Q.5 what do you mean by dimensionless numbers? Name any four dimensionless numbers.Ans..

**Answer : **

A dimensionless number is obtained by dividing the inertia force by viscous force or gravity force or pressure force or surface tension force or elastic force. As it is a ratio of one force to the other force, it has no dimensions, i.e. dimensionless. Some important dimensionless numbers which are used in model analysis of hydraulic structures and machines are given below -

(i) Reynold's number

(ii) Froude's number

(iii) Weber number

(iv) Euler number

RGPV May 2018