The effect of operational and geometrical parameters on the Jet pump efficiency were determined experimentally and numerically. Numerical investigation was held firstly to determine the effect of diffuser angle, mixing chamber length, pump area ratio and driving nozzle position on the efficiency of Jet pump. Commercial computational fluid dynamics (CFD) solver ANSYS FLUENT R 15. 0 using SST-turbulence model was used. The numerical results showed that Jet pump efficiency increases with decreasing both of diffuser angles and mixing chamber length up to a certain value and then pump efficiency decreases. Also, Jet pump efficiency increases with increasing pump area ratio up to a certain value and then pump efficiency decreases. It was found that maximum numerical efficiency is 37. 8 % for pump area ratio of 0. 271. In addition, the numerical results showed that the optimum relative length of mixing chamber is 5. 48 and the optimum value for diffuser angle at which the efficiency is a maximum value is 5º . Experimental tests were conducted to obtain the effects of various operational and geometrical parameters on the performance of the Jet pumps. A test rig was constructed using the optimum design from the numerical results. The CFD’ s results were found to agree well with actual values obtained from the experimental results.

During the operation of a water-Jet pump, cavitation generates noise and vibration, causes surface erosion of the hydraulic components, and reduces the performance of the pump. Suppressing the cavitation is beneficial for improving the stability of the energy system of the water-Jet pump. In order to investigate the mechanism of cavitation suppression and optimize the cavitation performance of the water-Jet pump, the unsteady cavitation flow was studied by numerical simulation and experiment in this paper. Using high-speed photography technology on a closed test platform, the cavitation flow structures in the water-Jet pump were captured, and the physical process of cavitation evolution was revealed. Based on this, in order to obtain the cavitation flow characteristics closely related to the cavitation performance, the cavitation flow in the impeller tip clearance was studied by numerical simulation, the vorticity variation rate in the tip clearance was analyzed, the effects of different cavitation conditions on the vorticity in the tip clearance were revealed. Additionally, this paper analyzed the pressure pulsation characteristics of the tip clearance under different cavitation conditions, and emphatically analyzed the influence of the cavitation flow on the tip clearance pressure pulsation.

This paper presents a novel technology for desilting dam reservoirs in a continuous and controlled manner. The proposed technology utilizes a suction system that incorporates two pumps: a dredge pump for removing and transporting sediments, and a high-pressure submersible pump for generating water Jets to create turbulent flows in the bottom sediment layers. To evaluate the effectiveness of the proposed technology, local experiments were conducted in two cases: with the suction pump alone and with the addition of water Jet flow. These experiments were conducted at the end of the reservoir of Zenouz Dam, which serves as a case study. The collected sediment mass was measured over time, and the resulting mass-time graphs revealed three distinct phases: ascending, descending, and constant. Based on the local conditions, soil properties and dredging system, the maximum sediment mass removal rates by the pump were 100 g/s for the case without water Jet and ranged from 200 to 430 g/s for the case with water Jet. Dimensional analysis was performed to determine the relationship between sediment yield and parameters such as sediment volumetric flow rate and sediment mass flow rate. The results showed that the variations of sediment discharge followed the same characteristic curves (discharge - height) of the pump. The average de-sedimentation efficiency was found to be 7-14% and 2-3% for the experimental pump modes with and without the Jet flow, respectively. This indicates that the water Jet flow has a significant influence on enhancing the de-sedimentation efficiency, and without it, the sediment removal would not be feasible.

In the current research, numerical analysis was used to investigate the flow behavior through the axial Jet-pump with various mixing chamber configurations (straight pipe and straight pipe-diffuser-straight pipe) in the presence of inlet swirling flow and its influence on the pump performance. The effects of introducing inlet swirling flow in the suction chamber and in the motive flow line, are numerically investigated. The optimum swirl angle in the suction chamber is found to be 45o which yields the maximum pump efficiency of 38.08 % for the second configuration of mixing chamber system. Consequently, the inlet swirl generally decreases the desired mixing chamber length. Additionally, the new mixing chamber configuration enhances the mixing process compared with the traditional mixing chamber. On the other hand, imparting a swirl in the motive line inversely affected the pump performance. Engendering a swirl in suction chamber causes an improvement by 12.76 % in the pump efficiency compared to the same pump configuration without swirl. The optimum tail pipe diffuser angle is found to be 3o.

Background and Objectives: Coronary artery bypass grafting (CABG) is usually performed through cardiopulmonary bypass (CPB). CPB, However, has been associated with several adverse effects. Recently, off-pump CABG technique is offered as an alternative to the standard on-pump CABG technique. The purpose of this study was to evaluate the safety of the off-pump technique by estimating serum enzymes e.g. Creatin Kinase (CK), CK-MB, Lactate dehydrogenase (LDH), Aspartate Transaminase (AST), measurement of cardiac troponin I and some postoperative complications.Materials and Methods: Ninety patients (75 males and 15 females) with angiographically defined CAD admitted to Shahid Madani Heart Hospital in Tabriz for coronary artery bypass grafting were selected. The off-pump technique was performed in 50 patients with mean age of 58‏. In 40 other patients with mean age of 56, the on-pump technique was applied. The blood samples were collected from the patients before, 6, 12 and 24 hours after the operation. The activities of CK, CK-MB, LDH, AST in all serum samples were measured by Cobas Mira autoanalyser, and cardiac troponin I concentration also was measured by Evernest model 3200 motion. Data regarding patient age, sex, familial history of cardiovascular diseases, number of vessels grafted, procedural time, transfusion of blood and blood pressure were recorded for the both groups of patients. Postoperative data regarding the incidence of complications including myocardial infarction, need for inotrop adminstration and death were also recorded.Results: In this study the activities of serum enzymes such as CK, CK-MB, LDH and AST after on-pump CABG technique were higher than those of off-pump technique (P< 0.05 in all cases). The levels of troponin I were significantly higher after on-pump CABG throughout the entire measurement period (P<0.01) compared with off-pump procedure. In both groups of patients no myocardial infarction was occurred during operation. In the off-pump technique procedural time was shorter and transfusion of blood was less than those of on-pump technique, but no difference was noticed among the other recorded data.Conclusion: Significant reduction in the release of enzymes and troponin I during operation by off-pump technique suggests that the technique causes less myocardial injury. On the basis of little changes in the activities of cardiac enzymes and troponin I in serum and presented data including a marked decrease in blood transfusion and shorter procedural time, it is concluded that off-pump CABG is a safe and effective technique in selected patients with appropriate coronary lesions.

in this research, their effects on the flight of airplanes were investigated. The study area is the country of Iran, and the flight routes of Kermanshah, Ahvaz and BandarAbbas to Tehran. The research data includes maps of the Vertical Transect (profile) of the Jet stream, the daily average of the Zonal wind (U-Wind) and meridional wind (V-Wind) components for the winter period of 2018 through NOAA/NCEP environmental databases. Also, flight route information was received from FlightRadar24 and Flightaware systems. First, by using Vertical Transect maps, the days containing strong U-Wind were extracted, and the average position of the core of the Jet Streams in the Zonal and meridional wind components, the Tropospheric level of 200 HP was detected. The list of flights was prepared, and the Zonal Wind maps were produced. Finally, the height of the flights was compared with the level of the currents of the Jet Streams, and the influence or lack of influence of the Jet Streams on the flights was studied. According to the results of the research, all the Jet Streams caused turbulence for all flights, and they caused a decrease in the speed of flights between Ahvaz and BandarAbbas to Tehran and an increase in the speed of flights between Kermanshah and Tehran according to the direction and type of Jet Streams. It was also found that all the Jet Streams had a speed of more than 90 knots, so the capacity to create tension and turbulence such as CAT was seen in them

This paper investigates the influence of a weak-Jet on the development of a turbulent axisymmetric strong Jet. A parametric study is carried out to evaluate simultaneously the effect to the Jets-spacing (S/D=3 and S/D=7. 5) and their velocity ratios in range 0≤ λ ≤ 1. The mixing phenomenon is studied numerically by the finite volume method using the 3D-RANS second-order model, which gives a good agreement with the available data. Three distinct regions of this type of Jets interaction are evidenced. This study confirms that the Jets spacing affects strongly the converging region and has a minor effect on the combining region. It is found that the weak Jet attracts the strong Jet and the combining region extends from 30D to 40D where the self-similarity of a single Jet is obtained. The Jet width decreases when velocity ratio and Jets spacing augment. In the combining region, in comparison with the free Jet, it is found that the addition of a weak-Jet increases the decay rate of the centerline velocity.