A study on water rocket dynamic characteristics in flight

• Main Authors: Feng-Yao Chang, 張峰垚
• Other Authors: Huei Chu Weng
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/44917541876573974190

碩士 === 中原大學 === 機械工程研究所 === 104 === This study theoretically explores the flight trajectory and dynamic characteristics of water rockets. Its main purpose is to analyze the effects of the inner air pressure and water amount of water rockets on its change of vertical flight altitude, velocity and acceleration over time. The Reynolds transport theorem is first used in the analysis to deduce the momentum conservation equation of water rockets. Then the continuity equation, Bernoulli equation, and the isentropic process relation are applied to infer the outlet fluid velocity and the relationship between the inner air pressure and water amount. Finally, through a numerical solution method, the initial value problem for water rocket space flight and dynamics is solved to predict the flight trajectory and dynamic characteristics, like the vertical flight altitude, velocity and acceleration of water rockets. Moreover, the numerical predictions can be compared with experimental data. The study results on a single-stage water rocket show that the numerical predictions can get the results close to the experimental data. The results further indicate that under a certain water amount in a single-stage water rocket, the greater the air pressure in the rocket, the higher the vertical flight altitude, the faster the maximum velocity and the bigger the maximum acceleration of the rocket. Moreover, under a certain air pressure in a single-stage water rocket, with the increase of water amount in the rocket, the vertical flight altitude increases, the maximum velocity becomes faster, but the maximum acceleration decreases at the beginning stage; however, after more than a certain amount of water, the vertical flight altitude reduces and the maximum velocity becomes slow. As to a double-stage water rocket, the numerical predictions can also get the results near to the experimental data. Furthermore, the capability of the one-way check valve between the upper part and lower part of the double-stage water rocket is an important factor to influence the flight trajectory and dynamic characteristics of the double-stage water rocket. Under a certain total water amount and air pressure, through an appropriate ratio of the water amount adjusted in the upper part and lower part of the double-stage water rocket, the best flight performance can be reached. Compared with the single-stage water rocket, the vertical flight height of the double-stage water rocket is significantly higher than that of the single-stage water rocket.