Date of Award

Spring 5-2024

Access Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Surabhi Singh

First Committee Member

Ebenezer Gnanamanickam

Second Committee Member

William Engblom

College Dean

James Gregory

Abstract

A combined numerical and experimental investigation of supersonic planar nozzles under different design conditions has been conducted. Supersonic planar nozzles are common geometries observed in supersonic wind tunnels and aircraft or rocket engines. For the important role they play in wind tunnel testing and aircraft propulsion, it is important to conduct a thorough numerical and experimental study to characterize their performance at different operating conditions. In this study, a de Laval nozzle was scanned to extract its contours and subsequently modeled to compare analytical and numerical performance expectations under design and off-design conditions. The nozzle was then installed in a supersonic blowdown wind tunnel to experimentally validate predicted effects of varying chamber pressure on nozzle performance, particularly within the overexpanded regime. Quantitative data in the form of wall pressure measurements and flow visualization via schlieren imaging were collected.

The investigation uncovered distinctive characteristics of overexpanded flow in planar nozzles, including internal separation and a well-defined shock structure. Decreasing the operating nozzle pressure ratio led to increased separation shock strength and more significant effects of overexpansion on nozzle performance and thrust capability. The shock interactions with the separated shear layer were evident, and downstream propagation of wave phenomena in the jet flow were observed. The design condition was simulated numerically, and while supersonic flow was present throughout the nozzle, some shocks were present in the nozzle flow leading to nonuniformities in the flowfield. To ensure reliable attainment of uniform design conditions, new nozzles with differing area ratios were designed and computationally validated. Three-dimensional numerical analysis ensured alignment with design requirements, including uniform core flow, minimal crossflow, and suitable turbulent boundary layer development. Nozzles have been developed for Mach 2 and 3 flow with the intent of creating a suitable test environment and studying these nozzle flows under design conditions.

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