Download presentation

Presentation is loading. Please wait.

Published byKellen Ficken Modified over 3 years ago

1
Lecture 2 Properties of Fluids Units and Dimensions 1

2
Engenharia do Ambiente Mecânica dos Fluidos Ambiental The elemental volume must be much larger than the free random path of a molecule. 2/19

3
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Density Dimensions and Units Dimensions Units: SIC.G.SGravitational (MK p S) kg m -3 g cm -3 UMM m -3 3

4
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Specific Weight, Dimensions and Units Dimensions Units: SIC.G.SGravitational (MK p S) N m -3 dine cm -3 kg m -3 4

5
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Other properties Temperature, is a measure of molecule kinetic energy, Specifi Gravity (dimensionless) SIC.G.SGravitational (MK p S) kkk 5

6
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Viscosity When a fluid is sheared, it begins to move at a strain rate inversely proportional to a property called its coefficient of viscosity,. 6

7
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Viscosity is responsible for the shear stress which opposes to the relative movement of elemental fluid volumes. Is null if there is no velocity gradient, so it destroys gradients, i.e. generates momentum diffusion. 7

8
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Viscosity Units SIC.G.SGravitational (MK p S) N m -2 s=kgm -1 s -1 (Poiseuille) dine cm -2 s = gcm -1 s -1 (Poise=10 Poiseuille) kg m -2 s=kgm -1 s -1 8

9
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Kinematic Viscosity SIC.G.SGravitational (MK p S) m 2 s -1 cm 2 s -1 m 2 s -1 9

10
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Flow between two plates 10

11
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Viscosity variability Varies much with temperature and weekly with pressure. In liquids: – Decreases with temperature, In gases: – Increases with temperature. 11

12
Engenharia do Ambiente Mecânica dos Fluidos Ambiental No Slip Condition 12

13
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Surface Tension Exists because intermolecular attraction forces are higher than between the liquid molecules and air. Is responsible for drop formation and for pressure increase inside the drop. 13

14
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Spherical droplet Surface tension decreases with temperature. This is why solubility increases with temperature. 14

15
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Capilarity 15

16
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Velocity, momentum, kinetic energy Momentum is the Force applied to a volume multiplied by the action time. A small force acting for long can generate big momentum. 16

17
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Dimensions consistency/homogeneity In one equation all terms must have the same dimensions. In Fluid mechanics this norm is usually respected. In many empirical laws (often in natural sciences) it is not, being a source of errors. Manning formula for friction is a tricky example of a non-homogeneous formula. 17

18
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Other properties computed from velocity 18

19
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Momentum and kinetic energy Momentum is often called impulse 19

20
Engenharia do Ambiente Mecânica dos Fluidos Ambiental Summary We have seen the main fluid properties, their dimensions and units. Viscosity is relevant only when there is movement and velocity gradients are present. In the next lecture we will see properties of the flow field. 20

Similar presentations

OK

Molecular Transport Equations. Outline 1.Molecular Transport Equations 2.Viscosity of Fluids 3.Fluid Flow.

Molecular Transport Equations. Outline 1.Molecular Transport Equations 2.Viscosity of Fluids 3.Fluid Flow.

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on kingdom monera and protista Ppt on trial and error theory Ppt on pi in maths what does median Ppt on latest technology in mobile Download ppt on world population day Ppt on indian culture and heritage Ppt on dynamic resource allocation in cloud computing Ppt on soft skills for teachers Ppt on standing order form Ppt on principles of peace building grants