For laminar flow, Reynolds number is correlated with power number as (where K, a constant which depends on the container geometry and shape of stirrer; Rei is Reynolds number for agitator; Di, stirrer diameter and N, stirrer speed)

• Np = K(Rei)-1
• Np = N2Di(Rei)-1
• Np = K(Rei)
• Np = KNDi(Rei)-2