# What is the resistance of fluids

## What is drag force - drag equation - definition?

### Calculation of the drag force

To theResilience to calculate, we need to know:

• theSkin friction coefficient , he is:C.D, friction = 0,00425
• the area of ​​thePen surface , she is:A = π.dh = 0.1169 m2
• the liquid density, that is:ρ = 714 kg / m3
• the core flow velocity, which is constant and equalVcore = 5 m / s

From theSkin friction coefficient, the same as thatFanning friction factor is , we can use the friction component of theResilience to calculateThe resistance is given by:

Assuming that a fuel assembly may have 289 fuel pins (17 × 17 fuel assembly), for example, theFrictional component theResilience then on the order ofKilonewtons . In addition, this resistance is based exclusively on the skin friction on the fuel bundle. However, the typical PWR fuel assembly contains other components that affect the hydraulics of the fuel assembly:

• Fuel rods . Fuel rods contain the fuel and combustible poisons.
• Upper nozzle . Provides the mechanical support for the fuel assembly structure.
• Floor nozzle . Provides the mechanical support for the fuel assembly structure.
• Spacing grid . Ensures precise guidance of the fuel rods.
• Guide thimble tube . Free tubing for control rods or in-core instruments.

As has been written, the second component of drag force is shape drag.Form resistance , alsoCalled pressure resistance, arises due to theshape andsize of the object. ThePressure resistance is proportional to the difference between the pressures acting on the front and back of the immersed body and the frontal area.