Water Level Rise Upstream a Permeable Barrier in Subcritical Flow: Experiment and Modeling

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
R. Martino ◽  
A. Paterson ◽  
M. Piva
Keyword(s):  
Control Volume ◽  
Mechanical Energy ◽  
Dimensionless Number ◽  
Main Role ◽  
Permeable Barrier ◽  
Water Level Rise ◽  
Physically Based ◽  
Finite Control ◽  
Simplifying Assumptions ◽  
Critical Flow Regime

This work addresses the dependence of water depth upstream a permeable barrier, h1, with discharge per unit channel width, Q/W, in sub-critical flow regime. The barrier, that extends over the entire width of the channel, is composed by smooth cylinders of small aspect ratio vertically mounted on the bottom in a staggered pattern and fully submerged in the flow. The height of the cylinders above the bottom was kept constant for all runs. Several configurations were considered by varying systematically the cylinders diameter, dv, the number of cylinders per unit area of the bed, or density, m, and the length of the barrier in the stream direction, Lv. A one-dimensional model was developed to predict the observed values of h1 and to obtain a sound basis taking into account the incidence of Q/W, m, dv and Lv. This model is based on fluid mechanics equations applied on a finite control volume for the flow in the test section, and it was deduced under simplifying assumptions physically-based. Finally, and based on the experimental results and the model predictions, the mechanical energy losses of the flow are analyzed. The main role played by a dimensionless number R, that takes into account the barrier's resistance to the flow, is highlighted.

Analysis of Heat, Mass, and Momentum Transfer in the Rain Zone of Counterflow Cooling Towers

1999 ◽  
Vol 121 (4) ◽  
pp. 751-755 ◽  
Author(s):  
E. de Villiers ◽  
D. G. Kro¨ger
Keyword(s):  
Momentum Transfer ◽  
Cooling Tower ◽  
Mechanical Energy ◽  
Performance Evaluations ◽  
Cooling Towers ◽  
Droplet Deformation ◽  
One Dimensional ◽  
Mechanical Energy Loss ◽  
Simplifying Assumptions ◽  
Semi Empirical

The rate of heat, mass, and momentum transfer in the rain zone of three counterflow cooling tower geometries is analyzed using simplifying assumptions and numerical integration. The objective of the analysis is to generate equations for use in a one-dimensional mathematical cooling tower performance evaluations. Droplet deformation is taken into account and momentum transfer is calculated from the air flow’s mechanical energy loss, caused by air-droplet interaction. A comparison of dimensionless semi-empirical equations and experimental data demonstrates the method’s capability to predict the pressure drop in a counterflow rain zone.

An evaluation of fire-plume properties simulated with the Fire Dynamics Simulator (FDS) and the Clark coupled wildfire model

2006 ◽  
Vol 36 (11) ◽  
pp. 2894-2908 ◽  
Author(s):  
Ruiyu Sun ◽  
Mary Ann Jenkins ◽  
Steven K Krueger ◽  
William Mell ◽  
Joseph J Charney
Keyword(s):  
Fluid Dynamics ◽  
Data Sets ◽  
Fire Plume ◽  
Fire Dynamics ◽  
Fire Model ◽  
Fire Dynamics Simulator ◽  
Physically Based ◽  
Vertical Grid ◽  
Simplifying Assumptions ◽  
Good Agreement

Before using a fluid dynamics physically based wildfire model to study wildfire, validation is necessary and model results need to be systematically and objectively analyzed and compared to real fires, which requires suitable data sets. Observational data from the Meteotron experiment are used to evaluate the fire-plume properties simulated by two fluid dynamics numerical wildfire models, the Fire Dynamics Simulator (FDS) and the Clark coupled atmosphere–fire model. Comparisons based on classical plume theory between numerical model and experimental Meteotron results show that plume theory, because of its simplifying assumptions, is a fair but restricted rendition of important plume-averaged properties. The study indicates that the FDS, an explicit and computationally demanding model, produces good agreement with the Meteotron results even at a relatively coarse horizontal grid size of 4 m for the FDS, while the coupled atmosphere–fire model, a less explicit and less computationally demanding model, can produce good agreement, but that the agreement is sensitive to surface vertical-grid sizes and the method by which the energy released from the fire is put into the atmosphere.

scholarly journals Study of the Impact of PV-Thermal and Nanofluids on the Desalination Process by Flashing

2020 ◽  
Vol 3 (1) ◽  
pp. 10
Author(s):  
Samuel Sami
Keyword(s):  
Experimental Data ◽  
Numerical Modeling ◽  
Solar System ◽  
Solar Radiation ◽  
Base Fluid ◽  
Control Volume ◽  
Proposed Model ◽  
Finite Control ◽  
The Impact ◽  
Mathematical And Numerical Modeling

In this study, a mathematical and numerical modeling of the photovoltaic (PV)-thermal solar system to power the multistage flashing chamber process is presented. The proposed model was established after the mass and energy conservation equations written for finite control volume were integrated with properties of the water and nanofluids. The nanofluids studied and presented herein are Ai2O3, CuO, Fe3O4, and SiO2. The multiple flashing chamber process was studied under various conditions, including different solar radiation levels, brine flows and concentrations, and nanofluid concentrations as well as flashing chamber temperatures and pressures. Solar radiation levels were taken as 500 w/m2, 750 w/m2, 1000 w/m2, and finally, 1200 w/m2. The nanofluid volumetric concentrations considered varied from 1% to 20%. There is clear evidence that the higher the solar radiation, the higher the flashed flow produced. The results also clearly show that irreversibility is reduced by using nanofluid Ai2O3 at higher concentrations of 10% to 20% compared to water as base fluid. The highest irreversibility was experienced when water was used as base fluid and the lowest irreversibility was associated with nanofluid SiO2. The irreversibility increase depends upon the type of nanofluid and its thermodynamic properties. Furthermore, the higher the concentration (e.g., from 10% to 20% of Ai2O3), the higher the availability at the last flashing chamber. However, the availability is progressively reduced at the last flashing chamber. Finally, the predicted results compare well with experimental data published in the literature.

Thermal Model of a PC

1994 ◽  
Vol 116 (2) ◽  
pp. 134-137 ◽  
Author(s):  
Ronald L. Linton ◽  
D. Agonafer
Keyword(s):  
Thermal Model ◽  
Control Volume ◽  
Turbulent Viscosity ◽  
Flow Distribution ◽  
Electronic Packages ◽  
Air Flow Rate ◽  
Simulation Code ◽  
Alternative Approach ◽  
Finite Control ◽  
Turbulence Effects

This paper presents an alternative approach to modeling box cooling in electronic packages. A finite-control-volume simulation code is used to simulate an IBM desktop Personal Computer. Only the geometry, the overall air flow rate, the turbulent viscosity and the power dissipations from each card must be specified. The simulation code predicts the flow distribution inside the PC, the convection coefficients, the turbulence effects, and the temperatures. Predicted component temperatures were compared to measured values.

Raised Floor Computer Data Center: Effect on Rack Inlet Temperatures When Adjacent Racks Are Removed

2003 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Fluid Dynamic ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Center Effect ◽  
Air Temperatures ◽  
Baseline Case ◽  
Finite Control

This paper focuses on the effect on inlet rack air temperatures when adjacent racks are removed. Only the above floor (raised floor) flow and temperature distributions were analyzed for various air flowrates exhausting from the perforated tiles and the rack. A Computational Fluid Dynamic (CFD) model was generated for the room with electronic equipment installed on a raised floor with particular focus on the effects on rack inlet temperatures of these high powered racks. The baseline case was with forty racks of data processing (DP) equipment arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide × 13.4 m long. Since the arrangement of the racks in the data center was symmetric only one-half of the data center was modeled. To see the effect of missing racks adjacent to high powered racks various configurations were analyzed. The numerical modeling was performed using a commercially available finite control volume computer code called Flotherm (Trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

Numerical Simulation of Fluid Flow and Heat Transfer in the Micro-Nozzle

2005 ◽  
Author(s):  
Longjian Li ◽  
Yihua Zhang ◽  
Wenzhi Cui ◽  
Tien-Chien Jen ◽  
Qinghua Chen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Control Volume ◽  
Slip Model ◽  
Control Volume Method ◽  
Propulsion Performance ◽  
Micro Nozzle ◽  
Flow And Heat Transfer ◽  
Finite Control ◽  
Mems Technology ◽  
Volume Method

Micro-nozzle, based on the MEMS technology, has played an important role in orbit positioning, attitude adjusting and other applications of micro-satellites. The continuous no-slip model of two-dimensional compressible laminar flow in the micro-nozzle was proposed and solved numerically by finite control volume method. The flow and heat transfer in the micro-nozzle were computed under different conditions, including different inlet pressures, different inlet temperatures and different divergent angles. Flow field and effects of these conditions on the propulsion performance were analyzed. Finally, simulated solutions were compared and validated with the experimental results.

Numerical Analysis of Impacts of Pressurized Pipes Onto Surrounding Structures Induced by Pipe Whipping

2006 ◽  
Author(s):  
D. Combescure ◽  
J. Aubert ◽  
P. Galon ◽  
J. Rousseau ◽  
C. Delaval
Keyword(s):  
Plate Thickness ◽  
Nuclear Industry ◽  
Dimensionless Number ◽  
Model Parameters ◽  
Linear Modeling ◽  
Pipe Elbow ◽  
Impact Forces ◽  
Simplifying Assumptions ◽  
Pipe Geometry ◽  
The Masses

In civil and military nuclear industry, the safety analysis requires to identify the damage induced by a pipe whipping. Due to the complexity of the phenomena and the pipe geometry and characteristics, the analyses are based on simplifying assumptions. For example, the pipe rupture which is assumed to occur at several predetermined positions along the pipe is usually considered as quasi-instantaneous and complete (double-ended guillotine break). The loading induced by the fluid in the pipe is also represented by an axial force at the pipe extremity. The analysis aims at determining the most vulnerable structures and equipment in the vicinity of the pipe. For this purpose, complete dynamic analyses can be performed but the complexity of the phenomena may require a too large modeling effort: important calculation time due to the geometric, material and contact non linearities, number of cases to be studied, large amount of numerical results to be analyzed... Non linear modeling may also be insufficient to verify the state of the impacted structures since empirical formulae are often preferred for perforation analysis because of their validity verified on experimental campaigns. The present paper focuses on a particular point and shows an analysis of numerical modeling of a pipe elbow impacting a metallic plate using the EUROPLEXUS fast transient dynamic software. Local and global results have been extensively analyzed in order to construct simplified models constituted by a limited number of masses and stiffnesses. The identification of the simplified model parameters -specially the masses- is based on the analysis of the local and average velocities, deformation and kinetic energies and impact forces between the impacting tube and the impacted plate. A parametrical study has been performed in order to identify the effect of the initial velocity of the projectile and the dimensions of the impacted plate (thickness and length). It has been confirmed the ratio between the pipe and plate thicknesses may be a good indicator to determine which structure may concentrate the main part of plasticity and so damage. Another dimensionless number proposed in the literature gives also reliable information to determine the pipe limit velocity corresponding to the onset of material plasticity in one of the structures.

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