عملکرد هیدرودینامیکی

Al-H2O2 battery is a primary flow battery used in underwater systems. These batteries are of interest for air-independent power sources in underwater vehicles. Currently, with the development of the use of light and smart underwater vehicles and the need to increase the durability of the submarine, special attention has been paid to these batteries. In this study, the effect of the separator membrance on the Al-H2O2 battery on the hydrodynamic and thermal performance of this battery has been investigated numerically and experimentally. The use of the separator is to prevent short circuit in the battery, to control the corrosion rate of aluminum and also to improve the performance of the battery. Comsol software has been used to simulate the hydrodynamic and thermoelectrochemical performance of the Al-H2O2 battery. Also, k-w turbulence model is used to solve momentum conservation equations. In order to validate the numerical results, experimental tests were performed. The numerical results were in good agreement with the experimental results. By increasing the current to two times in the case of using the separator, the average voltage has changed over time from 1.07 V in the case without the separator to 0.97 V in the case with the separator. The voltage change was about 10%, while the current increased by 100%. This indicates improved battery performance and higher power draw when using the separator. Experimental and numerical results showed that the use of a separator in the Al-H2O2 battery improves the performance of the battery due to the prevention of direct contact between the H2O2 and the aluminum surface.

Nowadays, designers have always been interested in the use of motion stabilizer systems, such as the interceptor and trim tab, especially for planing vessels. These systems can improve crew comfort and reduce fuel consumption with favorable effects on the hydrodynamic performance of these vessels, such as reduced resistance and trim angle. In the present study, the effect of the interceptor on the hydrodynamic performance of model scaled "1/15" a monohull vessel with 11 m long that was tested in the towing tank of Sharif University of Technology compared with numerical simulation by software STAR-CCM+. The results show that the installation of the interceptor on the vessel reduces the resistance to a maximum of %9.4 when the vessel is in planing mode and in particular the dynamic trim due to the shift of the center of pressure to the transom. Keywords: motion stabilizer systems؛ interceptor؛ planing vessels؛ hydrodynamic performance؛ resistance reduce؛ trim angle؛ numerical modeling؛ software STAR-CCM+

The numerical simulation of cavitation phenomenon in waterjet propulsion system, due to destructive effects and complicated and two-phase nature, is one of the greatest challenges in engineering and numerical modeling. Due to needing of very much cost for experimental studying this phenomenon in the cavitation tunnel, in this paper, the happening of cavitation in axial flow waterjet was simulated by computational fluid dynamics. The head, torque, and thrust due to cavitation and ignoring that were calculated in 3 flow rate values. The result showed good agreement with experimental data. One of the new studies in this paper is the investigation of the pattern of cavitation bulb forming on the tip and suction side of the rotor’s blade. Numerical simulation was performed, using the rotor and stator and with rotor only. Numerical solution is performed, using a the structured grid, the rotating reference frame, the periodic domain, and SST turbulence model in the steady form.

Propeller is one of the important marine propulsors for generating thrust to overcome the ship resistance. This paper presents the anlaysis of the skew propeller and propulsion for a submarine by using the Boundary Element Method (BEM). This method is useful for analysis and design of lifting bodies like hydrofoils and propellers. A five-bladed Highly Skewed Propeller (HSP) has been chosend for a submarine of 120 [Tones] with forward constant speed 8 [knots] and the calculated results of the hydrodynamic performance have presented. The efficiency values have been obtained 0.65 and 0.68 at two surfaces and submerged conditions, respectively.