Module 5: Schlieren and Shadowgraph
  Lecture 26: Introduction to schlieren and shadowgraph
 

Assumption 3: Under the assumption of infinitesimal displacements, the deflections are small. Therefore the Jacobian can be assumed to be linearly dependent on them by neglecting the higher powers of , and also their product. Therefore, the jacobian can be expressed as

(41)

Substituting in Equation 39, we get

(42)

Simplifying further we get

(43)

Using Equations 36 and 37 for , and integrating over the dimensions of the growth chamber, we get

(44)

Equation 44 is the governing equation of the shadowgraph process under the set of linearizing approximation 1-3. In concise from the above equation can be rewritten as

(45)