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Old Tuesday, May 17, 2016
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Default Fluid Dynamics Question from Past Paper
Can anyone please answer the question that why the speed of water in middle of a smooth flowing stream is higher than its speed on the sides?

In my view, the speed is higher in the middle due to less pressure and speed is lesser at the edges due to high pressure. Am I right or wrong?

Please do comment on my post.
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Old Tuesday, May 17, 2016
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not pressure. friction. the water to the sides faces resistance from the banks. the water in the middle faces least friction from the banks.
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Thanks Waqas. Are you sure that friction is the cause?
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It is due to viscosity.
Viscosity is actually deformation by shear stress in any fluid. Shear stress is directly proportional to rate of shear strain. Now shear stress is maximum in centre so viscosity is maximum. It is according to following equation.

T=u du/dy
T=Shear stress
du/dy= rate of shear strain

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Old Wednesday, May 18, 2016
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Quote:
Originally Posted by Sarah Mehar View Post
Can anyone please answer the question that why the speed of water in middle of a smooth flowing stream is higher than its speed on the sides?

In my view, the speed is higher in the middle due to less pressure and speed is lesser at the edges due to high pressure. Am I right or wrong?

Please do comment on my post.
It is due to Viscosity just like MKRMKR said. Viscosity is basically the friction in between the layers of the fluid to flow. It acts on the sides as well as at the bottom of a stream and due to these viscous effects a Boundary Layer is formed.

Boundary Layer is basically the range in which the viscous effects are applicable in between the layers. Boundary Layer has a specific thickness which is usually in millimeters.
So the fluid particles outside of this Boundary Layer are faster than the inside particles.

In this case Viscous Effects are dominant on the sides as well as at the bottom but not in the center, so the Speed of the fluid is Maximum in the center.
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Thanks Waqas. Are you sure that friction is the cause?
yea. Friction in fluids is called viscosity.
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So, its the viscosity.

Thanks eyeryone.
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Old Wednesday, May 18, 2016
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You are welcome.
So you're opting Physics for CE-2017 ? What's your preparation methodology and from where(For Physics only).
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Old Thursday, May 19, 2016
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Yes, Physics is my optional. Right now, I haven't chalked out a proper prepration strategy. I am just solving past papers.
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Old Thursday, May 19, 2016
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Yes, Physics is my optional. Right now, I haven't chalked out a proper prepration strategy. I am just solving past papers.
best strategy, solve past papers.
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