Vena contracta

Vena contracta is the point in a fluid stream where the diameter of the stream is the least, such as in the case of a stream issuing out of a nozzle, (orifice). (Evangelista Torricelli, 1643).

The maximum contraction takes place at a section slightly on the downstream side of the orifice, where the jet is more or less horizontal.

The effect is also observed in flow from a tank into a pipe, or a sudden contraction in pipe diameter. Streamlines will converge just downstream of the diameter change, and a region of separated flow occurs from the sharp corner of the diameter change and extends past the vena contracta.

The reason for this phenomenon is that fluid streamlines cannot abruptly change direction. In the case of both the free jet and the sudden pipe diameter change, the streamlines are unable to closely follow the sharp angle in the pipe/tank wall. The converging streamlines follow a smooth path, which results in the narrowing of the jet (or primary pipe flow) observed.

Measurement of the vena contracta is useful in echocardiography, where it describes the smallest area of the blood flow jet as it exits a heart valve. This corresponds to the Effective Orifice Area calculated for heart valves using the continuity equation.

Coefficent of contraction

It is the ratio between the area of the jet at the vena contracta to the area of the orifice.

Cc = area at vena contracta/ area of orifice

The typical value may be taken as 0.64


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Look at other dictionaries:

  • Vena contracta — Vena Ve na, n.; pl. {Ven[ae]}. [L. See {Vein}.] A vein. [1913 Webster] {Vena cava}; pl. {Ven[ae] cav[ae]}. [L., literally, hollow vein.] (Anat.) Any one of the great systemic veins connected directly with the heart. {Vena contracta}. [L.,… …   The Collaborative International Dictionary of English

  • vena contracta — The point of lowest pressure and highest velocity that s located 0.030 inch below the venturi s throat (minimum diameter). The center of the discharge nozzle or the trailing edge of the booster venturi is placed at the vena contracta …   Dictionary of automotive terms

  • vena contracta — /vee neuh keuhn trak teuh/, pl. venae contractae /vee nee keuhn trak tee/. Hydraul. any of the locations in a jet of fluid emerging from an orifice where the cross section of the jet is at a minimum, esp. the location of minimum cross section… …   Universalium

  • vena contracta — …   Useful english dictionary

  • Vena — Ve na, n.; pl. {Ven[ae]}. [L. See {Vein}.] A vein. [1913 Webster] {Vena cava}; pl. {Ven[ae] cav[ae]}. [L., literally, hollow vein.] (Anat.) Any one of the great systemic veins connected directly with the heart. {Vena contracta}. [L., literally,… …   The Collaborative International Dictionary of English

  • Vena cava — Vena Ve na, n.; pl. {Ven[ae]}. [L. See {Vein}.] A vein. [1913 Webster] {Vena cava}; pl. {Ven[ae] cav[ae]}. [L., literally, hollow vein.] (Anat.) Any one of the great systemic veins connected directly with the heart. {Vena contracta}. [L.,… …   The Collaborative International Dictionary of English

  • Vena portae — Vena Ve na, n.; pl. {Ven[ae]}. [L. See {Vein}.] A vein. [1913 Webster] {Vena cava}; pl. {Ven[ae] cav[ae]}. [L., literally, hollow vein.] (Anat.) Any one of the great systemic veins connected directly with the heart. {Vena contracta}. [L.,… …   The Collaborative International Dictionary of English

  • Venae — Vena Ve na, n.; pl. {Ven[ae]}. [L. See {Vein}.] A vein. [1913 Webster] {Vena cava}; pl. {Ven[ae] cav[ae]}. [L., literally, hollow vein.] (Anat.) Any one of the great systemic veins connected directly with the heart. {Vena contracta}. [L.,… …   The Collaborative International Dictionary of English

  • Venae cavae — Vena Ve na, n.; pl. {Ven[ae]}. [L. See {Vein}.] A vein. [1913 Webster] {Vena cava}; pl. {Ven[ae] cav[ae]}. [L., literally, hollow vein.] (Anat.) Any one of the great systemic veins connected directly with the heart. {Vena contracta}. [L.,… …   The Collaborative International Dictionary of English

  • VenAE portae — Vena Ve na, n.; pl. {Ven[ae]}. [L. See {Vein}.] A vein. [1913 Webster] {Vena cava}; pl. {Ven[ae] cav[ae]}. [L., literally, hollow vein.] (Anat.) Any one of the great systemic veins connected directly with the heart. {Vena contracta}. [L.,… …   The Collaborative International Dictionary of English

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