2300_Course_Manual_F2010

# When used as a flow meter in a pipeline the venturi

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When used as a flow meter in a pipeline, the venturi would be instrumented with taps at the throat and the maximum area sections. From the measured pressure difference, the ideal flow rate can be calculated. This can then be "corrected" using the known venturi coefficient to get the true flow rate. 2. Plot the static pressure distribution along the venture for each of the two flow rates. The pressures may be expressed in terms of head (eg. inches or mm of water gauge). On the same graphs and to the same scale, plot the static pressure distributions calculated using the simplified analysis. 3. For the two flow rates, what is the stagnation pressure on the centre line at the venturi throat? The static pressure? The dynamic pressure? 4. Discuss the flow through the apparatus, explaining why the actual flow differs from the idealized one. Specifically explain the trends in actual and ideal static pressures shown in the graphs in (2). Include a sketch of three approximate velocity profiles for the flow through the apparatus: one at upstream end of the venturi, one at the throat and one near the downstream end of the venturi. An arbitrary scale for velocity can be used, but the profiles must be consistent with the fact that the continuity equation must hold along the venturi.

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