For the purpose of automatic generation control (AGC), a portion of the propeller hydro-turbine units in China is adjusted to operate within a restricted range of 75%-85% load using computer-controlled AGC strategies. In engineering applications, it has been observed that when a propeller hydro-turbine unit operates under off-design conditions, a large-scale Vortex rope would occur in the draft tube, leading to significant Pressure fluctuations. Injecting air into the draft tube to reduce the amplitude of Pressure fluctuations is a common practice, but its effectiveness has not been proven on propeller hydro-turbine units. In this study, a CFD model of a propeller hydro-turbine was established, and 15 cases with different guide vane openings (GVO, between 31° and 45°) under unsteady conditions were calculated and studied. Two air admission measures were introduced to suppress the Vortex rope oscillation in the draft tube and to mitigate Pressure fluctuations. The reason for the additional energy loss due to air admission was then explained by the entropy production theory, and its value was quantified. This study points out that when injecting air, it is necessary to first consider whether the air will obstruct the flow in the draft tube. Finally, based on simulation and experimental data under various load conditions, Pressure fluctuation analysis (based on fast Fourier transform, FFT) was conducted to assess the effectiveness of air admission measures. This study can provide an additional option for balancing unit efficiency and stability when scheduling units using an AGC strategy.

Elevated intraocular Pressure (IOP) is a major risk factor for the development and progression of glaucoma. Previous prospective, randomized, long‑ term studies have demonstrated the strength of IOP reduction in slowing the progression of disease. It is well known that IOP is not a fixed value but fluctuates considerably over time. Although there have been some studies on IOP fluctuation and the progression of glaucoma, whether IOP fluctuation is an independent risk factor for glaucomatous damage and disease progression remains controversial. In this article, we reviewed the definition of IOP fluctuation, and both the evidence and the speculation for and against the effect of IOP fluctuation on glaucoma progression. Although conclusions seem to vary from study to study, we considered that different studies examined different groups of patients, at different stages of disease, and at different IOP levels. Our conclusion is that these apparently disparate results are not conflicting, but rather can be viewed as complementary. In clinical care, we recommend the consideration of IOP “ modulation” rather than just IOP “ reduction” when glaucoma patients are treated. Quality‑ based IOP control may be more effective than quantity‑ based IOP reduction to prevent or retard disease progression.

Geometry of the chute blocks in stilling basins plays a significant role in size and type of these structures. One of the most influencing factors in the design of the blocks is the fluctuating Pressure which may cause fatigue on the blocks. Despite investigations conducted by many researchers, there is not enough information about the Pressure fluctuation around chute blocks in compacted stilling basins such as Saint Anthony Falls (SAF) basins. In this paper, the results of a naval experimental work and measurement of Pressure fluctuations around chute blocks of SAF stilling basins are reported. The results show that the Pressure fluctuations around the chute blocks cannot be overlooked in designing such structures. The variation of Pressure fluctuation with Froude number of incoming supercritical flow at various faces of the chute block is reported, which shows an increasing trend of Pressure fluctuation. It is also observed that the submergence of hydraulic jump will decreasingly affect the Pressure fluctuations. The trend of variations will follow different patterns at the different faces of the block.

Intense Pressure pulsations, which are caused by the Vortex rope in the runner cone and the draft tube of pump-turbines, result in vibrations and noise under partial load conditions in turbine mode and also reduce the machine’s efficiency. The most common method for reducing these fluctuations is injecting air through the shaft. This method has some disadvantages such as, negative influence on efficiency, high cost, and technical difficulties. In the present paper, the concept of locating grooves on the conic surface of runner has been investigated. In this regard, the runner and the draft tube geometry have been designed according to the specifications and the accessible information of Siah-Bishe project. Afterwards, the 3-dimensional flow field has been solved numerically, using Ansys CFX package. The numerical results have been verified by investigating their independency from grid size and comparing the results with experimental ones. Maximum difference between the proposed and the existing design’s performance is than 2 percent. The results indicate that locating grooves on the conic surface of the runner results in an increase in the flow velocity beneath the runner cone. Moreover, Pressure pulsations have been decreased and the low-Pressure area at the beginning of the draft tube shrank. The maximum amount of decrease in Pressure pulsations has been recorded in two opening positions of the guide vanes (lower than 60% and more than 90% of design point). In addition, maximum efficiency drop in the revised design is less than 0.3 percent. Furthermore, because of the rotational direction change in the pump mode, the magnitude of the tangential velocity is increased.

Introduction: Intraocular Pressure (IOP) can be influenced by several factors including corneal thickness, gender, refractive error, and the presence of diabetes mellitus. In the present study, we systematically reviewed published literature to find association between variations of IOP due to strabismus surgery.Method: PubMed and Scopus were systematically searched with the following search terms: (intraocular Pressure OR IOP) AND (strabismus) for the articles in which the fluctuation of IOP before and after strabismus surgery had been evaluated. All types of articles including case series, cross-sectional, clinical trials, and cohort studies with no time limitation were included in this study. Systematically searches, selection of articles, and the extraction of data were performed by two reviewers independently.Result: 1617 out of 1674 articles were excluded due to duplication or irrelevancy. After step by step process of article selection, 57 relevant articles were included for further evaluation. However, only 8 articles met the inclusion criteria.Conclusions: The results of this report showed that IOP may vary due to strabismus surgery, and it decreases after the surgery.

Due to the distinctive structure of the test section, the open jet wind tunnel generates low-frequency Pressure fluctuations (LFFs) within the range of typical wind speeds. These fluctuations significantly compromise the quality of the flow field in the test section. The evolution of the flow structure and Vortex is analysed through the improved delayed detached eddy simulations (IDDES). The LFFs and the control mechanism in the open jet wind tunnel of Jilin University are then studied. The interaction between the large-scale Vortex shedding at the nozzle exit and the collector forms the edge feedback, which is the main reason for the Pressure fluctuation. According to the feedback mechanism, the LFFs are suppressed using the throat gap and by improving the collector shapes. The results show that the increase of the throat gap length at the collector can significantly alleviate the Pressure accumulation inside the collector. The change of the collector shapes can control the impact area and time of the incoming flow, or produce permanent Vortex structure to affect the impact shape of the Vortex and the flow field at the collector, which allows to control the LFFs. This study lays a solid foundation for further comprehension of the aerodynamic characteristics of the open jet wind tunnels.

In this paper, fluid flow in Francis turbine draft tube is simulated with and without water injection condition in unsteady state using actual and straight diffuser geometry of draft tube. Also a new method for selecting nozzle diameter for injection is proposed. Simulation is carried out using Fluent software and k-ε and SST k-ω turbulence models in the straight and actual geometries of the draft tube, respectively. In two considered geometries, results of proposed method for selecting the nozzle diameter, which is based on the ratio of the total loss to the Pressure recovery factor, have been compared with the method used in the previous researches, which was based on the total loss calculation. Inlet boundary conditions and validation are based on the experimental data. Results show that selecting nozzle diameter is depended on the geometry of the draft tube, and using the ratio of total loss to Pressure recovery factor approach for selecting nozzle diameter will improve the size of selected nozzle diameter up to 33%, velocity fluctuations up to 16. 3% and Pressure fluctuations amplitude up to 19% in draft tube.

Vortex extrusion (VE) is a severe plastic deformation technique which is based on the synergies between high strain accumulation and high hydrostatic Pressure. Such a high amount of Pressure places a mandate to seek the method for investigation of the load under processing conditions. For this, kinematically admissible velocity field and upper bound terms based on Bezier formulation are developed in order to investigate relative Pressure in the VE process. Effects of reduction in area, relative length, twist angle, and friction factor in power dissipation terms are systematically analyzed. It is demonstrated that the increase in twist angle, area reduction and friction factor in the VE process increases the relative Pressure, which the rates of these increase vary with twist angle. Moreover, the effect of the relative length is different in various frictional conditions. Results of conventional extrusion (CE) are in good agreement with those found by Avitzur for the effect of slug length and friction factor on the relative extrusion stress.

A stilling basin is one of the energy dissipaters downstream of a spillway. The place of maximum Pressure caused by jet impact and the effect of various factors on the amount and location of Pressure are important factors in designing of stilling basin. Extensive experimentally and few numerically researches have been carried out in this regard. In this research, dynamic Pressure fluctuations on the basin floor are studied using two phase flow finite volume numerical method considering different geometries of ogee spillway and sharp crested weir, height of spillways, different flow velocity, Froude number and type of stilling basin. Firstly, numerical results were compared with the experimental ones and relative errors of 8% to 12% have been achieved in this comparison. The results of numerical analysis of spillways with height of 5, 7, 9, 11 and 15 meters and Froude numbers between 3. 7 to 6. 2 for ogee spillways and between 4 to 6. 8 for sharp crested weirs showed that, hydraulic jump happens in 1/3 of the beginning of the stilling basin in all spillways. Maximum Pressure fluctuations increase from 62000 to 144000 Pa for ogee spillways and 54000 to 156000 for sharp crested weirs with the height of spillways. The influence of types of stilling basin on maximum Pressure fluctuations is also evaluated.

To investigate the accidental shutdown process for a large vertical and submersible mixed-flow pump unit in a drainage pumping station, a three-dimensional numerical method for this transition process was proposed according to the angular momentum balance theorem and rigid body rotation technology. We obtained the transient performance curves of the unit and the internal flow characteristics of the full flow channel. In addition, we also analyzed the energy loss distribution of the through-flow components during this progress based on the entropy production theory. The results show that the whole runaway process needs to go through four stages: the pump mode, the pump braking mode, the turbine mode, and the stable runaway mode. The Pressure amplitude changes greatly in impeller and guide vanes, and the main fluctuation frequency is the blade frequency. There are higher harmonic frequencies in the dynamic rotor-stator interface. As the rotating speed increases in turbine mode, the negative Pressure area near the impeller blade’s trailing edge gradually increases. The entropy production method can be used to determine the location, intensity of energy loss during the transient process. If the rotating speed exceeds the allowed value in the runaway turbine mode, the interaction between blade tip Vortex and hub Vortex rope may cause loss of stability.