Fundamental Physical Principles of Hydraulics : Part 1

Fundamental?..Any connection with mental disorder?...hahaha..Maybe if you don't master the fundamental...


What is the fundamental physical principles of Hydraulics?

Pressure

Back to the basic of hydraulic mentioned before; Hydraulic is the science of forces and movements transmitted by means of liquids

It belongs alongside hydro-mechanics. A distinction (phew..so many distinction in this blog) is made between hydrostatics and hydrodynamics.

What is Hydrostatics? it can be defined as dynamic effect through pressure times area (P x A) or in simple words, pressure that exerts statically.

Example: You as a good and cool father is happily organized a very extravaganza birthday party for your cute little princess. Since it is a super extravaganza event, so your wife ask you to buy a bunch of balloon , complete with a bear and rabbit faces on it. Well, without balloon it can't be called as extravaganza balloon. After exhausted for completing blowing manually th 1455th balloon of the year, you take one of it. You just staring into it. The balloon is nicely blown, resulting nice shape...Well..the connection here, the air (+ your unfiltered saliva) inside the balloon is a hydrostatic force. The air producing force that allowing the balloon to expand into the shape...that is it! the hydrostatic...

Hydrodynamics can be defined as dynamics effect through mass times acceleration ( m x a)..simple example..a turbine which rotating due to the impact produce by high speed moving fluid ( normally can be found at the dam)

Force and Area

Force normally noted as F symbol and area with A. The connection between Pressure, Force and Area are shown in the basic formula; P=F/A.However, pressure is different owing to the different size of area.

Pressure Transmission

Theoretically, if a force F1 acts via an area A1 on an enclosed liquid, a pressure P is produced which extends throughout the whole liquid (Pascal's Law).

Owing that the fact hydraulic system operate at very high pressures, it is possible to neglect the hydrostatic pressure. Therefore, when calculating the pressure in liquids, the calculations are based purely on pressure caused by external forces. Short said, for the solid bodies,the expression formula is ; P= F/A

Power Transmission

Bear in mind, and always remember that in a closed system the same pressure applies at every point (this is according the theory whereas for 100% system efficeincy). Thus, the shape of the container has no significant.

The fluid pressure in a system consists of a pair of piston with areas noted as A1 and A2, and two forces which can be noted as F1 and F2, can be describes by means of the following equations:

P1 = F1 / A1 and P2 = F2/A2

And when the system are in equilibrium:

P1 = P2

When the equation is already balanced, the following formula is produced:

F2/A2 = F1 / A1

Small forces from the piston can produce larger forces by increasing the area of working piston surface. This is the fundamental principle which is applied in every hydraulic system from the simple jack to complicated lifting platform. The force F1 must be sufficient to overcome the load resistance...


Easter Egg!!

The Part 1 ends here. As to give clear picture, I will provide simple problem solving on how this hydraulic equation works. This is the bonus of the Part 1....


Problem Statement:

A New Kia Forte SX1.6 has been sent to the workshop for servicing. The vehicle need to be lifted by the hydraulic jack. The approximate weight for the Kia Forte is around 1500kg. The main specs of the jack is it handle's piston area are 40cm square while the platform cylinder surface area are 1200cm square What force need to be applied at the jack's handle?

Solution:

Assume:


Step 1:
F1 = force need to be applied to the jack's handle
A1 = 40 cm square = 0.004m square

F2 = force from Kia Forte
A2 = 1200 cm square = 0.12m square


Step 2:
Find the F2 value first;

Basically; F = ma = mg

Given weight: 1500kg

So:

F2 = mg
= (1500)(9.81)
= 14 175 N


Step 3:

Now to find the F1 value;

We know that:

P1 = P2

F1/A1 =F2/A2

Thus;

F1=(F2 x A1) / A2

F1 = (14 175N x 0.004m square) / 0.12m square

F1 = 490.5N