Analysis of the Manifold Area Change in a Flat Solar Collector

2013 ◽  
Author(s):  
N. C. Uzarraga-Rodriguez ◽  
A. Gallegos-Muñoz ◽  
Luis A. Payan-Rodriguez ◽  
Juan M. Belman-Flores
Keyword(s):  
Water Flow ◽  
Solar Collector ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flow Distribution ◽  
Navier Stokes ◽  
Cross Sectional ◽  
Navier Stokes Equations ◽  
Area Change ◽  
Uniform Flow Distribution

A numerical analysis of the characterization of the water flow through a flat solar collector is presented. The manifold area change for minimizing the water flow variation in the solar collector is analyzed. The area ratio in the inlet and outlet of the manifolds were modified in a range of Am/Ao = 1 to 4, where Am and Ao are the cross-sectional area modified and original of the manifolds, respectively. The solar collector investigated is equipped with six riser tubes, which are attached to the manifolds pipe. The numerical study was developed in a commercial Computational Fluid Dynamics (CFD) using FLUENT®. This code allows to solve the Reynolds averaged Navier-Stokes equations and the transport equations of the turbulence quantities. The results shown that increasing the inlet and outlet area of the manifolds allow a more uniform flow distribution compared to the original configuration of the solar collector. It also shows that the overall pressure drop in the solar collector is reduced.

Numerical Study on an Outlet Plenum of the PBMR

2011 ◽  
Author(s):  
Jae-Woo Ju ◽  
Sang-Moon Lee ◽  
Kwang-Yong Kim
Keyword(s):  
Nuclear Reactor ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Navier Stokes ◽  
Horizontal Line ◽  
Performance Parameters ◽  
Navier Stokes Equations ◽  
Roof Support

Parametric study on an outlet plenum of a PBMR type gas cooled nuclear reactor has been carried out using three-dimensional Reynolds-Averaged Navier-Stokes equations. Shear stress transport turbulence model is used for analysis of turbulence. Two geometric parameters are selected, namely, displacement on the horizontal line and angle of rotation about the center of gravity of the roof support block. Pressure drop and uniformity of flow distribution in the outlet plenum have been considered as the performance parameters of an outlet plenum of the PBMR. The results show that the performance parameters are affected considerably by the location of the roof support block.

Wall proximity effects on flow over cylinders with different cross sections

2014 ◽  
Vol 92 (10) ◽  
pp. 1141-1148 ◽  
Author(s):  
Seyfettin Bayraktar ◽  
Sedat Yayla ◽  
Alparslan Oztekin ◽  
Haolin Ma
Keyword(s):  
Cross Sections ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Proximity Effects ◽  
Navier Stokes ◽  
Cross Sectional ◽  
Navier Stokes Equations ◽  
Finite Volume Discretization ◽  
Wall Proximity

This paper presents the results of a numerical study on flow characteristics over circular, square, and diamond cross-sectional cylinders. Investigations are performed in a two-dimensional domain using the finite volume discretization method solver for Reynolds number, Re = 20 000. Unsteady Reynolds averaged Navier–Stokes equations with Spalart–Allmaras turbulence model have been used as a turbulence closure. After the validation of the simulations with the available experimental data from the open literature, global characteristics of the flow field around different shaped cylinders near the wall have been presented. Effects of wall proximity on cylinders are investigated for four different gap width (G) to cylinder width (D) ratios.

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

A numerical study of the interaction between unsteay free-stream disturbances and localized variations in surface geometry

1989 ◽  
Vol 209 ◽  
pp. 285-308 ◽  
Author(s):  
R. J. Bodonyi ◽  
W. J. C. Welch ◽  
P. W. Duck ◽  
M. Tadjfar
Keyword(s):  
Numerical Solutions ◽  
Free Stream ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Surface Geometry ◽  
Navier Stokes Equations ◽  
S Waves ◽  
Tollmien Schlichting

A numerical study of the generation of Tollmien-Schlichting (T–S) waves due to the interaction between a small free-stream disturbance and a small localized variation of the surface geometry has been carried out using both finite–difference and spectral methods. The nonlinear steady flow is of the viscous–inviscid interactive type while the unsteady disturbed flow is assumed to be governed by the Navier–Stokes equations linearized about this flow. Numerical solutions illustrate the growth or decay of the T–S waves generated by the interaction between the free-stream disturbance and the surface distortion, depending on the value of the scaled Strouhal number. An important result of this receptivity problem is the numerical determination of the amplitude of the T–S waves.

Numerical Study of Viscous Flows Inside Partially Filled Spinning and Coning Cylinders

1996 ◽  
Vol 118 (2) ◽  
pp. 335-340 ◽  
Author(s):  
Mohamed Selmi
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Center Of Mass ◽  
Steady Motion ◽  
Practical Interest ◽  
Nonlinear Effects ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Practical Applications ◽  
Analysis And Design

This paper is concerned with the solution of the 3-D-Navier-Stokes equations describing the steady motion of a viscous fluid inside a partially filled spinning and coning cylinder. The cylinder contains either a single fluid of volume less than that of the cylinder or a central rod and a single fluid of combined volume (volume of the rod plus volume of the fluid) equal to that of the cylinder. The cylinder rotates about its axis at the spin rate ω and rotates about an axis that passes through its center of mass at the coning rate Ω. In practical applications, as in the analysis and design of liquid-filled projectiles, the parameter ε = τ sin θ, where τ = Ω/ω and θ is the angle between spin axis and coning axis, is small. As a result, linearization of the Navier-Stokes equations with this parameter is possible. Here, the full and linearized Navier-Stokes equations are solved by a spectral collocation method to investigate the nonlinear effects on the moments caused by the motion of the fluid inside the cylinder. In this regard, it has been found that nonlinear effects are negligible for τ ≈ 0.1, which is of practical interest to the design of liquid-filled projectiles, and the solution of the linearized Navier-Stokes equations is adequate for such a case. However, as τ increases, nonlinear effects increase, and become significant as ε surpasses about 0.1. In such a case, the nonlinear problem must be solved. Complete details on how to solve such a problem is presented.

Numerical Study of the Effect of Inlet Constriction on Bubble Growth During Flow Boiling in Microchannels

2005 ◽  
Author(s):  
Abhijit Mukherjee ◽  
Satish G. Kandlikar
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Boiling ◽  
Navier Stokes ◽  
Channel Cross Section ◽  
Vapor Bubbles ◽  
Reversed Flow ◽  
Cross Sectional ◽  
Parallel Microchannels ◽  
Energy Equations

Flow boiling through microchannels is characterized by nucleation of vapor bubbles on the channel walls and their rapid growth as they fill the entire channel cross-section. In parallel microchannels connected through a common header, formation of vapor bubbles often results in flow maldistribution that leads to reversed flow in certain channels. The reversed flow is detrimental to the heat transfer and leads to early CHF condition. One way of eliminating the reversed flow is to incorporate flow restrictions at the channel inlet. In the present numerical study, a nucleating vapor bubble placed near the restricted end of a microchannel is numerically simulated. The complete Navier-Stokes equations along with continuity and energy equations are solved using the SIMPLER method. The liquid-vapor interface is captured using the level set technique. The results show that with no restriction the bubble moves towards the nearest channel outlet, whereas in the presence of a restriction, the bubble moves towards the distant but unrestricted end. It is proposed that channels with increasing cross-sectional area may be used to promote unidirectional growth of the vapor plugs and prevent reversed flow.

Experimental and Numerical Study of Vortex Induced Vibrations on a Spool Model

2018 ◽  
Author(s):  
David Gross ◽  
Yann Roux ◽  
Benjamin Rousse ◽  
François Pétrié ◽  
Ludovic Assier ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Perturbation ◽  
Industry Standards ◽  
Vortex Induced Vibrations ◽  
Recommended Practices ◽  
Decay Tests

The problem of Vortex-Induced Vibrations (VIV) on spool and jumper geometries is known to present several drawbacks when approached with conventional engineering tools used in the study of VIV on risers. Current recommended practices can lead to over-conservatism that the industry needs to quantify and minimize within notably cost reduction objectives. Within this purpose, the paper will present a brief critical review of the Industry standards and more particularly focus on both experimental and Computational Fluid Dynamic (CFD) approaches. Both qualitative and quantitative comparisons between basin tests and CFD results for a 2D ‘M-shape’ spool model will be detailed. The results presented here are part of a larger experimental and numerical campaign which considered a number of current velocities, heading and geometry configurations. The vibratory response of the model will be investigated for one of the current velocities and compared with the results obtained through recommended practices (e.g. Shear7 and DNV guidelines). The strategy used by the software K-FSI to solve the fluid-structure interaction (FSI) problem is a partitioned coupling solver between fluid solver (FINE™/Marine) and structural solvers (ARA). FINE™/Marine solves the Reynolds-Averaged Navier-Stokes Equations in a conservative way via the finite volume method and can work on structured or unstructured meshes with arbitrary polyhedrons, while ARA is a nonlinear finite element solver with a large displacement formulation. The experiments were conducted in the BGO FIRST facility located in La Seyne sur Mer, France. Particular attention was paid towards the model design, fabrication, instrumentation and characterization, to ensure an excellent agreement between the structural numerical model and the actual physical model. This included the use of a material with low structural damping, the performance of stiffness and decay tests in air and in still water, plus the rationalization of the instrumentation to be able to capture the response with the minimum flow perturbation or interaction due to instrumentation.

3D modelling of the flow distribution in the delta of Lake Øyeren, Norway

2010 ◽  
Vol 41 (2) ◽  
pp. 92-103 ◽  
Author(s):  
Peggy Zinke ◽  
Nils Reidar Bøe Olsen ◽  
Jim Bogen ◽  
Nils Rüther
Keyword(s):  
Water Level ◽  
Cross Sections ◽  
Stokes Equations ◽  
Morphological Changes ◽  
Flow Distribution ◽  
Field Measurements ◽  
Navier Stokes ◽  
Error Sources ◽  
Navier Stokes Equations ◽  
Water Level Measurements

A 3D numerical model was used to compute the discharge distribution in the channel branches of Lake Øyeren's delta in Norway. The model solved the Navier–Stokes equations with the k–ɛ turbulence model on a 3D unstructured grid. The bathymetry dataset for the modelling had to be combined from different data sources. The results for three different flow situations in 1996 and 1997 showed a relative accuracy of the computed discharges within the range of 0 to±20% compared with field measurements taken by an ADCP at 13 cross sections of the distributary channels. The factors introducing the most error in the computed results are believed to be uncertainties concerning the bathymetry. A comparison between the computational results of the older morphology data from 1985–1990 and the model morphology from 1995–2004 indicated that morphological changes in this period had already had consequences for the flow distribution in some channels. Other important error sources were the inevitable use of averaged water level gradients because of unavailable water level measurements within the delta.

Numerical Prediction of Turbulent Wakes Behind a Square Cylinder

1998 ◽  
Vol 14 (1) ◽  
pp. 23-29
Author(s):  
Robert R. Hwang ◽  
Sheng-Yuh Jaw
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Wall Region ◽  
Square Cylinder ◽  
Mean Velocity ◽  
Navier Stokes Equations ◽  
Turbulent Vortex Shedding ◽  
Model Equations ◽  
Good Agreement

ABSTRACTThis paper presents a numerical study on turbulent vortex shedding flows past a square cylinder. The 2D unsteady periodic shedding motion was resolved in the calculation and the superimposed turbulent fluctuations were simulated with a second-order Reynolds-stress closure model. The calculations were carried out by solving numerically the fully elliptic ensemble-averaged Navier-Stokes equations coupled with the turbulence model equations together with the two-layer approach in the treatment of the near-wall region. The performance of the computations was evaluated by comparing the numerical results with data from available experiments. Results indicate that the present study gives good agreement in the shedding frequency and mean drag as well as in some phase profiles of the mean velocity.

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