Laminar Flow Around a Sinusoidal Interface Between a Porous Medium and a Clear Fluid

2003 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Renato A. Silva
Keyword(s):  
Porous Layer ◽  
Rate Increase ◽  
Numerical Solutions ◽  
Working Fluid ◽  
Engineering Systems ◽  
Laminar Regime ◽  
Clear Fluid ◽  
Atmospheric Boundary Layers ◽  
Porosity And Permeability ◽  
Flow Rate Increase

A number of natural and engineering systems can be characterized by some sort of porous structure through which a working fluid permeates. Atmospheric boundary layers over tropical forests and vegetation can be modeled as flow over a porous layer of irregular surface. In addition, in engineering systems one can have components that make use of a working fluid flowing over irregular layers of porous material. This paper presents numerical solutions for such hybrid medium, considering here a channel partially filled with a sinusoidal porous layer saturated by a fluid flowing in laminar regime. One unique set of transport equations is applied to both regions. Effects of Reynolds number, porosity and permeability on mean and turbulence fields are investigated. For a fixed inlet mass flow rate, increase of either porosity or permeability reduced the strength of the recirculating motion over the porous layer.

Turbulent Flow Around a Wavy Interface Between a Porous Medium and a Clear Domain

2003 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Renato A. Silva
Keyword(s):  
Reynolds Number ◽  
Porous Medium ◽  
Kinetic Energy ◽  
Numerical Solutions ◽  
Working Fluid ◽  
Turbulent Regime ◽  
Irregular Surface ◽  
Engineering Systems ◽  
Porosity And Permeability ◽  
Wavy Interface

Flow over forests and vegetation can be characterized by some sort of porous structure of irregular surface through which a fluid permeates. Also, in engineering systems one can have components that make use of a working fluid flowing over irregular layers of porous material. This paper presents numerical solutions for such hybrid medium, considering here a channel partially filled with a sinusoidal porous layer saturated by a fluid flowing in turbulent regime. One unique set of transport equations is applied to both regions. Effects of Reynolds number, porosity and permeability on mean and turbulence fields are investigated. Results indicate that around the peaks of the sinusoidal layer values of the turbulent kinetic energy are higher.

Application of a Macroscopic Turbulence Model to Simulation of Flow in a Channel With Equally Spaced Porous Fins

2003 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Luzia A. Tofaneli
Keyword(s):  
Turbulence Model ◽  
Numerical Solutions ◽  
Solid Material ◽  
Computational Domain ◽  
Clear Fluid ◽  
Periodic Cell ◽  
Porosity And Permeability ◽  
Spatially Periodic ◽  
Porous Fins ◽  
Turbulence Transport

In this work, numerical solutions are presented for turbulent flow in a channel containing fins made with porous material. The condition of spatially periodic cell is applied longitudinally along the channel. A macroscopic two-equation turbulence model is employed in both the porous region and the clear fluid. The equations of mass continuity, momentum and turbulence transport equations are written for an elementary representative volume yielding a set of equations valid for the entire computational domain. Results are presented for the velocity field as a function of Reynolds, porosity and permeability of the fins. Pressure drop along the channel is compared with the case of solid material.

Pressure Drop Characteristics of Parallel-Plate Channel Flow With Porous Obstructions at Both Walls

2003 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Luzia A. Tofaneli
Keyword(s):  
Numerical Solutions ◽  
Control Volume ◽  
Computational Domain ◽  
Algebraic Equations ◽  
Clear Fluid ◽  
Simple Method ◽  
Periodic Cell ◽  
Porosity And Permeability ◽  
Volume Method ◽  
Turbulence Transport

In this work, numerical solutions are presented for turbulent flow in a channel containing fins made with porous material. The condition of spatially periodic cell is applied longitudinally along the channel. A macroscopic tow-equation turbulence model is employed in both the porous region and the clear fluid. The equations of momentum, mass continuity and turbulence transport equations are written for an elementary representative volume yielding a set of equations valid for the entire computational domain. These equations are discretized using the control volume method and the resulting systems of algebraic equations is relaxed with the SIMPLE method. Results are presented for the velocity field as a function of Reynolds number, porosity and permeability of the fins.

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.

Experimental and Numerical Study of Transport Phenomena in a Simulated Hydrothermal Crystal Growth System of Fluid-Saturated Porous Layer

2000 ◽  
Author(s):  
D. Mishra ◽  
A. Pal ◽  
N. Nemick ◽  
A. K. Saha ◽  
V. Prasad ◽  
...  
Keyword(s):  
Temperature Field ◽  
Porous Layer ◽  
Hydrothermal System ◽  
Numerical Study ◽  
Transport Phenomena ◽  
Composite Layer ◽  
Staggered Grid ◽  
Working Fluid ◽  
Hydrothermal Crystal Growth ◽  
Numerical Predictions

Abstract A simulated, non-pressurized hydrothermal system consisting of a fluid-superposed porous layer is fabricated and used for visualization and measurement of the temperature field using liquid crystal thermography. The system is used for various boundary conditions with pure glycerine as the working fluid and the porous layer is made of 3mm diameter glass beads. Experimental data is recorded using a color CCD camera and flow visualization is obtained through a long exposure video photography. A calibration is performed to relate the temperature with scattered colors at an orthogonal angle to the incoming white light sheet. Quantitative temperature data is obtained through this calibration and compared with the numerical predictions. For numerical studies the system is modeled as a composite layer of fluid and porous charge using the Darcy-Brinkman-Forchheimer flow model. A two-dimensional curvilinear algorithm using finite volume technique with a non-staggered grid is used to simulate the temperature field and transport phenomena for various Rayleigh–Darcy number combinations of varying aspect ratio. The results, for the first time, make an attempt towards understanding the transport process in hydrothermal system through both numerical simulation and experimental validation.

Thermal Instability of a Fluid-Saturated Porous Medium Bounded by Thin Fluid Layers

1987 ◽  
Vol 109 (3) ◽  
pp. 677-682 ◽  
Author(s):  
G. Pillatsis ◽  
M. E. Taslim ◽  
U. Narusawa
Keyword(s):  
Porous Medium ◽  
Porous Layer ◽  
Thermal Instability ◽  
Numerical Solutions ◽  
Fluid Layer ◽  
Critical Rayleigh Number ◽  
Convective Motion ◽  
Wave Number ◽  
Thermal Conductivity Ratio ◽  
Fluid Layers

A linear stability analysis is performed for a horizontal Darcy porous layer of depth 2dm sandwiched between two fluid layers of depth d (each) with the top and bottom boundaries being dynamically free and kept at fixed temperatures. The Beavers–Joseph condition is employed as one of the interfacial boundary conditions between the fluid and the porous layer. The critical Rayleigh number and the horizontal wave number for the onset of convective motion depend on the following four nondimensional parameters: dˆ ( = dm/d, the depth ratio), δ ( = K/dm with K being the permeability of the porous medium), α (the proportionality constant in the Beavers–Joseph condition), and k/km (the thermal conductivity ratio). In order to analyze the effect of these parameters on the stability condition, a set of numerical solutions is obtained in terms of a convergent series for the respective layers, for the case in which the thickness of the porous layer is much greater than that of the fluid layer. A comparison of this study with the previously obtained exact solution for the case of constant heat flux boundaries is made to illustrate quantitative effects of the interfacial and the top/bottom boundaries on the thermal instability of a combined system of porous and fluid layers.

Shape Optimization of an Organic Rankine Cycle Radial Turbine Nozzle

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
David Pasquale ◽  
Antonio Ghidoni ◽  
Stefano Rebay
Keyword(s):  
Numerical Solutions ◽  
Organic Rankine Cycle ◽  
Strong Shock ◽  
Rankine Cycle ◽  
Expansion Ratio ◽  
Computational Grids ◽  
Working Fluid ◽  
Optimization Strategy ◽  
Radial Turbine ◽  
Wide Range

During the last decade, organic Rankine cycle (ORC) turbogenerators have become very attractive for the exploitation of low-temperature heat sources in the small to medium power range. Organic Rankine cycles usually operate in thermodynamic regions characterized by high pressure ratios and strong real-gas effects in the flow expansion, therefore requiring a nonstandard turbomachinery design. In this context, due to the lack of experience, a promising approach for the design can be based on the intensive use of computational fluid dynamics (CFD) and optimization procedures to investigate a wide range of possible configurations. In this work, an advanced global optimization strategy is coupled with a state-of-the-art CFD solver in order to assist in the design of ORC turbines. In particular, a metamodel assisted genetic algorithm, based on the so-called `off-line trained’ metamodel technique, has been employed. The numerical solutions of the two-dimensional (2D) Euler equations are computed with the in-house built code zFlow. The working fluid is toluene, whose thermodynamic properties are evaluated by an accurate equation of state, available in FluidProp. The computational grids created during the optimization process have been generated through a fully automated 2D unstructured mesh algorithm based on the advancing-Delaunnay strategy. The capability of this procedure is demonstrated by improving the design of an existing one-stage impulse radial turbine, where a strong shock appears in the stator channel due to the high expansion ratio. The goal of the optimization is to minimize the total pressure losses and to obtain a uniform axisymmetric stream at the stator discharge section, in terms of both the velocity magnitude and direction of the flow.

Simulation and Experimental Validation of a Magnetocaloric Microcooler

2006 ◽  
Author(s):  
Simone L. Ghirlanda ◽  
Sangchae Kim ◽  
Cesar F. Hernandez ◽  
Muhammad M. Rahman ◽  
Shekhar Bhansali
Keyword(s):  
Magnetic Field ◽  
Numerical Simulation ◽  
Experimental Validation ◽  
Working Fluid ◽  
Experimental Setup ◽  
Fluid Temperature ◽  
Micro Channel ◽  
Clear Fluid ◽  
Average Temperature ◽  
Small Magnetic Field

This research focuses on the simulation and experimental test and validation of a magnetocaloric microcooler that works under a small magnetic field obtainable by an electromagnet or a permanent magnet. The numerical simulation model of the cooler was constructed by finite element method. Three different kinds of bonded channel layers were used. The temperature change of the working fluid in the cooler was analyzed. The results from the simulation showed a clear fluid temperature difference between the outlet and inlet of the channel (ΔT) of 11 °C while the fluid average temperature ≈ 7.01 °C at the outlet of the microcooler. The microcooler was fabricated using the MEMS processes, and experimental setup was developed for testing of the microcooler. The cooling test was performed for coolers with different channel layers – only micro channel wafer, microchannels in Si-Si fusion bonded wafers and microchannels in glass-Si anodic bonded wafers. Simulated and experimental results of the cooler demonstrate the effect of the materials that were used for microchannels and intermediate plates, on the cooling characteristics.

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