Fluid Mechanics Lab

Posted by : Asad Ali Arshad Wednesday, 21 February 2018

Experiment no 2

2. Viscometer.pptx
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To Determine The Viscosity of Fluid Using Viscometer (Find The Viscosity of SAE-30 Lubrication Oil)

Viscometer:A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid.It is used for those fluids whose viscosity does not change under varying flow conditions.

Rheometers must be used when the viscosity does change with flow conditions.

Viscometers usually work by comparing a stationary object and a fluid flow, or vice versa. Hence, a viscometer could be placed in a fluid flow or moved through a stationary fluid.

The flow must have a Reynolds number in the laminar region in order to record accurate values. The measure of the resistance is taken by measuring the drag resistance during relative motion through the fluid

ØThe viscometer consists of a rotating inner cylinder mounted on a vertical spindle at the top and free at the bottom.

ØThis inner cylinder is hollow and rotates inside another fixed outer cylinder of a larger diameter as shown in Fig.

ØThe space between the outer and inner cylinders is filled with the liquid for which the viscosity is to be measured.

ØThe inner cylinder is rotated by means of a vertically falling weight, which imparts rotational motion to the cylinder by using a pulley and a cord arrangement.

For a given weight, W, the speed of rotation of the inner cylinder is higher when the viscosity of the fluid is lower and vice versa.

Apparatus: Viscometer

Procedure: 1. Insert the fluid in the outer cylinder of unknown viscosity.
2. Attach the first weight (W = 100 grams) to the cord. This weight is the sum of the weight of the pan and the weight in the pan.
3. Release the brake and measure the time elapsed to hit the ground.
4. Note the distance covered by the pan.
5. Repeat the above procedure for the other four weights.
6. The viscosity of the fluid is now the average of the five values obtained from the above steps.