Experiment to Find the Viscosity of Oil

Topics: Viscosity, Reynolds number, Fluid dynamics Pages: 8 (2104 words) Published: November 11, 2011
Division of Engineering
Assessed In-depth Report 2
EH0SCA: Foundation Science A
Experiment to find the
Viscosity of Oil

To be submitted one week from the
date of the laboratory session

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Summary
The purpose of this experiment is to use Stockes law to obtain the viscosity of an oil sample. During the experiment, there are a number of knowledge are associated with the final results such as Stockes law F = 6∏μrv. According to this equation, calculate the viscosity of an oil sample is simple when μ= g(ρs-ρf)D218μ∞. Therefore, it is essential to find out the value of terminal speed u∞ = Lt and measure the diameter of balls as well as utilizing ρs=m43π(D2)3 to calculate ρs. In addition, learning how to use the equipments also is contained such as micrometer and electronic weighing instrument during the experiment. However, there exist some errors associated many factors. For example, the measurements about the diameter and mass of ten balls are not accurate and when reading the data on the electronic weighing instrument and tubes is incorrect so that it influences the final result. Thus, in order to improve the result, it is necessary to read the data as accurately as possible and improve the accuracy of the electronic weighing instrument and other equipments. Although the final result is not prefect but it also assumes that Stockes’ flow exists.

Content

Summary……………………………………………………………………………….Page2

1. Objective……………………………………………………………………………….Page 5

2. Theory……………………………………………………………………………………Page 5

3. Apparatus……………………………………………………………………………..Page 6

4. Procedure……………………………………………………………………………..Page 6

5. Results and Calculations……………………………………………………….Page 8

6. Discussion …………………………………………………………………………..Page 11

7. Conclusion ………………………………………………………………………….Page 11

8. Reference …………………………………………………………………………….Page 13

Figures and Tables

Figure 3.1 the equipments in the experiment …………………………………7

Figure4.1 the graph to show procedure 5…………………………………….....7

Table 5.1 The known data………………………………………………………………….8

Table5.2The measured data (A)………………..……………………………………… 8

Table 5.3The measured data(B)…………………………………………………………9

Table5.5 The calculated data……………………………………………..………………9

1. Objective
The purpose of this experiment is to use Stockes law to obtain the viscosity of an oil sample.

2. Theory
Real fluids have viscosity. Consequently, the boundary layer fluid in contact with a stationary wall or surface is nearly at rest, whereas flow speeds in the center of a pipe or channel. Flow is typically laminar at low speeds; at higher speeds, flow tends to become turbulent. One more useful relation in viscous fluid flow is the expression for the magnitude F of force exerted on a sphere of radius r that moves with speed v through a fluid with viscosity μ. When v is small enough that there is no turbulence, the relationship is simple: F = 6∏μrv

This relation is called Stokes’s law.
A sphere falling in a viscous fluid reaches a terminal speed u∞for which the total force, including the weight of the sphere and the viscous retarding force, is zero, and the sphere no longer accelerates (neglect the effect of buoyancy of the sphere in the fluid). Let ρ be the density of the sphere; then the weight of the sphere is 43∏r3ρg. When the sphere reaches terminal speed, the total force on it is zero: 6∏μru∞ - 43∏r3ρg = 0

Or u∞= 29(r2gρ/μ)
Theory shows that a sphere falling in a liquid, at very low speed and therefore very low Reynolds number is subjected to Stokes’ flow. In this type of flow the sphere reaches a terminal or constant velocity where the acceleration is zero and all...