DEFINED as the RATIO of actual discharge from an ORIFICE to the theoretical discharge from the orifice.\({c_d} = \frac{{{Q_{act}}}}{{{Q_{th}}}} = \frac{{{V_{act}} \TIMES {A_{act}}}}{{{V_{th}} \times {A_{th}}}} = \frac{{{V_{act}}}}{{{V_{th}}}}.\frac{{{A_{act}}}}{{{A_{th}}}} = {C_v}.{C_c}\)