The design of a pipe elbow.
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Influence of Secondary Flow from Pipe Elbow on Turbulent Jets
Influence of Secondary Flow from Pipe Elbow on Turbulent Jets
Spring 2022
PURPOSE
To investigate the influence of secondary flow from pipe elbows on turbulent jet flow.
Terminology & Definitions
Terminology & Definitions
D - Diameter of the nozzle.
Self-similarity - In this case, turbulent flow can be described as self-similar when it is symmetrical.
Potential core - a central region of the jet that has uniform mean velocity.
VI - Virtual Instrument. An interface that LabView uses.
CONTEXT & MOTIVATION
Modern rockets have complex reaction control systems critical to ensuring proper flight, including maintenance of flight path, precise adjustments for landing, and other difficult maneuvers. Many systems use jets of pressurized gas as the avenue of this fine adjustment. As with any large aerospace system, every square inch of space is critical, and the design must be optimized to best use it. In order to fit a roll control system within the complex internal layout of a rocket, a 90º elbow can be placed after the jet nozzle to save space.
When the jet flows through the elbow and exits, secondary flow occurs in the form of internal vortices, and the velocity profile will differ. By characterizing these profiles, the fine thrust adjustments can be modeled and used as desired.
EXPERIMENT OVERVIEW
The system used to characterize elbow jet flow consisted of a fan and an automated measurement system. A pitot tube measured the pressure of the fluid being expelled from the jet at various points across the flow using the automated measurement apparatus. By using a pressure transducer and a LabView conversion VI, velocity was obtained.
Our experimental setup.
RESULTS
In the regions that were expected to correspond to self-similar behavior, the velocities could be represented by a single smooth curve, while the turbulence intensity of the jet showed two curves. This proved the existence of a potential core and jet boundary beginning at approximately 5D away from the nozzle of the jet.
A visual respresentation of the flow out of the pipe elbow.
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