5.2 Experimental Design
5.2.2 Captive model test
5.2.2.1 Effect of collective pitch angle settings
Figure 5.10 and Figure 5.11 show the thrust coefficient KT and torque coefficient KQ as the func-
tion of advance coefficient J for a range of the collective pitch angle
col, which is presented in percentage. In the captive model experiment, the rotational speed was maintained as constant during the tests.86
As can be seen in the graphs for KT with positive and negative
col, the thrust coefficients de- creases and increases gradually in absolute values as J increases respectively. Advance coeffi- cient J dramatically influences KT. The presented characteristics curve of CCPP is found to besimilar to that of the conventional propeller. It is noted that at a specific J, KT increases with the rise of
col.The torque coefficient KQ curves have the similar tendency as the thrust coeffi- cient curves.Figure 5.11. Effect of negative collective pitch angle settings.
The difference in the forward and reverse thrust with the positive and negative
col has been discussed in the previous section. The ability to rapidly generate significant reverse thrust could assist the underwater vehicle in the crash-back manoeuvre as well as in the stopping manoeuvre.87
Figure 5.12. Maximum open water efficiency of CCPP in the range of advance coefficient.
The maximum open water efficiency of CCPP for different positive collective pitch settings, shown in Figure 5.12, are presented in the range of advance coefficient. The experimental results show that CCPP has the maximum efficiency at J0.2, 0.4, 0.6 with
col 75% and at0.8, 1.0, 1.2
J with J100%. In general, the maximum open water efficiency of CCPP is
0.73
at J1 with the collective pitch setting
col 100%.5.2.2.2 Effect of horizontal cyclic pitch angle settings
The relationship between the horizontal force coefficient KY and the advance coefficient J for different cyclic pitch angle settings is presented in Figure 5.13.
It is interesting to note that KY sharply increases its absolute value as J increases. The reason for this characteristics is that it is due to the effect of water inflow velocity which alter the lift generated on each blade of the CCPP. Additionally, in a particular J value, the performance is consistent with the bollard pull condition.
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Figure 5.13. Effect of horizontal cyclic pitch angle settings.
5.2.2.3 Effect of vertical cyclic pitch angle settings
Similar to the previous section, the effect of vertical cyclic pitch angle settings on the CCPP per- formance is illustrated in Figure 5.14 by plotting the vertical force coefficient KZ against the ad- vance coefficient J for a range of cyclic pitch angles cyc.
The behaviour of the vertical force coefficient KZ with respect to J is similar to the behaviour
of the horizontal force coefficient KY. It can be found that the side force coefficients, KY and KZ, are not only dependent on cyc but also on J. These results suggest that the side forces could be
controlled by both variables cyc and J for the optimum performance.
Generally, the findings from the captive model test show a fairly consistent CCPP performance in the range of advance coefficients as in the bollard pull condition. In the underwater vehicle simulation at different manoeuvring, all effects have to be taken into account for the accurate performance prediction. The obtained empirical values can be analysed and saved in the form
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of look-up table which predict the CCPP manoeuvring forces as a function of pitch angle settings and advance coefficient.
Figure 5.14. Effect of vertical cyclic pitch angle settings.
5.3Summary
A series of comprehensive bollard pull and captive model tests were designed and conducted on the innovative propulsor named CCPP to evaluate its performance. The effects of the collec- tive and cyclic pitch settings on the CCPP performance have been examined and discussed. Ac- cording to the obtained results, it is shown that the CCPP is capable of generate an effective manoeuvring forces in both bollard pull and captive model conditions. The results also provide an insight into the relationship between these manoeuvring forces and controlled parameters that enables the simulation and control study of the underwater vehicle equipped with CCPP. As part of the research project, the experimental results from this study is used in a comparison study with experimental data of FPP to evaluate the effectiveness of an underwater vehicle per- formance
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CHAPTER 6
Manoeuvring Simulation
In chapter 6, an AUV simulation program named AUVSIPRO is proposed in the preliminary design stage to predict and compare the AUV manoeuvrability equipped with different propul- sion configurations. A series of primary manoeuvres standard for underwater vehicles are pre- sented to investigate the system feasibility. In order to derive the mathematical model in the simulator, the propulsor models are experimentally conducted in the towing tank, the hull hy- drodynamic coefficients are calculated using analytical, and system identification approaches. The system outputs are achieved by numerical method. The simulation program provides an effective platform to examine different the propulsion system configurations to an AUV as well as a torpedo shaped submarine.
Part of this chapter has been presented at “The Forth International Conference on Modelling and Simulation for Autonomous System in Rome, Italy 2017” and has been submitted to the “Ocean En- gineering, An International Journal of Research and Development”. Citations for conference paper and journal paper are:
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Tran M, Binns J, Chai S, et al. (2017). AUVSIPRO–A Simulation Program for Performance Pre- diction of Autonomous Underwater Vehicle with Different Propulsion System Configurations. International Conference on Modelling and Simulation for Autonomous Systems. Springer, 72-82.
Minh Tran, Hung Nguyen, Jonathan Binns, Shuhong Chai and Alex Forrest, A comparison study of two propulsion system configurations for an autonomous underwater vehicle, Ocean Engi- neering, An International Journal of Research and Development.
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6.1Introduction
In this chapter, a simulation program named AUVSIPRO is proposed using the MATLAB/SimulinkTM. The program is able to rapidly simulate the underwater vehicle equipped
with different propulsion systems in various defined standard manoeuvrability. This would greatly facilitate the design of vehicle propulsion system and provide a good understanding of the performance of an AUV. In addition, a wide range of control strategies could be applied in AUVSIPRO to validate the vehicle performance prior to practical implementation.
The chapter is structured as follows: Section 2 briefly describe the basic components and features of AUVSIPRO. A general description of the mathematical model of an underwater vehicle in- corporated in AUVSIPRO is presented in Section 3. Fundamental manoeuvrability to examine an underwater vehicle performance are proposed and the simulation results are presented in section 4. Section 5 summarises the chapter.