Uploaded March 2018 | Updated September 2026, 2 weeks ago
Let's run a CFD simulation from start to finish! In this video, we will be starting from a problem definition, and working our way to a full CFD solution. The problem we will be working through is that of a simple oblique shock. We have already solved this exact oblique shock example in one of my other videos (see link below).
===== NOTES =====
► You can mess around with the settings in the configuration file to see how it changes the solution. For example, you can get more well-defined shock by changing the way the convective fluxes are evaluated.
===== FILES TO DOWNLOAD =====
► Mesh File (.su2) and Configuration File (.cfg)
joshtheengineer.com/2018/02/28/how-to-run-su2-start-to-finish
===== RELEVANT VIDEOS =====
→ Download and Install SU2
goo.gl/KmkUgD
→ Oblique Shock Example
goo.gl/8yjUvy
===== RELEVANT LINKS =====
► SU2 Oblique Shock Test Case
su2code.github.io/tutorials/Inviscid_Wedge
===== PROGRAMS I USE (ALL FREE) =====
► SU2
su2code.github.io
► GMSH
gmsh.info
► Paraview
paraview.org
► VirtualBox
virtualbox.org/wiki/Downloads
► Notepad++
notepad-plus-plus.org
===== REFERENCES =====
→ The SU2 GitHub and website
→ Matt MacLean for introducing me to SU2 along with his GMSH tutorial
Let's run a CFD simulation from start to finish! In this video, we will be starting from a problem definition, and working our way to a full CFD solution. The problem we will be working through is that of a simple oblique shock. We have already solved this exact oblique shock example in one of my other videos (see link below).
===== NOTES =====
► You can mess around with the settings in the configuration file to see how it changes the solution. For example, you can get more well-defined shock by changing the way the convective fluxes are evaluated.
===== FILES TO DOWNLOAD =====
► Mesh File (.su2) and Configuration File (.cfg)
joshtheengineer.com/2018/02/28/how-to-run-su2-start-to-finish
===== RELEVANT VIDEOS =====
→ Download and Install SU2
goo.gl/KmkUgD
→ Oblique Shock Example
goo.gl/8yjUvy
===== RELEVANT LINKS =====
► SU2 Oblique Shock Test Case
su2code.github.io/tutorials/Inviscid_Wedge
===== PROGRAMS I USE (ALL FREE) =====
► SU2
su2code.github.io
► GMSH
gmsh.info
► Paraview
paraview.org
► VirtualBox
virtualbox.org/wiki/Downloads
► Notepad++
notepad-plus-plus.org
===== REFERENCES =====
→ The SU2 GitHub and website
→ Matt MacLean for introducing me to SU2 along with his GMSH tutorial



![Explained: Nozzle Mass Flow Rate
One of the important variables in determining how much thrust a rocket can produce is the mass flow rate. In this video, we will derive an expression for the mass flow rate through a converging or converging diverging nozzle.
NOTES
► This expression only works when the flow is choked. For a converging-diverging (CD) nozzle, the flow should always be choked (although you still need to check). A little more care is needed when using the expression for a converging nozzle, because a lot of converging nozzles operate under conditions where they are not necessarily choked.
RELEVANT VIDEOS
→ Rocketdyne F-1 Mass Flow Rate Example
https://goo.gl/Ezp54H
→ Converging-Diverging Nozzle
https://goo.gl/jrsyoJ
→ Sonic State (Critical, Star)
https://goo.gl/vhjESy
→ Area-Mach Number Relation [CPG]
https://goo.gl/j4FwQX
REFERENCES
► Notes by Matt MacLean
► Modern Compressible Flow, Anderson
► Elements of Gasdynamics, Liepmann and Roshko
► Gas Dynamics, Zucrow and Hoffman
THUMBNAIL IMAGE
By NASA (NASA Human Space Flight Gallery (image link)) [Public domain], via Wikimedia Commons Explained: Nozzle Mass Flow Rate](https://i.ytimg.com/vi/aMTmRCdmvVQ/mqdefault.jpg)
![Explained: Turbojet Thrust Equation
Lets derive the thrust equation for a turbojet engine! In this video Ill show you how to derive the thrust equation for a single-inlet, single-outlet air breathing engine (turbojet is kind of just a buzzword here, because the engine doesnt necessarily need to only be a turbojet).
Yes, this video is heavy on the math, but Im planning on starting a video series called In a Nutshell, which will take some of my math-heavy videos and break them down in to shorter, more easily understandable videos that focus on the big picture. Stay tuned for those.
RELEVANT VIDEOS/LINKS
→ Mass Conservation Derivation
https://goo.gl/Qx7PZ6
→ 1D Mass Conservation
https://goo.gl/hM46LU
→ Momentum Conservation Derivation
https://goo.gl/DuYHcG
→ 1D Momentum Conservation
https://goo.gl/8uo6VM
→ Surface Area Blog Post
https://goo.gl/1s2z2X
→ Turbofan Thrust Equation Derivation
http://www.joshtheengineer.com/2017/04/08/turbofan-thrust-equation/
EXTRA LINKS
► This is the Wikipedia page for Turbojets, and while I dont tend to like Wiki pages for math, take a look at the Net Thrust section.
https://en.wikipedia.org/wiki/Turbojet
ASSUMPTIONS
1) Flow is reversible external to the engine
2) Steady state
3) No viscous forces
4) No heat addition
5) No body forces
6) Velocity only has X-direction component
7) Momentum from fuel flow rate is negligible
THUMBNAIL PICTURE ATTRIBUTION
By Jeff Dahl [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 4.0-3.0-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/4.0-3.0-2.5-2.0-1.0)], via Wikimedia Commons
Modified slightly by me Explained: Turbojet Thrust Equation](https://i.ytimg.com/vi/aNyYxVHBSWQ/mqdefault.jpg)

![Converging-Diverging Nozzle Pressure Delineations
In my converging-diverging (CD) nozzle video (link below), we saw that there were seven different flow conditions in a nozzle. If know what exit-to-reservoir pressure ratio our engine is operating at (see notes below), then we can define what condition our nozzle is operating at based on three pre-computed pressure ratios:
1) Choked Isentropic Subsonic
2) Normal Shock at Nozzle Exit
3) Choked Isentropic Supersonic
In this video, we will compute the pressure ratios needed to obtain the three states listed above for a given nozzle area ratio (Ae/At).
NOTES
→ In this video, we can say that At = A* for each case because the flow is choked, and we do have sonic flow at the throat.
→ We generally know the exit-to-reservoir pressure ratio that our engine is operating at. For instance, if we are analyzing the Space Shuttle Main Engine (RS-25) on the launchpad, then we know the exit pressure is approximately 101.325 kPa. We also know from the engines specifications that the reservoir (or chamber) pressure is approximately 20.64 MPa. Dividing the two appropriately gives the pressure ratio we are looking for.
RELEVANT LINKS
→ Blog Post - Converging-Diverging Nozzle Pressure Delineations
http://www.joshtheengineer.com/2017/12/17/converging-diverging-nozzle-pressure-delineations/
→ Solving the Area-Mach Number Relation
http://www.joshtheengineer.com/2016/11/16/solving-the-area-mach-number-relation/
→ CD Nozzle MATLAB Code - GitHub
https://github.com/jte0419/Converging_Diverging_Nozzle
→ Compressible Flow Relations Code - GitHub
https://github.com/jte0419/Compressible_Flow_Relations
RELEVANT VIDEOS
→ Explained: Converging Diverging Nozzle
https://goo.gl/7MBSck
→ Area-Mach Number Relation [CPG]
https://goo.gl/t8QE9T
→ Normal Shock Relations
https://goo.gl/Bvv2jj
→ Stagnation Relations
https://goo.gl/yrT9D4
REFERENCES
► Modern Compressible Flow, Anderson
► Gas Dynamics, Volume 1, Zucrow and Hoffman
► Elements of Gasdynamics, Liepmann and Roshko Converging-Diverging Nozzle Pressure Delineations](https://i.ytimg.com/vi/b5q022xNgp0/mqdefault.jpg)



![Explained: Area-Mach Number Relation [CPG]
Can we approximate the exit Mach number of a rocket nozzle knowing only the area ratio? With a few assumptions, we certainly can! In fact, if we know how the area changes along a nozzle from the throat to the exit, we can calculate how the Mach number varies throughout the entire nozzle.
NOTES
► Ill make sure to never use my orange marker again
► If you download my Method of Characteristics MATLAB code from my GitHub (link below), you can see that the results of both match very closely!
HOW TO SOLVE AREA-MACH NUMBER RELATION
http://www.joshtheengineer.com/2016/11/16/solving-the-area-mach-number-relation/
ROCKET NOZZLE - METHOD OF CHARACTERISTICS
https://github.com/jte0419/Rocket_Nozzle_Design
RELEVANT VIDEOS
Area-Mach Number Differential Form
https://goo.gl/tDzBtM
Sonic State
https://goo.gl/j6yCxD
Stagnation-to-Static Relations
https://goo.gl/r5JZSQ
Normal Shock Relations
https://goo.gl/E5Lwac
REFERENCES
► Notes by Matt MacLean
► Modern Compressible Flow, Anderson
► Elements of Gasdynamics, Liepmann and Roshko
► Gas Dynamics, Zucrow and Hoffman
THUMBNAIL IMAGE
By NASA (http://mix.msfc.nasa.gov/abstracts.php?p=2388) [Public domain], via Wikimedia Commons Explained: Area-Mach Number Relation [CPG]](https://i.ytimg.com/vi/bdcxN0u5hMs/mqdefault.jpg)