Orifice Losses for Laminar Approach Flow

by Nagar S. Lakshmana Rao, Prof.; Civ. & Hydr. Engrg. Dept., Indian Inst. of Sci., Bangalore, India,
Kalambur Sridharan, Tech. Asst.; Civ. and Hydr. Engrg. Dept., Indian Inst. of Sci., Bangalore, India,

Serial Information: Journal of the Hydraulics Division, 1972, Vol. 98, Issue 11, Pg. 2015-2034

Document Type: Journal Paper


In all, 25 orifices are studied which include sharp-edged concentric, eccentric and segmental orifices, quadrant-edged concentric orifices and square-edged long orifices. The β ratio (ratio of orifice diameter to pipe diameter) is varied from 0.2 to 0.8 except for the long orifice for which studies are conducted for β = 0.2. The nature of variation of the loss coefficient with the Reynolds number is analyzed for different orifices. The loss coefficient curves for several orifices give an indication of the value of the critical Reynolds number at which the flow immediately downstream of the orifice ceases to be laminar even though the approach flow is laminar. In paritcular, for β = 0.8, a very sharp transition is seen in the loss coefficient curve. Based on interpolation of the experimental results, a comparison is made of the loss characteristics of the different types of orifices. The effect of Reynolds number, β ratio, edge radius, eccentricity, segmental opening and orifice length are studied.

Subject Headings: Reynolds number | Laminar flow | Critical flow | Pipelines | Rivers and streams | Curvature | Comparative studies

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