False

Explanation:
In case of any orifice, the velocity does not always remain constant. The velocity of fluid flowing through an orifice depends on various factors such as the size of the orifice, the pressure difference across the orifice, and the properties of the fluid. Therefore, the discharge cannot be calculated solely based on the assumption that the velocity remains constant.

Factors affecting the velocity and discharge through an orifice:

1. Size of the orifice: The size of the orifice affects the velocity and discharge of the fluid. A smaller orifice will result in a higher velocity and discharge, while a larger orifice will result in a lower velocity and discharge.

2. Pressure difference across the orifice: The pressure difference across the orifice also affects the velocity and discharge. A higher pressure difference will result in a higher velocity and discharge, while a lower pressure difference will result in a lower velocity and discharge.

3. Properties of the fluid: The properties of the fluid, such as its density and viscosity, also play a role in determining the velocity and discharge. A more viscous fluid will have a lower velocity and discharge compared to a less viscous fluid.

Calculation of the discharge through an orifice:

The discharge through an orifice can be calculated using the following equation:

Q = Cd * A * √(2gh)

Where:
Q = Discharge
Cd = Coefficient of discharge
A = Area of the orifice
g = Acceleration due to gravity
h = Head difference across the orifice

The coefficient of discharge takes into account the various factors that affect the velocity and discharge, such as the shape of the orifice, the roughness of the edges, and the contraction and expansion of the flow. Therefore, it is necessary to consider these factors and use the appropriate value of the coefficient of discharge in the calculation.

Conclusion:

In conclusion, the velocity does not always remain constant in case of any orifice. The velocity and discharge through an orifice depend on various factors such as the size of the orifice, the pressure difference across the orifice, and the properties of the fluid. Therefore, it is important to consider these factors and use the appropriate equations, such as the discharge equation mentioned above, to calculate the discharge accurately.