Evaluation of Local Heat Transfer and Visualization of an Impinging Jet Acoustically Perturbed

An integrated approach has been employed to characterize the flow field and heat transfer configuration, in witch air jets undergoes to regime transition. Heat/mass transfer analogy has been used to infer the local heat exchange. A naphthalene film is ablated from the substrate disk, due to jet exposure, and from the local naphthalene loss rate the local heat transfer is then inferred. Under natural conditions the investigated impinging jet is substantial laminar and coherent structures are created upon excitation with acoustical perturbations and need to be investigated in the jet vicinity. Two laser techniques are employed: Laser Döppler Velocimetry (LDV) and Particle Image Velocimetry (PIV). Both techniques have been used in order to investigate the influences and coherent structures generated in the jet by acoustic perturbation forced in the flow. With the acoustical perturbation a substantial increase of the local heat transfer coefficient was observed.