Hey Vin, great video! I just have few concerns: 1. In your expression for thrust, particularly dynamic pressure (D8*G8^2) I think you forgot to divide it by 2. 2. Thrust is calculated as integral over whole surface. Instead of multiplying by A at each y, I think you should rather multiply by dA - an area of infinitesimal ring of radius equal y, and then sum all results. 3. Try this: CFD-Post -> Calculators -> Function Calculator -> Function: force, Location: nozzlewall. I also tried to acquire pressure and velocity at exit using massFlowAve function, but my calculations give me only half the value of "force". To conclude, I am very thankful for your videos. You inspired me to choose rocket nozzle design for topic of my Bachelor's project and with each video I learn a lot of new stuff. Keep promoting Aerospace Engineering ;)
Thanks for your feedback. Keep in mind the more complex method is not suitable for UA-cam as I have to make content that is easily learnable by beginners as well
How do you know for sure the function calculator -> force on nozzle wall gives the pressure force? The ANSYS documentation shows the force dialog box and says it computes pressure and viscous forces.
At around 5:55 minutes you show your nozzle from your CFD. I was wondering if you used eulerian methods to solve the CFD or if you didn't include the energy equations from N-S. The Shock formation just looks strange to me but it might be that I have been looking at over-expanded nozzles.
Hi, does this flow is categorized as an under expanded flow? I still don't get a point to differentiate an under expanded and over expanded flow I thought the under expanded flow will spread all over without mach change in the centerline thanks
the flow is under-expanded since the exit pressure is greater than the ambient or atmospheric pressure. The flow remains expanded as you said because there is no back pressure developed as seen in the case for over-expanded flows
Hello sir, As per calculation we get the back flow pressure for nozzle exit, but for Pressure outlet for this domain how should we calculate the pressure and temperature (i.e., 39365 and 243k)
Are there any public scripts out there that run the calculations for nozzle dimensions for a 98 mm high powered rocket with APCP? Great video by the way.
@VDEngineering...at which height u have caonsidered for outside pressure and temp. bcoz the pressure and temp. which have taken doesnt fit with ISA table neither correct to calculations... plzz do rply... its realy vry vry imp. for me... ty
If one doesn’t know the coordinates of the nozzle outlet, I found an easy way to get it. Simply go to function calculator, function:max val, location: outlet, variable: y and it will print out the max value for y, ie the tip of your nozzle exit. You can also use individual points and use the probe function to find the coordinates.
can i use the same equations even for the nozzles of a cold gas thruster? also, what would be the difference in calculations if we attach a pipe between the tank and converging section?
Yes, you can do as long as nozzle to exit pressure ratio is beyond 2. Attaching the pipe would make no difference in flow characteristics, provided that the pipe does not reduce the inlet pressure upstream of the converging section beyond critical pressure ration (2bar for exit pressure of 1bar) due to heat loss through walls of the pipe.
If this is verification of cd nozzle, how would one be able to validate the method you did on cfd? If you would compare it to experimental data, what would you compare exactly?
You measure the Mach Number along axis inside the nozzle. During experiments Mach numbers and static Temperature are measured experimentally by Pitot tube.
@3:48 How can the throat velocity be mach=1 and 858.2 m/s at the same time? Shouldn't the throat be choked at M=1? I thought that was a property of a CD nozzle.
![[CFD] Pressure-Inlet Boundary Conditions](http://i.ytimg.com/vi/Er2j5Kq17as/mqdefault.jpg)
I just finished an MSME and and started a career in CFD. I'm totally subbing to your channel!
Hey Vin, great video! I just have few concerns:
1. In your expression for thrust, particularly dynamic pressure (D8*G8^2) I think you forgot to divide it by 2.
2. Thrust is calculated as integral over whole surface. Instead of multiplying by A at each y, I think you should rather multiply by dA - an area of infinitesimal ring of radius equal y, and then sum all results.
3. Try this: CFD-Post -> Calculators -> Function Calculator -> Function: force, Location: nozzlewall. I also tried to acquire pressure and velocity at exit using massFlowAve function, but my calculations give me only half the value of "force".
To conclude, I am very thankful for your videos. You inspired me to choose rocket nozzle design for topic of my Bachelor's project and with each video I learn a lot of new stuff.
Keep promoting Aerospace Engineering ;)
Thanks for your feedback. Keep in mind the more complex method is not suitable for UA-cam as I have to make content that is easily learnable by beginners as well
@@VDEngineering sure thing. For that reason, I think function: force would be the easiest way ;)
How do you know for sure the function calculator -> force on nozzle wall gives the pressure force? The ANSYS documentation shows the force dialog box and says it computes pressure and viscous forces.
great work sir .. simple way of teaching
At around 5:55 minutes you show your nozzle from your CFD. I was wondering if you used eulerian methods to solve the CFD or if you didn't include the energy equations from N-S. The Shock formation just looks strange to me but it might be that I have been looking at over-expanded nozzles.
There is no Mach disc is all
Hi, does this flow is categorized as an under expanded flow? I still don't get a point to differentiate an under expanded and over expanded flow
I thought the under expanded flow will spread all over without mach change in the centerline
thanks
the flow is under-expanded since the exit pressure is greater than the ambient or atmospheric pressure. The flow remains expanded as you said because there is no back pressure developed as seen in the case for over-expanded flows
Hello sir,
As per calculation we get the back flow pressure for nozzle exit, but for Pressure outlet for this domain how should we calculate the pressure and temperature (i.e., 39365 and 243k)
Are there any public scripts out there that run the calculations for nozzle dimensions for a 98 mm high powered rocket with APCP? Great video by the way.
Wjat r the boundary conditions should we have to give at inlet and outlet for thermal analysis plz do share information or video in ansys
@VDEngineering...at which height u have caonsidered for outside pressure and temp. bcoz the pressure and temp. which have taken doesnt fit with ISA table neither correct to calculations...
plzz do rply...
its realy vry vry imp. for me...
ty
Ansys doesn't work with my laptop. May I use Solidwork simulation instead of ANSYS?
How do you determine the rate that the Mach diamonds will disapate?
If one doesn’t know the coordinates of the nozzle outlet, I found an easy way to get it. Simply go to function calculator, function:max val, location: outlet, variable: y and it will print out the max value for y, ie the tip of your nozzle exit. You can also use individual points and use the probe function to find the coordinates.
Hi. Where did you find parameters of combustion chamber like pressure or temperature ? Is it on some article/ book or you came up with them?
You have to go through and calculate them yourself but you need to know propellant flow. risacher.org/rocket/eqns.html
can i use the same equations even for the nozzles of a cold gas thruster? also, what would be the difference in calculations if we attach a pipe between the tank and converging section?
Yes, you can do as long as nozzle to exit pressure ratio is beyond 2. Attaching the pipe would make no difference in flow characteristics, provided that the pipe does not reduce the inlet pressure upstream of the converging section beyond critical pressure ration (2bar for exit pressure of 1bar) due to heat loss through walls of the pipe.
Can i use the same equations for my aerospike simulation too? Also did you link the compressible flow calculator ?
Aerospike is slightly different
Thanks！
You inspire me very much.
If this is verification of cd nozzle, how would one be able to validate the method you did on cfd? If you would compare it to experimental data, what would you compare exactly?
You measure the Mach Number along axis inside the nozzle. During experiments Mach numbers and static Temperature are measured experimentally by Pitot tube.
What to do if mach number is not available in variables in CFD POST PROCESSING for exporting mach number
How can I get a software to calculate thrust and nozzle sizes
How do you solve for mach number
Pls try explain hypersonic nozzle design and how write MATLAB programming.
Where can i download your EXCEL Thrust calculations ?
@3:48 How can the throat velocity be mach=1 and 858.2 m/s at the same time? Shouldn't the throat be choked at M=1? I thought that was a property of a CD nozzle.
It is still mach 1. Just a higher temperature in the mach equation causing the higher velocity than in atm.
@@BrandonKent136 ahhh. Thank you, that makes sense.
What exactly is a slip line?
Thank you a lot, Bro!
I can't export mach number. How can I find or calculate ?
You have to enable it first that's why
@@VDEngineering How can I enable? Can you help me please ?
Good day brother. May I ask for the inputs in this simulation? thanks
extremely thank you teach us how to make nuke
Thanks bro!
this guy could teach us how to make a guided missile if he could lol
Haha no, only a Senior Fellow at Raytheon could.