Interferometric tomography for flow visualization of density fields in supersonic jets and convective flow

Abstract

Tomographic methods are used for the investigation of three-dimensional compressible flow fields by means of interferometric methods. A modified algebraic reconstruction technique algorithm is applied. The algorithm proved to give reliable reconstructions from experimentally measured projection data in the case of an unrestricted angular view. The method was used for the reconstruction of density distributions of weakly perturbed supersonic free jets exiting from a deformed Laval nozzle. Even small perturbations of the jet resulted in significant three-dimensional effects. Reconstruction of a multiple system of jets emanating from a sievelike nozzle showed mutual interactions between the constituent jets. For the investigation of unsteady flows a setup for the recording of holographic interferograms was designed. Here, because of experimental restrictions, only a limited angular range of views was accessible. In the context of this limited-view geometry, reconstructions revealed considerable distortions for objects containing steep gradients.

Tomographic imaging of nonsymmetric multicomponent tailored supersonic flows from structured gas nozzles

“…In general, multiple measurements of the flow along different axes are combined, and the 3D density map is extracted using mathematical procedures such as filtered backprojection [27] or algebraic reconstruction techniques (ART) [28]. Often, some modifications of general ART are used, such as averaging ART (AVART) [29] or simultaneous iterative reconstruction technique (SIRT) [30,31]. Tomographic measurements are also needed for superposed or colliding flows, or when the initially symmetric gas flow is perturbed by inserting wires [32] or other obstacles [33], or by machining with a high-intensity laser pulse [34,35].…”

The diagnostic study of optical tomography for high-temperature flow fields in the open system

“…Up to now, this technique has been mainly used in the structural visualization for low temperature [1,2], low and high speed complex flow fields [3][4][5], the density measurement [6], as well as the temperature measurement for the flow fields whose temperature is not too high [7]. Until now, it is rarely reported that this technology could be used in the structural visualization, or the temperature and the electron number density measurement for the high-temperature complex flow fields [8].…”

Analysis on the feasibility of optical tomography in measuring gas jet flow velocity

“…As a result, OCT has played important roles in visualizing various flow [1] and hot flow fields [2,3], as well as being applied in measuring key parameters for various flow fields [1,[4][5][6][7]. In view of these advantages and applications of OCT, the feasibility of it on measuring flow velocity distribution of gas jet flow field is worthy to be analyzed.…”