Скачать или смотреть Find the coefficient of discharge (Cd), contraction (Cc), Coefficient of velocity (Cv)

Civil Engineering Study
Fluid Mechanics



jet of liquid at vena-contracta and the theoretical velocity of jet. It is denoted by Cv
𝐶𝑣 =
𝑎𝑐𝑡𝑢𝑎𝑙 𝑣𝑒𝑙𝑜𝑐i𝑡𝑦 𝑜f j𝑒𝑡 𝑎𝑡 𝑣𝑒𝑛𝑎𝑐𝑜𝑛𝑡𝑟𝑎𝑐𝑡𝑎
𝑡ℎ𝑒𝑜𝑟𝑒𝑡i𝑐𝑎𝑙 𝑣𝑒𝑙𝑜𝑐i𝑡𝑦
36
=
𝑉
√2𝑔ℎ
The value of Cv varies from 0.95 to 0.99 for different orifices, depending on the shape, size of
the orifice and on the head which flow takes place. Generally the value Cv=0.98 is taken for
sharp-edged orifices.
2. Coefficient of contraction (Cc): It is defined as the ratio of the area of the jet at vena
contracta to the area of the orifice. It is denoted by Cc.
𝐶𝑐 =
𝑎𝑟𝑒𝑎 𝑜f j𝑒𝑡 𝑎𝑡 𝑣𝑒𝑛𝑎𝑐𝑜𝑛𝑡𝑟𝑎𝑐𝑡𝑎, 𝑎𝑐
𝑎𝑟𝑒𝑎 𝑜f 𝑡ℎ𝑒 𝑜𝑟ifi𝑐𝑒, 𝑎
The value of Cc varies from 0.61 to 0.69 for different orifices, depending on the shape, size of
the orifice and on the head which flow takes place. In general, the value of Cc may be taken
0.64
3. Coefficient of discharge (Cd): It is defined as the ratio of the actual discharge from an
orifice to the actual discharge from an orifice to the theoretical discharge from the
orifice. It is denoted by Cd.
𝐶𝑑 =
𝑎𝑐𝑡𝑢𝑎𝑙 𝑑i𝑠𝑐ℎ𝑎𝑟𝑔𝑒
𝑡ℎ𝑒𝑜𝑟𝑒𝑡i𝑐𝑎𝑙 𝑑i𝑠𝑐ℎ𝑎𝑟𝑔𝑒
=
𝑎𝑐𝑡𝑢𝑎𝑙 𝑣𝑒𝑙𝑜𝑐i𝑡𝑦 × 𝑎𝑐𝑡𝑢𝑎𝑙 𝑎𝑟𝑒𝑎
𝑡ℎ𝑒𝑜𝑟𝑒𝑡i𝑐𝑎𝑙 𝑣𝑒𝑙𝑜𝑐i𝑡𝑦 × 𝑡ℎ𝑒𝑜𝑟𝑒𝑡i𝑐𝑎𝑙 𝑎𝑟𝑒𝑎
= 𝐶𝑣 × 𝐶�