# Bulk Modulus

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Bulk modulus, abbreviated as B or K, also called bulk modulus of elasticity, is the elastic relationship between an applied pressure that acts to change the volume of the substance and the ability of a substance to withstand changes in volume when under compression.

## Bulk Modulus formulas

 $$\large{ K = p\; \frac {V_i}{ V_c } }$$ $$\large{ K = \frac { 1 }{ \beta } }$$ $$\large{ K = \frac {v^2 \; \rho} { Ca } }$$ (Cauchy number)

### Where:

$$\large{ K }$$ = bulk modulus

$$\large{ V_c }$$ = change in volume (volume differential)

$$\large{ Ca }$$ = Cauchy number

$$\large{ \beta }$$   (Greek symbol beta) = compressibility

$$\large{ p }$$ = pressure

$$\large{ v }$$ = velocity of flow

$$\large{ V_i }$$ = initial volume