Upload
carver
View
97
Download
7
Tags:
Embed Size (px)
DESCRIPTION
The Physics of Javelin Throwing. How to Make the Javelin Fly Far 101. Maximize release velocity Maximize the aerodynamic efficiencies of the javelin Maximize the height of release without compromising the first two items. Qualities of the Javelin and How T hey A ffect F light. - PowerPoint PPT Presentation
Citation preview
The Physics of Javelin Throwing
How to Make the Javelin Fly Far 101
• Maximize release velocity
• Maximize the aerodynamic efficiencies of the javelin
• Maximize the height of release without compromising the first two items
Qualities of the Javelin and How They Affect Flight
The Evolution of Javelin Design
Matti Jarvin - 1932
And Then Came the Scientific Application of Bernoulli’s Principle
• Bernoulli's Principle states increased air velocity produces decreased pressure on the top of an airfoil (top)
• Lift is produced by an airfoil through a combination of this decreased pressure above the airfoil and increased pressure beneath it (bottom)
Credits - AVStop Magazine Online, Helicopter Handbook
1986 Rule Change2011-2012 NCAA Rule Book
Maximizing Aerodynamic GainesRelease velocity and aerodynamic efficiency are not correlated. Therefore, additional distance can be gained independent of release speed by maximizing aerodynamic efficiency.
Aerodynamic gains are achieved by increasing lift and decreasing drag simultaneously
Optimizing Release AnglesThe javelin’s vertical orientation angle describes the angle of the
javelin in relation to the ground. The angle of attack is the angle between
the release speed the vertical orientation angle of the javelin
The javelin’s horizontal orientation angle describes the direction of the
javelin to the left or right. The angle of sideslip is the angle between the
release speed and javelin’s horizontal orientation.
Optimizing Release Angles
Creating Lift By utilizing a negative horizontal javelin angle and adding a slight negative sideslip angle in combination with a clockwise rotation about the javelin shaft, additional lift can be created. The rotation of the javelin causes air hitting the side of the javelin to increase the air flow over the top of the javelin, decreasing air pressure, and creating lift as described in Bernoulli's Principle.
Decreasing DragA small angle of attack reduces the surface area exposed to the air. A throw with a 0 degree angle of attack creates 10 times less drag than a javelin thrown with a 10 degree angle of attack. If all other variables remain consistent, this translates to a 7 meter difference in the throw’s distance.
Similarly, increasing
sideslip angles also increases
drag.
Decreasing Drag
Rotation about the long axis of a javelin can also reduce drag. Just as the spinning wheels of a bicycle keep it from tipping side to side, thespinning of the javelin
around the long axis helps it to resist forward rotation. The spinning of the javelin also stabilizes the vibration in the shaft similarly to how the rifling of a gun stabilizes the bullet.
Decreasing Drag
Angular Velocities and Aerodynamics
Angular velocity about the center of mass in the vertical plane (forward rotation) should be no greater than 9 degrees per second. Rotation faster than this, cancels out gains due to lift. A throw rotating at 18 degrees per second will result in a throw roughly 25m less than a throw rotating under 9 degrees per second.
Angle of attack also affects angular velocity. A positive angle of attack creates drag on the underside of the tail and will cause the javelin to pitch forward. A negative angle of attack creates drag on the top side of the nose and will not cause the same pitching reaction.
Angular Velocities and Aerodynamics
Angular Velocities and Aerodynamics
The trunk tilt angle represents the lean of the torso relative to
true vertical. It describes the
orientation of the trunk, the line of the
hips and the shoulders.
An excessive trunk tilt angle will result in an increase in angular velocity
Trunk Tilt Angle
Drills that address excessive angular velocity in the vertical plane due to trunk
tilt by setting up an effective block:1) Sprint drills to promote good running posture2) Transition Drill to set up good posture in the cross
overs3) Special Strength Drills for the C Position (Square
throws, Three Step Tire Drills, Static Holds)4) Staggered Square Drills to promote proper hip
position in the block
Angular Velocities and Aerodynamics
Angular Velocities and Aerodynamics
Similarly, angular velocities in the horizontal plane
also effect aerodynamic
efficiencies. The greater the
horizontal rotation, the faster the angle
of sideslip will increase.
Christian Nicolay
Drills to address excessive angular velocities in the horizontal plane do to
shoulder Rotation:
1) Pullie Drill2) Poll Drill3) Basketball Throws4) Reverse Pulls
Angular Velocities and Aerodynamics
Maximizing Release Velocity
Release velocity is directly correlated to a throw’s distance. There is both a horizontal and vertical component to release velocity. Because humans
are far more efficient at creating horizontal speed, vertical speed
should only be increased so long as the horizontal component isn’t
diminished.
Technical Elements Affecting Release VelocityTemporal Rhythm
1. Time of throwing procedure (time from contact of the last right foot to release)
2. Time of the single support phase (time spent on the last right foot until the left foot hits)
3. Time of the delivery phase (time from left foot contact to release)
Technical Elements Affecting Release Velocity
Maintenance of Runway Speed Through the Throwing Procedure
Jan Zelezny
Drills that Address Inefficient Maintenance of Runway Speed:
1) Running Mechanics to address posture in the carry and transition phases of the throw
2) Crossover drills addressing posture and stride length, and footfall frequency
3) Right foot action (Soft Step): One step off a low box, 3 step off a low box, down hill throws
Technical Elements Affecting Release Velocity
Technical Elements Affecting Release Velocity
Left Lower Extremity Angles1. Left knee flexion angle - left leg should be
straight at during the delivery phase
2. Left leg angle – the angle should increase in the delivery phase
Technical Elements Affecting Release Velocity
Hip Shoulder Separation
Hip shoulder separation represents trunk twist. Trunk twist is used to convert linear motion to rotational. It can also be very effective in increasing the speed of each body segment in order away from the trunk out to the javelin in a whipping motion.
Technical Elements Affecting Release Velocity
Efficient Summation of Joint Speeds: the Whipping Action
Drills Addressing Efficient Summation of Joint Speeds:
1) Hip activation drill series (low, mid and high positions)
2) Leverage drills (double arm wall drill, single arm wall drill, alternate wall drill, one or two hand square throws with medicine ball, turbo javelin, or javelin)
Technical Elements Affecting Release Velocity
Additional Elements Affecting Distance
1. Height of Release - as high as possible without reducing speed
2. Angle of Release – between 29 and 35 degrees to maximize speed of release and lift.
Tom Petronoff
Special Thanks To:
Steve Leigh, M.S.And
Bing Yu, Ph.D.
Center for Human Movement ScienceDivision of Physical Therapy
The University of North Carolina at Chapel Hill
Under the USATF Scientific Services ProjectFor providing the biomechanical analysis of the javelin throw
cited in this presentation.