Dynamic Responses of Partially Cavitated Hydrofoil Cascade to Axial Gust in Bubbly Water

1984 ◽  
Vol 106 (3) ◽  
pp. 312-318
Author(s):  
Tetsuo Nishiyama ◽  
Hideya Nishiyama
Keyword(s):  
Water Conservation ◽  
Pressure Rise ◽  
Volume Ratio ◽  
Gain Factor ◽  
Dynamic Responses ◽  
Cavity Model ◽  
Cavity Pressure ◽  
Reduced Frequency ◽  
The Mean ◽  
Unsteady Discharge

A method for analysis by singularity representations is presented for dynamic responses of partially cavitated hydrofoil cascade to axial gust in bubbly water. Conservation laws of mass and momentum are applied to take account of the unsteady parts of cavity area, cavity termination thickness, and cavity pressure for unsteady partial cavity model. Also, the cavitation compliance and mass flow gain factor obtained from the cavity model determined are considered in relations to cavity length, reduced frequency, and air volume ratio. Comparisons of the mean unsteady pressure rise and unsteady discharge difference are also made with the available former results.

Frequency Dependence of Mass Flow Gain Factor and Cavitation Compliance of Cavitating Inducers

1996 ◽  
Vol 118 (2) ◽  
pp. 400-408 ◽  
Author(s):  
S. Otsuka ◽  
Y. Tsujimoto ◽  
K. Kamijo ◽  
O. Furuya
Keyword(s):  
Mass Flow ◽  
Present Model ◽  
Cavity Length ◽  
Incidence Angle ◽  
Low Frequency ◽  
Gain Factor ◽  
Cavity Model ◽  
Frequency Limit ◽  
Closed Cavity ◽  
Reduced Frequency

Unsteady cavitation characteristics are analyzed based on a closed cavity model in which the length of the cavity is allowed to oscillate. It is shown that the present model blends smoothly into quasi-steady calculations at the low frequency limit, unlike fixed cavity length models. Effects of incidence angle and cavitation number on cavitation compliance and mass flow gain factor are shown as functions of reduced frequency. The cavity volume is evaluated by three methods and the results are used to confirm the accuracy and adequacy of the numerical calculations. By comparison with experimental data on inducers, it is shown that the present model can simulate the characteristics of unsteady-cavitation qualitatively.

scholarly journals The importance of pial blood supply to the development of peritumoral brain edema in meningiomas

1997 ◽  
Vol 2 (4) ◽  
pp. E6 ◽  
Author(s):  
Michael Bitzer ◽  
Lars Wöckel ◽  
Andreas R. Luft ◽  
Ajay K. Wakhloo ◽  
Dirk Petersen ◽  
...  
Keyword(s):  
Brain Edema ◽  
Blood Supply ◽  
Tumor Size ◽  
Tumor Volume ◽  
Volume Ratio ◽  
Total Tumor Volume ◽  
Pial Vessels ◽  
Peritumoral Brain Edema ◽  
Tumor Region ◽  
The Mean

The authors studied the pial and dural blood supplies in 74 intracranial meningiomas and quantified their associated peritumoral brain edema (PTBE). The extent and localization of pial blush in relation to the total tumor volume were determined angiographically. The amount of edema and tumor size were calculated using computerized tomography. The edema-tumor volume ratio was defined as Edema Index (EI). There were 49 meningiomas with PTBE; of those tumors, 46 were supplied by pial vessels, and three were supplied exclusively by dural vessels. Tumors without PTBE showed no pial blush. The mean EI in meningiomas with pial blush was significantly larger (EI = 3.0) than in meningiomas without pial supply (EI = 1.1; p < 0.0001). Meningiomas in which 10% of the whole tumor volume was supplied by pial vessels had only a small mean EI of 2.2, whereas tumors with pial blood supply greater than or equal to 20% had a mean EI of 3.3 (p < 0.026). In 69.9% of cases with pial blood supply, major portions of the edema were located adjacent to the tumor region supplied by pial vessels. Edema index differences among tumors of different subgroups, as defined by size or histology, were significantly related to the pial supply in each subset. Thus, pial blood supply may be causative for the development of PTBE in meningiomas.

An Experimental Investigation of Flow-Induced Cavity Resonance

2001 ◽  
Author(s):  
Paul J. Zoccola ◽  
Theodore M. Farabee
Keyword(s):  
Experimental Investigation ◽  
Energy Production ◽  
Pressure Fluctuations ◽  
Cavity Resonance ◽  
Cavity Pressure ◽  
Novel Technique ◽  
Cavity Opening ◽  
The Mean ◽  
Marine Applications ◽  
Opening Phase

Abstract Excitation of cavity resonance by flow over an aperture is often a source of unwanted noise in aerospace, automotive, and marine applications. An experimental investigation of this phenomenon was conducted. Detailed measurements of the cavity pressure and the velocity field in the opening were performed in a quiet flow facility. Spectral data on cavity pressure fluctuations obtained for a variety of configurations were analyzed over a range of speeds to determine the behavior of both sheartones and cavity tones during non-resonant and resonant conditions. The mean and fluctuating velocity profiles as well as the cross-spectral properties between the velocity components and cavity pressure were also obtained within the cavity opening. Phase between the velocity components and the pressure was used to calculate the streamwise convection velocities across the opening. A novel technique used to measure vorticity allowed calculation of the measured energy production in the opening. The data support the finding that the resonant and non-resonant conditions are distinguished by the behavior of the convection velocity and by the distribution of energy production in the flow field.

Influences of Wind Barriers on the Train Running Safety on a Highway-Railway One-Story Bridge

2021 ◽  
pp. 2140009
Author(s):  
Ye Liu ◽  
Yan Han ◽  
Peng Hu ◽  
C. S. Cai ◽  
Xuhui He
Keyword(s):  
Dynamic Responses ◽  
Response Analysis ◽  
Train Track ◽  
Wheel Load ◽  
Wind Barrier ◽  
The Mean ◽  
Wind Pressures ◽  
Track Bridge ◽  
Fluctuating Wind ◽  
Bridge System

In this study, the influences of wind barriers on the aerodynamic characteristics of trains (e.g. a CRH2 train) on a highway-railway one-story bridge were investigated by using wind pressure measurement tests, and a reduction factor of overturning moment coefficients was analyzed for trains under wind barriers. Subsequently, based on a joint simulation employing SIMPACK and ANSYS, a wind–train–track–bridge system coupled vibration model was established, and the safety and comfort indexes of trains on the bridge were studied under different wind barrier parameters. The results show that the mean wind pressures and fluctuating wind pressures on the trains’ surface decrease generally if wind barriers are used. As a result, the dynamic responses of the trains also decrease in the whole process of crossing the bridge. Of particular note, the rate of the wheel load reductions and lateral wheel-axle forces can change from unsafe states to relative safe states due to the wind barriers. The influence of the porosity of the wind barriers on the mean wind pressures and fluctuating wind pressures on the windward sides and near the top corner surfaces of the trains are significantly greater than the influence from the height of the wind barriers. Within a certain range, decreasing the wind barrier porosities and increasing the wind barrier heights will significantly reduce the safety and comfort index values of trains on the bridge. It is found that when the porosity of the wind barrier is 40%, the optimal height of the wind barrier is determined as approximately 3.5[Formula: see text]m. At this height, the trains on the bridges are safer and run more smoothly and comfortably. Besides, through the dynamic response analysis of the wind–train–track–bridge system, it is found that the installation of wind barriers in cases with high wind speeds (30[Formula: see text]m/s) may have an adverse effect on the vertical vibration of the train–track–bridge system.

Pulmonary capillaries are recruited during pulsatile flow

2002 ◽  
Vol 92 (3) ◽  
pp. 1183-1190 ◽  
Author(s):  
Robert G. Presson ◽  
William A. Baumgartner ◽  
Amanda J. Peterson ◽  
Robb W. Glenny ◽  
Wiltz W. Wagner
Keyword(s):  
Pulsatile Flow ◽  
Left Atrial ◽  
Pulmonary Arterial Pressure ◽  
Pressure Rise ◽  
Capillary Recruitment ◽  
Pulmonary Capillaries ◽  
Pulmonary Capillary ◽  
Direct Measurements ◽  
Pulmonary Arterial ◽  
The Mean

Capillaries recruit when pulmonary arterial pressure rises. The duration of increased pressure imposed in such experiments is usually on the order of minutes, although recent work shows that the recruitment response can occur in <4 s. In the present study, we investigate whether the brief pressure rise during cardiac systole can also cause recruitment and whether the recruitment is maintained during diastole. To study these basic aspects of pulmonary capillary hemodynamics, isolated dog lungs were pump perfused alternately by steady flow and pulsatile flow with the mean arterial and left atrial pressures held constant. Several direct measurements of capillary recruitment were made with videomicroscopy. The total number and total length of perfused capillaries increased significantly during pulsatile flow by 94 and 105%, respectively. Of the newly recruited capillaries, 92% were perfused by red blood cells throughout the pulsatile cycle. These data provide the first direct account of how the pulmonary capillaries respond to pulsatile flow by showing that capillaries are recruited during the systolic pulse and that, once open, the capillaries remain open throughout the pulsatile cycle.

scholarly journals Soil and Water Conservation in Rainfed Vineyards with Common Sainfoin and Spontaneous Vegetation under Different Ground Conditions

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1058 ◽  
Author(s):  
Nahed Ben-Salem ◽  
Sara Álvarez ◽  
Manuel López-Vicente
Keyword(s):  
Water Conservation ◽  
Cover Crop ◽  
Sediment Traps ◽  
Sediment Yields ◽  
Rainfall Depth ◽  
Ephemeral Gullies ◽  
Ground Conditions ◽  
Spontaneous Vegetation ◽  
The Mean ◽  
Moisture Conditions

Soil erosion seriously affects vineyards. In this study, the influence of two vegetation covers on topsoil moisture and the effect of different physiographic conditions on runoff and sediment yields were evaluated in a rainfed vineyard formed by four fields (NE Spain) during 15 months. One field had spontaneous vegetation in the inter-row areas, and three fields had a cover crop of common sainfoin. Moisture conditions were dry and stable in the vineyards’ rows, wet and very variable in the inter-row areas and wet and very stable in the corridors. Topsoil moisture in the areas with common sainfoin was much higher than in the rows (62–70%), whereas this difference was lower with spontaneous vegetation (40%). Two runoff and sediment traps (STs) were installed in two ephemeral gullies, and 26 time-integrated surveys (TIS) were done. The mean runoff yields were 9.8 and 13.5 L TIS−1 in ST2 and ST3. Rainfall depth (12 mm) and erosivity (5.2 MJ mm ha−1 h−1) thresholds for runoff initiation were assessed. The mean turbidity was 333 (ST2) and 19 (ST3) g L−1. Changes in the canopy covers (grapevines and vegetation covers), topography and rainfall parameters explained the runoff and sediment dynamics.

scholarly journals Quantification of Environmental Flow Requirement for some Rivers in West Java

2020 ◽  
Vol 148 ◽  
pp. 07003
Author(s):  
Waluyo Hatmoko ◽  
Levina ◽  
Radhika ◽  
Amirwandi ◽  
Rendy
Keyword(s):  
Water Conservation ◽  
Environmental Flow ◽  
Dry Season ◽  
Mean Flow ◽  
West Java ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Tennant Method ◽  
The Mean ◽  
Flow Requirement

Sustainable Development Goal (SDG). Water management is making a balance between water for livelihood and water as a resource. Environmental Flow Requirement (EFR) is water conservation, on the side of the water for livelihood, to sustain the river ecosystem. In Indonesia, the common quantification of EFR is dependable flow Q95%. However, there are alternative quantities: a) Guideline of irrigation states that 5% from the available water in the river is for environmental purposes; b) Adoption of the Tennant Method of using 10% of the mean flow; and recently Food and Agriculture Organization (FAO) in the framework of SDG proposed that in Java Island the EFR is from 40% to 50% of the mean annual flow. This paper discusses several ways of quantification of the EFR in Indonesia, and apply the different EFR quantities to Citarum, Cimanuk, and Cimandiri Rivers in West Java. It is concluded that EFR quantity according to FAO that might be suitable for the rivers in the pristine catchments in the southern part of West Java is too high for the rivers in the northern part of West Java which is heavily populated and maturely developed. Furthermore, the dependable flow of Q95% is found to be close to the quantity of FAO, but in the dry season, Q95% is more suitable. It is recommended using a modified FAO that combine with Q95% during the dry season.

scholarly journals Investigation of Stochastic Seismic Response and Index Correlation of an Arch Dam Using Endurance Time Analysis Method

2020 ◽  
Vol 2020 ◽  
pp. 1-23
Author(s):  
Qiang Xu ◽  
Shutong Xu ◽  
Jianyun Chen ◽  
Jing Li
Keyword(s):  
Seismic Response ◽  
Failure Modes ◽  
Response Spectrum ◽  
Volume Ratio ◽  
Arch Dam ◽  
Dynamic Responses ◽  
Rock Foundation ◽  
Time Analysis ◽  
Endurance Time ◽  
Joint Opening

The seismic dynamic response and correlation between various indicators of an arch dam under a series of stochastic earthquake excitation are analysed. Seismic response assessment of a concrete arch dam is conducted through nonlinear endurance time analysis (ETA) of a typical arch dam. The 289 m high Baihetan arch dam in Southwest China (as a case study) is subjected to a set of 10 three-component endurance time acceleration histories (ETAHs) synthesised on the basis of the design site acceleration response spectrum to increasing peak ground acceleration (PGA). The effects of dam-reservoir-foundation interaction, radiation damping of infinite rock foundation, and nonlinearities of dam material and joint contact elements are considered. The indices to failure modes of damage propagation through the dam body and the deformation and joint opening beyond the limit states of the arch dam are identified. Dynamic responses, including deformation, joint opening, and damage distribution, are statistically analysed. The dispersion and correlation of indicators are analysed by employing the coefficient of variation and coefficient of correlation, respectively. The deterministic relationships between contraction joint opening, displacement, and damage volume ratio are obtained by using a multivariate fitting method. The results show that those failure indices have similar exponential trends, and seismic intensity parameters exert a significant influence on seismic response and damage under increasing PGA. The results of correlation and fragility analysis demonstrate that damage volume ratio and the sum of joint opening are consistent, which can provide a strong scientific basis for predicting earthquake damage.

Nonlinear dynamic response analysis on gear-rotor-bearing transmission system

2016 ◽  
Vol 24 (9) ◽  
pp. 1632-1651 ◽  
Author(s):  
Shihua Zhou ◽  
Guiqiu Song ◽  
Mengnan Sun ◽  
Zhaohui Ren
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Nonlinear Dynamic ◽  
Nonlinear Differential Equations ◽  
Transmission System ◽  
Dynamic Responses ◽  
Response Analysis ◽  
Light Load ◽  
Rotor Bearing ◽  
The Mean

A coupled lateral-torsional nonlinear dynamic model with 16-degree-of-freedom (16-DOF) of gear-rotor-bearing transmission system (GRBTS) is developed after comprehensive considering the nonlinear features associated with time-varying meshing stiffness, backlash, transmission error, friction force, input/output load, gravity and gear eccentricity. Based on the nonlinear differential equations, the coupled multi-body dynamic responses of the GRBTS are demonstrated using the Runge-Kutta numerical method, and the effects of friction coefficient and mean load on the dynamic characteristics are investigated. The results show that the friction force could enlarge the vibration amplitude and affect the low frequency components seriously. The mean load excitation has a complicated influence on the coupled GRBTS, and the torsional vibration is the dominate response. Whereas the mean load excitation has a certain extent vibration suppression, and light load and heavy load could no longer effectively control the nonlinear vibration of the GRBTS. With the increasing of rotational speed, the friction coefficient and mean load ranges of the chaotic behavior widen and the chaotic characteristics strengthens. It is shown that small parameter random perturbation might be propagated in the vibration system and lead to relatively large vibration of the system. The contribution to provide a reference for the design and study of gear system.

Preparation of Ultra-Fine Clarithromycin Particles by Anti-Solvent Recrystallization

2016 ◽  
Vol 680 ◽  
pp. 534-537 ◽  
Author(s):  
Jing Xu
Keyword(s):  
Volume Ratio ◽  
Acetone Solution ◽  
Ultrafine Powders ◽  
Precipitation Temperature ◽  
Temperature And Precipitation ◽  
Water Solvent ◽  
Acetone Water ◽  
Ft Ir ◽  
Solvent Systems ◽  
The Mean

Ultrafine drug powders have higher bioavaibability than the larger signed particles. Ultrafine powders of clarithromycin were produced by anti-solvent recrystallization with the acetone - water solvent systems. The effects of volume ratio of clarithromycin acetone solution to anti-solvent, stirring speed, precipitation temperature and precipitation time on the preparation process were investigated. The results show that ultrafine powders can be yielded and well-controlled under the following optimal conditions: the volume ratio of clarithromycin acetone solution to anti-solvent 1:10, stirring speed 900 r/min, precipitation temperature 20°C, and precipitation time 10 min. The ultrafine powders with the rod-shape and the mean diameter of 1.8μm with the narrow distribution were successfully obtained. The yield of drug powders is more than 83%. The powders were analyzed with FT-IR and metalloscope. The purity of drug powders is more than 98%, according with Chinese Pharmacopoeia. The operation of the experiment was very simple, and the powders were separated easily.

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