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Old Feb 15th 2014, 09:04 AM   #1
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Question fluid shear stress in Polar coordinate

Dear all
please help me to understand about how to derive the fluid shear stress in Polar coordinate.

see as follows
http://i.imgur.com/lqizIbt.jpg

than u for ur help!!
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Old Feb 21st 2014, 05:53 AM   #2
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Let's start with fundamentals. Fluid stress is proportional to the rate of change of velocity in one direction per unit distance in the orthogonal direction. In other words - how quickly velocity changes across a flow front. In polar coordinates the rate of change of radial velocity per unit circumference is is:




The rate of change of tangential velocity per unit radial distance is



where omega = angular velocity in radians/second. Since omega = v_theta/r you get:



If this is unclear it may help fo you to draw out a sketch to see how it works.

Last edited by ChipB; Feb 21st 2014 at 01:19 PM.
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Old Feb 25th 2014, 06:17 PM   #3
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thank u for ur help ^^
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