## 8.14.2 Operating Pressure, Gauge Pressure, and Absolute Pressure

FLUENT avoids the problem of roundoff error (discussed in Section  8.14.1) by subtracting the operating pressure (generally a large pressure roughly equal to the average absolute pressure in the flow) from the absolute pressure, and using the result (termed the gauge pressure). The relationship between the operating pressure, gauge pressure, and absolute pressure is shown below. The absolute pressure is simply the sum of the operating pressure and the gauge pressure:

 (8.14-1)

All pressures that you specify and all pressures computed or reported by FLUENT are gauge pressures.

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