Rayleigh's method of dimensional analysis

Rayleigh's method of dimensional analysis is a conceptual tool used in physics, chemistry, and engineering. This form of dimensional analysis expresses a functional relationship of some variables in the form of an exponential equation. It was named after Lord Rayleigh.

The method involves the following steps:

1. Gather all the independent variables that are likely to influence the dependent variable.
2. If R is a variable that depends upon independent variables R₁, R₂, R₃, ..., R_n, then the functional equation can be written as R = F(R₁, R₂, R₃, ..., R_n).
3. Write the above equation in the form R = C R₁^a R₂^b R₃^c ... R_n^m, where C is a dimensionless constant and a, b, c, ..., m are arbitrary exponents.
4. Express each of the quantities in the equation in some base units in which the solution is required.
5. By using dimensional homogeneity, obtain a set of simultaneous equations involving the exponents a, b, c, ..., m.
6. Solve these equations to obtain the value of exponents a, b, c, ..., m.
7. Substitute the values of exponents in the main equation, and form the non-dimensional parameters by grouping the variables with like exponents.

Drawback – Rayleigh’s method doesn't provide any information regarding number of dimensionless groups to be obtained as a result of dimensional analysis.

See also

• Physical quantity
• Buckingham π theorem

References