alireza pazhan

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.

Improving hydrodynamic components and increasing stability at high speeds has always been one of the most important challenges in the design of high-speed vessels. One of the most important methods to achieve the aforementioned goals is the use of stern appendages such as trim tab, wedge, and interceptor. In the present study, the effect of changing the geometrical components of the wedge on the performance of the high speed vessel has been evaluated using a numerical method. These evaluations have been carried out to investigate the way and extent of the influence of the wedge on the components of resistance and dynamic stability of the vessel. In this regard, after validating the numerical results, the effect of the wedge at a height of 2 and 3 mm and a span equal to 50 and 100% of the vessel's width on the hydrodynamic performance has been investigated. The results show that the use of the wedge at the optimal height and span by increasing the pressure in the stern has reduced the pressure difference in the bow and stern of the vessel so that in the optimal condition, the total resistance value and the trim angle compared to the base vessel are on average 5.04 and 32.04 respectively. It has decreased by 3.0%. Also, the results show that increasing the geometrical components of the wedge has increased the pressure created in the stern of the vessel, which in the optimal condition has improved the longitudinal stability and prevented porpoising instability.

With the development of AUVs, accurate calculation of hydrodynamic coefficients in the equations of motion of these vehicles increased significantly, and accurate calculation of hydrodynamic coefficients for predicting maneuverability, dynamic stability, and controller design is of particular importance. One of the effective parameters in the uncertainty of the results obtained from the regression methods for calculating the hydrodynamic coefficients is the clearance between the control surfaces and the body. In this article, to investigate the effect of the clearance on some linear hydrodynamic coefficients of the maneuver, a numerical analysis has been performed on the Suboff benchmark model, and the damping and added mass coefficients have been studied using static and dynamic tests. The vertical clearance of the control surfaces from the body is considered a variable and the analysis has been done at several clearance from the body. The numerical results, after validating with the model results, showed that the hydrodynamic coefficients become independent of the distance between the body and the control surfaces from the distance of 0.06 meters. Also, in the static drift test, with the increase in the clearance of the control surfaces from the body, the hydrodynamic coefficient related to the sway force and the hydrodynamic coefficient related to the yaw moment decrease. However, in the pure sway test, with the increase in the clearance, the hydrodynamic coefficient related to the sway force decreases, and the hydrodynamic coefficient related to the yaw moment first decreases and then increases.