We were discussing the basic concept of Lagrangian and Eulerian method and types of fluid flow in the subject of fluid mechanics in our recent posts. Now we will start a new topic in the field of fluid mechanics i.e. discharge or flow rate with the help of this post.

So we will see here a very basic term used in fluid mechanics i.e. Discharge or flow rate.

Flow rate is basically defined as the quantity of a fluid flowing through a section of pipe or channel per unit time.

Flow rate or discharge = Quantity of fluid flowing through a section of pipe/Time

For incompressible fluid, such as water, flow rate will be defined as the ratio of volume of fluid flowing through the section and time.

For compressible fluid, such as gas, flow rate will be defined as the ratio of weight of fluid flowing through the section and time.

#### Symbol

Fluid flow rate or discharge will be represented by Q.

### Unit of flow rate

#### For incompressible fluid i.e. liquid

Flow rate or discharge = Volume of fluid flowing through a section of pipe/Time
Unit: m3/s

#### For compressible fluid i.e. gas

Flow rate or discharge = Weight of fluid flowing through a section of pipe/Time
Unit: Newton/s or N/s

### Mathematical form of discharge or flow rate

Let us consider that we have one pipe of diameter D and water is flowing through this pipe with a velocity of V. Flow rate of discharge through the section of the pipe will be given by following formulas as mentioned here.

#### Q = A x V

Where, A is the area of cross-section of the pipe through which water is flowing

We will now go ahead to discuss the concept of continuity equation in our next post.

Do you have any suggestions? Please write in comment box.

### Reference:

Fluid mechanics, By R. K. Bansal