For stabilization of zero speed ships active anti roll Tanks and gyro stabilizers are used.Because of antiroll tank limitations on working frequencies gyro stabilizers are proposed. A nonlinear model for ship is used to simulate hydrodynamic forces.Wave’s disturbances are considered as non-parametric uncertainty. A sliding mode controller is used for roll stabilizing.A nonlinear h infinity controller is designed to reduce the disturbance effects on the ship. The designed sliding mode controller uses more control energy from h infinity controller. Instead roll reduction of the sliding mode controller is grater from the other one. The main concept of the used model in this article was taken from an authority that ship model data estimated from real ship with Halcyon gyro actuator. Roll reduction increases by applying designed controllers in wide range of sea states. In addition nonlinear effects intended in this article. Simulation results based on Jonswap wave spectrum demonstrates the performance of robust system in confrontation with wave perturbations.

Background & Purpose: Volatile organic compounds (VOCs) significantly affect the chemistry of atmosphere and human health and petroleum storage has been identified as largest emitters of VOCs. With models of air pollution can model the concentration and distribution of VOCs from oil Tanks. The aim of this study was to investigate and model of VOCs emissions from an oil Tanks field in Iran using the Tanks 4.0.9d software and the distribution of these compounds in the study area using AERMOD model.Materials & Methods: In this study, the rate and percentage of monthly emissions of VOCs from 22 oil storage Tanks in 12 months year 2014 (1392-1393) using the Tanks software were determined according to losses and tank type in Esfahan, Iran. Then, by using AERMOD model the maximum concentration of VOCs in the area with the surface of 10´10 km2 and with a network distance of 200m and then in the range of 50´50 km2 and with a network of 1000 m in the statistic period of 12 months and for a average time of 1, 3, 8 and 24 hours, one-month and one -year statistical period at the height of 1.5m of the Earth's surface was determined and the distribution of VOCs in the area was simulated and displayed by GIS software.Results: The results of Tanks software showed that the studied Tanks were annually emitted 1485801.26 tons VOCs in which the Tanks with external floating roof 99.98% and with fixed vertical roof 0.017% were contributed. The results of AERMOD software also indicated that maximum concentrations of VOCs occur in the area 10´10 km2 in cold seasons. This phenomenon is due to reduce of mixing depth and resulting in the formation of the inversion phenomenon.Conclusions: This work can help plant engineers to decide on an appropriate strategy to control VOCs. Employing the Tanks with fixed vertical roof and modification of operational pattern could lead to a reduction of VOCs emissions and eventually affect the economical, ecological and hygienic aspects.

One way to reduce the effect, of water hammer in hydraulic conduits is to build a proper surge tank. Surge Tanks dissipate the mass oscillation and reduce the transmitted pressure into hydraulic conduits. The design of Differential Surge Tanks usually includes the proper determination of diameter of the main tank and the riser, the heights of the main tank and the riser, and the area of orifices such that they guarantee the acceptable hydraulic performance. In this paper, the design of differential surge Tanks has been formulated in the form of an optimization problem in which the objective function is to minimize the total cost. Hydraulic conditions that have to be satisfied for a good performance of the system, comprise the constraints of the problem. The optimization problem has been solved using the Barrier method. The outputs are the basic design parameters that make detailed design of surge tank possible. To show the capabilities of the method, the surge tank of Appalachia dam has been designed by the proposed algorithm and compared to similar design of other research.

Risk assessment of probable hazards, is one of the major stages for upgrading safety level of existent process or a process in design phase. Risk assessment is a method for deciding is safety upgrading of a unit economical or not. In developed countries, risk assessment is essential for process unit. In this paper in order to introduce risk assessment, its implementation steps such as hazard identification, consequence modeling and risk calculation method such as risk matrix and F-N curve have been discussed. Consequence modeling of hazards such as fire, explosion and toxic releases, which may occur due to human error or failure of equipment, is an important stage of risk assessment that nowadays carried out by computer softwares. At last, a case study of risk assessment has been studied for ammonia storage Tanks of a petrochemical complex by using software PHAST for consequence modeling.

A finite element analysis is presented for sloshing and impulsive motion of liquid-filled conical Tanks during lateral anti-symmetric excitation. The performed analyses led to the development of a number of charts which can be used to identify the natural frequency, the mode shapes of conical Tanks for both fundamental and the cos (q) -modes of vibration. Conical tank geometry was described with several parameters namely, bottom radius (Rb) total height of liquid (h), angle of inclination of the Tanks (qi), as variables. Numerical result of the free vibration was obtained for the cases of conical Tanks with qi=0 and compared with existing experiments and other predicated results, showing a good agreement between the experiment and numerical results.

In this work, a series of three-dimensional unsteady numerical simulations are performed to study the stability and interface dynamics of a thermocline-based lab-scale single tank Thermal Energy Storage system (TES). The stability of thermocline is analysed by introducing relatively cold fluid for a short period at the inlet of the TES. Numerical simulations are performed for three inlet flow disturbances (weak, medium and strong) and three stratification levels (sharp, moderate and large). The fluid injected at the inlet rolls-up and interacts with the thermocline which causes spatio-temporal disruption of the stable stratification inside the TES. It was found that the three-dimensional simulations bear some resemblance to the two-dimensional case but also show crucial differences. The propagation of the injected cold fluid and the subsequent interaction with the thermocline are analysed. A wide gamut of flow structures is identified inside the TES depending on the degree of stratification and level of disturbance. Finally, the oscillatory nature of interface and associated mixing mechanism are addressed. The simulation indicates that the oscillations at the interface are through the successive generation of countersign vorticity which retards/suppresses the propagation of the vortex ring. In the case of large interface, internal waves are generated by the periodic array of vortices which generates a standing wave pattern near the Brunt-Va ̈isa ̈la ̈ frequency‎.