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ABSTRACTS

This experiment about free and forced vortex.

INTRODUCTION

Analysis of fluid flow is often accomplished by simplifying assumptions with respect to the kinematics of the flow, by assuming simplified patterns of fluid motion as represented by streamlines. Vortex motion is a basic flow pattern; it is defined as motion in circular paths. There are two types of vortices distinguished in the dynamics of the motion and the resulting velocity distributions. These are forced and free vortices.

The forced vortex is caused by external forces on the fluid such as the impeller of a pump. In a forced vortex motion, the fluid mass is made to rotate by means of some external source of power, which exerts a constant torque on the fluid mass and, therefore, the fluid mass rotates with a constant angular velocity. For example, a vertical cylinder containing liquid and rotating around its central axis with a constant angular velocity flow through the impeller of a centrifugal pump.

In the free vortex motion, the fluid mass rotates without any external force. It rotates either by internal action or due to some rotation previously imported to it. For example, flow through an opening at the bottom of a shallow vessel such as washbasin or a bath tub, flow around a bend, whirpools, or tornadoes.

In this experiment, a forced vortex is created by a rotating plate filled with blades while free vortex is created by only a rotating plate.

OBJECTIVES

To determine the surface profile of a forced vortex.

To investigate the physical phenomena associated with a free vortex

RESULTS

Experiment 1: Free Vortex

Diameter at Centre, D (mm)Measured Height, h (mm)Pitot Tube Head Difference, H (mm)Pressure Head / Depth of the Pitot Tube, X (mm)r (mm)r (mm)1/r (1/mm)

489592824.05760.001736

4382133421.5462.30.00216

3154195115.5240.30.00416

2146257210.5110.250.00907

Experiment 2: Forced Vortex

Distance from Centre(mm)ho (mm)

1st2nd3rd

0946936

30967039

70987144

1001027347

No of revolutions in 60s273033

Angular Velocity(rad/s)2.833.143.46

CALCULATION

Diameter at Centre, D (mm)Measured Height, h (mm)Pitot Tube Head Difference, H (mm)Pressure Head / Depth of the Pitot Tube, X (mm)r (mm)r (mm)1/r (1/mm)

489592824.05760.001736

4382133421.5462.30.00216

3154195115.5240.30.00416

2146257210.5110.250.00907

Gradient of the graph = 5751 mm3

=5751 Therefore, K = 10622 mm2/s

=

= 442.6 mm/s

As a result,

r(mm)Calculated Velocity (mm/s)

24.0442.6

21.5494.0

15.5685.3

10.51011.6

Experiment Values

Experiment 2: Forced Vortex

Distance from Centre(mm)ho (mm)

1st2nd3rd

0946936

30967039

70987144

1001027347

No of revolutions in 60s273033

Angular Velocity(rad/s)2.833.143.46

Calculation

For the 1rd volumetric flow rate:

Number of revolutions in 60 seconds: 38

=

QUOTE

= 2.83 rad / s

h =

= 94

= 94.0mm (calculated)

Calculated value :

Distance from Centre(mm)h (mm)

1st2nd3rd

0946936

3094.469.436.37

7096.071.038.0

10098.173.140.1

No of revolutions in 60s273033

Angular Velocity(rad/s)2.833.143.46

Forced Vortex (1st)

Forced Vortex (2nd)

Forced Vortex (3rd)

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