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Development of an App for Compressible Flow “App4Comp”
Andrés Adam AlberdiP. Javier Gamez-Montero
TEEM’15 Conference, Porto
October 2015
2
Index
1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 International Standard Atmosphere
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
3
1. IntroductionIndex1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
• It is though to be a learning and teaching activity
• It is open source and customizable by everyone
• Wants to create an Educational Software Experience for the user
An App for educational use in aeronautical engineering
TEEM’15 Conference, Porto
4
2. Compressible Flow In Practice
• Fluid mechanics in compressible regimes are not always intuitive, and can get very complex
• They are often simplified to basic cases, but involve complex formulas
• For a working engineer, these problems forces him to move from the “working place” to the “calculus place”
• For a student, this means a difficult verification even for the simple problems, and a slow obtaining of intermediate results in an exercise, that grant no new concepts
• With the mobile technology nowadays, these problems are outdated, as a mobile device is fully capable of solving those formulas
When calculus gets hard, our mobile device can do it for us
TEEM’15 Conference, Porto
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
5
3. App4Comp
Applications• To solve problems in class, by everyone, as part of the teacher’s explanation• To check the validity of the results obtained at self-study, outside the classroom• To obtain intermediate results within a bigger problem• To test even more cases, just out of curiosity
What does it include?
• International Standard Atmosphere (ISA)• Isentropic Flow• Normal Shockwave• Convergent-divergent nozzle• Fanno Flow
Objective: To develop and App for compressible flow, free, easy to use and aimed to students.
TEEM’15 Conference, Porto
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
6
3.1 International Standard Atmosphere
Atmospheric properties change with altitude, and are calculated through formulas very easy to forget
• Once all inputs are written, calculations are done when “Calculate” is pressed.
• If any input is incorrect, calculations will be stopped and an error message shown.
• Input units can be changed by pressing them.
Source: http://www.physicalgeography.net
• For more information, the user presses the button “?”
TEEM’15 Conference, Porto
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
Painting by Abie Daviswww.theminionfactory.com
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Normal Shockwave
3.2 Isentropic Flow and Normal Shockwave
Calculates temperature, pressure and density as a function of the Mach
number
Source: http://www.nptel.ac.in/
hTp
Ma
Isentropic Flow
Relates the properties of the flow before and after the shockwave:• Temperature, pressure and density• Velocity• Throat area
TEEM’15 Conference, Porto
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
Source: www.murdoconline.net
8
3.3 Convergent-Divergent NozzleAdapted Mode
Possible inputs:• Pressure relation• Temperature relation• Area relation (A2/A*)• Exit Mach
Calculates parameter relations within a fully adapted nozzle.
Generic Mode
Calculates operating parameters for a non-adapted nozzle.
Needs dimensional inputs to define the case.
Often implies a complex iterative process, so creating an exercise of this is complicated
TEEM’15 Conference, Porto
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
Source: http://space.stackexchange.com
9
3.3 Convergent-Divergent NozzleGeneric Mode
Operating regimes
Source: http://www.engapplets.vt.edu
BD
F
Limiting cases
• Case B: The flow gets to sonic conditions, but expands subsonically
• Case D: The flow expands supersonically and isentropically until the end, where it creates a shockwave
• Case F: The flow expands supersonically and isentropically until the end, where it discharges at ambient pressure
TEEM’15 Conference, Porto
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
10
3.4. Fanno Flow
Theoretical analysis of the effects of viscous friction with the walls of a duct
Hypothesis and definition of the problem• Adiabatic, steady and unidimensional
flow• Calorically perfect gas• Straight duct of constant area• The force in the wall is determined by
Darcy’s coefficients correlations
𝜏𝑤=18 𝑓 𝜌𝑉
2
1
𝑓12
≈−1.8 log ( 6.9𝑅𝑒𝑑+( 𝜀
𝑑3.7 )
1.11
)
TEEM’15 Conference, Porto
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
11
3.4. Fanno Flow
Theoretical analysis of the effects of viscous friction with the walls of a duct
Inputs• Hydraulic diameter of the duct, D• Heat capacity ratio, ϒ• Mach numbers at inlet and outlet• Mean friction coefficient
Outputs• Length of the duct, L• Length for becoming chocked, L*• Ratios between inlet and outlet
properties
TEEM’15 Conference, Porto
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
12
4. ConclusionThe purpose of this app is to provide a portable and useful tool to solve compressible flow problems in a theoretical, first-approximation, aimed mainly to students.
App4Comp solves problems related to:• International Standard Atmosphere• Isentropic Flow• Normal Shockwave• Convergent-Divergent Nozzle• Fanno Flow
It has been taken into account that the App should be intuitive and easy to use.
App4Comp can be used in education for:• Speed up the in-class solving of examples by the teacher, allowing to see a bigger
amount of cases• Check the validity of results obtained by students on their autonomous work• Calculate intermediate results within a bigger problem, also speeding up the
whole process• Help the teacher create new problems• Explore new cases just out of curiosityTEEM’15 Conference, Porto
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
13
4. Conclusion
App4Comp can be downloaded for free on https://sites.google.com/site/app4comp
The source code of the App is available to anybody who requests it, in App Inventor
TEEM’15 Conference, Porto
The App will be introduced in Fluid Mechanics subjects to get the user experience
An Evaluation and Assessment of Student Learning must be done through e-surveys
Mobile Apps can become a very useful tool for education, together with the Virtual Campus
A new step could be, for education, a web-app with more capabilities
Index1. Introduction
2. Compressible Flow In Practice
3. App4Comp
3.1 ISA
3.2 Isentropic Flow and Normal Shockwave
3.3 Convergent-Divergent Nozzle
3.4 Fanno Flow
4. Conclusion
14
Thanks for your attention!
Andrés Adam Alberdi
Questions?
https://sites.google.com/site/app4comp
