This
is a beta 1.5b version of the FoilSim III 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 Thomas.J.Benson@nasa.gov.
Due to IT
security concerns, many users are currently experiencing problems running NASA Glenn
educational applets. There are
security settings that you can adjust that may correct
this problem.
FoilSim III
With this software
you can investigate how an aircraft wing produces
lift and drag by changing the values of different factors
that produce aerodynamic forces.
There are several different versions of FoilSim III which
require different levels of experience with the package,
knowledge of aerodynamics, and computer technology.
This web page contains the off-line student version of the program.
It includes an off-line user's manual which describes the
various options available in the program.
More experienced users can select a
version of the program which does not include
these instructions and loads faster on your computer.
GENERAL INSTRUCTIONS
This program is designed to be interactive, so you have to work with the program.
There are a variety of choices which you must make regarding the analysis and the display
of results. There are two main input devices used to make a choice, a push button
or a drop menu. To operate a button, move the cursor over the button and
left click with the mouse. The push buttons occur in groups, and the chosen option is
shown as a yellow, "lighted" button.
The drop down menu has a descriptive word displayed and an arrow at the right of the
box. To make a choice, left click on the arrow, hold down and drag to
make your selection.
The current values of the design variables are presented to you in boxes.
By convention, a white box with
black numbers is an input box and you can change the value of the number. A black box with
yellow numbers is an output box and the value is computed by the program.
To change the value in an input box, select the box by moving the cursor into the box
and clicking the mouse, then backspace over the old number, enter a new number,
then hit the Enter key on your keyboard. You must hit Enter
to send the new value to the program.
For most input variables you can also use a slider located next to the input box.
Click on the slider bar, hold down and drag the slider bar to change values, or
you can click on the arrows at either end of the slider.
At any time, to return to the original default conditions,
click the red Reset button at the upper right of the program.
If you see only a grey box at the top of this page, be sure that Java is
enabled in your browser. If Java is enabled, and you are using the Windows XP
operating system, you need to get a newer version of Java. Go to this link:
http://www.java.com/en/index.jsp,
try the "Download It Now" button, and then select "Yes" when the download box from Sun
pops up.
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.
SCREEN LAYOUT
The
program screen is divided into four main parts:
On the
top left side of the screen is the View Window.
The view window includes a graphic of the airfoil that you are
designing and several buttons which control the graphic.
Details of the window
are given in the Graphics section of this page.
On the
upper right side of the screen is the Control Panel.
The control panel holds several push buttons which
control the input and output to be displayed. Input choices have
blue letters and the selected input panel appears at the lower left.
Output choices have red letters and the output panel appears at the lower
right.
You will always see the computed lift, drag, Reynold's number
and lift to drag ratio. You can display lift and drag as numerical
values or as dimensionless coefficients.
Details of the input variables
and output variables are given below.
On the
lower right side of the screen is the Output Window.
The output can be presented as
graphs of airfoil performance,
a probe which you can move through the flowfield,
a lift and drag gages, or printed
numerical values of certain parameters.
You select the type of output displayed by using the push
buttons labeled "Output:" on the upper right panel.
On the
lower left side of the screen is the Input Window.
Various input panels are displayed in this window.
You select the input panel by using the push
buttons labeled "Input:" on the upper right panel.
GRAPHICS
The View Window contains a schematic drawing of the wing that
you are designing and some buttons to control the schematic drawing.
Possible choices are colored blue
while the selected option is colored yellow.
Edge shows
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 left of the window. If you get lost, pushing
the red Find button will return the airfoil to the initial position.
Top shows
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.
Moving shows
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.
Frozen is
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.)
Streamlines
are collections of the particle traces to form a solid flow line.
Geometry
shows only the geometry of the wing or airfoil with some descriptive
labels but with no flow field.
OUTPUT
VARIABLES
There are several different output options available for the
Output Window at the lower right.
You select the type of output by using the push buttons
on the control panel. The default setting is Plot and
a graph will appear in the window. The type of graph is described
below and you can vary the plot by using the Plot Selection input panel.
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
listed below and selcted from an Input Panel.
The default plot
is the Surface Pressure. The yellow line will be a plot of the
lower surface pressure, and the magenta line a plot of the upper surface
pressure. For reference, the green line shows the value of free stream
pressure.
You may also display
the Surface Velocity. As with the pressure, the yellow line will
be a plot of the lower surface, and the magenta line a plot of the upper
surface.
You may also display
the Drag Polar. A drag polar is a plot of lift coefficient versus
drag coefficient for a selected geometry at various angles of attack.
The remaining plot
choices show Lift, Drag, Lift Coefficient -Cl, or
Drag Coefficient - Cd 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 Gages
shows the current value of lift (or lift coefficient) and drag
(or drag coefficient) displayed
in scientific notation. The gages are displayed in the output window
and move as the lift and drag are varied. This display shows the relative
sensitivity of lift and drag to the input variables.
The Probe
lets you explore the flow around the wing. A probe control panel appears
in the output window when you select "Probe" from the control 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 gauge.
The performance
options provides a written list of important input and computed variables
in the Output Window. You have two options for performance output;
the Data option gives the computed lift, drag and flow conditions, the
Geometry option shows the coordinates of the airfoil geometry and the
local value of velocity and pressure. These numbers correspond to the
plots of velocity and pressure described above.
Some additional output
from the program is displayed on the control panel and some input panels.
You can choose to display the lift or the lift
coefficient by using the drop menu on the control panel. Similarly, you
can either display the drag or the drag coefficient. The value
is displayed in the output box to the right of the drop menu. Lift and drag
may be expressed in either Imperial (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, density, and viscosity 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 in the calculation of induced drag. The Reynold's number is the
ratio of inertial forces to viscous forces and affects the calculated value of the drag
Reynold's number and lift to drag ratio are displayed on the control panel.
INPUT
VARIABLES
The input variables
are located on input panels that are displayed at the lower left.
You can select the input to display by using the push buttons on
the control panel. You can choose to vary the Shape,
the Size, or perform a Flight Test of a wing design. You can also display
the Plot Selection Panel and a panel to control the Analysis used in FoilSim III.
If you choose to
Flight Test, 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 choice box 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,
you can select a Joukowsky airfoil shape (J-foil), an ellipse, or a thin plate
cross section by using the choice box. 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. There are some push buttons on the airfoil Shape
input panel to let you chose some "basic" airfoil shapes: symmetric airfoil, flat bottom foil,
negative camber, flat plate, high camber, curved plate, or ellipse. Clicking on these
buttons will set a representative value of camber, thickness, and angle of attack.
You can
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 and the
span of the cylinder.
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 has an effect
on the lift and drag of the wing. If you have selected
a cylinder or ball shape, this input panel is not used.
There are a variety
of Analysis options in FoilSim III. The option being used is shown
by a yellow lighted button on the Analysis panel. You can change the analysis
by clicking on a white button. The default lift calculation includes a
Stall Model that decreases the lift for angles of attack greater than
10 degrees. The option is to use the Ideal Flow analysis that neglects
viscous and compressibility effects. The actual calculations are done with ideal
flow and the stall model corrects for flow separation at high angles of attack.
The actual calculation is done for a two-dimensional foil. The Aspect Ratio
correction includes the 3D wing tip effects on lift. The Induced Drag correction
includes the 3D wing tips effects on drag. The drag is determined by a table look-up
for experimentally determined values of drag coefficient. The values were obtained at
a specific Reynold's number. The Reynolds number correction includes
the effects of changing Reynolds number to the test conditions.
NEW FEATURES
The NASA Glenn Educational
Programs Office will continue to improve and update FoilSim III based on user input.
Changes from previous versions of the program include:
On 20 Feb 13,
version 1.5a was released. This version was developed to support a NASA project
to study a wind-powered rover on Venus. It models the surface atmospheric conditions
on Venus. Later extensions of this version will include a weight calculation for
all wings.
On 21 Mar 11,
version 1.4d was released. This version modifies the geometry output
to include the volume of the wing. This addition was prompted by user email.
On 17 Feb 11,
version 1.4c was released. This version modifies the plotting package
to include more significant figures for small amounts of lift and drag. This fix
was prompted by user email.
On 29 Nov 10,
version 1.4b was released. This version corrects
a graphics problem with the drag coefficient as a function of angle of attack, camber,
and thickness. And we have corrected a drag determination error for negative camber
airfoils.
On 23 Nov 10,
version 1.4a was released. In response to a user email, we have some basic
airfoil shapes available on the airfoil "Shape" input panel.
On 23 Sep 10,
version 1.3b was released. In response to user emails, we have moved the
choice button for Imperial or Metric Units back to the control panel.
On 27 Jul 10,
version 1.3a was released. This is the first release version for FoilSim III and
includes drag which was not available in FoilSim II. Earlier versions of FoilSim III
were developmental versions and not released to the public.