Blockages in water supply systems can arise from diverse causes, leading to pollution, energy loss, and reduced system performance. Detecting and addressing these Blockages is crucial for managing pressurized systems like water supply and pipe networks. Analyzing pressure signals is a common method for detecting defects, with transient pressure signals being particularly effective compared to steady-state signals. This study focuses on experimentally investigating the impact of extended Blockages on pressure signal characteristics in viscoelastic pipelines within the time and frequency domains. Elastic Blockages of varying lengths and diameters were used in a laboratory experimental model of a viscoelastic pipeline. The findings reveal that Blockages cause changes in the pressure signal shape, resonance frequencies, and phase in different domains. These changes are more pronounced with longer and higher percentage Blockages. Increasing Blockage length amplifies phase shifts and wave reflections, with pressure increase delayed by damping. Higher Blockage percentages induce phase shifts and amplitude reflections during transient flow. Transient flow intensity affects only amplitude, not phase, with more pronounced reflections at high intensity. Blockage location influences the distribution of phase and amplitude frequencies. Geometric changes induce phase shifts and alter amplitude frequencies, while hydraulic characteristics solely impact amplitude.

Stepped spillways are one of the types of weirs used in waterway systems. This structure is used to discharge measurement, energy dissipation, and water aeration. Due to engineers' tendency towards environmental sustainability and not manipulating natural landscapes, porous spillways made of stone in the form of gabions are a suitable alternative to impermeable concrete spillways. These spillways have technical, economic, environmental, and hydraulic priorities compared to conventional concrete stepped spillways. Porous spillways are a suitable alternative to the usual concrete spillways in water transmission and distribution systems due to their high hydraulic and technical performance on the one hand and negligible negative environmental impact on the other hand.In this research, the hydraulic performance of the porous stepped spillway under free flow conditions has been investigated in a laboratory manner. This research investigates the effect of different variables including flow rate, upstream Blockage, and porosity, on the discharge coefficient of the porous spillway. The materials used in the porous spillway were selected from four gradations between 1.13 and 4 cm with a uniformity coefficient close to 1. Each porous spillway was tested for seven Blockages between zero and 100%. Also, the results were compared with a solid stepped spillway model with and without Blockage. In the following, it has been extracted to present the empirical relationship of the discharge coefficient in these spillways under Blockage conditions, using the dimensional analysis of effective dimensionless parameters under free flow conditions.Finally, in the final part, based on the dimensional analysis, two empirical relationships are presented using SPSS and GEP (gene-expression programming) for calculating the free flow discharge coefficient for porous stepped spillways.The results showed that the free flow discharge coefficient increases with the size of the filling material. The percentage increase in discharge coefficient for porous stepped spillways is approximately 34 to 230% higher than that of solid spillways. Unlike solid spillways, whose free flow discharge coefficient increases with increasing the flow rate, in porous stepped spillways, the trend of free flow discharge coefficient changes in low flow rates is downward. With an increasing flow rate, it gradually becomes horizontal and then increases with a slight slope. As the Blockage increases, the flow coefficient in the porous stepped spillway gradually decreases. In Blockages above 80%, the flow coefficient of the porous stepped spillway is insignificantly different from the solid stepped spillway. In the solid stepped spillway, in the percentage of obstructions below 80%, the obstacle does not affect the free discharge coefficient. The presence of Blockage upstream of the porous stepped spillways sometimes reduces the discharge coefficient by more than 70%. The extraction of empirical relationships based on the GEP meta-heuristic model has higher accuracy than those extracted from the nonlinear multivariate regression using SPSS. The average error of the relation of the GEP porous stepped spillway free discharge coefficient was 4%, and the nonlinear multivariate regression model was 7%.

Tehran Research Reactor (T.R.R.) is a pool-type, 5 MW thermal research reactor. One probable event is that if some external objects or debris fall down into the reactor core and cause obstruction of the coolant flow through one of the fuel assemblies, decreasing the surface flow area, ceases the coolant flow, and also raises the fuel and sheaths temperature. Thermal hydraulic analysis of this event has been studied using RELAP5 system code. This report is related to the partial and total obstruction of a single Fuel Element (F.E.) and cooling channel of 27 F.E. equilibrium core of the T.R.R. Such event may lead to severe accident for such type of research reactors, since it may cause a local dry out and eventually loss of the F.E. integrity. Two scenarios are analysed in order to emphasize the severity of the mentioned accident. The first is a partial Blockage of hot F.E. which is considered for four different obstruction levels of the nominal flow area: 25%, 50%, 75% and 93%. The second is related to an extreme case which consists of the total Blockage of the same F.E. The reactor power is derived through the kinetic point calculation in the RELAP5 code. The point kinetic feedbacks including the fuel temperature (Doppler coefficient) and the coolant density coefficient have been considered through the applied model. The main results obtained from the RELAP5 calculations are as follows: 1. In case when the flow Blockage is under 93% of the nominal flow area of an average F.E., only the increase of the coolant and clad temperatures are observed with no integrity of the F.E. consequences. The mass flow rate remains sufficient enough and cools the clad safely 2. In the case of a total obstruction in the nominal flow area, it is seen that the severe accident is due to dryout conditions and reaches promptly, while melting of the cladding occurs.

Turbine blades are one of the most sensitive and important hot parts of gas turbines, so that the efficiency and life of turbines are directly related to the operation of these components. Therefore, to prevent damage caused by high temperatures, they must be properly cooled. The common method of cooling these parts is to pass the cooling fluid through their complex internal channels. Nondestructive testing of thermography, is one of the new methods for detecting imperfections in these cooling paths which is considered in this article. Thermal loading is applied in an active manner by hot steam generator system. In order to identify the capability of this system in the detection of the residuals in the cooling system of blades, 3 kinds of different blades are studied and tested using active thermography. Results show the appropriateness of the system in detection of the Blockages in all three blades. But it worth to notify that the success of the system is strongly related to the best detection of the system parameters as steam pressure, temperature and Fluid flow. So, the best parameters are chosen as: pressure of 2bars, ambient temperature of 25 oC and the maximum fluid of the hot steam.

Due to the problems of hydraulic structures at blocking bodies in debris flows this research has been carried out. Hence, in this study the effect of the trap drop bodies such as logs and branches of trees on piano key weirs at individual step was considered. The debris flows, decreasing in discharge capacity and raising the water level can be expected in the piano key weirs. The experiments of this research were performed on two piano key weirs with 10 and 30 cm in height on an experimental flume, 12 meters in length, 80 cm width and height of 70 cm. On these weirs three parapet walls with 2.5, 3.5 and 4.5cm height were installed. As a hydraulically criterion, Individual branches and logs in debris flow were studied. Individual experiments showed that the diameter and the upstream head of spillway affect the likelihood of Blockage. However, both the increasing in diameter and head decreasing, increase the Blockage. Therefore the probability blocking increases in D/H>1 and it decreases at D/H<0.3.

Introduction: Culverts are common structures for runoff drainage system in the design and construction of roads and railways, in both urban and rural areas. Due to the nature of runoff flow, large amount of sediments, foliage, urban waste and debris materials may accumulate in the entrance of culverts, particularly in flood events. Blockage in the culvert’ s entrance can result in a significant increase in flood risk, through elevated flood levels and diverted flow paths through the urban or rural areas (Rigby et al., 2002). Sudden Blockage in a runoff system is also one of the common problems. The study of culvert’ s Blockage would be useful in the prediction and prevention of flood hazard in the vicinity of drainage systems. Current study deals with this problem in box culverts. Blockage effects on the upstream water level were investigated using both experimental and numerical modeling. The FLOW-3D model was chosen, because the sufficiency of this model for such flow conditions was already reported by several studies such as Abad et al. (2008), Salamat Ravandi (2011) and Gunal et al. (2019). Methodology: Experimental tests were conducted in Hydraulic Laboratory of Water Engineering Department in Bu Ali Sina University, Hamedan, Iran. The box culvert models made of glass and smooth water pipes used as circular culvert models. The experimental setup includes a glass wall flume with 10m length, 0. 5m width and 0. 6m deep. Rectangular plates in different sizes were used in order to make sudden Blockage into the culverts. An extensive experiment tests was conducted under different flow condition and Blockage scenarios, and 21 experimental data sets were provided. The FLOW-3D model, Version 11. 3, was performed on the main server of Water Institute at the University of Tehran, and adapted to the experimental data sets from this study. The stability and sensitivity of this model have been tested according to: mesh cell size, simulation time step, turbulent model, and culvert hydraulic characteristics such as wall roughness. The simulation convergence was achieved with an efficient simulation time step of 80 seconds. Three different mesh blocks were used for pre-simulation cases, and a block in block with 1. 0 cm and 0. 5 cm mesh cell sizes were chosen as the best meshing scenario. The RNG was found to be an appropriate turbulence model. The slope of culvert barrel was changed from horizontal to 0. 005 in the flow direction, and the roughness coefficient modified from 0. 00085 m to 0. 001 m in the culvert barrel. The relative error of simulated water levels and discharge for calibrated model were to be in the order of acceptance ranges, and the simulation FLOW-3D model was adjusted as an efficient and reliable tool. The FLOW-3D model was then calibrated and verified using the experimental data sets, and was used to simulate different flow conditions into the culverts, under different entranceBlockage scenarios. Results and discussion: Effect of the inlet Blockage on upstream water level was tested for three flow rates (the design discharge of 27. 5 lit/s, and two lower discharges of 10. 5 lit/s and 16. 5 lit/s), in four different sizes of inlet Blockage (B). Simulation results showed a good agreement in upstream backwater level in all cases. In the case of flow with 16. 5 lit/s, upstream water level raised from 28. 5 cm in non-blocked inlet to 31. 4, 34. 2 and 38. 5 cm in presence of 20%, 40% and 60% blocked inlet area, respectively. The rate of the upstream water level increase (DHu) against the reduced inlet area (1-B) represents a higher rate for discharges smaller than the culvert-design discharge. The evaluated equations for upstream water level enhancement were: 𝐷 𝐻 𝑢 =-0. 48(1-B)+45. 089 (1) 𝐷 𝐻 𝑢 =-0. 82(1-B)+75. 663 (2) in which, Eq. (1) is for design discharge and Eq. (2) for the smaller discharges. Blockage has been affected flow in the barrel and in the downstream of the culvert. Investigation of turbulent characteristics and shear velocity values in both the barrel and downstream indicated the impact of blocked inlet. Turbulent energy of flow in the 60% blocked-inlet area was 5 times greater than that of non-blocked inlet for the design discharge. Also shear velocity in the same Blockage situation increased by 2 times in downstream which results in a greater scouring power of the flow downstream. Sorourian et al. (2015) reported this phenomenon with even higher scour downstream of blocked culverts. Maximum value of shear velocity increased with the increase level of Blockage in the all flow condition, however in the design discharge it seems to be constant for Blockages greater than 40%. Conclusion: The FLOW-3D model was calibrated and validated to simulate the flow into the culverts. Influence of inlet obstruction on the upstream water level and flow characteristics into the barrel and downstream of the culvert was investigated. The results show a linear increase in the upstream water level by decreasing the percentage of culvert inlet. The upstream water level for the design discharge was lower than the other tested discharges. Changes in turbulent flow properties and shear velocity inside the barrel and downstream were also investigated in the presence of obstruction. Shear velocity increased 3 times in the presence of 80% Blockage for 10. 5 lit/s. and for the design discharge (27. 5 lit/s) with 60% inlet Blockage increased 2 times. The turbulence energy for the design discharge has also increased by about 5 times. The present results confirm the previous studies on the effect of the culvert inlet obstruction on the geometry of the scour hole downstream of culverts.

This paper investigates numerically the flow and heat transfer in air (Pr=0.71) by mixed convection past a heated square cylinder under aiding buoyancy effect in a confined channel. The numerical simulations are performed in the range of parameters 20£Re£45 and 1.61x103£Gr£6.33´103 for a fixed Blockage ratio D/L of 0.1. The combination in the present study of these two Re and Gr parameters is reduced so that the Richarson number varies from 0,8 to 8, in order to neglect neither free convection (Ri<0.1) nor forced convection (Ri>10). The steady two-dimensional governing equations are solved by the finite volume formulation using the open source OpenFoam ® code. The representative flow structure, isotherm patterns and local Nusselt number evolution are presented and discussed. The effect of both the Reynolds number and the buoyancy parameter on the fluid flow and the heat transfer are also analyzed. It is found that the wake region size strongly depends on both Reynolds and Grashof numbers and this region is shown to increase in size increasing the Reynolds number and/or decreasing the Grashof number. Moreover, increasing the Reynolds number leads to a heat transfer enhancement more pronounced on the front face of the obstacle, whereas increasing the Grashof number leads to a heat transfer enhancement more pronounced on the side faces.

Culvert is one of the main structures in drainage systems at crossing with railways and roads. Flood flows, along with the transport of sediments and floating debris, can cause Blockages and backwater, thereby reducing flood flow capacity. The main purpose of this study was to physically model and numerically simulate the effects of different percentages of Blockages on culvert hydraulic characteristics. Blockage effects investigated in 21 laboratory experiments. Complementary tests were carried out with the use of OpenFOAM numerical tool box. Three Blockage scenarios have been numerically simulated with 20, 40 and 60 percent coverage of inlet area. The numerical model was calibrated using the experimental data. The simulation results of OpenFOAM in different culvert inlet Blockages indicated that the LES turbulent model is more adaptive than RAS models. The main flow characteristics were compared with the corresponding simulation results from the trademark FLOW-3D model, and showed good agreement for verification purpose. Results for different flows (i.e. 40, 60 and 100 percent of the design discharge) showed that the increasing rate of upstream water level is not identical, and is higher for the lower discharges. Blockage also intensifies turbulence and shear stress levels in the outlet section. For design discharge, the 40 percent Blockage resulted in the increase of shear stresses up to 10 times, which cause severe scour in downstream channel.

Hydro-suction is an appropriate and economical method for dredging deposited sediment at reservoirs. In this study, a physical model was made and some experiments were designed to analyze the ranges of Blockage depth in different hydraulic conditions. In the model, 80 tests were conducted using three diameters (d), three water heads (H) and different diving depths of pipe inlet (Z) from the sediment level to the Blockage depth. In general, the results indicated that the more increase in the diving depth, the higher hydro-suction efficiency. In some of the experiments, a vortex flow was observed under the pipe inlet. The results indicated that the formed vortex flow have a positive effect on the hydro-suction efficiency. The results associated to the Blockage depth approved that hydro-suction systems with larger pipe diameter and more water head have a greater Blockage depth (Zb). The Froude number (Fr) analysis indicated that an increase in Fr would cause increment efficiency and Blockage depth of hydro-suction system. Subject to a constant pipe diameter, the results revealed that increasing the H/d ratio equal to 66. 66 and 133. 33%, would enhance the Zb/d ratio equal to 58. 89 and 112. 22%, respectively.