Q$15.$ The energy equation for a non$-$isothermal fluid flow is given by

$hat(C{)}_p(\frac{\text{d}\text{e}\text{l}\text{T}}{\text{d}\text{e}\text{l}\text{t}}+u*gradT)=kgra{d}^{2}T+2(E$:$E)+S_e$

where $E$ is the rate$-$of$-$strain tensor. Considering three$-$dimensional flow on a Cartesian frame of reference, compute $2E$:$E.$ Is it linear o nonlinear? What is the physical significance of the computed term in the above equation?