Study On The Shape Of The Shell Of An Underwater Thermal Glider And Its Experiment

Underwater thermal slider is an important weapon for human tomarch towards the vast ocean and conquer it. As a kind of AUV(automotive underwater vehicles) powered by buoyancy with friendshipwith environment and low noise, the thermal ocean slider is promised to bewidely applied into science research, military actions and economicactivities. Compared with the traditional electricity powered AUV, thermalocean slider has better endurance of each journey without need to beequipped with battery by applying the ocean thermal energy as the sourceof power and changing the thermal energy into mechanical energy throughspecial power plant.Nonetheless, it is noticed that the temperature difference of thethermocline of the ocean is always less than20degree Celsius and thetemperature gradient is always less than0.2℃/m. The exploitable energyquality is low; therefore, the thermal ocean slider has to face the situationof low thermal efficiency and low power of the thermal engine. In order tosail continuously under such situation, it is a must for the underwaterthermal glider to have high hydrodynamic performance, such as lower dragand greater lift. Under above consideration, the thesis made it as one of thestarting point for the shape design that pick up the best one with highesthydrodynamic performance.The shell occupies the most space and area of the entire underwaterthermal glider, as the main body of it. It is obviously that thehydrodynamic performance counts a lot for the hydrodynamic performanceof the entire glider. In another hand, the capacity performance is ignorable since the underwater thermal glider needs to be equipped with a largeamount of sub-systems and meters, not namely, dynamical systems,sensors, and scientific meters (variously defers by the specific function). Inorder to integrate the hydrodynamic and capacity performance, the thesisintroduced a performance index of capacity versus drag coefficient ratio. Itis further proposed that the final standing point for the shell design wasmaking the choice of the one with higher capacity versus drag coefficientratio.The thermal glider controls its moving situation by controlling the netbuoyancy through the change of the volume of its phase-change material,though equipped with no external propelling systems. Nonetheless, thechange of net buoyancy just makes the up and down movement applicable.In order to realize the horizontal and pitching movement to make the glidersail freely, it is necessary to equip the glider with horizontal wings and tailwings. Respectively, the horizontal wings change the lift into propellingforce and the tail wings produces side force. The thesis set the design ofwings with great lift-drag ratio as the goal at first. Then, the thesisanalyzed the optimal section and horizontal parameters of both wings'shape by applying CFD technology and empirical formulas of theperformance of wing. Further, the installation position of the both wingswere optimized by applying method of numerical calculation, as the result,the wing could be well functioned with good mechanic effect by payingsmall increment of drag of the slider.The place to conduct the experiment needs to be considered after thecompletion of shape design and prototype in order to test the realperformance of it. It will be costly and uneasy to make the place ofexperiment in the sea or lake with thermocline, even facing the risk oflosing the model since the underwater natural environment is socomplicated. For this reason, the thesis studied the way to establish indoorocean thermocline based on the theory of similarity to provide aexperiment environment with high repeatability and convenience. The parameters of the pool, namely scaling factor, main dimensions,temperature field, and dynamical similar number. Finally, it was proved thedesigned temperature gradient was obtained in the pool by temperaturesensors' test, in the other word, it was understood the simulation ofthermocline was viable in the pool.In order to examine the hydrodynamic performance of the glider, thehydrodynamic test system was established on the pool, which consists ofthe towing system, force measurement system and data acquisition system.Before the hydrodynamic test, the reliability of the DIYforce-measurement unit was verified by the calibration experiment. In thehydrodynamic test, the scaled glider model was sailing in the cruisingspeed in different attack angles.The first hand data of the drag of theunderwater thermal glider in different attack angles was obtained, whichwould be the basis of further design of power system of the underwaterthermal glider. The accuracy of the hydrodynamic simulation of the poolwas also verified by doing scaled model experiment, comparing with theresult of the numerical calculation.