Thanks. Yes, in general, the EGL would not be a straight line. Turbulent head losses vary roughly as V^2, and you would expect more losses in the expansion zone after the throat. The EGL would be a straight line for fully developed flow in in uniform diameter pipe. That's Chapter 6 material, and more than I wanted to cover here. I hope that helps.
Thanks for this presentation! Just have some doubts!! How does fluid flow from low pressure region to high pressure region? Why do we refer energy loss as pressure loss most of the time? And how does pressure increase the discharge?
Consider flow is from low to high pressure in the discharge of a venturi. At the flow moves away from the throat the average velocity decreases and some of the fluid kinetic energy gets converted back to pressure. That's why pressure increases in the flow direction at the discharge. It is called "pressure recovery". I hope that helps.
I assume you are asking about the Venturi: You are expressing a misconception that I also had as a student. Here is one way to think about this effect: The velocity at point 2 is higher than at point 1. Since energy is conserved, where did all that kinetic energy at point 2 come from? In order for the fluid to move faster at point 2, it must have been accelerated by a net pressure force to the right, i.e. the kinetic energy comes from work done by the pressure force. Thus, from F=ma, for fluid to accelerate as it moves from 1 to 2, the pressure at point 1 must be higher than at point 2. The net force must be to the right, i.e., p_2
Yes. The EGL remains constant only in the ideal friction case. But in the real world you always have energy losses in the flow direction. So, the EGL decreases because of energy losses (due to turbulence, wall viscous friction & pressure losses across a valve.) I hope that helps.
All the videos (and pdf downloads) for this introductory Fluid Mechanics course are available at: www.drdavidnaylor.net/
Excellent explanations and demos
Thanks. Glad to hear it was helpful.
This video makes me understand. Thank you.
Thank you. The explanation was really good.
Thanks for the nice comment. Glad to be helpful.
Thank you, this was very helpful for me to review hydraulics before my first job out of college as water resources engineer!
Same here, I'm about to start a similar job and reviewing as much as I can before. Did it work out well for you?
this video is amazing!
Great explanation ,pls do more hydraulic and hydrology videos
thanks professor
The high speed camera with the match stick makes me think of that hymn- OUR GOD IS AN AWESOME GOD.
Thanks explanation HGL
Glad to help. Best of luck with your studies.
thank you >3
Thanks for this amazing presentation. @ 23:01: I am wondering if EGL would be not necessarily the straight line you showed in the video?
Thanks. Yes, in general, the EGL would not be a straight line. Turbulent head losses vary roughly as V^2, and you would expect more losses in the expansion zone after the throat. The EGL would be a straight line for fully developed flow in in uniform diameter pipe. That's Chapter 6 material, and more than I wanted to cover here. I hope that helps.
Thanks for this presentation!
Just have some doubts!!
How does fluid flow from low pressure region to high pressure region? Why do we refer energy loss as pressure loss most of the time? And how does pressure increase the discharge?
Consider flow is from low to high pressure in the discharge of a venturi. At the flow moves away from the throat the average velocity decreases and some of the fluid kinetic energy gets converted back to pressure. That's why pressure increases in the flow direction at the discharge. It is called "pressure recovery". I hope that helps.
I don't understand why the pressure head decreases at point 2 because I would think since the area decreases, the pressure would increase?
I assume you are asking about the Venturi: You are expressing a misconception that I also had as a student. Here is one way to think about this effect: The velocity at point 2 is higher than at point 1. Since energy is conserved, where did all that kinetic energy at point 2 come from? In order for the fluid to move faster at point 2, it must have been accelerated by a net pressure force to the right, i.e. the kinetic energy comes from work done by the pressure force. Thus, from F=ma, for fluid to accelerate as it moves from 1 to 2, the pressure at point 1 must be higher than at point 2. The net force must be to the right, i.e., p_2
when you have losses, you add them to get to EGL?
Yes. The EGL remains constant only in the ideal friction case. But in the real world you always have energy losses in the flow direction. So, the EGL decreases because of energy losses (due to turbulence, wall viscous friction & pressure losses across a valve.) I hope that helps.
Name of the textbook,please?
It's in the description: Course Textbook: F.M. White and H. Xue, Fluid Mechanics, 9th Edition, McGraw-Hill, New York, 2021.