Which parameter in the choked flow equation represents the ratio of specific heats?

• A. Gamma
• B. R
• C. T0
• D. Cd

Answer: (A)

In choked flow the parameter that represents the ratio of specific heats is the dimensionless gamma. This gamma equals cp/cv and sets how energy stored in the gas changes with temperature and pressure. It appears in the speed of sound formula a = sqrt(gamma * R * T), so the throat flow speed is tied to gamma. In the standard critical-flow expression for mass flux, gamma multiplies into factors like sqrt(gamma) and the term (2/(gamma+1))^((gamma+1)/(2(gamma-1))). Because of these appearances, gamma directly controls the maximum possible mass flow through the nozzle.

The other options aren’t ratios of heats: R is the specific gas constant, T0 is the stagnation temperature, and Cd is a discharge coefficient accounting for non-idealities.