1. FLUID MECHANICS LECTURE
ÓBUDA UNIVERSITY
FLUID MECHANICS LECTURE
Only using inside
Dr. Ferenc Szlivka
professor
Dr. Szlivka: Fluid mechanics 4.

2. Kinematics and continuity 4. chapter
Dr. Szlivka: Fluid mechanics 4.

3. Dr. Szlivka: Fluid mechanics 4.
Plain flow
Dr. Szlivka: Fluid mechanics 4.

4. Streamlines around a semi sphere and bridge pillar
Dr. Szlivka: Fluid mechanics 4.

5. Streamlines around a drop
Dr. Szlivka: Fluid mechanics 4.

6. Streamlines around a drop looked from a moving system
Dr. Szlivka: Fluid mechanics 4.

7. Dr. Szlivka: Fluid mechanics 4.
Unsteady streamlines
Dr. Szlivka: Fluid mechanics 4.

8. Dr. Szlivka: Fluid mechanics 4.
Streamlines around an airfoil
Dr. Szlivka: Fluid mechanics 4.

9. Dr. Szlivka: Fluid mechanics 4.
Hot jet flow
Dr. Szlivka: Fluid mechanics 4.

10. Streamlines around a car
Dr. Szlivka: Fluid mechanics 4.

11. Dr. Szlivka: Fluid mechanics 4.
The path line: the way of a particle.
The streamline: the line which is tangential to the velocity in every point of it.
The streak line: the line of the particles coming from the same point of the stream (of the space)
Dr. Szlivka: Fluid mechanics 4.

12. Dr. Szlivka: Fluid mechanics 4.
Kármán vortex street
Dr. Szlivka: Fluid mechanics 4.

13. Kármán vortex street in a wind tunnel
Dr. Szlivka: Fluid mechanics 4.

14. Continuity law for a steady flow
Dr. Szlivka: Fluid mechanics 4.

15. Continuity law in differential form
Steady flow
Constant density flow
Dr. Szlivka: Fluid mechanics 4.

16. Dr. Szlivka: Fluid mechanics 4.
The volume flow rate or discharge is the volume of fluid flowing past a section per unit time.
The mass flow rate is the mass of fluid flowing past a section per unit time.
Dr. Szlivka: Fluid mechanics 4.

17. Dr. Szlivka: Fluid mechanics 4.
Outflow through window with grille
Calculate the volume flow rate coming out through the windows!
The velocity of air is v= 4 m/s,
The length of the square is, H=2m.
The area of grille is Agr=1m2.
Dr. Szlivka: Fluid mechanics 4.

18. Dr. Szlivka: Fluid mechanics 4.
Solution:
First we should calculate the magnitude of free area
The area of window:
The free area:
The volume flow rate:
Dr. Szlivka: Fluid mechanics 4.

19. Dr. Szlivka: Fluid mechanics 4.
Outflow through a rain grille
The air is flowing with v=2,6 m/s through a HELIOS type square rain grille.
The velocity vector and the normal vector of the area have an angle a=450 .
A length of the square is b=395 mm = 0,395m.
The free surface area is 80% of the whole area.
Dr. Szlivka: Fluid mechanics 4.

20. Dr. Szlivka: Fluid mechanics 4.
Solution:
First we should calculate the magnitude free area
The velocity vector component projected to the normal vector of area
And the volume flow rate:
Dr. Szlivka: Fluid mechanics 4.

21. Dr. Szlivka: Fluid mechanics 4.
Continuitate in compressor
The air is flowing in the suction side with velocity.
It was measured the pressure and the temperature
of the incoming and outgoing air.
Dr. Szlivka: Fluid mechanics 4.

22. Dr. Szlivka: Fluid mechanics 4.
Data:
Questions:
a./ Calculate the velocity at the pressure side ( )!
b./ Calculate the power of the politropic state change between the pressure
and the suction side.
Dr. Szlivka: Fluid mechanics 4.

23. Dr. Szlivka: Fluid mechanics 4.
Solution:
a./ The mass flow rate are the same in the pressure and the suction side of the compressor:
The incoming density:
The outgoing density
From the densities we can calculate the velocity on the pressure side:
Dr. Szlivka: Fluid mechanics 4.

24. Dr. Szlivka: Fluid mechanics 4.
Solution:
b./ Let’s apply the politropic state equation:
The politropic power is the next:
Dr. Szlivka: Fluid mechanics 4.

25. Dr. Szlivka: Fluid mechanics 4.
Vorticity and potential vortex
Dr. Szlivka: Fluid mechanics 4.

26. Dr. Szlivka: Fluid mechanics 4.

27. Dr. Szlivka: Fluid mechanics 4.
Potential or irrotational and vortex flows
Dr. Szlivka: Fluid mechanics 4.

28. Dr. Szlivka: Fluid mechanics 4.
Potential vortex
Dr. Szlivka: Fluid mechanics 4.

29. Dr. Szlivka: Fluid mechanics 4.
Vorticity, rotation, angular velocity y
Dr. Szlivka: Fluid mechanics 4.

30. Dr. Szlivka: Fluid mechanics 4.
Vorticity, rotation in a 3D coordinate system
Dr. Szlivka: Fluid mechanics 4.

31. Dr. Szlivka: Fluid mechanics 4.
Potential vortex and G, the circulation
Dr. Szlivka: Fluid mechanics 4.

32. Dr. Szlivka: Fluid mechanics 4.