is a beta 1.4n version of the FoilSim II 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 firstname.lastname@example.org.
With this software
you can investigate how an aircraft wing produces
lift by changing the values of different factors
that affect lift.
If you are an experienced user of FoilSim,
or if you plan to use your browser Print command to save output,
or if you are using Internet Explorer, it is recommended that you use a slightly different
version of FoilSim II .
This altered version does not include the following tutorial.
You can also investigate the role of aerodynamics in
pitching a baseball by using another interactive
Java Applet called
If you experience difficulties when using the sliders to change variables,
simply click away from the slider and then back to it.
If the arrows on the end of the sliders disappear, click in the areas where
the left and right arrow images should appear, and they should reappear.
To return to the original default conditions, click the red Reset
button at the left middle of the program.
The program screen
is divided into three main parts:
At the top
of the screen are two graphics windows. The left window is the View
window in which you can display a drawing of the airfoil or wing you
are designing with the flow of air around the airfoil. The right window
is the Output window in which you can display a plot of the flow
variables, a lift meter, or a probe to investigate the flow field. Details
are given in Graphics.
In the middle
of the screen on the left is the control panel. You can control the
type of analysis and the units used in the display by using the white
menu buttons. To operate a menu button, click on the arrow to the
right and make your selection from the drop menu. The interactive inputs
to the program are displayed on the input panel to the right of the
control panel. You can select the input panel to be displayed by using
the blue and white buttons in the middle of the control panel. You can
also select the type of graphical output by using the white and red
buttons on the right side of the control panel. Details of the input
and output variables are given below.
At the bottom
of the screen is a large text window in which output from the program
is displayed. Output can be printed using the browser Print command.
You can save the airfoil geometry and surface
flow variables by pushing the Save Geom button on the control
panel. You can save flow conditions and calculated lift by pushing the
Save Data button on the control panel.
There are two main
graphics displays. At the top left is the View window of the airfoil
and flow field and at the top right is the Output plot of flow
You can select the
type of schematic shown in the View window by using the buttons
located around the graphics window. Possible choices are colored blue
while the selected option is colored yellow.
the wing as viewed looking along the leading edge. The cross section
appears as an airfoil or circle with the flow going from left to right.
You can move the picture within the window by moving the cursor into
the window, holding down the left mouse button, and dragging the airfoil
to a new location. You can also "Zoom" in close to the airfoil by using
the green slider at the right of the window. If you get lost, pushing
the red Find button will return the airfoil to the initail position.
the wing as viewed from above looking down onto the planform. The flow
is from bottom to top. Since FoilSim only solves for the two-dimensional
flow past objects, you won't see any flow in this view. It is provided
only to display the geometry of the wing area.
Side - 3D
shows an orthographic projection of the three dimensional wing.
particles flowing past the airfoil. The particles are drawn as line
"traces". The inclination of the trace is at the local flow angle, and
the left most part of the trace is the particle location. Particles
are being periodically released from a constant streamwise location
upstream of the airfoil.The streamwise distance between any two particles
is proportional to the local velocity.
a snapshot of the moving particles. In this view, you can change the
streamwise release point of the particles by moving the cursor into
the view window, holding down the left mouse, and dragging the particles
to the left or right. In this view, the particles are color coded by
the time at which they are released. (All of the yellow particles were
released at the same streamwise location at the same time.)
are collections of the particle traces to form a solid flow line.
shows only the geometry of the wing or airfoil with some descriptive
labels but with no flow field.
There are several different output options available in the
You can select the type of output
by using the white and
red buttons on the control panel. If you select Plots, a panel
will appear in the output window which allows you to select the
type of plot.
If you display a plot and begin to change the
input variables, it may become necessary to rescale the plot axes by
pushing the white Rescale button at the lower left of the window.
The types of available plots are
The default plot
is the Surface Pressure. The yellow line will be a plot of the
lower surface pressure, and the white line a plot of the upper surface
pressure. For reference, the green line shows the value of free stream
You may also display
the Surface Velocity. As with the pressure, the yellow line will
be a plot of the lower surface, and the white line a plot of the upper
surface. If the Stall Model is used and the wing stalls, these
plots are not available.
The remaining plot
choices show Lift or Lift Coefficient -Cl versus each
of the input variables.
For these plots, the current value of the flow conditions is shown as
a red dot on the plot.
The Lift Meter
shows the current value of lift (or lift coefficient) displayed
in scientific notation. The meter is displayed in the output window
and moves as the lift is varied.
lets you explore the flow around the wing. A probe control panel appears
in the output window when you select "Probe" from the conrtrol panel.
By default, the probe is
turned off. You turn the probe on by pushing one of the white buttons
on the probe panel. The probe itself will then appear in the view window. You
change the location of the probe using the sliders to the left and below
the gauge on the probe panel. The value of the pressure or the velocity at the location
of the probe tip (magenta ball on the view window) is displayed on the
gauge. Or a green trail of "smoke" is swept downstream from the probe
location. You turn the probe off by using the red button located above
The input variables
are located on input panels that are displayed below the Output window.
You can select the input to display by using the blue input buttons on
the control panel. You can choose to vary the Shape,
the Size, or perform a Flight
Test. To change the value of an input variable, simply move the slider.
Or click on the input box, select and replace the old value, and hit
Enter to send the new value to the program. By convention, input boxes
have a white background and black numerals, while output boxes have a
black background and green numerals.
If you choose to
Flight Test (the default choice), you can change the value of
lift by varying the speed, or the altitude.
You can flight test your wing on the earth (default), on Mars, or in
the water by using the menu button at the upper right. You can also
choose to specify your own values of temperature and pressure for air,
or to specify your own fluid by providing a value of the fluid density.
If you choose Shape/Angle,
you can select a classic airfoil shape, an ellipse, or a thin plate
cross section by using the menu button. You can change the camber,
thickness, or the angle of attack of
the cross section. The definitions of these geometric variables are given
on the wing geometry web page. You can also
choose to investigate the lift created by a rotating
cylinder, or a spinning ball. For these
problems you must specify the spin rate and radius.
If you choose Size,
you can vary the layout of the wing. You can change the chord, span,
or the wing area. The ratio of the span to the chord
is called the Aspect Ratio and this parameter also has an
on the lift of the wing. If you have selected
a cylinder or ball shape, this input panel is not used.
from the program is displayed in output boxes. By convention, output boxes
have a black background and green numerals.
You can choose to display the lift or the lift
coefficient by using the menu button on the control panel. The value
is displayed in the output box to the right of the menu button. Lift
may be expressed in either English or metric units (pounds or Newtons).
On the Flight Test input panel is a group of output boxes that give the
atmospheric conditions of the air. The pressure,
temperature, and density will change depending on the altitude and planetary
inputs. On the Size input panel the geometric aspect ratio of the
wing is displayed. The aspect ratio is defined to be the square of the
span divided by the wing area
and is included here for later calculations of wing drag.
The Learning Technologies
Project will continue to improve and update FoilSim II based on user input.
Changes from previous versions of the program include:
On 7 Oct 02,
version 1.4n was released. This version includes the effects of
aspect ratio on lift and some small modifications suggested by users,
including the "Rescale" option on the plots.
On 1 Dec 00,
version 1.4 was released. This version includes some additional shapes
(cylinder and ball), larger graphics output selections (density and
lift coefficient plots), different environments (water, non-standard
earth atmosphere, and specified fluid density) and a different layout
of the view panel. Corrections have also been made to the particle traces.
On 28 July 00,
version 1.3 was released. This version includes some additional airfoil
shapes (ellipse and plate), larger graphics output, and a (hopefully)
cleaner layout of input panels.
On 28 Feb 00,
a stall model was added. This model is invoked by using the blue on
white Input Choices button. The default analysis mode is Ideal
Flow, in which the stall model is turned off. If you choose Stall
Model and the angle of attack is greater than 10 degrees, you will
see the flow begin to separate from the surface of the airfoil, as it
does on real airfoils. The lift will continue to increase up to about
15 degrees; then it will decrease. This behavior is observed on real
airfoils as seen on the slide describing the effects of angle
of attack on lift.