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fluctuation in specified constant inlet condition

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Old   January 2, 2008, 03:32
Default fluctuation in specified constant inlet condition
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In CFX 11.0, I am monitoring the total pressure at the inlet of a combustion chamber. At the inlet I have specified Total Pressure (stable)=11 atm. But I notice in the monitor point, small fluctuations of the Total Pressure. The monitor point is given as areaAve(Total Pressure)@inlet. Why am I getting this fluctuation in the constant inlet condition? In CFX 11.0
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Old   January 3, 2008, 05:59
Default Re: fluctuation in specified constant inlet condit
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Look for conservative and hybrid values in CFX help. Monitor points show conservative values.
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Old   January 4, 2008, 13:10
Default Re: fluctuation in specified constant inlet condit
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The boundary condition is applied at the element faces, not the nodes. The "conservative" nodal value is the value solved over the control volume next to the boundary, which is actually part of the solution.

For post-processing purposes the boundary values are also written to the nodes as a boundary only field. Post presents these as "hybrid" fields. By selecting the "hybrid" values, you'll get the conservative values for all internal nodes and boundary values at the boundaries. Thus, if you look a the "hybrid" value of Total Pressure on your inlet in Post you'll see it is at your specified value.

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