Understanding Hydraulics

Hydraulics is a part of the "hydrodynamic" associated with the
movement of water or flow mechanics.

Judging from the flow mechanics, there are two kinds of streams that
flow channel closed and open channel flow. Two kinds of flow are
common in many cases but differ in one important provision. The
difference is the presence of free surface.Open channel flow has a
free surface, while the closed channel flow has no free surface
because the water fills the entire cross section of the channel.

Thus the surface has an open channel flow associated with the
atmosphere, being a closed channel flow has no direct relationship
with the atmospheric pressure.

As we know, water flows upstream to downstream propagators (unless
there is a force that causes the reverse flow direction) until it
reaches a certain water surface elevation, for example:

- Surface water in lakes,

- Surface water in the sea

The journey of water can also be added by the buildings are made by
humans, such as:

- Irrigation Channels,

- Pipe,

- Culverts,

- Other artificial channels or canals

Although in general planning the channel characteristics are shown for
an artificial channel, the hydraulic concept can also be applied
equally well to the natural channel.

If the channel is open to atmosphere, such as rivers, canals,
culverts, then the flow is called an open channel flow or flow of the
free surface.

If the utility has a full cross section such as flow through a pipe,
called a closed channel flow or full flow.

The types of flow:

Based on the monitoring time is:
Steady Flow (Steady Flow)
Unsteady flow (unsteady flow)

Based on the monitoring space is:
Uniform flow (Uniform Flow)
Changed flow (Varied flow)

Characteristics of flow average velocity depth
Steady, uniform V = constant y = constant
Steady, nonuniform V = V (x) y = y (x)
Unsteady, uniform V = V (t) y = y (t)
Unsteady, non-uniform V = V (x, t) Y = y (x, t)


This type of flow that may occur in open channels is:
Changed Fast Flow (Rapidly Varied Flow)
Changed Slow Flow (Gradually Varied Flow)


Elements of Geometry

1. Sectional area (A)

2. The width of the surface (B)

3. Roving wet (P), and

4. Hydraulic radius (R)


The definition of the channel cross section is a cross-section taken
perpendicular to the direction of flow, is called a vertical cross
section taken with a vertical cross section.

Thus, if the base is horizontal, cross-channel line will be equal to
the vertical cross section.

Sectional forms consist of:

A. The cross-section shape Trapezoid

Trapezium cross-sectional shape is the form commonly used for
irrigation canals or drainage channels, because it has the form of
natural channels, where the slope of the ridge adjust to the angle of
natural slope of land used for the channel.

B. Four cross-section or shape Square Triangle

This form is a simplification of the trapezium form normally used for
drainage channels through the narrow land.

C. The cross-section shape Circle

This form is usually used at road crossings, the channel is usually
called the culvert.

Sifat-Sifat Terpenting Sebuah Zat Cair

Dalam berbagai masalah teknik sipil, sering kita membutuhkan analisis dari perilaku zat cair atau air pada khususnya. Misalnya dalam membangun sebuah bendungan atau instalasi pipa PDAM, akan banyak kita temui masalah yang berhubungan dengan kelakuan zat cair, dalam hal ini air itu sendiri. Maka di sinilah pentingnya mempelajari sifat-sifat zat cair dalam mekanika fluida. Karena dengan berdasar pada sifat-sifat zat cair inilah kita dapat menjelaskan serta memprediksi perilaku fluida yang lebih kompleks.

Zat cair dan gas memiliki sifat yang mirip. Secara umum, suatu zat disebut fluida jika:

Tidak melawan perubahan bentuk. Atau dengan kata lain selalu menyesuaikan diri dengan lingkungannya.
Tidak mengadakan reaksi terhadap gaya geser, yaitu gaya yang bekerja sejajar dengan permukaan lapisan-lapisan zat dan mencoba menggeseer lapisan-lapisan itu antara satu dengan yang lainnya.

Dalam bidang teknik sipil kita hanya mempelajari sifat-sifat air saja. Karena hanya dengan fluida inilah kita akan bergelut, terutama dalam konstruksi bangunan-bangunan air. Sifat-sifat terpenting dari air adalah:

. Mempunyai rapat massa serta berat jenis

Apabila volume wadah zat cair lebih besar daripada volume zat cair itu sendiri, zat cair akan membentuk permukaan horizontal yang berhubungan langsung dengan atmosfer

Zat cair atau air memiliki sifat tidak dapat dimampatkan atau incompressible

Zat cair memiliki kekentalan, kohesi dan adhesi, serta tegangan permukaan