Role of Experiments in Engineering

Laboratory experiments are important for improving our understanding of physical phenomena that occur in nature as well as in engineering equipment. The present chapter discusses experimental techniques used in studies related to fluid mechanics and heat transfer.

Determination of Fluid Properties

In continuum mechanics the physical principles of mass balance and Newton's second law of motion are supplemented by constitutive relations that describe material behavior. For example, the stress-strain rate relationship for a Newtonian fluid is written as

Here is the stress tensor, the rate of strain tensor, the Kronecker-delta, the velocity vector and the thermodynamics pressure. Quantities and appearing appearing in this equation are material dependent parameters and are hence fluid properties. These must be determined from simple laboratory experiments in which , , and are independently known. Once and are tabulated for a variety of fluids the constitutive relation becomes a useful tool for solving engineering problems.