Assessment on Effects of Under-Relaxation Factors on 2D Incompressible Laminar Flow over a Backward-Facing Step (BFS)

2012 ◽  
Vol 225 ◽  
pp. 55-59
Author(s):  
Yogeswaran Sinnasamy ◽  
Noor Arbiah Yahaya ◽  
Shahnor Basri ◽  
Abdul Aziz Jaafar ◽  
Azmin Shakrine Mohd Rafie
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Laminar Flow ◽  
Computational Studies ◽  
Backward Facing Step ◽  
Relaxation Factor ◽  
2D Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
Relaxation Factors ◽  
Error Percentage

In this paper, the effects of changing under-relaxation factors for different variables on the numerical solution of 2D incompressible laminar flow over a backward-facing step (BFS) are studied using PHOENICS commercial Computational Fluid Dynamics (CFD) software. This is conducted by changing under-relaxation factors for velocities and pressure during the 2D simulation. Ten different batches of under-relaxation factor for pressure ranging from 0.1 to 1.0 were used while the values of under-relaxation factor for velocities were manipulated between 0.1 and 1.0. For each batch of the computation, the error percentage of pressure and velocities were obtained. Based on this work, it is found that the recommended values of under-relaxation factor for pressure to achieve lower error percentage are between 0.6 and 0.8. Based on findings of the study, the appropriate values of under-relaxation factor for pressure and velocities can be selected to achieve the levels of error percentage permitted for computational studies.

CFD Study of Pitch Variations On Helically Coiled Pipe in Laminar Flow Region

2020 ◽  
Author(s):  
Anwer Faraj ◽  
Itimad D J Azzawi ◽  
Samir Ghazi Yahya ◽  
Amer Al-damook
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Laminar Flow ◽  
Friction Factor ◽  
Flow Structure ◽  
Flow Region ◽  
Alternative Solution ◽  
Experimental Investigations ◽  
Coil Diameter ◽  
Computational Fluid Dynamics Cfd

Abstract Experimental investigations of the flows inside helically coiled pipe are difficult and may also be expensive, particularly for small diameters. Computational fluid dynamics (CFD) packages, which can easily construct the geometry and change the dimensions with 100% of accuracy, provide an alternative solution for the experimental difficulties and uncertainties. Therefore, a computational fluid dynamics (CFD) study was conducted to analyse the flow structure and the effect of varying the coil pitch on the coil friction factor, through utilising different models' configurations. Two coils were tested, all of them sharing the same pipe and coil diameter: 0.005m and 0.04m respectively. Pitch variations began with 0.01 and 0.05 m for the first, second model respectively. In this study, the velocity was analysed, and the effects of this reduction on coil friction factor were also examined using laminar flow. The results were validated by Ito's equation for the laminar flow.

Efficiency prediction for storage chambers using computational fluid dynamics

1996 ◽  
Vol 33 (9) ◽  
pp. 163-170 ◽  
Author(s):  
Virginia R. Stovin ◽  
Adrian J. Saul
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Particle Tracking ◽  
Critical Value ◽  
Complex Geometries ◽  
Bed Shear Stress ◽  
Breadth Ratio ◽  
Computational Fluid Dynamics Cfd ◽  
Simulated Flow

Research was undertaken in order to identify possible methodologies for the prediction of sedimentation in storage chambers based on computational fluid dynamics (CFD). The Fluent CFD software was used to establish a numerical model of the flow field, on which further analysis was undertaken. Sedimentation was estimated from the simulated flow fields by two different methods. The first approach used the simulation to predict the bed shear stress distribution, with deposition being assumed for areas where the bed shear stress fell below a critical value (τcd). The value of τcd had previously been determined in the laboratory. Efficiency was then calculated as a function of the proportion of the chamber bed for which deposition had been predicted. The second method used the particle tracking facility in Fluent and efficiency was calculated from the proportion of particles that remained within the chamber. The results from the two techniques for efficiency are compared to data collected in a laboratory chamber. Three further simulations were then undertaken in order to investigate the influence of length to breadth ratio on chamber performance. The methodology presented here could be applied to complex geometries and full scale installations.

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