This
is a beta 1.2 version of the CurveBall program, and you are invited
to participate in the beta testing. If you find errors in the program or
would like to suggest improvements, please send an e-mail to benson@grc.nasa.gov.
CurveBall
With this software you can investigate how a big league pitcher throws
a curveball by changing the values of the factors
that affect the aerodynamic forces on the ball.
These are the same forces that generate the lift
of an aircraft wing, which can be investigated with another Java Applet
called FoilSim II.
If you are an experienced user of CurveBall, you may prefer a slightly different version of
CurveBall.
To return to the original default conditions, click the
Reset button.
SCREEN
The program screen is divided into three main parts:
At the top of the screen is a graphics window. By moving between
Ballpark and Flowfield, you can display a drawing of the
infield and your pitch trajectory or you can
see the flow of air around the ball. In both cases you are looking down
onto the ball or the infield. The simulation is two dimensional with
the ball spinning about an axis pointing into the Earth (or Mars). The
force occurs side to side; we are not concerned
about the ball falling towards the surface.
Below the graphics window, on the left of the screen are inputs
and outputs associated with the atmosphere
through which the ball moves. To the right of the graphics choice button,
a black output box shows the side force on the baseball. The force can
be computed in either English or metric units and is also displayed
on a force gage directly below the output box. The bar on the gage is
colored yellow when the force is
negative (pushes the ball to the left of home plate as viewed from the
mound) and cyan when the force is
positive (pushes the ball to the right of home plate as viewed from
the mound.) Below the gage are some input/output boxes. By convention
input boxes have a white background and black numerals and you can key
in new values. If the box has green numerals on a black background it
is an output box and you cannot key in values. Below the boxes is a
choice button labeled Location. The default is Specify, which
allows you to type in the atmospheric conditions at your ballpark. You
can specify the temperature, the atmospheric
pressure, and the relative humidity of
the air; the program will calculate the air density
that affects the side force. You may choose, however, to use a standard
day (average) atmosphere at several different locations displayed on
the choice button menu. Try setting up a pitch and changing the location.
What happens to the trajectory?
Below the graphics window on the right of the screen are inputs to
set up and throw the pitch. You can be a right hander or a lefty by clicking
on the round buttons. To set up a pitch, you must specify the speed
and the spin on the ball, the spot on the pitcher's
mound from which you release the ball, and the angle at which you release
the ball. A small arrow on the ball in the graphics window will help you determine
these values. And the red bar on the ball shows the direction and rate of spin.
If you push the blue button marked Set Up Next Pitch you will not see
where the ball will go until you push the red Throw the Pitch button.
Otherwise, as you change inputs, you will see the pitch trajectory. Above the
blue button you will see a box that judges your pitch as a ball or a strike
and tells you how far from the center of the plate the pitch first crossed the
front of the plate.
CurveBall - Baseball
Simulation: 
