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velocity more than INLET velocity

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Old   May 11, 2003, 23:32
Default velocity more than INLET velocity
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Have a simple geometry of a 1cm diameter pipe. After 3 cm (from left to right)length of pipe the diameter increases to 1.2cm expanding downward. Upper wall of the pipe remains same. Have now an expansion of length 7cm giving total of 10 cm. at left side of this geometry a velocity inlet is conditioned and at right side an outflow. Velocity is given 0.0015 m/s at left side velocity inlet. Displaying contours and computing min max veolity is giving maximum velocity 0.0019 m/s which is greater than 0.0015 m/s. Is the expansion causing the velocity to increase? Or any thing wrong?
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Old   May 12, 2003, 17:02
Default Re: velocity more than INLET velocity
Shiping Liu
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The maximum velocity must be greater than 0.0015m/s if you set a uniform veolity at inlet, because the velocity becomes non-uniform inside the pipe. Is it turbulent flow?
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Old   May 13, 2003, 04:34
Default Re: velocity more than INLET velocity
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Once the flow is fully develloped you have a velocity profile. The velocity you entered is an average. Parabolic profile as below.

_________________________________ - v=0 -- --- ----v max --- -- -________________________________

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Old   May 13, 2003, 04:56
Default Re: velocity more than INLET velocity
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_____________________ - v=0 --- ---- ----- v max ---- --- - _____________________

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