Viscometer

This ppt is about Types of viscometer

1. BITS EDU CAMPUS FLUID MECHANICS Subject: Viscometer

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3. Topics Introduction Types of viscometer

4. Viscometer What Is Viscometer? A Viscometer is an instrument used to measure the viscosity of a fluid. It is also known as V iscosimeter . For liquids with viscosities which vary with flow conditions , an instrument called a rheometer is used. Viscometers only measure under one flow condition.

5. Types of Viscometer Rotational Viscometer Vibrational Viscometer Oscillation Viscometer Falling Piston Viscometers F alling Sphere V iscometer

6. Rotational Viscometer Rotational viscometer gathers data on a material’s viscosity behavior under different conditions. Rotational viscometers can be used for the accurate measurement of viscosity for both Newtonian and non-Newtonian fluids.

7. Fig: Rotational Viscometer

8. Vibrational Viscometer A Vibrational V iscometer is used for continuous direct measurement of viscosity in pipes and/or tanks. Vibratory Viscometers are better suited to measure non- newtonian liquids

9. Fig: Vibrational Viscometer

10. Oscillation Viscometer The oscillating piston viscometer technology has been adapted for small sample viscosity and micro-sample viscosity testing in laboratory applications. It has also been adapted to measure high pressure viscosity and high temperature viscosity measurements in both laboratory and process environments

11. Fig: Oscillation Viscometer

12. Falling Piston Viscometers The principle of viscosity measurement in this rugged and sensitive industrial device is based on a piston and cylinder assembly. The piston is periodically raised by an air lifting mechanism, drawing the material being measured down through the clearance (gap) between the piston and the wall of the cylinder into the space which is formed below the piston as it is raised.

13. Fig: Falling Piston Viscometer

14. Falling Sphere Viscometer The falling ball viscometer is based on Stokes’ Law. This type of viscometer consists of a circular cylinder filled by the liquid under investigation. A standard ball is allowed to fall down this tube over a calibrated distance of 100 mm. Stokes' law can be used to calculate the viscosity of the fluid. A series of steel ball bearings of different diameter are normally used in the classic experiment to improve the accuracy of the calculation.

15. George Gabriel Stokes derived an expression for the frictional force exerted on spherical objects with very small Reynolds numbers in a continuous viscous fluid by changing the small fluid-mass limit of the generally unsolvable Navier -Stokes equations : where: F is the frictional force, r is the radius of the spherical object, is the fluid viscosity, and is the particle's velocity.

16. Fig:Falling Sphere Viscometer

17. If the particles are falling in the viscous fluid by their own weight, then a terminal velocity, also known as the settling velocity, is reached when this frictional force combined with the buoyant force exactly balance the gravitational force . The resulting settling velocity is given by: where: V s is the particles' settling velocity (m/s) r is the Stokes radius of the particle (m), g is the gravitational acceleration (m/s 2 ), ρ p is the density of the particles (kg/m 3 ), ρ f is the density of the fluid (kg/m 3 ), and is the (dynamic) fluid viscosity (Pa s).  

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