attack was increased up to 18°. The pitching moment increased for angles of attack up to about 9°, and then decreased, becoming negative above 12°, indicating nose-down rotation. We used a pseudo supporting rod to simulate a javelin attached to a support, as used in a conventional setup, and confirmed that this interferes with the javelin by creating differences between the aerodynamics forces acting on the javelin with and without the pseudo supporting rod.

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Optimization Calculation of Javelin Throwing Results

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.716-717.764 ◽

2014 ◽

Vol 716-717 ◽

pp. 764-766

Author(s):

Min Jiang ◽

Ji He Zhou

Keyword(s):

Mathematical Model ◽

Wind Tunnel ◽

Initial Velocity ◽

Angle Of Attack ◽

Wind Tunnel Experiment ◽

Aerodynamic Efficiency ◽

Optimization Calculation ◽

Computer Optimization ◽

Necessary And Sufficient

On the basis of javelin wind tunnel experiment, we established mathematical model of javelin flight to conduct a computer optimization and got the conclusions. When the initial velocity is in the range of 25m/s-30m/s, the best throwing condition is: the throwing angle is 40°, the angle of attack is 11°. The javelin throwing condition is not zero angle of attack was necessary and sufficient for obtained aerodynamic efficiency.

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Laser Displacement Sensors for Wind Tunnel Model Position Measurements

Sensors ◽

10.3390/s18124085 ◽

2018 ◽

Vol 18 (12) ◽

pp. 4085 ◽

Cited By ~ 2

Author(s):

Matthew Kuester ◽

Nanyaporn Intaratep ◽

Aurélien Borgoltz

Keyword(s):

Wind Tunnel ◽

Angle Of Attack ◽

Pitching Moment ◽

Two Dimensional ◽

Temperature Drift ◽

Wind Tunnel Model ◽

Multiple Sensors ◽

Displacement Sensors ◽

Tunnel Model ◽

Linear Encoder

Wind tunnel measurements of two-dimensional wing sections, or airfoils, are the building block of aerodynamic predictions for many aerodynamic applications. In these experiments, the forces and pitching moment on the airfoil are measured as a function of the orientation of the airfoil relative to the incoming airflow. Small changes in this angle (called the angle of attack, or α ) can create significant changes in the forces and moments, so accurately measuring the angle of attack is critical in these experiments. This work describes the implementation of laser displacement sensors in a wind tunnel; the sensors measured the distance between the wind tunnel walls and the airfoil, which was then used to calculate the model position. The uncertainty in the measured laser distances, based on the sensor resolution and temperature drift, is comparable to the uncertainty in traditional linear encoder measurements. Distances from multiple sensors showed small, but statistically significant, amounts of model deflection and rotation that would otherwise not have been detected, allowing for an improved angle of attack measurement.

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Effect of Reduced Frequency on Longitudinal Oscillatory Derivatives of an Airfoil Based on Wind Tunnel Data

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1016.465 ◽

2014 ◽

Vol 1016 ◽

pp. 465-470

Author(s):

F. Rasi Marzabadi ◽

Ramin Kamali Moghadam

Keyword(s):

Wind Tunnel ◽

Angle Of Attack ◽

Pitching Moment ◽

Longitudinal Dynamic ◽

Reduced Frequency ◽

Wind Tunnel Data ◽

Derivatives Of

Longitudinal dynamic derivatives of an airfoil oscillating in pitching and plunging motions were calculated using variation of pitching moment coefficients with angle of attack in various conditions, based on wind tunnel data. The effect of reduced frequency on variation of longitudinal oscillatory derivatives was investigated, in three different regions of oscillation: before, over and post stall conditions. The results showed that reduced frequency has significant effects on longitudinal oscillatory coefficients in different conditions for both types of oscillations.

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Parametric study of a corrugated airfoil in a forward flight at ultra-low Reynolds number

SN Applied Sciences ◽

10.1007/s42452-020-04105-y ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Mahmoud E. Abd El-Latief ◽

Khairy Elsayed ◽

Mohamed M. Abdelrahman

Keyword(s):

Reynolds Number ◽

Phase Difference ◽

Lift Force ◽

Thrust Force ◽

Angle Of Attack ◽

Initial Angle ◽

Aerodynamic Forces ◽

Forward Flight ◽

Propulsive Efficiency ◽

Stroke Amplitude

AbstractIn the current study, the mid cross section of the dragonfly forewing was simulated at ultra-low Reynolds number. The study aims to understand better the contribution of corrugations found along the wing on the aerodynamic performance during a forward flight. Different flapping parameters were employed. FLUENT solver was used to solve unsteady, two-dimensional, laminar, incompressible Navier–Stokes equations. The results revealed that any stroke amplitude less than 1cm generated no thrust force. The stroke amplitude had to be increased to form the reversed Kármán vortices responsible for generating thrust force. The highest propulsive efficiency was found in the Strouhal number range 0.2 < St < 0.4 with a peak efficiency of 57% at St = 0.39. Changing the phase difference between pitching and plunging motions from advanced to synchronized caused lift force to drop 91% and thrust force to increase by 15%. On the other hand, changing the phase difference from synchronized to delayed caused lift and thrust forces to increase by 89% and 36%, respectively, and propulsive efficiency to deteriorate significantly. In all performed simulations, the airfoil was assumed to start motion from rest with no initial angle of attack. The increase in initial angle of attack generates a very high lift force with a fair loss for both thrust force and propulsive efficiency. The decomposition of flapping motion into its elementary motions revealed that the aerodynamic forces generated are a non-linear superposition from both pure pitching and pure plunging aerodynamic forces. This can be attributed to the non-linear interaction between unsteady vortices generated from these decomposed motions.

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The Aerodynamics of an Actively Twisted Wing

Aerospace ◽

10.1115/imece2005-81213 ◽

2005 ◽

Author(s):

James R. Sonnenmeier ◽

Oladipo Onipede ◽

Andrew J. Detar ◽

Heather L. Myers

Keyword(s):

Wind Tunnel ◽

Shape Memory Alloy ◽

Angle Of Attack ◽

Aerodynamic Performance ◽

Simple Test ◽

Wind Tunnel Experiments ◽

Aerodynamic Forces ◽

Aerodynamic Model ◽

Separate Control ◽

Control Surfaces

Aerodynamic performance of aircraft can be changed by moving separate surfaces which are mechanically connected to the main wing and moved with complex linkages. A possible alternative method of changing performance with less mechanical complexity is presented. Instead of separate control surfaces, the shape of complete aerodynamic structures can be changed with shape memory alloy (SMA) materials as part of the structure. In this work SMA wire is wrapped around a simple test wing. When activated by heating, the wire contracts which results in twisting the wing. The angle of attack along the wingspan changes which changes the aerodynamic forces on the wing. This could be used to optimize the flight condition. Results are presented from initial wind tunnel experiments which show the change in lift due to twisting. Aerodynamic models that account for the variable angle of attack along the span are also developed. The results from the experiments and aerodynamic model are compared.

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Optimum Release Conditions for the New Rules Javelin

International Journal of Sport Biomechanics ◽

10.1123/ijsb.3.3.207 ◽

1987 ◽

Vol 3 (3) ◽

pp. 207-221 ◽

Cited By ~ 10

Author(s):

Mont Hubbard ◽

LeRoy W. Alaways

Keyword(s):

Angular Velocity ◽

Initial Conditions ◽

Angle Of Attack ◽

Pitching Moment ◽

Velocity Change ◽

Optimal Angle ◽

Rule Change ◽

Speed Range ◽

Main Effects ◽

Aerodynamic Lift

Changes in the rules for construction of the men's javelin have dramatically altered the pitching moment profile as a function of angle of attack. Thus the optimal release conditions are different for the new javelin. Optimal release conditions are presented for nominal release velocities in the range 20 < vn < 35 m/s. Although the optimal release angle remains roughly constant near 30° over this speed range, the optimal angle of attack and pitching angular velocity change substantially with speed. The main effects of the rule change have been (a) to decrease the achievable range at a nominal velocity vn = 30 m/s by about 10% by making it impossible to take advantage of the javelin's potentially large aerodynamic lift forces, and (b) to make the flight much less sensitive to initial conditions.

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Comparison of Aerodynamic Properties of Badminton Feather and Synthetic Shuttlecocks

Proceedings ◽

10.3390/proceedings2020049104 ◽

2020 ◽

Vol 49 (1) ◽

pp. 104

Author(s):

Kenichi Nakagawa ◽

Hiroaki Hasegawa ◽

Masahide Murakami

Keyword(s):

Wind Tunnel ◽

High Stability ◽

Angle Of Attack ◽

Pitching Moment ◽

Wind Tunnel Experiments ◽

Aerodynamic Stability ◽

Fluid Forces ◽

Moment Coefficient ◽

Aerodynamic Properties ◽

The Difference

The purpose of this study is to investigate the difference in aerodynamic properties between the feather shuttlecock and the synthetic shuttlecock. In particular, we focus on the aerodynamic stability of the two types of shuttlecock during impulsive change of an angle of attack (flip movement). Wind tunnel experiments are performed by using two types of the badminton shuttlecock (feather and synthetic shuttlecocks) to measure the fluid forces, and to visualize the flow fields around the shuttlecock. It is confirmed that the pitching moment coefficient at a near-zero angle-of-attack for feather shuttlecock is larger than that for synthetic shuttlecock. The results indicate that the feather shuttlecock demonstrates high stability in response to the flip phenomenon.

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