Views 
(Visited 194 times, 1 visits today)
   PDF Download PDF Downloads: 171

 Open Access -   Download full article: 

Numerical Simulation for Visualising Effect of Surface Roughness on Flow in Simple Pipe

Abhishek Sharma1, Vishal Gupta2*, Abhishek Kumar Jain2 and Sudeep Kumar Singh3

1National Institute of Technology, Rourkela. 2Maulana Azad National Institute of Technology, Bhopal (M.P.), India. 3Amity School of Engineering and Technology, Bijwasan. Corresponding Author E-mail: vishalgupta.manit@gmail.com

ABSTRACT: With advances in computational power and mathematics, CFD has emerged as boon for design optimisation in various fields. We are surrounded with fluids from every side. And the physics of fluid is very difficult to understand if all the aspects of real life are considered. The flow even inside a simple pipe is very complex to observe practically. Head loss occurs due to friction in pipes and leads to loss of energy. In this paper, effect of surface roughness in pipes has been simulated and results in graphical and pictorial form have been presented. The simulation have been done with CFX code using SST turbulence model

KEYWORDS: Computational fluid dynamics; steady state; frictional head loss

Copy the following to cite this article:

Sharma A, Gupta V, Jain A. K, Singh S. K. Adaptation of Sustainable Neighbourhood Elements (Snes) in Malaysian Urban Neighbourhood Planning. Ultra Engineer 2015;3(1)


Copy the following to cite this URL:

Sharma A, Gupta V, Jain A. K, Singh S. K. Adaptation of Sustainable Neighbourhood Elements (Snes) in Malaysian Urban Neighbourhood Planning. Ultra Engineer 2015;3(1). Available from: http://ultra-engineer.org/?p=248


Introduction

Earlier there were only experimental techniques available to predict the performance of turbo machinery and calculating the losses in flowing fluid even in pipes. The experiments were done on models. But observation of behaviour of flow was very difficult to observe and studying local parameters was very difficult [5]. With the advances in the field of computational mathematics and computational power, a lot of development has been taken place in the field of Computational Fluid Dynamics. Detailed flow analysis, study of local parameters, flow visualisation, detailed pressure and velocity distribution can be studied with the help of CFD [1,2]. There are many software packages available in the field of CFD [8]. The main objective of this paper is to discuss the effect of friction in pipes on flow.

Geometric Modeling and Common Input Data.

Geometry in 2D or 3D is needed for numerical flow simulation depending the nature of problem. The geometry which is flow domain is descritised into small elements called mesh over which governing equations are solved.

Geometric Modeling

For studying the effect, geometry of pipe of 200 mm with diameter of 10 mm is considered. One side of pipe is described as inlet and other is kept open to atmosphere. Modeling has been done in ANSYS ICEM CFD 14.0.  3-D view of pipe is shown in Fig.1.

Geometric Modeling and Common Input Data.

Geometry in 2D or 3D is needed for numerical flow simulation depending the nature of problem. The geometry which is flow domain is descritised into small elements called mesh over which governing equations are solved.

Geometric Modeling

For studying the effect, geometry of pipe of 200 mm with diameter of 10 mm is considered. One side of pipe is described as inlet and other is kept open to atmosphere. Modeling has been done in Ansys Icem Cfd 14.0.  3-D view of pipe is shown in Fig.1.

Click here to View figure Figure 1: Geometry of Pipe

 

Click here to View figure

Meshing

Tetra mesh has been used for meshing 3D domain and for 2D surfaces triangular elements are used. Prism layer has been applied at pipe surface for capturing boundary layer effect. Mesh quality is checked for orthogonlity and aspect ratio to be within recommended values of Ansys- Cfx. Meshing of pipe is shown in Fig 2.

Figure 2: Meshing of Pipe Figure 2: Meshing of Pipe

 

Click here to View figure

Table 1: Summary of mesh data is given in 

Part Name Number of nodes Number of elements Element type
Inlet 196 145

105

Triangular

Quadrilateral

Outlet 203 145

111

Triangular

Quadrilateral

Pipe wall 8772 17472 Triangular
Flow domain 56238 151623

52416

Tetrahedral

Wedges

Common input data

Input data is needed for defining the working fluid and overall physics. The values used in present analysis is mentioned in Table 2.

Table 2: Common input data

Analysis type Steady state
Domain Type Fluid domain
Fluid type Water
Reference Pressure 1 atm
Domain Motion Option Stationary
Mesh Deformation Option None
Fluid Temperature 250C
Turbulence Model SST
Density of Water 997 Kg/m3

Boundary conditions

Boundary such as inlet, outlet, wall, symmetry etc are needed to be defined and the value of obtained results also depends a lot on the values of boundaries defined. Flowing boundary conditions are defined for present work:

Inlet Boundary Condition

The mass flow rate and its direction with normal direction to the inlet of pipe is specified.

Outlet Boundary Condition

The reference pressure at the outlet was set equal to 1 atmospheric.

Wall Conditions

The walls of the domain is assumed to be smooth and no slip condition is assigned for smooth wall and its value is changed for varying the roughness of pipe.

 Formulae used

Total head and loss coefficient are computed using the following formulae:

Total head at inlet of pipe

Total head at outlet of pipe

Head loss coefficient

Mesh independency test

Mesh independency test has been done by considering three mesh sizes for the domain. The simulation is done for discharge of 0.001 m3/sec. The flow in pipe jet is assumed to be ideal, with a constant velocity profile. Results of mesh independency are given in Table 3.

Table 3: Mesh independency test

No. of elements No. of nodes Drop in pressure head Time taken
61047 19976 2.68 m 2 minutes
103075 39459 2.76 m 4 minutes
204039 56238 2.76 m 12 minutes

Drop in pressure head is free of mesh above 39459 nodes but for better pictorial visualisation and for further simulation, mesh with 56238 nodes is considered.

Results and Discussion

The analysis is carried out for six different values of pipe surface roughness. Roughness of pipe considered are 0 μm (smooth pipe), 0.0015 mm (PVC and glass pipes), 0.045 mm (steel pipes), 0.15 mm (galvanised iron pipes), 0.26 mm (cast iron pipes), 1.5 mm (concrete pipes). The RMS residual was set to 10-6 for termination of the analysis. The analysis provided pressure, velocity and turbulent kinetic energy distribution within the flow domain and at boundaries.

Figure 4: Variation pressure for smooth pipe Figure 4: Variation pressure for smooth pipe

 

Click here to View figure

 

Figure 5: Water velocity streamlines for smooth pipe Figure 5: Water velocity streamlines for smooth pipe

 

Click here to View figure

As observed from Fig.3, it is seen that turbulent kinetic energy increases from inlet to outlet. This may be due to boundary layer effect. Fig.4 shows variation of pressure from inlet to outlet which decreases gradually. Water velocity streamlines in Fig.5 indicates highest velocity at centre of pipe and least at the surface of pipe. Velocity at boundary also decreases from inlet to outlet.

Vol-3No-1_NUME_Abhi_fig6 Figure 6: Variation in turbulent kinetic energy for PVC pipe

 

Click here to View figure

 

Figure 7: Variation in turbulent kinetic energy for steel pipe Figure 7: Variation in turbulent kinetic energy for steel pipe

 

Click here to View figure

 

Figure 8: Variation in turbulent kinetic energy for galvanised iron pipe Figure 8: Variation in turbulent kinetic energy for galvanised iron pipe

 

Click here to View figure

 

Figure 9: Variation in turbulent kinetic energy for cast iron pipe Figure 9: Variation in turbulent kinetic energy for cast iron pipe

 

Click here to View figure

 

Figure 10: Variation in turbulent kinetic energy for concrete pipe Figure 10: Variation in turbulent kinetic energy for concrete pipe

 

Click here to View figure 

 

Figure 11: Variation in pressure for pvc pipe Figure 11: Variation in pressure for pvc pipe

 

Click here to View figure

 

Figure 12: Variation in pressure for steel pipe Figure 12: Variation in pressure for steel pipe

 

Click here to View figure

 

Figure 13: Variation in pressure for galvanised iron pipe Figure 13: Variation in pressure for galvanised iron pipe

 

Click here to View figure

 

Figure 14: Variation in pressure for cast iron pipe Figure 14: Variation in pressure for cast iron pipe

 

Click here to View figure

 

Figure 15: Variation in pressure for concrete pipe Figure 15: Variation in pressure for concrete pipe

 

Click here to View figure

Variation in turbulent kinetic energy can be seen from Fig. 6 to Fig.10. The variation in turbulent kinetic energy from inlet to outlet increases as roughness of the surface of pipe increases.

Pressure decreases from inlet to outlet in all the cases as seen from Fig.11 to Fig.15. Highest pressure difference is observed for concrete pipe.

Table 4: Variation in head loss coefficient and turbulent kinetic energy

 

Pipe type

Roughness size (mm) Turbulent kinetic energy  

Head loss coefficient

Inlet Outlet
Smooth pipe 0.0000 0.5799 0.6247 0.24708293
PVC Pipe 0.0015 0.5806 0.6648 0.25556047
Steel pipe 0.0450 0.5874 1.2989 0.34785651
Galvanised iron pipe 0.1500 0.5965 2.0326 0.44445985
Cast iron pipe 0.2600 0.6077 2.5555 0.49256872
Concrete pipe 1.5000 0.5837 4.6547 0.61886265

The average values of pressure, velocity and turbulent kinetic energy at inlet and outlet were obtained using function calculator in CFD- Post from simulation results. The values of loss coefficient is given in Table 4. It is observed from Table 4 that head loss coefficient decreases with increase in grain roughness size of pipe and is observed to be maximum for concrete pipe.

Conclusions

It is observed from numerical simulation results that pressure at the inlet of pipe is more as compared to outlet and decreases gradually. The comparison of head loss coefficients and pressure distribution indicates that PVC pipes lead to less loss of energy. It may also be concluded that CFD is good tool to predict the performance of pipes in less time. The effect of friction on the performance of turbo machines can also be studied with the help of CFD.

Nomenclature

CFD   Computational fluid dynamics

g         Acceleration due to gravity

H        Head

ρ         Density of the fluid

P        Pressure

TP      Total pressure

RMS  Root mean square

SST    Shear stress transport model

in        Inlet

out     Outlet

References

  1. Xiao Y X, Zeng C J, Zhang J, Yan Z G and Wang Z W, “Numerical analysis of the bucket surface roughness effects in Pelton turbine”, 6th International Conference on Pumps and Fans with Compressors and Wind Turbines, IOP Conf. Series: Materials Science and Engineering 52 (2013) 052032.
  2. Gupta V, Prasad V, 2012, “Numerical Investigations for Jet Flow Characteristics on Pelton Turbine Bucket”, International Journal of Emerging Technology and Advanced Engineering, Volume 2, Issue 7, pp 364-370.
  3. Rajak Upendra, Prasad Vishnu, Khare Ruchi, 2012, “Numerical Flow Simulation using Star CCM+”, The International  Institute  for  Science, Technology  and  Education Proceeding of International Conference on Recent Trends in Applied Sciences with Engineering Applications, Vol.3, No.6, pp 34-41.
  4. ANSYS CFX 13 software manuals.
  5. Modi P.N. and Seth S.M., 2011, Hydraulics and Fluid Mechanics including Hydraulic Machines, Standard Book House, Delhi.
  6. Bansal R.K., 2010, A Textbook of Fluid Mechanics and Hydraulic Machines, Laxmi Publications, Delhi.
  7. Garde R.J., 2009, Turbulent Flow, New Age International Pvt. Limited, New Delhi.
  8. Chapra S.C. and Canale R.P., 2001, Numerical Methods for Engineers, Tata Mc Graw Hill Publishing Company Ltd., New Delhi.
  9. Anderson John D., 1995, Computational Fluid Dynamics, McGraw-Hill Inc., New York.
  10. http://en.wikipedia.org/wiki/Friction_loss on 11/03/2015
(Visited 194 times, 1 visits today)

2 comments

  1. Hi,I log on to your new stuff named “Numerical Simulation for Visualising Effect of Surface Roughness on Flow in Simple Pipe – Ultra Engineer” on a regular basis.Your humoristic style is witty, keep up the good work! And you can look our website about اغانى شعبى 2017.

  2. When I saw these lace frontal https://www.youtube.com/watch?v=ny8rUpI_98I on line, I loved them. I’m hoping all over again.

Leave a Reply

Your email address will not be published.