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Basics of Fluid Mechanics, 2014a

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9.4. SUMMARY OF DIMENSIONLESS NUMBERS 315<br />

9.4.2 Relationship Between Dimensionless Numbers<br />

The Dimensionless numbers since many <strong>of</strong> them have formulated in a certain field<br />

tend to be duplicated. For example, the Bond number is referred in Europe as Eotvos<br />

number. In addition to the above confusion, many dimensional numbers expressed the<br />

same things under certain conditions. For example, Mach number and Eckert Number<br />

under certain circumstances are same.<br />

Example 9.16:<br />

Galileo Number is a dimensionless number which represents the ratio <strong>of</strong> gravitational<br />

forces and viscous forces in the system as<br />

Ga = ρ2 gl 3<br />

μ 2<br />

(9.XVI.a)<br />

The definition <strong>of</strong> Reynolds number has viscous forces and the definition <strong>of</strong> Froude<br />

number has gravitational forces. What are the relation between these numbers?<br />

Example 9.17:<br />

Laplace Number is another dimensionless number that appears in fluid mechanics which<br />

related to Capillary number. The Laplace number definition is<br />

La = ρσl<br />

μ 2<br />

(9.XVII.a)<br />

Show what are the relationships between Reynolds number, Weber number and Laplace<br />

number.<br />

Example 9.18:<br />

The Rotating Froude Number is a somewhat a similar number to the regular Froude<br />

number. This number is defined as<br />

Fr R = ω2 l<br />

g<br />

(9.XVIII.a)<br />

What is the relationship between two Froude numbers?<br />

Example 9.19:<br />

Ohnesorge Number is another dimensionless parameter that deals with surface tension<br />

and is similar to Capillary number and it is defined as<br />

Oh =<br />

μ √ ρσl<br />

(9.XIX.a)<br />

Defined Oh in term <strong>of</strong> We and Re numbers.

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