shear stress of internal flow

shahin · February 15, 2016, 04:57

hi
does the shear stress of internal flow(channel) depend on just Reynolds number or it depends on mean velocity,too?
thank you.

LuckyTran · February 16, 2016, 00:48

It depends on many things (density, viscosity, temperature, age of the universe, and many other things). The wall shear stress is proportional to the square root of the friction velocity.

For fully developed internal flows, the friction velocity is linearly proportional to both the bulk velocity which is also linearly proportional to Reynolds number. For non fully-developed flows, the relationship may be non-linear and unknown.

shahin · February 16, 2016, 15:51

my problem is fully turbulent flow in infinite channel .and i want to know that is shear stress constant in different H and bulk velocity and equal Reynolds?
other thing is constant and fluid is air and flow is incompressible.
thank you.

LuckyTran · February 16, 2016, 19:26

For high enough Reynolds number, the friction factor is constant. Hence the shear stress varies with bulk velocity and Reynolds number.

shahin · February 17, 2016, 04:16

Thank you for your attention.

February 15, 2016, 04:57	shear stress	#1
shahin New Member shahin Join Date: Dec 2015 Posts: 14 Rep Power: 10	hi does the shear stress of internal flow(channel) depend on just Reynolds number or it depends on mean velocity,too? thank you. Last edited by shahin; February 15, 2016 at 05:59.

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February 16, 2016, 00:48		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,668 Rep Power: 65	It depends on many things (density, viscosity, temperature, age of the universe, and many other things). The wall shear stress is proportional to the square root of the friction velocity. For fully developed internal flows, the friction velocity is linearly proportional to both the bulk velocity which is also linearly proportional to Reynolds number. For non fully-developed flows, the relationship may be non-linear and unknown.

February 16, 2016, 15:51		#3
shahin New Member shahin Join Date: Dec 2015 Posts: 14 Rep Power: 10	my problem is fully turbulent flow in infinite channel .and i want to know that is shear stress constant in different H and bulk velocity and equal Reynolds? other thing is constant and fluid is air and flow is incompressible. thank you.

February 16, 2016, 19:26		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,668 Rep Power: 65	For high enough Reynolds number, the friction factor is constant. Hence the shear stress varies with bulk velocity and Reynolds number.

February 17, 2016, 04:16		#5
shahin New Member shahin Join Date: Dec 2015 Posts: 14 Rep Power: 10	Thank you for your attention.