Question

An experiment is conducted with a fluid of density 1 kg/m³ at 10 m/s velocity. The free stream static pressure is 100 kPa and the local static pressure is 101 kPa. What is the pressure coefficient at the location?
1. 70
2. 80
3. 20
4. 50

Answer 1

Correct Answer - Option 3 : 20

Concept:

The pressure coefficient is the ratio of the pressure force to the inertia force.

It is a dimensionless parameter used in many aerodynamics and hydrodynamic applications.

i.e.\({C_P} = \frac{{{P_1} - {P_2}}}{{\frac{1}{2}σ {V^2}}} = \frac{{{\rm{\Delta }}P}}{{\frac{1}{2}σ {V^2}}}\)

where Cp is the pressure coefficient,

ΔP is pressure difference between at any point to the free stream pressure

σ is density of the fluid

and V is the free stream velocity of the flow.

Calculation:

Given, P₁ = 100 kPa, P₂ = 101 kPa, ρ = 1 kg/m³ and V = 10 m/s

\({C_P} = \frac{{\left( {101 - 100} \right) \times {{10}^3}}}{{\frac{{1 \times {{10}^2}}}{2}}} = \;20\)