Abstract
The jet from a round Laval nozzle followed by a cylindrical duct with an inner diameter of 10 mm and a length of 50 mm is investigated experimentally. The Laval nozzle has a design Mach number of 1.5. Quantitative flow visualization of the jet issued from the duct exit is performed over a range of nozzle pressure ratios from 2.0 to 4.5 using the rainbow schlieren deflectometry combined with the computed tomography to investigate the jet three-dimensional structure. The flow features of the near-field shock systems in the jets are displayed with the density contour plot at the cross-section including the jet centerline. Effects of the nozzle pressure ratio on the density profile along the jet centerline are clarified quantitatively. In addition, a comparison between the present experiment and the previous one with a conventional Laval nozzle for jet centerline density profiles is carried out to examine the effect of the cylindrical duct. Furthermore, the three-dimensional structures of overexpanded and underexpanded jets are demonstrated with the isopycnic surfaces to visualize the internal flow features.
Highlights
Quantitative flow visualization of the jet issued from the duct exit is performed over a range of nozzle pressure ratios from 2.0 to 4.5 using the rainbow schlieren deflectometry combined with the computed tomography to investigate the jet three-dimensional structure
The density fields of jets from a round Laval nozzle followed by a cylindrical duct were measured by the rainbow schlieren deflectometry
The three-dimensional density fields of the jets were reconstructed by the convolution back-projection (CBP) method to investigate the effects of the nozzle pressure ratio on the jet structure
Summary
To understanding the prominent characteristics of complex shock-containing flows, schlieren and shadowgraph methods [1] have been widely used as optical tools because of its simple optical arrangement with a higher degree of resolu-. A comprehensive and thorough review of the rainbow schlieren technique is presented by Agrawal and Wanstall [12], where methods to acquire quantitative density data including mathematical relationship, numerical algorithms, system design criteria, hardware issues, calibrations of rainbow filters, and so on are summarized. The rainbow schlieren deflectometry is applied for jets from a round Laval nozzle followed by a cylindrical duct Such a Laval nozzle followed by a long duct attracts special attentions on applications for the cold spray technology [14] [15], which includes a deposition process in which small particles in the solid state accelerate to high velocities in a supersonic gas jet and deposit on the substrate material. The previous experimental data [10] on a jet issued from a conventional Laval nozzle without a long duct is used for a comparison with the present experimental data
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
