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PROPERTIES OF FLUID

Before studying Fluid mechanics, we have to have basic idea of following properties of fluid. Some properties may rely on other ones.

Density
Density is a measure of mass per unit volume. At a point density can be expressed as follow

ρ=lim┬(δV→0)⁡〖δm/δV 〗
ρ -Density
m-Mass
V-Volume

When considering an volume it has completely filled with same fluid (material) Density can be expressed as follow.

ρ =⁡〖m/V 〗
Dimension of density - [M][〖L]〗^(-3)
SI Unit of density - kgm^(-3) ,

Other Units of density which are generally used - lb〖ft〗^(-3) ,gcm^(-3)

Specific weight (Unit density) - γ

Specific weight is the measure of weight per unit volume can be expressed as follow.

γ =⁡〖mg/V 〗 g -accelaration due to the gravity
Hence there is a direct relation between density and specific weight.
γ =⁡〖ρg 〗
Dimension of Specific weight = [M][〖L]〗^(-3) × [L] 〖[T]〗^(-2)
=[M][〖L]〗^(-2) [T]^(-2)
SI Unit – Nm^(-3)
Relative Density (Specific Gravity) - S

Relative Density of a substance =⁡〖(Density of the substance )/(Density of the standard substance) 〗

Water is generally used as the standard substance. This is a dimensionless and unitless property.

Pressure – P
Due to the collision of molecules, FluidS exert force on surfaces which are in contact with them. This Force per unit contacted area can be defined as pressure.

Pressure(P)=⁡〖(Force (F))/(Area (A)) 〗

At a point, it can be expressed as follow.

P=lim┬(δA→0)⁡〖δF/δA 〗

Dimension of Pressure – [M][〖L]〗^(-1) [T]^(-2)
SI units of pressure – Nm-2

How to design sections in SAP2000

Section properties are another specific characteristic in structural member. Therefor we have to concern about that. Previous post on SAP2000 we delivered on how to define materials. In our flow of the designing simple beam, next step is how to define section properties.

In this case we design a beam section. Then we concern about section option. Let’s go on frame section designing.

First go on below steps for frame section designing

> Properties > Section…

If you go on above path you can get a window of some options like in designing.

In default software has section named . After the getting below points you can get the idea of what is the section given by software.

In this window you get 5 options. Let’s see what are these.

1. Import New Property…

In this case you have to import fie from your computer. After the clicking you have another window but you cannot define any sections with only these tabs if you haven’t any section files in your computer. Other options are discus in below topics.

2. Add New Property…

After the clicking on this tab you can see same window like in above tab. First you have to select your material. By selecting your material, you can see sections are changing because this software is based on considering practical situation too.

After the clicking on your section you can get another window for change the dimensions and material properties. Insert your data and click on for finishing the section define.
In the case of selecting material type which called , you can design your own shape.

3. Add Copy of Property…

Like the material define. By this option we can get the copy of existing section.

4.Modify / Show Property…

Same as the name of the option.You can see the properties of existing section. Then you can get the properties on default section also.

5. Delete property

For deleting the existing fame section.

FLUID MECHANICS INTRODUCTION

There are four phases that matters can exits which are ,

1) Solid
2) Liquid
3) Gases
4) Plasmas

A fluid is a substance that continually flows or deforms under an applied shear stress or external force. Since solids forms when molecules are highly packed. Solids do not easily deform or flow under stress or force. So Excluding Solids all other phases of matter can be considered as fluids.

In Engineering , we have to study behavior of the fluids under Fluid mechanics.

After installing the software, you can see the interface of the SAP2000. Just the looking interface is complex. It has so many tools and options. For the get some idea of the software, we can analyse simple beam member.

First you have to go option and then click on . After that you can see new window with some features. This software is logical software and you have to clear idea of what you doing.

In this example we go for simple beam design therefor we go on option. There are many options to design beam but Beam option is the easiest one. But make sure you make sure choose the correct units. It is important.

After choosing beam option you will get new window. In this window you have input number of spans and span length. Section properties not change. Then press .
By finishing above steps, we can obtain our simple beam on our software.

Next article should contain how to apply loads and precisely design our beam.