International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056

Volume: 04 Issue: 05 | May -2017 www.irjet.net p-ISSN: 2395-0072

Computational Optimization of Water Jet Machining: Effect of Nozzle Jet

Diameter Ratio
Mithilesh Kumar Gupta1, Sanjay Sakharwade2

1M. Tech Scholar, Mechanical Engineering Department, RCET Bhilai, India

2Associate professor, Mechanical Engineering Department, RCET Bhilai, India
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - In this paper focuses on the computational inside flow field and outside high pressurized AWJ nozzle
analysis of a water jet (WJ) machining. For this a using ANSYS fluent. The obtained result shows that shock
computational model of water jet machining has been zone and wall jet zone in the external flow field of nozzle,
simulated by using ANSYS Fluent. A CAD model of nozzle has there exist free jet zone; the section of abrasive jet farther
been developed by using geometrical model of ANSYS. During from the target wall is of free jet structure; the shock
analyzing the effect operating pressure and nozzle parameter pressure field on the target wall is standard distribution; the
has examined. The effect of nozzle jet diameter ratio has been best shock range is 2-7 times the exit diameter of nozzle; the
observed on nozzle turbulent intensity, skin friction coefficient shock pressure of jet is proportional to the inlet pressure,
and velocity magnitude. The validated the obtained finite and is inversely proportional to the range.
volume results a comparison has been made with previous Anwar et al. 2013, use finite element (FE) method for AWJ
available literature and the result are showing good trend. foot print in which modelling, simulation and validation has
been done for various transverse speed and pump pressure.
Key Words: Jet diameter ratio, skin friction, Turbulence The obtained result of material removal rate is compared
Intensity. with experimental data and the profile of kerf formation has
also been examined.
1. INTRODUCTION Radim et al. 2013, investigates the cut wall during AWJ
process of non-corroding steels treated by cryogenic
Water jet cutting have a considerable niche in the material temperatures in liquid nitrogen. They reveal that the
processing industry. Like laser cutting instruments they are cryogenic temperatures significantly influence the material
accurate, easily managed and cause very little loss of structure and respective properties. The main aim of their
material. However, abrasive jet cutting does not involve high work is to enhance the material reliability in a wide range of
temperatures, which is characteristic to laser cutting, and as production systems and operation conditions.
a result they are suitable for practically any material. Liu et al. 2004, using CFD an ultrahigh velocity waterjets
Furthermore, the instrumentation required for high-speed and abrasive waterjets (AWJs) model has been modeled
jets is simpler and much cheaper. Consequently, jet cutting using Fluent. The model consist of 2 and 3 phase flow
can be implemented in a broad range of industries, ranging condition in which water and abrasive particle where
from small machine shops and quarries, to large sheet metal, allowed to flow at different velocity and volume fraction.
composites or ceramic processing in the car and aircraft Axinte et al. 2010, presents a geometrical model of the jet
industries. footprint (kerf) in maskless controlled-depth milling
applications. The model firstly capable to evaluate the
material specific erosion (etching) rate that is attained from
2. LITERATURE REVIEW
the jet footprint by taking the limiting conditions (high jet
feed rates) of the model. Once this is found, the jet footprint
Shiou and Asmare 2015, presents surface roughness can be predicted accurately for any jet feed speed.
improvement of Zerodur optical glass by means of an Wan and lim 2003, analyze transient flow in abrasive
innovative rotary abrasive fluid multi-jet polishing suspension jet cutting machines. The effort has been made in
process. Even though tauguchi approach has also been order to explore the problem of line and nozzle clogging,
implement. It has observed that 98.33% improvement in which would be overcome by the higher operating pressures
surface roughness has been achieved and the factors and the employing smaller nozzles for fine-beam systems.
effecting the surface roughness has also been discussed. Chen and siores 2003, investigates the characterization of
Wang et al.2014 conducts experimental investigate to different materials' cut surfaces using a scanning electron
explore the effect of different process parameters such as microscope. The effect of abrasive particle distribution in the
jet impact angle, standoff distance, water pressure, jet on striation development has discussed and examined by
abrasive particle diameter on material removal rate, means of laser Doppler anemometry.
removal depth and surface roughness for hard and brittle Hassan and kosmol 2001, develop a FEM model for AWJM
material, the alumina ceramic are used as base material. in explain the work piece- abrasive particle interaction. The
Baisheng et al. 2011, perform numerical simulation for model can predict the depth of deformation consequently

© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3151
 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017 www.irjet.net p-ISSN: 2395-0072

due to abrasive particle impact. The main aim of the develop x2 momentum equation
model is to predict the depth cut without performing
experimentation. In the results the dynamic behavior of the u2* u * u * p *  u * u * 
AWJ has been explored and the results are compared with
 u1* *2  u2* *1   *  Pr  *2  *2 
t * x1 x2 x 2  x1 x2 
the experimental work and shows good consistency.
Soiores et al. 1996, optimize the AWJ cutting technology Gr Pr 2 T *
for ceramics, experimentally by using statistical design
principles. A new cutting head oscillation technique has been Energy equation
employed and it has found that the cutting quality improves
by 30%. T * T * T *   2T *  2T * 
 u1* *  u2* *   *2  *2 
El-domiaty an rahman 1997, developed abrasive waterjet t * x1 x2  x1 x2 
model using two elastic-plastic erosion models. The model is
valid only for brittle material. The model has ability to Since in order to check the accuracy of developed
predict depth of maximum depth of cut on the basis of computational model which is coupled with Navier stokes
fracture toughness and hardness. Moreover, parametric equation and additional boundary conditions are provided
analysis has also been carried in order to investigate the through which heat transfer and mass flow, stress, etc other
parameter affect on maximum depth of cut. parameters are calculated and contour figures are
Wang 2002, develop a semi empirical model for abrasive generated and illustrated in the in this paper.
water jet (AWJ) cutting of composite layered materials.
During cutting of laminates, it starts delaminating form layer 4. METHODOLOGY
to layer, which results in failure of cutting process. Using the
developed model, the depth of jet penetration can be The governing equation of water jet machining is solved
determined and the performance can be enhanced during by using ANSYS Fluent solver. Since it's quite complex to
cutting process. solve the differential equation of motion manually, therefore
computational tool FEV tool has been applied to solve the
3. MATHEMATICAL MODELLING governing equation. In ANSYS 14.5 computational model has
been developed in geometrical section with given
In system water jet machining is been analyzed with geometrical parameters from the base paper i.e. [7-8]. After
different aspect ratio. The wall shear stress is analyzed that the geometrical model is extended to mesh section in
during cuting process and the effect of nozzle jet diameter which complete geometry of WJ is discretized into various
ratio has also examined, in additional to varying the numbers of nodes and elements i.e. (27,857 and 27,456)
orientation also the heat transfer and shear stress is taken in using mapped meshing the detail of meshing is given in
consideration with the wall surface of the nozzle. figure 5.2. Moreover, the geometrical mesh model is further
The equations governing this problem are those of Navier- named such inlet, outlet, axis, wall section, etc. so that proper
Stokes along with the energy equation. The Navier-Stokes boundary conditions can applied in order to evaluate
equations are applied to incompressible flows and performance characteristics of water jet machining.
Newtonian fluids, including the continuity equation and the
equations of conservation of momentum on the x and y

According to equations
u2 u u
 u1 1  u2 1 
t x1 x2
1    2u  2u 
    21  21   g  (T  T )
 x2  x1 x2 
u1* u2*
 0
x1* x2*
x1 momentum equation

u1* u* u * p *  u * u * 
 u1* 1*  u2* 1*   *  Pr  1*  1* 
t * x1 x2 x1  x1 x2  Fig. 1: Computational model detail of WJ nozzle

© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3152
 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017 www.irjet.net p-ISSN: 2395-0072

5. RESULTS AND DISCUSSION

The equation of motion of abrasive water jet machine is

solved by using control volume approach and all the
governing equation are solved by using ANSYS- Fluent solver
in which all the partial differential continuity and
momentum equation are solved by iterative process till all
the solution gets converged.
In order to validate the present work a computational
model of water jet machine has been developed and
compared with the available literature of Numerical
Simulation and Experimental work of Huang et al. [7-8] and
found that the obtained results are within acceptable limit
and showing same trend as shown in figure 4.

Fig. 2: Model Geometry

Fig. 3: Mesh computational model

Table 1 Operating parameters of water jet machining Ref.

[7-8]

(Proposed)
Parameter Value Value
Inlet Diameter 4mm 4mm
Converging angle,θ 26.560 300
Converging length 4mm 4mm
Focus tube length 17mm 18mm
Exit Diameter 1.3mm 0.65
Volume fraction 13% 7-10%
Density of primary
phase 998.2kg/m3 998.2kg/m3
Density of Fig. 4: Validation of present work with the Numerical
secondary phase 2300kg/m3 2300kg/m3 Simulation and Experimental work of Huang et al. [7-8]
Slip of Phases No Slip No slip
Turbulence model k-ϵ k-ϵ
Flow Incompressible Incompressible
Mode of operation Steady state Steady state
Stokes number 0.3552 0.3552

© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3153
 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017 www.irjet.net p-ISSN: 2395-0072

Fig - 5 : counter of pressure coefficient

Fig- 7 : Contour of skin friction coefficient

Fig- 8 : Effect of operating pressure on skin friction

coefficient across nozzle length

Fig – 6: Effect of operating pressure on pressure Figure 8 effect of operating pressure on skin friction
coefficient across the nozzle length coefficient across nozzle length. It has been found that on
increasing the operating pressure, skin friction coefficient
Figure 6 illustrates the effect of operating pressure on drastically increases till it reaches the peak and then there is
pressure coefficient across the nozzle length. It has been a significant drop and get constant. This is due to change in
observed that as the operating pressure enhances the rate of cross section from converge region to focal region. Since the
pressure drop across the axis and wall surface significantly skin friction coefficient is proportional to flow Reynolds
increases. It has also been scrutinized that the foremost drop number and corresponding to flow velocity.
in pressure across the axis and the wall surface is in the
region where nozzle cross section changes i.e. from Therefore, it can be concluded that at converge region
convergence region to Focal region. velocity increases rapidly which results in an increase in
coefficient. But the fluid flow is not fully developed in the
From this it can be also be revealed that on changing the converge region and when flow velocity changes there is a
sudden cross section abrupt change drop in pressure takes sudden decrease in skin friction due to sudden contraction
place. The same representation has been seen in figure 5. which corresponded to a loss of flow energy. This can be
revealed from figure 7 and it can be seen in nozzle length
between 0.020-0.015. Moreover, as the operating pressure
increases skin friction increases correspondingly to velocity.

© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3154
 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017 www.irjet.net p-ISSN: 2395-0072

Effect of jet diameter ratio Figure 10 demonstrates effect of operating pressure along
with nozzle jet diameter ratio on velocity magnitude. It has
seen that with increasing jet diameter ratio, the velocity
linearly increases. However, also on increasing operating
pressure the velocity increases. This is due to pressure is
inversely proportional to velocity and at the exit velocity
increases as per continuity equation Av=const as conferred
by Bernoulli equation.

It can also be revealed that the velocity magnitude at

400bar is 15.98% more as compared to 300bar. Whereas,
the rate of enhancement of velocity at 300bar is 4.92% and
5.69% at 400bar as jet diameter increases. From this it is
clear that as the operating pressure increases this rate of
enhancement of velocity significantly increases.

Fig- 9: Effect of jet diameter ratio on skin friction

coefficient

Figure 9 shows the effect of jet diameter ratio on skin

friction coefficient. It has been examined that skin friction
coefficient decreases linearly as nozzle jet diameter ratio
increases. Furthermore, on increasing operating pressure,
the rate of decline in skin friction is more noteworthy for
lower operating pressure. This is because of increase in the
jet diameter ratio means the surface area increases
eventually, the pressure decreases and results in decreases
in skin friction. Fig – 11 : Effect of operating pressure along with nozzle
It has also been observed that the rate of decline of skin jet diameter ratio on turbulent intensity across the axis
friction coefficient at 300bar is 37.378% more significant as and the wall surface.
compared to skin friction coefficient at 400bar. However, as
the operating pressure increases this rate of decline of skin Figure 11 illustrates the effect of operating pressure along
friction coefficient decreases remarkably. with nozzle jet diameter ratio on turbulent intensity across
the axis and the wall surface. It has been seen that the
turbulent intensity across the axis decreases significantly as
increasing jet diameter ratio of nozzle. It has been also found
that the rate of decrease in turbulent intensity across the
axis decreases as operating pressure increases. It has been
also concluded that at higher values of the jet diameter ratio
the turbulent intensity across the axis get constant. But
across the outlet the turbulent intensity decreases
continuously.

6. CONCLUSION

Cutting velocity of the nozzle increases as operating pressure

increases
As operating pressure increases, the skin friction coefficient
increases. At the critical region i.e. region between
convergence and focal region the skin friction coefficient
Fig -10 : Effect of operating pressure along with nozzle jet reaches its maximum value and sudden decrease has been
diameter ratio on velocity magnitude seen after that and gets constant in focal region of the nozzle.

© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3155
 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017 www.irjet.net p-ISSN: 2395-0072

At the critical region, the turbulent intensity within nozzle is A study for 908 jet impact angle”, CIRP Annals -
maximum and as operating pressure increases it increases. Manufacturing Technology 59 (2010) 341–346
While at the focal region the turbulent intensity remains
constant. [10]NIE Baisheng , WANG Hui, LI Lei, ZHANG Jufeng, YANG
On increasing jet diameter ratio, skin friction coefficient Hua, LIU Zhen, WANG Longkang, Li Hailong, “Numerical
decreases linearly. Moreover, on increasing operating investigation of the flow field inside and outside high-
pressure the rate of decline in skin friction is more pressure abrasive waterjet nozzle”, Procedia Engineering
significant for lower operating pressure. 26 (2011) 48 – 55
It has found that with increasing jet diameter ratio the [11] UHLÁŘ Radim, HLAVÁČ Libor, GEMBALOVÁ Lucie,
velocity linearly increases. However, also on increasing JONŠTA Petr,and ZUCHNICKÝ Ondřej, “Abrasive Water
operating pressure the velocity increases. Jet Cutting of the Steels Samples Cooled by Liquid
Increasing the jet diameter ratio the pressure significantly Nitrogen”, Applied Mechanics and Materials Vol. 308
decreases. This is because of increase in area leads to (2013) pp 7-12
decrease in pressure. Therefore, pressure magnitude
[12]Adnan Akkurt, “The effect of cutting process on surface
decreases less radically as operating pressure increases.
microstructure and hardness of pure and Al 6061
The turbulent intensity across the axis decreases aluminium alloy”, Engineering Science and Technology,
significantly as jet diameter ratio increases and get constant an International Journal xxx (2014) 1e6
when at higher at jet diameter ratio. While, the outlet the
turbulent intensity continuously goes on decreasing. [13]Yong Wang, Hongtao Zhu, Chuanzhen Huang, Jun Wang,
Peng Yao, Zhongwei Zhang, “A Study on Erosion of
REFERENCES Alumina Wafer in Abrasive Water Jet Machining”,
Advanced Materials Research Vol. 1017 (2014) pp 228-
233
[1] E. Siores, W. C. K. Wong, L. Chen, J. G. Wager, “Enhancing
[14]Fang-Jung Shiou∗, Assefa Asmare, “Parameters
Abrasive Waterjet Cutting of Ceramics by Head
optimization on surface roughness improvement
Oscillation Techniques”, CIRP Annals - Manufacturing ofZerodur optical glass using an innovative rotary
Technology Volume 45, Issue 1, 1996, Pages 327–330 abrasive fluidmulti-jet polishing process “,Precision
[2] A. E1-Domiaty I and A. A. Abdel-Rahman, “Fracture Engineering xxx (2015) xxx–xxx
Mechanics-Based Model of Abrasive Waterjet Cutting for
Brittle Materials”, Int J Adv Manuf Technol (1997)
13:172-181
[3] A.I Hassan and J. kosmol, “Dynamic elastic-plastic
analysis of 3D deformation in abrasive water jet
machining”, journal of material processing technology
113 (2001) 337-341
[4] J. Wang, D.M. Guo, “A predictive depth of penetration
model for abrasive waterjet cutting of polymer matrix
composites”, Journal of Materials Processing Technology
121 (2002) 390–394
[5] F.L chen and E. siories, “The effect of cutting jet variation
on surface striation formation in abrasive water jet
cutting”, journal of material processing technology
135(2003) 1-5
[6] H. Liu , J. Wang, N. Kelson , R.J. Brown, “A study of
abrasive waterjet characteristics by CFD simulation”,
Journal of Materials Processing Technology 153–154
(2004) 488–493
[7] GuihuaHu, Wenhua Zhu, Tao Yu and Jin Yuan,
“Numerical Simulation and Experimental Study of
Liquid-solid Two-phase Flow in Nozzle of DIA Jet”, IEEE
international conference korea (2008)
[8] Guihua Hu, Wenhua Zhu, Tao Yu, and Jin Yuan,
“Numerical Simulation and Experimental Study of
Liquid-Solid Two-Phase Flow in Nozzle of DIA Jet”, ICIC
2008, CCIS 15, pp. 92–100, 2008. © Springer-Verlag
Berlin Heidelberg 2008
[9] D.A. Axinte , D.S. Srinivasu , J. Billingham, M. Cooper,
“Geometrical modelling of abrasive waterjet footprints:
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3156