A Virtual Laboratory On Fluid Mechanics

2006-1991: A VIRTUAL LABORATORY ON FLUID MECHANICS
Ruiqing Jia, China University of Mining and Technology
Dr. Ruiqing Jia currently holds a position as Visiting Professor at Stevens Institute of Technology
in Hoboken, New Jersey, USA. From 1992 to 2004, he was a Professor in the Mechanical
Engineering Department at China University of Mining and Technology (CUMT) in Beijing. He
received a Bachelor’s degree in Mechanical Engineering from Taiyuan University of Technology
in 1982 and a Ph.D. degree in Mechanical Engineering from CUMT in 1992. His research
interests are fluid mechanics and virtual environments.
Shanjun Xu, China University of Mining and Technology
Mr. Shanjun Xu received a Bachelor’s degree in Mechanical Engineering and Automation from
China University of Mining and Technology in Beijing in 2004. Currently, he is pursuing a
Master’s degree in Mechatronics Engineering. His research interests include mechanical design,
hydrodynamics, mechatronics engineering and virtual environments.
Songyun Gao, China University of Mining and Technology
In 2004, Ms. Songyun Gao received a Bachelor’s degree in Mechanical Engineering and
Automation from China University of Mining and Technology in Beijing in 2004. Currently, she
is pursuing a Master’s degree in Mechatronics Engineering. Her research interests include
mechanical design, robotics, hydrodynamics, mechatronics engineering and virtual environments.
EL-Sayed Aziz, Stevens Institute of Technology
Dr. El-Sayed Aziz holds a faculty position in the Mechanical Engineering Department at
Mansoura University, Egypt. Currently, he is working as research scientist at Stevens Institute of
Technology in Hoboken, New Jersey, USA. He received B.S. and M.S. degrees in Mechanical
Engineering from Mansoura University, Egypt, in 1991 and a Ph.D. in Mechanical Engineering
from Stevens Institute of Technology in 2003. His research interests include knowledge-based
engineering systems; computer-integrated design and manufacturing; Finite Element Analysis;
software development and applications; as well as remote and virtual laboratories.
Sven Esche, Stevens Institute of Technology
Dr. Sven K. Esche is currently holding a position as Associate Professor of Mechanical
Engineering at Stevens Institute of Technology in Hoboken, New Jersey, USA. In 1989, he
received an undergraduate degree in Applied Mechanics from Chemnitz University of
Technology (Germany). After working for three years at Mercedes Benz AG in Stuttgart
(Germany), he obtained M.S. and Ph.D. degrees in Mechanical Engineering from The Ohio State
University in Columbus, Ohio, USA in 1994 and 1997, respectively. His current research
interests include multi-scale modeling of thermo-mechanical processing of metals, integrated
product and process design under conditions of uncertainty and risk as well as remote sensing and
control of distributed devices with special focus on remote laboratories.
Constantin Chassapis, Stevens Institute of Technology
Dr. Constantin Chassapis is Professor and the Director of the Mechanical Engineering
Department, Professor, at Stevens Institute of Technology. His research interests are in
knowledge-based engineering systems; computer-aided design and manufacturing;
structure-property modeling and characterization of polymers and polymer composites. He has
received the best paper award from SPE’s Injection Molding Division, the distinguished Assistant
Professor Award at Stevens, an Honorary Master’s Degree from Stevens Institute of technology,
and the Tau Beta Pi Pi Academic Excellence Award. He has been an active member in ASME,
and SPE.
© American Society for Engineering Education, 2006

A Virtual Laboratory on Fluid Mechanics
Abstract
This paper describes the development of an interactive Web-based virtual laboratory on fluid
mechanics at Stevens Institute of Technology (SIT),1
which integrates animations, graphics and
analysis results in order to achieve a realistic feel of the experiment and to enhance the students’
understanding of some complex concepts of fluid mechanics. Based on existing real
experimental setups, different experiment simulations were implemented using the Python
programming language, such as a wind tunnel and an air flow rig. In the wind tunnel experiment,
the lift forces for several kinds of airfoils can be experimented with virtually. The users can
specify certain parameters for controlling the simulations and obtain the corresponding lift force
outputs, including tables, figures and data listings. Furthermore, the users can display a 3-D
rendering of the wind tunnel equipment in the graphical user interface as well as a 2-D animation
of the stream lines. The simulation achieves a good degree of accuracy for steady state
conditions over a wide range of parameters.
Key words: Virtual laboratory, fluid mechanics, wind tunnel, air flow rig, Python programming
language
Introduction
Fluid mechanics is the study of fluids, i.e. gases and liquids. It is one of the most challenging
areas of engineering sciences with difficult to understand concepts. Many kinds of experimental
equipment are used to study the various phenomena of fluid mechanics, such as wind tunnels,
Reynolds number rigs and fluid flow rigs. While such equipment is very helpful to students for
better understanding theoretical concepts through experimentation, it is also difficult to analyze
arbitrary fluid motion. Currently, modern information technology based on the Internet is rapidly
being adopted in engineering education as a tool for enhancing the educational experience of
students residing on campus as well as beyond the local campus. Many educational instructors
have implemented virtual and remote laboratories.2,3,4,5
Chaturvedi et al.6
developed a thermo-
fluids laboratory titled “Venturimeter as a Flow Measuring Device” as a computer-based
experiment for undergraduates. This virtual experiment combines three unique aspects: the use of
computer-generated data to recreate the physical phenomenon, virtual experimentation and
measurements on a computer, and the coupling of the virtual experiment with the LabVIEW
software to introduce students to digital data acquisition and analysis. Gillet et al.7
described the
development and sharing of Web-based experimentation resources. Their program integrates the
necessary components to carry out hands-on practice in a flexible learning context. At the same
time, the experimental devices of this program can be accessed by more students from remote
locations at any time over the Internet. A physical laboratory called SoftLab was developed at
Purdue University8
to provide an environment for both physical experiments and numerical
simulations. A more realistic Fluids Laboratory9
as an integrated learning environment was
developed by IIHR-Hydroscience & Engineering at The University of Iowa. This laboratory is
configured to provide unrestricted and user-friendly access to comprehensive insights in fluid
mechanics and hydraulics. With the addition of the Virtual Fluids Lab, experiments can be
conducted online at any time and from any place.

This paper describes the development of several virtual laboratories at SIT, including a wind
tunnel and an air/oil flow rig. In the wind tunnel experiment, the lift forces for several kinds of
airfoils, for instance a plain-flap airfoil and a slotted-flap airfoil, can be experimented with
virtually. The students can specify certain parameters for controlling the simulations and obtain
the corresponding lift force outputs, including tables, figures and data listings. Furthermore, the
students can display a 3-D rendering of the wind tunnel equipment as well as a 2-D animation of
the stream lines in the graphical user interface. In the virtual flow rig, the air/oil flow through a
pipe is being modeled. An entrance region with a nearly inviscid upstream is modeled, followed
by retardation of the axial flow at the wall and consequently acceleration of the center core flow
to satisfy the incompressible continuity requirement. At a finite distance from the pipe entrance,
the boundary layers merge and the inviscid core disappears10
.
Architecture of Virtual Fluid Laboratory
As a virtual part of the remote laboratory system at SIT,11,12,13,14
the virtual laboratory is
developed to complement the existing remotely operated experiments. Many students are
enabled to perform the experimental simulations simultaneously through the Internet from any
place at any time. Figure 1 shows the general structure of the remote laboratory, including the
real and virtual experiments. The real wind tunnel can be operated remotely through the Internet.
At the same time, the students can perform the dynamic and interactive virtual experiment over
Internet. The virtual laboratories are implemented using the OpenGL Python programming
language. Python is an interpreted, interactive, object-oriented programming language15,16,17,18
offering very high level dynamic data types.
Figure 1: Remote laboratory structure

Virtual Wind Tunnel Laboratory
The wind tunnel can be used to conduct experiments on airfoils as well as on various bodies.
Generally, the main experimental result for an airfoil is the lift force while for other bodies it is
the drag force. Because the airfoils and bodies are quite different in their properties and
associated models, we are designing separate virtual laboratories for airfoils and bodies.
Airfoil Wind Tunnel: Figure 2 depicts the graphical user interface of the virtual wind tunnel with
an airfoil. The lift forces for several kinds of airfoils can be determined. The students can display
a 3-D rendering of the wind tunnel and a 2-D animation of the stream lines. The lift forces are
output in the form of an output table, an output graph or output data.
Figure 2: Virtual wind tunnel laboratory with airfoil
The students are enabled to select the input parameters (angle of attack, area of airfoil), select the
system of units and request the corresponding results by clicking the “Plot” button as shown in
Figure 3. If the students want to get the outputs for a specific velocity, they can input it in the
Default Inputs block and then click the “Output the Results” button. For example, if the angle of
attack is 8°, the area of the airfoil is 5 m2
and the specified velocity is 222 m/s, the students
obtain the outputs shown in Figure 4.
Figure 3: Input panel of virtual wind tunnel laboratory

Figure 4: Output panel of virtual wind tunnel laboratory
Figure 5 shows the selection panel for choosing an airfoil from the available airfoil models.
Upon selection of a specific airfoil, all outputs including lift forces, lift coefficients, Reynolds
number and Mach number are refreshed automatically. For example, when “airfoil with-camber”
is selected, the 2-D animation of the stream lines is displayed in the 2-D area. Alternatively, the
students can click the output buttons “Lift Force”, “Coefficients” and “Distribution” in the 2-D
animation area to display the corresponding outputs (see Figure 6, Figure 7 and Figure 8). In
order to better visualize the wind tunnel, the students can also click the button “3D Picture” in
order to render the virtual wind tunnel laboratory with an airfoil, whereby the students can even
“operate” the virtual wind tunnel by pressing the “Start” and “Stop” buttons.
Figure 5: Airfoil model selection panel

Figure 6: Lift force as a function of velocity
Figure 7: Lift coefficient as a function of angle of attack
Figure 8: Lift force distribution
The virtual laboratory contains the main characteristic parameters of airfoils. Airfoils are
designed to generate a lift force, Lf, normal to the free stream flow. Performance characteristics
of airfoils are normally given in terms of the dimensionless lift coefficient and drag coefficient.
For a specific angle of attack, α, the lift coefficient CL is a constant, even for different velocities
V. Table 1 summarizes the relationships between the parameters that determine the lift forces of
the airfoils.

Table 1: Airfoil parameters
No. Parameters Equations Notes
1 Lift coefficient ( )
S
q
Lf
C 0
L = S: planform area of airfoil
2 Drag coefficient ( )
S
q
Df
C 0
D = Df: drag force
3 Dynamic pressure 2
0
0 V
5
.
0
q ρ
= ρ: density of air
4 Lift force S
q
C
Lf 0
L
= q0: dynamic pressure of air
5 Reynolds Number v
Vb
Re = V: free-stream velocity
v: viscosity of air
b: characteristic length
6 Mach Number a
V
Ma = a: speed of sound
V: speed of airplane
Experimental results for the lift coefficients for the airfoil types listed in Figure 5 are
summarized in Table 2. In these relationships, the working area of the angle of attack α is
different for different airfoils.
Table 2: Experimental lift coefficients for various airfoil types
No. Airfoils Equations of lift coefficients Angle of attack
1 With camber CL1=0.1096α
CL1=-0.0017α²+0.05α+0.96
(0º<α≤12º)
(12º<α<18º)
2 Without camber CL2=0.1096α+0.357
CL2=-0.0224α²+0.493α-1.2586
(-3º<α≤8º)
(8º<α<18º)
3 Plain flap CL3=0.103α+1.542 (-3º<α<10º)
4 External airfoil flap CL4=0.103α+1.714 (-3º<α<10º)
5 Slotted flap CL5=0.103α+2.114 (-3º<α<9º)
6 Double-slotted flap CL6=0.103α+2.629 (-3º<α<7º)
7 Leading-edge slat CL7=0.103α+0.743 (-3º<α<15º)
8 Kline Fogleman airfoil CL8=-0.0011α²+0.0931α-0.3548 (4º<α<50º)
Body Wind Tunnel: The virtual wind tunnel can also be used to conduct experiments on various
bodies such as cubes, cups and disks. Figure 9 depicts the graphical user interface of the virtual
laboratory with various bodies. Firstly, the students need to select a 2-D or 3-D body in the
“Model Selection” panel. Then, they can input the necessary parameters, such as the sizes of the
selected body, and click the “Plot” button to generate the outputs. At most three parameters (size
B: width, size H: height and size L: length) are used to describe the 2-D or 3-D bodies with
various cross sections. 2-D bodies are described by at least two size parameters. For example,

one can use diameter B and length L to describe a “Round Rod”. The students are automatically
prompted for the necessary input parameters, for instance “Size H” and “Size L” for “Square
cylinder”. After the body has been selected, stream lines can be displayed. The graphical user
interface for the virtual 3-D wind tunnel with bodies was designed similarly to the airfoil wind
tunnel.
Figure 9: Graphical user interface of virtual wind tunnel laboratory with bodies
Virtual Air/Oil Flow Rig Laboratory
While an experimental air flow rig is usually an open system, a hydraulic system must be a
closed system with the liquid circulating. Therefore, we designed different virtual laboratories
for air and oil systems.
Air flow rig: This virtual laboratory describes the internal flow of air in a pipe. An internal flow
is constrained by the bounding walls. The viscous effects grow and meet to permeate the entire
flow. There is an entrance region with a nearly inviscid upstream, followed by retardation of the
axial flow at the walls, thus accelerating the center core flow so as to maintain the
incompressible continuity requirement. At a finite distance from the entrance, the boundary
layers merge and the inviscid core disappears. The tube flow is then entirely viscous, and the
axial velocity adjusts slightly further. At the entrance length of x=Le it no longer changes with x
and is said to be fully developed. This process can be analyzed through the virtual laboratory of
the air flow rig. The corresponding graphical user interface is shown in Figure 10. The main
input parameters are the flow rate Q and the temperature T. Furthermore, either the SI or BG
systems must be selected. In addition, the students can input specific points of interest for which
the results are desired. Figure 11 and Figure 12 depict the velocity distributions at the specified
points of interest in 2-D and 3-D, respectively.

Figure 10: Graphical user interface of virtual air flow rig laboratory
Figure 11: 2-D velocity distribution in sections A, B, C and D
Figure 12: 3-D velocity distribution along the pipe
Table 3 summarizes the relevant fluid mechanics parameters for an air flow rig. These equations
are embedded in the virtual laboratory of the air flow rig. There are several kinds of output,
including a 3-D model, 2-D plotting and data tables. The students can obtain the results for the
Reynolds number Re, the average velocity V, the pressure difference ∆P and the entrance length
Le.

Table 3: Relevant fluid mechanics parameters for air flow rig
No. Parameters Equations Notes
1 Average Velocity
A
Q
V =
A: section area of pipe
Q: flow rate
2 Reynolds Number
( ) ( ) 7
0
0 10
Re ×
×
= T
T
RT
p
air µ
R: universal gas constant
T: temperature in kelvins
3 Pressure Difference
( ) 2
2
5
.
0
5
.
0 V
D
L
hl
V
hm
P ρ
ρ +
=
∆
hm = 0.02: head loss
hl: treated as smooth pipe
4 Entrance length d
Re
06
.
0
Le air
= d: pipe diameter
Liquid flow rig: Many hydraulic systems use water as transfer medium while airplane oils,
hydraulic oils and lubrication oils are common industrial oils. The liquid flow rig incorporates
the properties of these liquids similarly to the air flow rig. Figure 13 depicts the graphical user
interface of virtual liquid flow rig laboratory. Figure 14 shows a 3-D rendering of the liquid flow
rig. The students first select the liquid to be used in the input panel, such as for instance “10#
hydraulic oil”. Then, the students can input the necessary input parameters including the flow
rate (e.g. 0.06 m³/s) and the temperature (e.g. 33°C), and press the “Run” button. The outputs
displayed in the graphical user interface are shown in Figure 13. If so desired, the students can
obtain the output for a specific point, such as for instance at axial L = 2222 mm, radial r = 0 mm
and pipe diameter d = 80 mm. Furthermore, the Reynolds number, pressure difference and
entrance length are displayed when the “Refresh” button is pressed. Similarly to the virtual wind
tunnel, in the virtual liquid flow rig the users can generate an animation of the liquid flow using
the “Start” and “Stop” buttons.
Figure 13: Graphical user interface of virtual liquid flow rig laboratory

Figure 14: Virtual equipment of flow rig
Conclusions
Virtual student laboratories are emerging rapidly. They are expected to play an increasingly
important role in engineering and science education. This article describes an interactive tool for
teaching undergraduate fluid mechanics. Six virtual laboratories were designed and implemented
at SIT, including an airfoil wind tunnel, a body wind tunnel, an air flow rig and a liquid flow rig.
The Python programming language was found to be a powerful tool for the implementation of
virtual laboratories.
Student can control the shape, size, and inclination of the airfoil and see a schematic drawing of
the airfoil with varying conditions to explore the effects of flow. The effects of airfoil camber,
thickness and angle of attack can be studied interactively. This tool also allows student to
measure lift force acting on an airfoil set at various angles of attack.
Expansion of the set of available virtual fluid mechanics experiments include an air flow jet, a
liquid flow jet, a Reynolds number rig, a Bernoulli equation rig, a stream line rig and a loss
coefficients of hydraulic elements rig.

References
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[15] Homepage of The Python Software Foundation: http://www.python.org/
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[18] Python script conversion by SourceForge: http://www.py2exe.org/
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