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Author's Reply 



ALI H. NAYFEH 



The growth rate in a parallel flow can be 

 unambiguously defined, but it cannot be unambig- 

 uously defined in a nonparallel flow. Because the 

 eigenf unctions are functions of y as well as x, 

 Saric and Nayfeh (1977) note that stable flows may 

 be termed unstable and vice versa. Saric and 

 Nayfeh (1977) discussed in great detail the differ- 

 ent possible definitions of the growth rate and 

 compared these definitions with all available exper- 

 imental data for the Blasius flow. They found that 



all the experimental data (neutral curves or growth 

 rates) obtained at the values of p for which |u| 

 has a maxima can be correlated with the nonparallel 

 results if the growth rate is defined as in (55) . 

 For the heated liquid problem, we arrived at the 

 same conclusion. Including the distortion of the 

 eigenfunction with the streamwise position, the 

 definition, (56) , underpredicts the growth by 

 large amounts . 



