Morphological, structural and textural variations in the 1988–1990 andesite lava of Lonquimay Volcano, Chile

1992 ◽  
Vol 129 (6) ◽  
pp. 657-678 ◽  
Author(s):  
J. A. Naranjo ◽  
R. S. J. Sparks ◽  
M. V. Stasiuk ◽  
H. Moreno ◽  
G. J. Ablay
Keyword(s):  
Flow Rate ◽  
Outer Wall ◽  
Chamber Pressure ◽  
Effusion Rate ◽  
Central Channel ◽  
Flow Front ◽  
Local Flow ◽  
Flow Rate Increase ◽  
Lava Morphology ◽  
Andesite Lava

AbstractThe 1988–1990 eruption of Lonquimay Volcano, Chile (38°S) formed a 10.2 km long andesite lava with a volume of 0.23 km3 over a period of 13 months. The lava extrusion rate decreased with time as chamber pressure and vent dimensions decreased. The velocity of the flow front decreased exponentially with distance from vent as a consequence of cooling and the increase of apparent viscosity at the flow front. The lava developed a central channel which decreased in width and depth with time. Three prominent lava levées were formed on each margin and resulted from abandonment as the channel decreased in width as a result of a rapid decrease of flow rate over the first 100 days of activity. A fourth major levée developed in February, during a brief period of flow rate increase down the main channel, but its walls were gradually exposed as the lava depth again decreased due to declining flow rate. The structure of lava levées depended on their age and longevity of the flow in the adjacent channel. Initial levées were formed in the first few days as the lava spread laterally and then retreated, leaving levées of massive lava. More mature rubble levées were formed during the next month by the lava pushing and then shearing aa and blocky breccia which formed on the cooling flow margin. Fragmentation and abrasion formed a characteristic zonation in the levées. A basal zone consists of very poorly sorted matrix-rich breccia with very rounded vesicular clasts and bimodal grain size distribution. The basal breccia zone strongly resembles block and ash flow deposits. This zone passes up into a zone of clast-supported clinker breccia which becomes increasingly matrix-poor and coarser with clasts becoming more angular upwards. The crest of the levée is composed of large (10–100 cm) angular to subangular blocks with no matrix. The zoned levées form after the active lava channel suddenly narrows. Lava depth initially increases and breccias are deposited on the channel margins and acquire the zoned structure by progressive shearing and accretion of clinkery aa breccia. The lava level then drops exposing the steep inner scarp of a levée. The most mature levée type formed in a long-lived channel over several months. The outer wall of the levée consists of zoned breccia, but the inner wall consists of a massive curving wall of strongly foliated lava with well-developed horizontal striations and ductile Reidel shears. The massive foliated facies is a consequence of prolonged flow which coats strongly sheared lava onto the inner levée wall. Scanning electron microscopy shows that the aa clinker clasts and foliated lava from the levée walls form at low melt fractions (⋚ 15%). In the last three months of the eruption the flow front ceased to advance but thickened as lava drained from proximal regions and intruded into the interior of the distal lava. The last stages of lava movement were characterized by updoming in the central channel. A lava surface feature, named here ‘Armadillo structure’, was formed by deformation of the cooler but still ductile lava crust. The deformation caused by underflow produced Reidel shears dipping upstream and doming of the lava due to rotation of the shear planes. The study demonstrates that lava morphology, structure and texture are strongly influenced by variations of effusion rate, local flow rate, channel topography and thermal maturity of the lava, which is reflected in downstream changes in viscosity.

scholarly journals Understanding the local flow rate peak of a hopper discharging discs through an obstacle using a Tetris-like model

2019 ◽  
Vol 21 (2) ◽  
Author(s):  
Guo-Jie Jason Gao ◽  
Jerzy Blawzdziewicz ◽  
Michael C. Holcomb ◽  
Shigenobu Ogata
Keyword(s):  
Flow Rate ◽  
Local Flow

Effect Of The Rib Inclination Angle On Liquid Film Spreading Over The Structured Surface

2015 ◽  
Vol 10 (1) ◽  
pp. 42-49
Author(s):  
Aleksandr Pavlenko ◽  
Oleg Volodin ◽  
Vladimir Serdyukov
Keyword(s):  
Liquid Film ◽  
Flow Rate ◽  
Inclination Angle ◽  
High Speed ◽  
Film Flow ◽  
Complex Geometry ◽  
Experimental Studies ◽  
Local Flow ◽  
Structured Packing ◽  
Film Spreading

Results of experimental studies on hydrodynamics of the film flow of liquid nitrogen over the surface of the single elements of structured packing are presented. The effect of inclination angle of the large ribs and perforation on the zones of liquid film spreading over the corrugated surface with microtexture at different Reynolds numbers of the film is shown based on a comparison of experimental data. It is shown that the angle of large rib inclination has a significant influence on redistribution of the local flow rate of liquid flowing on the surface with complex geometry. Analysis of results of the high-speed video revealed that in a vicinity of the vertical lateral edges of corrugated plates, the intense rivulet flows are formed, including those with separation from the film flow surface. This negative factor can lead to significant liquid accumulation and flow near the vertical edges of the structured packing and on the inner wall of the heat exchanging apparatuses and, finally, to a significant increase in the degree of maldistribution of local liquid flow rate over the crosssection, for instance, of the distillation columns.

Effects of Inlet Mass Flow Distribution and Magnitude on Reactant Distribution for PEM Fuel Cells

2005 ◽  
Vol 3 (1) ◽  
pp. 45-50 ◽  
Author(s):  
M. McGarry ◽  
L. Grega
Keyword(s):  
Fuel Cell ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Separation ◽  
Flow Distribution ◽  
Pem Fuel Cells ◽  
Local Flow ◽  
Flow Rates ◽  
Large Active Area ◽  
Mass Flow Rates

The mass flow distribution and local flow structures that lead to areas of reactant starvation are explored for a small power large active area PEM fuel cell. A numerical model was created to examine the flow distribution for three different inlet profiles; blunt, partially developed, and fully developed. The different inlet profiles represent the various distances between the blower and the inlet to the fuel cell and the state of flow development. The partially and fully developed inlet profiles were found to have the largest percentage of cells that are deficient, 20% at a flow rate of 6.05 g/s. Three different inlet mass flow rates (stoichs) were also examined for each inlet profile. The largest percent of cells deficient in reactants is 27% and occurs at the highest flow rate of 9.1 g/s (3 stoichs) for the partially and fully developed turbulent profiles. In addition to the uneven flow distribution, flow separation occurs in the front four channels for the blunt inlet profile at all flow rates examined. These areas of flow separation lead to localized reactant deficient areas within a channel.

An analytical and experimental study of a hybrid rocket motor

2014 ◽  
Vol 228 (13) ◽  
pp. 2475-2486 ◽  
Author(s):  
Hadi Rezaei ◽  
Mohammad Reza Soltani
Keyword(s):  
Flow Rate ◽  
Low Cost ◽  
Specific Impulse ◽  
Combustion Products ◽  
Rocket Motor ◽  
Chamber Pressure ◽  
Hybrid Rocket ◽  
Hybrid Rocket Motor ◽  
Chemical Propulsion ◽  
Rate Case

The hybrid rocket motor is a kind of chemical propulsion system that has been recently given serious attention by various industries and research centers. The relative simplicity, safety and low cost of this motor, in comparison with other chemical propulsion motors, are the most important reasons for such interest. Moreover, throttle-ability and thrust variability on demand are additional advantages of this type of motor. In this paper, the result of an internal ballistic simulation of hybrid rocket motor in a zero-dimensional form is presented. Further to validate the code, an experimental setup was designed and manufactured. The simulation results are compared with the experimental data and good agreement is achieved. The effect of various parameters on the motor performance and on the combustion products is also investigated. It is found that increasing the oxidizer flow rate, increases the pressure and specific impulse of the motor; however, the slope of the specific impulse for the high flow rate case reduces. In addition, by increasing the combustion chamber pressure, the specific impulse is increased considerably. The initial diameter of the fuel port does not have significant effect on the pressure chamber and on the specific impulse. Addition of a percentage of an oxidizer like ammonium perchlorate to the fuel increases the specific impulse linearly.

scholarly journals Influence of Blade Wrap Angle on the Hydrodynamic Radial Force of Single Blade Centrifugal Pump

2021 ◽  
Vol 11 (19) ◽  
pp. 9052
Author(s):  
Linwei Tan ◽  
Yongfei Yang ◽  
Weidong Shi ◽  
Cheng Chen ◽  
Zhanshan Xie
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
High Efficiency ◽  
Rate Increase ◽  
Radial Force ◽  
Horizontal Component ◽  
Flow Rate Increase ◽  
Wrap Angle ◽  
External Characteristics ◽  
Blade Wrap Angle

To investigate the effect of blade wrap angle on the hydrodynamic radial force of a single blade centrifugal pump, numerical simulation is conducted on the pumps with different blade wrap angles. The effect of the wrap angle on the external characteristics and the radial force of a single blade centrifugal pump was analyzed according to the simulation result. It is found that, with the increase of the blade wrap angle, the head and efficiency of the single blade centrifugal pump are improved, the H-Q curve becomes steeper, and the efficiency also increased gradually, while the high-efficiency area is narrowed. The blade wrap angle has a great effect on the radial force of the single blade centrifugal pump. When the blade wrap angle is less than 360°, the horizontal component of the radial force is negative and the value is reduced with the increase of the wrap angle of the blade. When the wrap angle is larger than 360°, the horizontal component of the radial force is positive and the value increases with the increase of the wrap angle. Under part-loading conditions, the radial force of the single blade pump is significantly reduced with the increase of the blade wrap angle. When the wrap angle is smaller than 360°, the radial force decreases with the flow rate increase. In the condition that the wrap angle is larger than 360°, the radial force increases with the flow rate increase.

Three-Dimensional Computational Fluid Dynamics Prediction of Turbocharger Centrifugal Compression System Instabilities

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Rick Dehner ◽  
Ahmet Selamet
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Flow Reversal ◽  
Constant Speed ◽  
Local Flow ◽  
Stall Cells

The present work combines experimental measurements and unsteady, three-dimensional computational fluid dynamics predictions to gain further insight into the complex flow-field within an automotive turbocharger centrifugal compressor. Flow separation from the suction surface of the main impeller blades first occurs in the mid-flow range, resulting in local flow reversal near the periphery, with the severity increasing with decreasing flow rate. This flow reversal improves leading-edge incidence over the remainder of the annulus, due to (a) reduction of cross-sectional area of forward flow, which increases the axial velocity, and (b) prewhirl in the direction of impeller rotation, as a portion of the tangential velocity of the reversed flow is maintained when it mixes with the core flow and transitions to the forward direction. As the compressor operating point enters the region where the slope of the constant speed compressor characteristic (pressure ratio versus mass flow rate) becomes positive, rotating stall cells appear near the shroud side diffuser wall. The angular propagation speed of the diffuser rotating stall cells is approximately 20% of the shaft speed, generating pressure fluctuations near 20% and 50% of the shaft frequency, which were also experimentally observed. For the present compressor and rotational speed, flow losses associated with diffuser rotating stall are likely the key contributor to increasing the slope of the constant speed compressor performance curve to a positive value, promoting the conditions required for surge instabilities. The present mild surge predictions agree well with the measurements, reproducing the amplitude and period of compressor outlet pressure fluctuations.

The Effect of Angle and Flow Rate Upon Hemodynamics in Distal Vascular Graft Anastomoses: An In Vitro Model Study

1991 ◽  
Vol 113 (4) ◽  
pp. 458-463 ◽  
Author(s):  
R. S. Keynton ◽  
S. E. Rittgers ◽  
M. C. S. Shu
Keyword(s):  
Stagnation Point ◽  
Flow Rate ◽  
In Vitro Model ◽  
Laser Doppler Anemometry ◽  
Bypass Graft ◽  
Outer Wall ◽  
Model Study ◽  
Vitro Model ◽  
Junction Angle

A steady flow, in vitro model of distal arterial bypass graft junctions was used to examine the effects of junction angle and flow rate on the local velocity field. Three test sections were fabricated from Plexiglas™ tubing having anastomotic junction angles of either 30, 45, or 60 deg. Flow visualization revealed velocity profiles skewed toward the outer wall with a flow split around a clear stagnation point along the outer wall. Laser Doppler anemometry [LDA] measurements confirmed a distinct stagnation point at the outer wall and both reverse and forward shear were detected immediately upstream and downstream, respectively, of this site. Axial velocities and shear rates along the outer wall were higher than along the inner wall and occurred in the junction angle order: 45, 60, and 30 deg. This study clearly identified changes in wall shear which varied with the anastomotic angle and flow rate.

Flow at the Centrifugal Pump Impeller Exit With Circumferential Distortion of the Outlet Static Pressure

2004 ◽  
Vol 126 (1) ◽  
pp. 81-86 ◽  
Author(s):  
Soon-Sam Hong ◽  
Shin-Hyoung Kang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Total Pressure ◽  
Static Pressure ◽  
Mean Flow ◽  
Simple Method ◽  
Local Flow ◽  
Flow Angle ◽  
Flow Parameters ◽  
Relative Flow

The effects of circumferential outlet distortion of a centrifugal pump diffuser on the impeller exit flow were investigated. A fence with sinusoidal width variation was installed at the vaneless diffuser exit. The flow field was measured at the impeller exit with and without the fence, using a hot film probe and an unsteady pressure sensor. Flow parameters varied with the circumferential position and the mean flow parameters plotted against the local flow rate at each circumferential position showed loops along the quasi-steady curves, which were obtained from the result without the fence. Simple theoretical calculations were used to predict the velocity components at the impeller exit with the relative flow angle or total pressure assumed. Good result was obtained when the relative flow angle was assumed to vary quasi-steadily, not constant with the local flow rate. The radial velocity was also reasonably predicted when the total pressure was assumed to vary quasi-steadily. A simple method is proposed to predict the impeller exit flow with downstream blockage in two-step sequence: the first step deals with the diffuser alone to obtain static pressure distribution at the diffuser inlet, while the second step deals with the impeller alone to obtain velocity components distribution at the impeller exit.

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