Effect of Nozzle Pressure Ratio on Thrust and Flow Behavior in a Supersonic De Laval Nozzle

<p>Supersonic nozzles operate across a range of flow regimes. While an ideally expanded condition yields optimal thrust, practical propulsion systems rarely operate at this design point due to variations in altitude and engine operating conditions. As a result, nozzles frequently operate in off-design conditions. In overexpanded regime, where the exit pressure is lower than the ambient pressure, shock-induced separation may occur within the divergent section of the nozzle, potentially degrading nozzle performance. Understanding the aerodynamic behavior of nozzles operating under off-design conditions is therefore important for improving propulsion system performance and stability. In particular, direct thrust measurements provide a key metric for evaluating nozzle efficiency and validating theoretical or computational predictions of nozzle performance. This thesis aims to characterize the aerodynamic performance of an asymmetric planar de Laval nozzle operating in overexpanded conditions for different nozzle pressure ratios (NPRs). The nozzle is designed to produce Mach 2.045 flow at a design NPR of 8.39. Off-design conditions are generated by varying the stagnation pressure using a pressure regulator. Nozzle performance is evaluated through direct thrust measurements and wall static pressure data collected along the nozzle surface. The net thrust is obtained by measuring the force exerted by the exhaust jet on a baffle plate positioned at the nozzle exit. The plate is mounted on a linear slider mechanism and compresses a load cell when subjected to jet force. This configuration provides a simple and inexpensive method of thrust measurement suitable for cold-flow laboratory experiments. Compared with floating-type thrust stands, the baffle plate configuration reduces structural complexity and potential measurement uncertainties while allowing rapid testing of different nozzle geometries. Surface pressure measurements are obtained from pressure taps located along the top wall of the nozzle to provide spatial pressure distributions and insight into internal flow features. By varying the nozzle pressure ratio, this study investigates the influence of off-design operating conditions on nozzle performance and internal flow behavior. In addition to supporting research objectives, the thrust measurement facility developed in this work is designed to serve as an instructional experiment for the undergraduate course AE 315 Experimental Aerodynamics at Embry-Riddle Aeronautical University.</p>

Name thesis:degree_name

Master of Science in Aerospace Engineering

Level thesis:degree_level

Thesis - Open Access

Discipline thesis:degree_discipline

Aerospace Engineering

Year

2026

Author dc:creator

• Jain, Esha

• Supersonic nozzle
• Overexpanded flow
• Thrust measurement
• Shock-induced separation
• Schlieren imaging
• Compressible flows
• Experimental aerodynamics
• Supersonic impinging jet
• Aerodynamics and Fluid Mechanics
• Aeronautical Vehicles
• Aerospace Engineering
• Computer-Aided Engineering and Design
• Propulsion and Power
• Space Vehicles

Repository record dc:identifier

https://commons.erau.edu/edt/975

OAI identifier oai:identifier

oai:commons.erau.edu:edt-2026