Experimental Study on Flow in a Supersonic Centrifugal Impeller

1979 ◽  
Vol 101 (1) ◽  
pp. 32-39 ◽  
Author(s):  
Y. Senoo ◽  
H. Hayami ◽  
Y. Kinoshita ◽  
H. Yamasaki
Keyword(s):  
Experimental Data ◽  
Shock Wave ◽  
Dimensional Analysis ◽  
Relative Velocity ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Critical Conditions ◽  
Centrifugal Impeller ◽  
One Dimensional ◽  
Detached Shock Wave

An impeller of a supersonic centrifugal compressor was tested in a casing without a diffuser so that the flow range was not limited by the diffuser. Regarding the impeller, emphasis was placed on critical conditions such as inducer stall and surge. Experimental data were examined based on a one-dimensional analysis and a quasi-three-dimensional analysis. Furthermore, the variation of shroud pressure with respect to time at many locations was utilized to guess the details of flow behavior between impeller blades near the shroud, and the contour of isobars was compared with that predicted by a quasi-three-dimensional analysis. When the inlet relative velocity was supersonic, a detached shock wave and a shock wave in a blade channel were recognized, but the compressor operated efficiently, although such condition existed only in a narrow flow range limited by surge and choke.

scholarly journals Assessment of CFD turbulence models for free surface flow simulation and 1-D modelling for water level calculations over a broad-crested weir floodway

Water SA ◽  
2019 ◽  
Vol 45 (3 July) ◽  
Author(s):  
Ahmed M Helmi
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Water Level ◽  
Dimensional Analysis ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Cfd Simulations ◽  
One Dimensional ◽  
The Mean ◽  
The One

Floodways, where a road embankment is permitted to be overtopped by flood water, are usually designed as broad-crested weirs. Determination of the water level above the floodway is crucial and related to road safety. Hydraulic performance of floodways can be assessed numerically using 1-D modelling or 3-D simulation using computational fluid dynamics (CFD) packages. Turbulence modelling is one of the key elements in CFD simulations. A wide variety of turbulence models are utilized in CFD packages; in order to identify the most relevant turbulence model for the case in question, 96 3-D CFD simulations were conducted using Flow-3D package, for 24 broad-crested weir configurations selected based on experimental data from a previous study. Four turbulence models (one-equation, k-ε, RNG k-ε, and k-ω) ere examined for each configuration. The volume of fluid (VOF) algorithm was adopted for free water surface determination. In addition, 24 1-D simulations using HEC-RAS-1-D were conducted for comparison with CFD results and experimental data. Validation of the simulated water free surface profiles versus the experimental measurements was carried out by the evaluation of the mean absolute error, the mean relative error percentage, and the root mean square error. It was concluded that the minimum error in simulating the full upstream to downstream free surface profile is achieved by using one-equation turbulence model with mixing length equal to 7% of the smallest domain dimension. Nevertheless, for the broad-crested weir upstream section, no significant difference in accuracy was found between all turbulence models and the one-dimensional analysis results, due to the low turbulence intensity at this part. For engineering design purposes, in which the water level is the main concern at the location of the flood way, the one-dimensional analysis has sufficient accuracy to determine the water level.

Analysis of the Exit Flow Angle and Characteristics of Flow in Axial Turbine Cascades

2020 ◽  
Author(s):  
Narmin B. Hushmandi ◽  
Per Askebjer ◽  
Magnus Genrup
Keyword(s):  
Dimensional Analysis ◽  
Three Dimensional ◽  
Flow Coefficient ◽  
Reference Plane ◽  
Exit Angle ◽  
Design Work ◽  
Flow Angle ◽  
Axial Turbine ◽  
One Dimensional ◽  
The One

Abstract Despite a wealth of sophisticated CFD-methods, most designs are still based on one-dimensional and two-dimensional inviscid analytical tools. In such methods, realistic loss and angle assessment are indeed critical in order to arrive at correct loading, flow coefficient and reaction. The selected values are normally retained through the detailed design sequence for each iteration. This means that the throat sizing and hence the gauge angle is largely based on the early design work within the through-flow environment. Even one-degree error in angle estimation will turn into a rather large capacity error. For most designs, the exchange rate between capacity and gauge angle is on the order of 3–5 percent, per degree exit angle. In a previous publication, a methodology and equations were presented to assess the exit flow in an axial turbine blade row by Mamaev in Russian nomenclature and the tangential coordinate system. The approach, provided a unified and flow-physics based method for assessing exit angles from the geometry features like gauge angle, uncovered turning and flow features like Laval number, etc. Analysis of those formulas showed good agreement with physical flow pattern in real cascades for sub and transonic blade cascades. In this work, the same basic principal procedure is followed by employing the more international agreed nomenclature of blades such as an axial reference plane and Mach number. In the current work, the one-dimensional analysis results were compared with the three dimensional numerical modelling of a full annulus two-stage turbine. Analysis of the results showed the inherent unsteadiness specially outside the rotor blade cascades, however, comparison of the mass averaged exit angle with the one dimensional analysis showed satisfactory agreement.

Preliminary Ship Design Using One and Two-Dimensional Models

1999 ◽  
Vol 36 (02) ◽  
pp. 102-112
Author(s):  
Michael D. A. Mackney ◽  
Carl T. F. Ross
Keyword(s):  
Finite Element ◽  
Dimensional Analysis ◽  
Three Dimensional ◽  
Two Dimensional ◽  
One Dimensional ◽  
Dimensional Finite Element ◽  
Dimensional Models ◽  
Support Conditions ◽  
The One ◽  
Three Dimensional Finite Element

Computational studies of hull-superstructure interaction were carried out using one-, two-and three-dimensional finite element analyses. Simplification of the original three-dimensional cases to one- and two-dimensional ones was undertaken to reduce the data preparation and computer solution times in an extensive parametric study. Both the one- and two-dimensional models were evaluated from numerical and experimental studies of the three-dimensional arrangements of hull and superstructure. One-dimensional analysis used a simple beam finite element with appropriately changed sections properties at stations where superstructures existed. Two-dimensional analysis used a four node, first order quadrilateral, isoparametric plane elasticity finite element, with a corresponding increase in the grid domain where the superstructure existed. Changes in the thickness property reflected deck stiffness. This model was essentially a multi-flanged beam with the shear webs representing the hull and superstructure sides, and the flanges representing the decks One-dimensional models consistently and uniformly underestimated the three-dimensional behaviour, but were fast to create and run. Two-dimensional models were also consistent in their assessment, and considerably closer in predicting the actual behaviours. These models took longer to create than the one-dimensional, but ran in very much less time than the refined three-dimensional finite element models Parametric insights were accomplished quickly and effectively with the simplest model and processor, but two-dimensional analyses achieved closer absolute measure of the displacement behaviours. Although only static analysis with simple loading and support conditions were presented, it is believed that similar benefits would be found for other loadings and support conditions. Other engineering components and structures may benefit from similarly judged simplification using one- and two-dimensional models to reduce the time and cost of preliminary design.

Application of Viscous Flow Computations for the Aerodynamic Performance of a Backswept Impeller at Various Operating Conditions

1988 ◽  
Vol 110 (3) ◽  
pp. 303-311 ◽  
Author(s):  
C. Hah ◽  
A. C. Bryans ◽  
Z. Moussa ◽  
M. E. Tomsho
Keyword(s):  
Experimental Data ◽  
Viscous Flow ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
Flow Phenomena ◽  
Overall Performance ◽  
Real Flow ◽  
Operating Points

Three-dimensional flowfields in a centrifugal impeller with backswept discharge at various operating points have been numerically investigated with a three-dimensional viscous flow code. Numerical results and experimental data were compared for the detailed flowfields and overall performance of the impeller at three operating conditions (optimum efficiency, choke, and near-surge conditions). The comparisons indicate that for engineering applications the numerical solution accurately predicts various complex real flow phenomena. The overall aerodynamic performance of the impeller is also well predicted at design and off-design conditions.

Numerical Investigation of the Thermal Behavior in a Hydrogen Tank During Fast Filling Process

2011 ◽  
Author(s):  
Youhei Takagi ◽  
Naoya Sugie ◽  
Kazuhiro Takeda ◽  
Yasunori Okano ◽  
Tooru Eguchi ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Dimensional Analysis ◽  
Three Dimensional ◽  
Hydrogen Gas ◽  
Tank Wall ◽  
Filling Process ◽  
Adiabatic Wall ◽  
Buoyant Force ◽  
One Dimensional ◽  
Dimensional Simulation

To investigate the thermal behavior during fast hydrogen filling process, the simple one-dimensional analysis considering the heat conduction in tank wall and the three-dimensional numerical simulation dealing with inner gas region were carried out. The numerical analyses were subject to the fast filling test of 35 MPa hydrogen gas into 34 litter tank for 80 seconds. The one-dimensional analysis predicted the temperature rise and the heat loss into surrounding air qualitatively and the averaged temperature of tank wall was underestimated. On the other hand, the three-dimensional simulation overestimated the temperature distribution because of using adiabatic wall condition. However, the effects of buoyant force and convective flow on local thermal profile were fully explained from our numerical results.

Unified Criterion for Brittle–Ductile Transition in Mechanical Microcutting of Brittle Materials

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
X. Cheng ◽  
X. T. Wei ◽  
X. H. Yang ◽  
Y. B. Guo
Keyword(s):  
Experimental Data ◽  
Three Dimensional ◽  
Brittle Materials ◽  
Chip Thickness ◽  
Threshold Value ◽  
Cutting Edge ◽  
Critical Conditions ◽  
Dominant Factor ◽  
Process Conditions ◽  
Brittle Ductile Transition

Various brittle–ductile transition (BDT) criteria have been developed in the literature to estimate the critical conditions for ductile microcutting of brittle materials. This study provides a unified criterion to efficiently and accurately estimate the critical condition based on the indentation model on brittle materials. The unified criterion correlates with the cutting edge radius, material properties, and a dimensionless coefficient fitted by the experimental data. It shows that the cutting edge geometry is the dominant factor and the maximum undeformed chip thickness (MUCT) can be used as the unified criterion in BDTs. Based on the proposed model, microturning and micromilling have been analyzed to determine the threshold value of the MUCT for ductile microcutting. The model has been validated by the experimental data. Based on the models and three-dimensional geometrical model of microcutting, a further analysis shows that the process conditions greatly affect the microcutting efficiency even though all the conditions may achieve the ductile-regime cutting.

Precursor shock waves at a slow—fast gas interface

1976 ◽  
Vol 76 (1) ◽  
pp. 157-176 ◽  
Author(s):  
A. M. Abd–El–Fattah ◽  
L. F. Henderson ◽  
A. Lozzi
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Shock Wave ◽  
Shock Waves ◽  
Plane Shock ◽  
One Dimensional ◽  
Irregular Wave ◽  
Irregular Systems ◽  
Theory And Experiment ◽  
Good Agreement

This paper presents experimental data obtained for the refraction of a plane shock wave at a carbon dioxide–helium interface. The gases were separated initially by a delicate polymer membrane. Both regular and irregular wave systems were studied, and a feature of the latter system was the appearance of bound and free precursor shocks. Agreement between theory and experiment is good for regular systems, but for irregular ones it is sometimes necessary to take into account the effect of the membrane inertia to obtain good agreement. The basis for the analysis of irregular systems is one-dimensional piston theory and Snell's law.

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