How do calculate the drag force due to viscosity if the shape of the object is not a perfect sphere (in my case, a semi aerofoil (drag coefficient of 0.09))? Thanks a lot!
Sir, I'm a bit confused. The water viscosity value you used is in the SI units? because normally it should be x10^{-3} times the value taken in the video.
Hi, love your channel. I would like to know what happens to a body immersed completely in a nc fluid in a vessel that is accelerated? How much distance between the body and vessel wall so they don't touch? Thanks in advance. Hope you have time to answer. 💙
There is a significant mistake determining the area A. It is A=2*pi*r*(Length 1), but not the cross section area. That`s why the Cd does not depend on the dimensions of the body, but only on its form
Thank you for the help Sir. I have a question on force of drag. I can remember that the drag force is equal to 6πmRv in viscous fluid so that we could calculate the terminal velocity out of that but then why is it something else here?
In this and next video, shouldn't the viscosity coefficient be 0.001002 pascal*sec? Then come out of the result that the viscosity force would be less than drag force.
SIR, in previous videos drag force is taken as 6πηrv here it is different and named as viscous force.but here drag force is taken in terms of drag coefficient .SIR i am confused please help mE
they're the same thing, this video double counted the same force. Substitute Cd = (24/Re) = (24u/pVD), you will get F = 6πuRV. (at Re < 10, viscous effect dominate therefore you get the same equation.)
Viscosity is the measure of how the molecules in the fluid interact. Drag is caused by the interaction between the object and the fluid and depends mostly on the object's shape.
Drag and viscosity are two kinds of resistive forces, that depend on the nature of how the solid interacts with the fluid. For laminar flow, viscosity governs, while for turbulent flow, drag governs. Viscosity is caused by fluid shear forces, while drag is caused by the impact forces of fluid molecules striking the solid object's surface and rebounding. Viscosity resistance is proportional to velocity, while drag is proportional to velocity squared.
Hello, are you claiming that Stoke's law force and the drag force are two separate forces? Do you have an explanation for where this comes from? Thank you for your video.
There is Stoke's law, and the drag force. (Stoke's law is a law (or equation)). There is only 1 "drag force", but if you take a closer look the contributors to the drag force are the shape of the object, the diameter of the object, and the viscosity of the liquid, and then there is also the "skin" effect of the material. Two objects with the exact same shape, size, and mass made from different materials will experience a different drag force.
Thanks for answering! Can I please recommend a video on how to choose characteristic length for strange situations (other then a pipe.. what about a spinning cylinder with water inside? Like Taylor couette without the inner cylinder for example... I'm lost in choosing characteristic length and having trouble finding good resource.
they're the same thing, this video double counted the same force. Substitute Cd = (24/Re) = (24u/pVD), you will get F = 6πuRV. (at Re < 10, viscous effect dominate therefore you get the same equation.)
How do calculate the drag force due to viscosity if the shape of the object is not a perfect sphere (in my case, a semi aerofoil (drag coefficient of 0.09))? Thanks a lot!
Sir, I'm a bit confused. The water viscosity value you used is in the SI units? because normally it should be x10^{-3} times the value taken in the video.
Hi, love your channel. I would like to know what happens to a body immersed completely in a nc fluid in a vessel that is accelerated? How much distance between the body and vessel wall so they don't touch? Thanks in advance. Hope you have time to answer. 💙
We have videos on that in this playlist: PHYSICS 33A TEST YOUR KNOWLEDGE: FLUID STATICS
There is a significant mistake determining the area A. It is A=2*pi*r*(Length 1), but not the cross section area. That`s why the Cd does not depend on the dimensions of the body, but only on its form
Ac is the cross sectional area
Thank you for the help Sir. I have a question on force of drag. I can remember that the drag force is equal to 6πmRv in viscous fluid so that we could calculate the terminal velocity out of that but then why is it something else here?
There are different ways to approach viscosity and drag forces.
In this and next video, shouldn't the viscosity coefficient be 0.001002 pascal*sec? Then come out of the result that the viscosity force would be less than drag force.
Pierre, Good catch. The viscosity coefficient is usually expressed in terms of milli Pascal * sec and I didn't convert it to Pascal * sec. Thanks.
Thank you Pierre. Five years later your comment still helps clear up confusion 😀.
why force caused by viscosity of water with object 6pi? where do you get that 6pi? does it in the formula or somewhere?
That was derived through experiment and calculations by some very smart people before us.
SIR, in previous videos drag force is taken as 6πηrv here it is different and named as viscous force.but here drag force is taken in terms of drag coefficient .SIR i am confused please help mE
Drag forces are relative to objects moving through a fluid.
I also have the same doubt than apoorv trivedi. Is viscous force a drag force? Please explain it better. Thank you.
they're the same thing, this video double counted the same force. Substitute Cd = (24/Re) = (24u/pVD), you will get F = 6πuRV. (at Re < 10, viscous effect dominate therefore you get the same equation.)
Lemon Chan where did you get 24? ( sorry for my lack of knowledge )
Can You add a reference from where you got all this equation
Every good physics book should have these equations. I don't remember all the various references we used to make 9000 + videos. :(
so Total force = F(gravity) + F(bouyancy) + F (Viscosity) +F(drag ) ?
sorry i dont get the difference between the viscosity and drag
Viscosity is the measure of how the molecules in the fluid interact. Drag is caused by the interaction between the object and the fluid and depends mostly on the object's shape.
Drag and viscosity are two kinds of resistive forces, that depend on the nature of how the solid interacts with the fluid. For laminar flow, viscosity governs, while for turbulent flow, drag governs. Viscosity is caused by fluid shear forces, while drag is caused by the impact forces of fluid molecules striking the solid object's surface and rebounding. Viscosity resistance is proportional to velocity, while drag is proportional to velocity squared.
Thank you so much
You're welcome!
thx
you are welcome
Hello, are you claiming that Stoke's law force and the drag force are two separate forces? Do you have an explanation for where this comes from? Thank you for your video.
There is Stoke's law, and the drag force. (Stoke's law is a law (or equation)). There is only 1 "drag force", but if you take a closer look the contributors to the drag force are the shape of the object, the diameter of the object, and the viscosity of the liquid, and then there is also the "skin" effect of the material. Two objects with the exact same shape, size, and mass made from different materials will experience a different drag force.
wait why do we need viscous force AND drag force why are they different?
The viscous force is related to the property of the liquid. The drag force is related to shape of the object traveling (falling) through the liquid.
Thanks for answering!
Can I please recommend a video on how to choose characteristic length for strange situations (other then a pipe.. what about a spinning cylinder with water inside? Like Taylor couette without the inner cylinder for example... I'm lost in choosing characteristic length and having trouble finding good resource.
We still need to continue with the course on fluid dynamics (no time at the moment as we are covering many other topics as well.
they're the same thing, this video double counted the same force. Substitute Cd = (24/Re) = (24u/pVD), you will get F = 6πuRV. (at Re < 10, viscous effect dominate therefore you get the same equation.)
@@Boeing7478F so do you just calculate the viscosity force then?
Total force = F(gravity) - F(bouyancy) -F (Viscosity) ?