professor i have a question . professor you said in this video that in a supersonic flow area and velocity both are decreases and when Mach number is one flow is sonic in nozzle throat but after throat , area is increase in diverging nozzle. how supersonic flow is here?
Thank you for the lecture! Now I have a question if you don't mind. With compressible flows some things are reversed to the common sense and without the specific knowledge it's hard to predict how the flow will behave. For example, at the end of this lecture we have studied that if back pressure is less than 0,5283 of the Po, then no more flow will pass through the throat. Therefore it doesn't really matter if we have 0,5·Po or vacuum pressure as a back pressure, the mass flow rate will be the same. The exact value we can define as m_max = 0,6847 · Po · A* / (R · To)^0,5 BUT from this equation we can see that the mass flow rate can be increased by increasing the Po. How does that work? From the math point of view the bigger the Po the smaller is P/Po with the same numbers of P. Then how does the bigger flow occur? Using common sense I feel that it's correct, but it's not the best idea to use common sense to a compressible flow. Let's say we have this converging nozzle and a compressor after it. Compressor sucks the air from the back chamber and the overall amount of air in the back chamber will reduce only if the compressor sucks faster, then the air can come in. However, if we put this setup to the big room with the total pressure of 2·Po, max mass flow rate could be doubled if our compressor still can cope with it. I'm curious whether this example is true and if things work this way.
21:12 Wait a second? if dA/dv is positive and the change in area is positive ( A2 > A1) then the only posible outcome is that the change in velocity be positive as well (v2 > v1) Ergo the velocity gets larger (as you originally said)
You are right. For M>1, increasing the area leads to an increase in the velocity. But note that the professor was talking about what happens if the area decreases. This leads to a decrease in velocity
My doubt is what if we inject a supersonic gas flow inside convergent section of c-d nozzle such that the speed remains supersonic even at throat,is any such condition possible?
Thank you so much for these lectures! There couldn't be anything more noble than sharing knowledge. Thank you
Your'e my favorite professor!
Wow thank you so much for this video, I was totally in the dark
professor i have a question . professor you said in this video that in a supersonic flow area and velocity both are decreases and when Mach number is one flow is sonic in nozzle throat but after throat , area is increase in diverging nozzle. how supersonic flow is here?
Michael Jordan of Fluid Mechanics!
Brilliant lecturer!
Thanks!
We agree
thank you so much, it was really useful.
Thank you sir ! Keep it up
mind blowing lecture
Thank you for the lecture!
Now I have a question if you don't mind.
With compressible flows some things are reversed to the common sense and without the specific knowledge it's hard to predict how the flow will behave.
For example, at the end of this lecture we have studied that if back pressure is less than 0,5283 of the Po, then no more flow will pass through the throat. Therefore it doesn't really matter if we have 0,5·Po or vacuum pressure as a back pressure, the mass flow rate will be the same. The exact value we can define as m_max = 0,6847 · Po · A* / (R · To)^0,5
BUT
from this equation we can see that the mass flow rate can be increased by increasing the Po. How does that work? From the math point of view the bigger the Po the smaller is P/Po with the same numbers of P. Then how does the bigger flow occur?
Using common sense I feel that it's correct, but it's not the best idea to use common sense to a compressible flow.
Let's say we have this converging nozzle and a compressor after it. Compressor sucks the air from the back chamber and the overall amount of air in the back chamber will reduce only if the compressor sucks faster, then the air can come in.
However, if we put this setup to the big room with the total pressure of 2·Po, max mass flow rate could be doubled if our compressor still can cope with it.
I'm curious whether this example is true and if things work this way.
Great lecture
what is limitation of mach number before the isentropic equation for p/po, t/to fails?
Can someone send me a link to get a PDF format of the gas table...
thank you professor.
You're welcome!
I have a question, sir. Why do we need to limit out studies to only with isentropic flow, sir? What about non-isentropic flow?
There is limited time in the course.
God bless you sir...
21:12 Wait a second? if dA/dv is positive and the change in area is positive ( A2 > A1) then the only posible outcome is that the change in velocity be positive as well (v2 > v1)
Ergo the velocity gets larger (as you originally said)
You are right. For M>1, increasing the area leads to an increase in the velocity. But note that the professor was talking about what happens if the area decreases. This leads to a decrease in velocity
@@aprendiendoC Exactly, a converging nozzle act as a diffuser for supersonic flow.
My doubt is what if we inject a supersonic gas flow inside convergent section of c-d nozzle such that the speed remains supersonic even at throat,is any such condition possible?
I guess it will reduce the velocity to C and bring Mach Number back to 1 at throat. As dA/dv is positive and dA is negative , dv will be negative.!!
Thank you, really useful yet I prefer there's no music at all
We need some intro music to get people excited about fluid mechanics.
can someone pls tell me how we got the last equation for mass flow through nozzle
use ideal gas law and remember that you need to convert the T star in the speed of sound equation to T_0 using the factor he provided
P_0/RT_0=rho_0
Excuse me can I contact you, to show you an equation to discuss.?
What is P₀?
The pressure at stagnation points - points where the fluid is moving at a velocity of zero isentropically (no change in entropy)
thanx sir
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