Sharif Digital Repository

Labyrinth side weir is one type of weirs, which can be used when the length of opening is limited. One of the advantages of labyrinth side weir is to increase the effective length of weir perpendicular to the flow and, therefore, diverting more discharge with the same flow depth and weir geometry (opening and height). Discharge coefficient should be determined to investigate the weir performance and estimate the discharge passing over the weir. In this paper, hydraulic performance of labyrinth side weir with asymmetric geometry has been experimentally studied. The change to the geometry of ordinary labyrinth side weirs causes an increase in the effectiveness of the length of weir as being... 

Side weirs are hydraulic control structures widely used in irrigation, drainage networks and waste water treatment plants. These structures can be used for adjusting and diverting of flow with minimum energy loss. In spite of many studies were carried out on rectangular side weirs, the studies on oblique and labyrinth side weirs are scarce. In this study, based on the experimental data from more than 210 laboratory tests and through using the multivariable nonlinear partial least square (PLS) method, two nonlinear equations are presented for discharge coefficient CM of triangular labyrinth side weirs with one and two cycles. The obtained empirical equations relating CM with the relevant... 

Side weirs are widely used for level control and flow regulation in hydraulic engineering applications such as irrigation, land drainage, and sewer systems. These hydraulic structures allow a part of the flow to spill laterally when the surface of the flow in the main channel rises above the weir crest. The supercritical flow over a side-weir is a typical case of spatially varied flow with decreasing discharge. This study is aimed at investigating the variations of specific energy along the side-weir using experimental results. Some diagrams have been presented in terms of dimensionless ratio of diverted discharge to total discharge. These diagrams which can be used in the design of side... 

Free surface vortex and air entrainment are not favorable experiences in hydropower and pumping projects. While complete omission of vortex and air entrainment is not always cost effective, partially weakened free-surface vortex flow is more economical and practical. Hence, in this study, a comprehensive set of experiments were conducted to partially reduce vortex strength and air entrainment at vertical pipe intakes, using rectangular anti-vortex plates. This phenomenon results in increasing water discharge compared with a corresponding free-surface vortex for the same water depth, i.e. in cases of shaft spillway. The plates were used as singles and in pairs and placed symmetrically and... 

The study of air-water, two-phase flows in hydraulic structures such as pressurized flow tunnels, culverts, sewer pipes, junctions, and similar conduits is of great importance for design purposes. Air can be provided by vortices at water intakes, pumping stations, aerators, steep channels, etc. Under certain conditions, air may also be introduced into pressurized intake systems, which may form large bubbles in portions of the pipe. The bubbles may, in turn, cause an unstable slug flow, or other flow patterns, that leads to sever periodic transient pressure. In this paper, an experimental model (a circular and transparent pipeline, 90 mm in ID and 10 m in length) is used to predict pressure... 

Thee enclosed basin has certain natural frequencies of seiche, depending on the geometry of the water boundaries and the bathymetry of water depths. Therefore, the variation in the water surface at a point becomes irregular, as caused by the combination of several natural frequencies, which may be considered as the superposition of sinusoidal frequency components of different amplitude. This paper is mainly concerned with the motion of an incompressible irrotational fluid in a closed rectangular basin with internal impervious barriers. An analytical solution is presented for predicting the characteristic of generated waves in these types of basin. The equations of free water surface... 

A rectangular labyrinth weir has a very good flood release capacity as well as strong economical and structural advantages. In this study, combined analytical and experimental investigations were undertaken for a rectangular labyrinth weir. The analytical model is based on the synthesis of general weir equations and spatially varied flow dynamic equations. A comprehensive set of experiments led to characterisation of the flow behaviour for low and high heads over the weir and indicated the influences of weir geometry on the release capacity. The results show that this type of weir represents an effective weir alternative and could be five times more efficient than a corresponding traditional... 

A comprehensive set of experiments was performed on weirs placed obliquely in a rectangular open channel. The main objectives were to investigate the effect of the weir angle relative to the approach flow direction on the behaviour and the hydraulic flow characteristics and to examine methods such as using upstream guide vanes and inclined aprons to increase the effective oblique weir length. Results indicate that by increasing the oblique angle, the effective length of the oblique weir increases significantly. Relationships are provided for the threshold submergence and the effective length of the oblique weir. Design recommendations are also presented for the use of guide vanes and... 

The study of water hammer in air-water, two-phase flows in hydraulic structures such as pressurized pipelines and tunnels, siphons, culverts, and junctions is of great importance for design purposes. Water hammer if combined with a periodic slug flow would lead to severe periodic transient pressure fluctuations inside the conduit. Laboratory experiments have been conducted to investigate waterhammer pressure inside a horizontal rectangular conduit carrying a two-phase, air-water slug flow. Tests were performed in an experimental apparatus comprising a 6.8-m-long transparent pipeline 0.06 m wide and 0.1 m high. By rapidly closing a control gate at the end of the conduit, propagating pressure... 

Air-water two-phase flow usually occurs during a sudden rise in water level at a tunnel or during the falling of the water level at an upstream reservoir while entering the conduit. When this happens, different flow patterns are generated, due to the hydraulics of flow and fluid properties. An analytical/numerical model, based on the assumption of a rigid incompressible water column and a compressible air bubble, is derived, to simulate pressure fluctuation, void fraction, air/water flow rate and water velocity in a closed conduit, including water depth at the upper reservoir, due to air bubbles becoming trapped in the water, for the highest possible number of flow patterns. It is a... 

Air in water flow is a frequent phenomenon in hydraulic structures. The main reason for air entrainment is vortices at water intakes, pumping stations, tunnel inlets, and so on. The accumulated air, in a conduit, can evolve to a different flow pattern, from stratified to pressurized. Among different patterns, slug is most complex with extreme pressure variations. Due to lack of firm relations between pressure and influential parameters, study of slug flow is very important. Based on an experimental model, pressure fluctuations inside a circular, horizontal, and inclined pipe (90 mm inside diameter and 10 m long) carrying tow-phase air-water slug flow has been studied. Pressure fluctuations... 

In the present study, methods for improving the hydraulic performance of labyrinth side weirs in a rectangular channel are reported based on model experimentation. For this purpose different arrangements and configurations of groups of guide vane plates and piles in the side weir flow field were tested. Experiments were conducted on labyrinth side weirs of different lengths and sill heights fitted in the test section of a rectangular glass-walled channel. Depths of flow were measured in both longitudinal and crosswise directions at regular intervals and their profiles were studied. It was found that the discharge coefficient of the labyrinth side weirs under these conditions gave... 

One of the sources of disturbance at intakes is the occurrence of free-surface vortices with an air core. The most common solution for avoiding air-entrainment is the use of anti-vortex devices and, especially, plates for large pipe or shaft intakes. If plates are used, then, the geometry and position of them should be studied experimentally. Since only general guidance for use of plates is available, a study for the more precise placement of plates is needed. Hence, a comprehensive set of experiments have been carried out using rectangular plates with different dimensions and at various positions with respect to the vertical outlet pipe intakes and two different pipe diameters (D = 75 and... 

An experimental investigation has been carried out to verify characteristics of pressure fluctuations inside a circular, horizontal and inclined pipeline (90mm inside diameter and 10 m long) carrying two-phase air-water flow in a controlled manner (operating at room temperature and normal pressure). The pressure fluctuation was considered to be due to interaction between the fluid and air bubble compressibility in the pipe. The fluctuating pressure was studied in detail while the flow pattern was mainly slug, wavy or stratified flow. The tests were carried out varying with time, space, water flow rate/air flow rate ratio and pipe inclination. The pressure fluctuations were measured... 

Incomplete self-similarity (ISS) concept is employed to develop the equations from existing experimental results of flow over an oblique rectangular sharp-crested weir for both free and submerged flow. The stage-discharge relationship is obtained by theoretical analysis, based on the application of the dimensional analysis and the ISS theory. For analysis, the relations were found by trial and error procedure using the SPSS mathematical computer program that estimates the relation among multi-variable functions. Thus, equations to estimate the flow characteristics for both free and submerged flow are proposed. The results show a better compatibility with the experimental data than the... 

The thermo-mechanical behavior of energy piles has been studied extensively in recent years. In the present study, a numerical model was adapted to study the effect of various parameters (e.g. heating/cooling temperature, head loading condition and soil stiffness) on the thermo-mechanical behavior of an energy pile installed in unsaturated sandstone. The results from the simulations were compared with measurements from a thermal response test on a prototype energy pile installed beneath a 1-story building at the US Air Force Academy (USAFA) in Colorado Springs, CO. A good agreement was achieved between the results obtained from the prototype and the numerical models. A parametric evaluation... 

Despite various applications of hydrogels, they have poor gel strength and low resistance against crack propagation which lead to the limitation of their applications. For overcoming this inherent weakness, the current study has focused on the simultaneous utilization of interpenetrating polymer network (IPN) structure and nanocomposite hydrogels. It is known that IPN and nanocomposite gels can improve gel strength. The combination of IPN and nanocomposite structure was developed in hydrogels for improving gel strength. For this purpose, bentonite was successfully modified with a cationic surfactant, (3-methacrylamidopropyl) trimethyl ammonium chloride (MAPTAC), as intercalate, and... 

Despite the various uses of hydrogels, one of their weaknesses is the poor gel strength. To overcome this restriction, the current study has focused on simultaneously employing an interpenetrating polymer network (IPN) structure and nanocomposite hydrogels. Through this approach, the influence of nanofiller in the single network and IPN hydrogel properties was also studied in detail. For this purpose, a novel full interpenetrating polymer network (IPN) hydrogel nanocomposite based on 2-acrylamido-2-methylpropane sulfonic acid (AMPS)/acrylic acid (AA)–sodium acrylate (AANa) was synthesized in two steps through a facile solution polymerization with incorporation of modified bentonite (MBE) as...