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CSME 2020/10
Volume 41 No.5
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605-614
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Dynamic Characteristic Analysis of a Two-Stage Water Rocket in Flight
Feng-Yao Changa and Huei Chu Wenga
aDepartment of Mechanical Engineering, Chung Yuan Christian University, Taoyuan 32023, Taiwan, ROC.
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Abstract:
This study explored the flight trajectory and dynamic characteristics of a two-stage water rocket theoretically. The main purpose is to analyze the influences of the air pressure and water volume in the first and second stages of the water rocket on the vertical flight height, velocity, and acceleration of the second stage (upper part of the water rocket) over time. During flight, the pressure difference caused by a one-way check valve between the first stage and the second stage is a key factor determining the separation of the two stages. This flight modeling is based on the water rocket's momentum conservation equation, the outlet fluid velocity condition, and the relationship between internal air pressure and water volume. Through a numerical solution for the problem, the vertical flight height, velocity and acceleration of the water rocket were predicted. These predictions were compared with experimental data in advance. It was found that results in predictions are close to the experimental data, and the check valve in the two-stage water rocket can effectively make the rocket’s vertical flight height higher than that of the single-stage water rocket. The larger the check valve pressure difference that the one-way check valve can withstand, the higher the flight height of the second stage after being detached from the first stage. Under a certain air pressure and total water volume in the water rocket, the best flight performance can be achieved by adjusting the water volume ratio between the upper and lower parts of the water rocket.
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Keywords: water rockets, dynamic model, numerical-analysis, flying experiment.
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*Corresponding author; e-mail:
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©
2020
CSME , ISSN 0257-9731
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