One-dimensional analysis of a sleeved-piston gas gun

A one-dimensional analysis of a compressible vapor flowing within the evaporator section of a heat pipe is presented. Comparisons between the theoretical results and existing heat pipe data show that the presence of gasdynamic choking can limit the heat transfer capacity of a heat pipe operating at sufficiently low vapor pressures.

Download Full-text

Water storage in wetted strips under irrigated coffee trees with different criteria of irrigation management

Engenharia Agrícola ◽

10.1590/s0100-69162013000200004 ◽

2013 ◽

Vol 33 (2) ◽

pp. 249-257 ◽

Cited By ~ 1

Author(s):

Alberto Colombo ◽

Lívia A. Alvarenga ◽

Myriane S. Scalco ◽

Randal C. Ribeiro ◽

Giselle F. Abreu

Keyword(s):

Dimensional Analysis ◽

Drip Irrigation ◽

Irrigation Management ◽

Water Storage ◽

Moisture Distribution ◽

Water Volume ◽

Two Dimensional ◽

One Dimensional ◽

Irrigation Interval ◽

The One

The increasing demand for water resources accentuates the need to reduce water waste through a more appropriate irrigation management. In the particular case of irrigated coffee planting, which in recent years presented growth with the predominance of drip irrigation, the improvement of drip irrigation management techniques is a necessity. The proper management of drip irrigation depends on the knowledge of the spatial pattern of soil moisture distribution inside the wetted strip formed under the irrigation lines. In this study, grids of 24 tensiometers were used to determine the water storage within the wetted strip formed under drippers, with a 3.78 L h-1 discharge, evenly spaced by 0.4 m, subjected to two different management criteria (fixed irrigation interval and 60 kPa tension). Estimates of storage based on a one-dimensional analysis, that only considers depth variations, were compared with two-dimensional estimates. The results indicate that for high-frequency irrigation the one-dimensional analysis is not appropriate. However, under less frequent irrigation, the two-dimensional analysis is dispensable, being the one-dimensional sufficient for calculating the water volume stored in the wetted strip.

Download Full-text

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 ◽

10.17159/wsa/2019.v45.i3.6739 ◽

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.

Download Full-text

A quasi-one-dimensional analysis of small-signal current gains in lateral transistors

IEEE Transactions on Electron Devices ◽

10.1109/t-ed.1978.19267 ◽

1978 ◽

Vol 25 (11) ◽

pp. 1283-1290 ◽

Cited By ~ 3

Author(s):

G.V. Ram ◽

M.S. Tyagi

Keyword(s):

Dimensional Analysis ◽

Small Signal ◽

One Dimensional

Download Full-text

The Mechanics and Thermodynamics of Steady One-Dimensional Gas Flow

Journal of Applied Mechanics ◽

10.1115/1.4009740 ◽

1947 ◽

Vol 14 (4) ◽

pp. A317-A336 ◽

Cited By ~ 1

Author(s):

Ascher H. Shapiro ◽

W. R. Hawthorne

Keyword(s):

Heat Transfer ◽

Dimensional Analysis ◽

High Speed ◽

Gas Flow ◽

Gas Injection ◽

Wall Friction ◽

Analytical Treatment ◽

Area Change ◽

One Dimensional ◽

Recent Developments

Abstract Recent developments in the fields of propulsion, flow machinery, and high-speed flight have emphasized the need for an improved understanding of the characteristics of compressible flow. A one-dimensional analysis for flow without shocks is presented which takes into account the simultaneous effects of area change, wall friction, drag of internal bodies, external heat exchange, chemical reaction, change of phase, injection of gases, and changes in molecular weight and specific heat. The method of selecting independent and dependent variables, and the organization of the working equations, leads, it is believed, to a better understanding of the influence of the foregoing effects, and also simplifies greatly the analytical treatment of particular problems. Examples are given first of several simple types of flow, including (a) area change only; (b) heat transfer only; (c) wall friction only; and (d) gas injection only. In addition, examples of flow with combined effects are given, including (a) simultaneous friction and area change; (b) simultaneous friction and heat transfer; and (c) simultaneous liquid injection and evaporation. A one-dimensional analysis for flow through a discontinuity is presented, allowing for energy, shock, drag, and gas-injection effects, and for changes in gas properties. This analysis is applicable to such processes as: (a) the adiabatic normal shock; (b) combustion; (c) moisture condensation shocks; and (d) steady explosion waves.

Download Full-text