velocity more than INLET velocity

May 12, 2003, 00:32

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?

May 12, 2003, 18:02

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?

May 13, 2003, 05:34

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 --- -- -________________________________

Mcgregor

May 13, 2003, 05:56

_____________________ - v=0 --- ---- ----- v max ---- --- - _____________________

May 12, 2003, 00:32	velocity more than INLET velocity	#1
neu Guest Posts: n/a	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?

May 12, 2003, 18:02	Re: velocity more than INLET velocity	#2
Shiping Liu Guest Posts: n/a	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?

May 13, 2003, 05:34	Re: velocity more than INLET velocity	#3
McGregor Guest Posts: n/a	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 --- -- -________________________________ Mcgregor

May 13, 2003, 05:56	Re: velocity more than INLET velocity	#4
mcgregor Guest Posts: n/a	_____________________ - v=0 --- ---- ----- v max ---- --- - _____________________

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