scholarly journals Physical and analytical modeling of rhythmic karst springs

2021 ◽  
Vol 83 (3) ◽  
pp. 109-119
Author(s):  
Xianxuan Xiao ◽  
Qiang Zhang
Keyword(s):  
Physical Model ◽  
Analytical Modeling ◽  
Process Analysis ◽  
Cycle Duration ◽  
Water Tank ◽  
Flow Measurements ◽  
Karst Springs ◽  
Karst Depression ◽  
Soluble Rock ◽  
Model Components

Rhythmic Karst Springs (RKSs) are rare geologic features that rhythmically outflow water. A mechanical model for the rhythmic flow with rhythmic spill-over configuration was constructed in this work. The evolution of the RKS was revealed by using geological process analysis. The analytical model can directly explain the existence of RKSs in soluble rock regions and their formation mechanism in nature. Visual observations and flow measurements were performed using a laboratory physical model of RKS. The physical model components included a soluble rock simulation area, karst pipes, cave-reservoir, karst depression terrain, water tank, rhythmic spring, and the outflow measurement system. Groups of tests were carried out to recreate the process of RKS functioning and to confirm the rhythmic cycle duration and the threshold of replenishment intensity. This research helped to interpret the behavior of rhythmic springs using the recharge and evacuation of the subsurface cave-reservoir by means of fluid mechanics and groundwater hydraulics theories.

Vortex excitation of prisms with elongated rectangular, H and [vdash ] cross-sections

1986 ◽  
Vol 163 ◽  
pp. 149-169 ◽  
Author(s):  
Yasuharu Nakamura ◽  
Masamichi Nakashima
Keyword(s):  
Shear Layer ◽  
Cross Section ◽  
Cross Sections ◽  
Shear Layers ◽  
Water Tank ◽  
Shear Layer Instability ◽  
Flow Measurements ◽  
Trailing Edges ◽  
Rear Part ◽  
Flow Visualizations

This is an experimental investigation of vortex excitation of prisms with elongated rectangular, H- and [vdash ]-shaped cross-sections, where the depth parallel to the flow is much greater than the height perpendicular to the flow. Measurements are made of free oscillations in a wind tunnel and flow visualizations in a water tank. The flow around elongated bluff prisms is dominated by the impinging-shear- layer instability where the separated shear layers become unstable in the presence of different kinds of shape of the rear part of the cross-section, which may include sharp trailing edges. The two unstable shear layers interact with each other when they meet together downstream of the prism, thereby forming Kármán vortices with the same frequency of oscillation. The former impinging-shear-layer instability is largely responsible for vortex excitation of elongated bluff prisms.

Mathematical modeling of aluminum degassing by the impeller injector technique validated by a physical modeling

2014 ◽  
Vol 1611 ◽  
pp. 49-54 ◽  
Author(s):  
M. Hernández-Hernández ◽  
W. F. Cruz-Mendez ◽  
C. Gonzalez-Rivera ◽  
M. A. Ramírez-Argáez
Keyword(s):  
Mathematical Model ◽  
Physical Model ◽  
Gas Flow ◽  
Process Analysis ◽  
Liquid Aluminum ◽  
Bubble Diameter ◽  
Operating Parameter ◽  
Gas Flow Rate ◽  
The Mathematical Model ◽  
Kinetics Of

ABSTRACTA mathematical model is developed to describe deoxidation of water in a physical model of a batch aluminum degassing reactor equipped with the rotor-injector technique, assuming that deoxidation kinetics of water is similar to dehydrogenization of liquid aluminum. Degassing kinetics is described by using mass transport and mass balance principles by assuming that degassing kinetics can be characterized by a mass transfer coefficient, which depends on the process variables. The transport coefficient and the average bubble diameter are estimated with correlations reported in the literature for similar gas-injection systems. The water physical model helped to validate the mathematical model and to perform a process analysis by varying: 1) Gas flow rate (20 and 40 l/min); and 2) Impeller’s angular velocity (290 and 573 rpm). Results from the model agree well with measurements of deoxidation kinetics at low impeller rotating speeds. At high rotating speeds the model is still valid but less reliable because it does not take into account the formation of the vortex at the free surface. Nevertheless, the model provides predictions of the influence of every operating parameter and it can be used as a good approximation for real systems.

An Experimental Investigation Into Potential Nuclear Reactor Vessel Flow Instabilities

2010 ◽  
Author(s):  
Jeffrey A. Brown ◽  
James W. Rowland ◽  
H. Joseph Fernando
Keyword(s):  
Physical Model ◽  
Transient Flow ◽  
Plant Protection ◽  
Reactor Vessel ◽  
Flow Instabilities ◽  
Engineering System ◽  
Flow Conditions ◽  
Steam Generators ◽  
Pressurized Water ◽  
Flow Measurements

An investigation into the increase in Plant Protection System (PPS) alarms at a three-unit US Pressurized Water Reactor (PWR) plant has determined that the alarms are the result, in part, of a hydraulic instability that has developed within the Reactor Coolant System (RCS) following the replacement of the steam generators in all three units of the Palo Verde Nuclear Generating Station (PVNGS). An experimental effort has been established by Arizona Public Service Company and Arizona State University in an attempt to determine the cause of these instabilities. Preliminary investigations have determined that the time scale of these instabilities is consistent with larger scale transient flow processes of the reactor vessel. Accordingly, the flow characteristics were assessed and localized flow measurements made using a one-fifth scale physical model of the upper plenum region of the reactor core of the Combustion Engineering System 80 reactor vessel to verify the postulation that large vortex structures referred to as “precessing” vortices [Ref. 1] affect the core exit flow conditions resulting in the noted flow instabilities. The physical model investigation was complemented by numerical analysis based on a Computational Fluid Dynamics (CFD) code performed for the same geometry. Benchmarking of the CFD model by the scaled physical model is intended to provide increased confidence in the CFD code. If verified, the CFD code may be modified so as to establish corrective actions for this condition, where physical modeling would probably be time consuming and cost prohibitive. The initial results for the physical and computational models demonstrate very good agreement between the measured and calculated flows in the upper-plenum region. The results of the complementary experimental and analytic evaluations do not support the presence of any large scale vortices of appropriate space scales that could affect flow conditions within the upper-plenum region. The elimination of the reactor vessel as the source of the instabilities suggests that the replacement steam generators may be the root cause of the flow instabilities. There is a possibility, however, that frequencies pertinent to vortices may be triggering mechanisms for flow instabilities in the entire system.

The Failure Process Analysis on a Numerical Model of a Branching-Out Tunnel under Lateral Overload Action

2008 ◽  
Vol 33-37 ◽  
pp. 129-132
Author(s):  
Qiang Yong Zhang ◽  
Yong Li ◽  
Wei Shen Zhu ◽  
Jian Guo Zhang ◽  
Han Peng Wang
Keyword(s):  
Physical Model ◽  
Process Analysis ◽  
Failure Process ◽  
In Situ Stress ◽  
Complicated Structure ◽  
Construction Costs ◽  
Western Development ◽  
New Type ◽  
The Stability ◽  
In Situ Stress Field

As the implementations of the western development in China, more and more tunnels will get through the western mountains in China. In order to economize the construction costs, a new type of underground structural form called branching-out tunnel must be applied. The failure process of the branching-out tunnel under lateral overload action is also greatly complicated, which is related with the depth of the mountains, the branching-out angle, the in-situ stress field, the thickness of the middle wall and so on. This paper uses the 3D-physical model of geo-mechanical model tests to study the stability and failure process of this complicated structure, especially the part of the middle wall. The physical model is built up in a new kind of analogy material. In the process of the whole experiments, different lateral pressures imposed on both of the lateral planes of the physical model. According to different lateral pressures, we have attained the change of the stress and displacement field and looked into the failure process of the pivotal positions in the branching-out tunnel. We also use finite element method analysis software RFPA (Realistic Failure Process Analysis) to simulate the whole failure process of the branching-out tunnel. Finally, we have got the load-bearing safety reliability of this complicated structure through comparative analysis of physical modeling and numerical simulation.

Interaction process analysis.

1950 ◽  
Vol 14 (3) ◽  
pp. 235-235
Author(s):  
No authorship indicated
Keyword(s):  
Process Analysis ◽  
Interaction Process

Clinical and Experimental Analysis of 201Thallium Uptake of the Heart

1978 ◽  
Vol 17 (04) ◽  
pp. 142-148
Author(s):  
U. Büll ◽  
S. Bürger ◽  
B. E. Strauer
Keyword(s):  
Oxygen Consumption ◽  
Left Ventricle ◽  
Muscle Mass ◽  
Myocardial Oxygen Consumption ◽  
Animal Experiments ◽  
Left Ventricular ◽  
Left Ventricular Wall ◽  
Ventricular Wall ◽  
Flow Measurements ◽  
Myocardial Flow

Studies were carried out in order to determine the factors influencing myocardial 201T1 uptake. A total of 158 patients was examined with regard to both 201T1 uptake and the assessment of left ventricular and coronary function (e. g. quantitative ventriculography, coronary arteriography, coronary blood flow measurements). Moreover, 42 animal experiments (closed chest cat) were performed. The results demonstrate that:1) 201T1 uptake in the normal and hypertrophied human heart is linearly correlated with the muscle mass of the left ventricle (LVMM);2) 201T1 uptake is enhanced in the inner (subendocardial) layer and is decreased in the outer (subepicardial) layer of the left ventricular wall. The 201T1 uptake of the right ventricle is 40% lower in comparison to the left ventricle;3) the basic correlation between 201T1 uptake and LVMM is influenced by alterations of both myocardial flow and myocardial oxygen consumption; and4) inotropic interventions (isoproterenol, calcium, norepinephrine) as well as coronary dilatation (dipyridamole) may considerably augment 201T1 uptake in accordance with changes in myocardial oxygen consumption and/or myocardial flow.It is concluded that myocardial 201T1 uptake is determined by multiple factors. The major determinants have been shown to include (i) muscle mass, (ii) myocardial flow and (iii) myocardial oxygen consumption. The clinical data obtained from patient groups with normal ventricular function, with coronary artery disease, with left ventricular wall motion abnormalities and with different degree of left ventricular hypertrophy are correlated with quantitated myocardial 201T1 uptake.

Partition Coefficient of 133Xe between Blood and Eye Tissues

1975 ◽  
Vol 14 (04) ◽  
pp. 301-309
Author(s):  
A. Marczak ◽  
A. Moszczyńska-Kowalska ◽  
H. Kowalski
Keyword(s):  
Partition Coefficient ◽  
Aqueous Humour ◽  
Vitreous Body ◽  
Flow Measurements ◽  
Solubility Coefficient ◽  
Eye Muscles ◽  
Eye Tissues ◽  
Relative Solubility ◽  
Blood Flow Measurements

SummaryThe relative solubility coefficient of 133Xe and the tissue-blood partition coefficient for the aqueous humour vitreous body, conjunctiva and external eye muscles of the rabbit were determined in vitro at 37° C and at various haematocrit values. The partition coefficient for haematocrit 40 was: for the aqueous humour 0,49 ml/ml, for the vitreous body 0,50 ml/ml, for the conjunctiva 0,81 ml/g and for the external eye muscles 0,77 ml/g. It was found that the solubility of 133Xe in rabbit erythrocytes is about 50 per cent higher than that in human red cells. The consequences of this fact for the precision of blood flow measurements by the method of tissue clearance are discussed.

Investigation of the influence of the flow structure on the accuracy of flow measurement before a hydrometric structure in an open channel

2020 ◽  
pp. 41-44
Author(s):  
Anatoly Kusher
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Water Flow ◽  
Flow Measurement ◽  
Water Discharge ◽  
Critical Depth ◽  
Flow Measurements ◽  
Study Results ◽  
Flow Velocity Profile ◽  
Upstream Flow

The reliability of water flow measurement in irrigational canals depends on the measurement method and design features of the flow-measuring structure and the upstream flow velocity profile. The flow velocity profile is a function of the channel geometry and wall roughness. The article presents the study results of the influence of the upstream flow velocity profile on the discharge measurement accuracy. For this, the physical and numerical modeling of two structures was carried out: a critical depth flume and a hydrometric overfall in a rectangular channel. According to the data of numerical simulation of the critical depth flume with a uniform and parabolic (1/7) velocity profile in the upstream channel, the values of water discharge differ very little from the experimental values in the laboratory model with a similar geometry (δ < 2 %). In contrast to the critical depth flume, a change in the velocity profile only due to an increase in the height of the bottom roughness by 3 mm causes a decrease of the overfall discharge coefficient by 4…5 %. According to the results of the numerical and physical modeling, it was found that an increase of backwater by hydrometric structure reduces the influence of the upstream flow velocity profile and increases the reliability of water flow measurements.

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