Sharif Digital Repository

Selective withdrawal is withdrawing water with desired quality from a reservoir and has many applications in water quality management of reservoirs. Topographic effects such as a sill alter the withdrawal layer properties. In this study, the effect of a sill on selective withdrawal of a two-layer fluid through a line sink at the bottom of a rectangular reservoir is studied using two-layer hydraulics theory, numerical model and laboratory experiments. Experiments were done for studying surge, and the results are compared with two-layer hydraulics theory and numerical model. After reservoir gate is opened, some disturbances upstream of sill lead to creation of a surge. The results show this is... 

Numerical and laboratory models were used to investigate gravity exchange flow caused by spatial heterogeneity in water temperature, through emergent vegetation with varying diameter along their height (denoted by the parameter ) causing varying stem frontal area along vertical axis. Numerical model was used to anticipate flow characteristics and their alterations relative to non-dimensional vegetation diameter ratio. A set of Teflon dowels with various heights was used to simulate considered vegetative cross-section changes along vertical axis. Interface profile, toe velocity and flow rate were studied. Interface height and flow rate were inquired near the gate where expected to be... 

Settlement and tilt of structures due to liquefaction of subsoil layers is a major cause of damage during earthquake. Among different soil profile type, two layered soil is very common which was reported many times in differen earthquakes. Settlement of structures was measured by means of empirical methods before which were not viable because they do not consider different effective parameters. Consequently, different experimental studies performed to shed light on different aspects of liquefaction phenomena. In these studies, researchers consider some of the main parameters which have effect on the soil, otherwise, they neglected some important factors. So, numerical procedure is more... 

The planet earth has a variety of periodic motions in space, with periods varying from a day to thousands of years. The essence of studying the rotational motion of our planet is closely related to various phenomena such as, the long term variation of the earth’s climate, volcanic activities, ice ages, earth’s past dynamics, etc. furthermore, understanding the precise motion of the earth is an essential part of our astronomical observations. One of the many kinds of rotational motions, which has attracted many attentions is called Chandler wobble. Any irregularly shaped solid body rotating about some axis that is not aligned with its figure axis will wobble as it rotates. Although it has... 

The accuracy, speed, and ability to do work in hazardous environments has led to the development of robots in everyday life. Accordingly, research on quadruped robots for use in military environments is expanding. Designing control algorithms for walking and stepping on quadruped robots is one of the most important parts of the design of these robots, which creates complex movements despite the lack of sophisticated equipment in the robots. One of the robot gaiting control methods is dynamic based method that is based on the robot’s dynamics and resistant to perturbations. Trajectory based method is another robot gaiting control method that is inspired from CPG algorithm and has learning... 

In nature, tidal currents are visible in gorges and in saltwater and freshwater collisions. In the study of behavior of different types of flow, it is usually assumed that the pressure is hydrostatic and the equations are solved based on this assumption. In the Approach Controlled regime observed during the double layer in 1993, the modeling performed using the equations derived from this assumption did not fit the results of the experiments. This demonstrates the inability of the hydrostatic pressure assumption to solve this particular regime. Hence, the equations were written on the basis of non-hydrostatic pressure and then the observed results were in accordance with the results of the... 

The motion of a surface wave in a two-layer fluid can lead to generation of sub-harmonic interfacial waves through a nonlinear resonant interaction mechanism. The interfacial waves grow exponentially in time until they reach a maximum amplitude and then oscillate down to a final amplitude, referred to as ultimate amplitude, in long term. This may lead to considerable mixing of the layers in miscible fluid and increase the thickness of the diffuse layer. Experiments show that the diffuse layer causes frequency shift and decreases the ultimate amplitude. In this study, long time behavior of interfacial waves in a two layer immiscible fluid was investigated. A two-layer immiscible system... 

In this research, two-layered sheets of copper and stainless steel 316 were produced by roll bonding. These sheets provide a combination of properties of copper and stainless steel; including high strength, thermal conductivity and corrosion resistance, as well as low weight and cost-efficient means of production. The effects of thickness reduction, different preheat temperatures and varying heating conditions after rolling on bond strength were studied. In some specimens, an aluminum sheet was used as a middle-layer, which significantly improved the bonding quality. In order to observe the interface of the bonded specimens, optical microscope images of the cross sections were studied.... 

Determination of soil bearing capacity has been a subject for both geotechnical engineers and designers for a long time and a variety of relationships have been proposed to determine the ultimate bearing capacity of homogeneous soils. One of the most primitive equations in bearing capacity of foundations, which was Based on prandtl's (1920) bearing capacity, with some modifications, was proposed by Terzaghi. In many lands, the soft clay layer Located in a low depth of subsurface soil profile. Either the foundation should be laid in greater depth on the stiff clay or a layer of compacted sand can be used to improve the ultimate bearing capacity. Most of the recent works, which have done so...