The study of nonmodal amplification of distributed body forces in channelflows of viscoelastic fluids has provided useful insights into the mechanismsthat may govern the initial stages of transition to elastic turbulence.However, distributed body forces are not easy to implement in experiments andso there is a need to examine amplification of localized body forces. In thiswork, we use the linearized governing equations to examine such amplificationin Poiseuille flow of FENE-CR fluids. We first identify the wall-normallocation at which the impulsive excitations experience the largestamplification and then analyze the kinetic energy of the fluctuations and theresulting flow structures. For both a Newtonian fluid at high Reynolds numbersand a viscoelastic fluid at low Reynolds numbers, the largest amplificationoccurs for disturbances that are located near the channel wall. Our analysis ofthe energy evolution shows that a localized body force in the spanwisedirection has the largest impact and that the streamwise velocity component ismost affected. For viscoelastic fluids we observe the development of vorticalstructures away from the source of impulsive excitation. This feature is lessprominent in Newtonian fluids and it may provide a mechanism for triggering theinitial stages of transition to elastic turbulence.
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