Alignment and application of the conical shadowgraph flow visualization technique

An optical bench study has been carried out to assess the effects of both beam alignment and nonconical disturbances in the application of conical shadowgraphy for flow visualization. Conical and quasiconical plastic test models were immersed in a refractive index matching fluid and then examined by shadowgraphy with a conical light beam. The results show that problems of interpretation may arise due to both axial and transverse beam misalignment. Among these difficulties, axial misalignment with positive vertex displacement is the least serious. Also, the effect of a particular nonconical disturbance field was found to introduce fewer difficulties of interpretation than that of beam misalignment.