SEN719 Literature Review: Analysis of Marine Propeller Simulation

This literature review provides an overview of waterjet propulsion as a modern marine propulsion system, highlighting its advantages over conventional propellers in specific operating conditions. It discusses the evolution of marine thrusters, comparing waterjet systems to turbomachines and mari...Read More

Introduction
Waterjet propulsion is considered as modern system of propulsion. This technique of propulsion
though it is not majorly conventionally used propeller but its characteristics supersedes the
convection propellers on operating conditions. Over the years now the waterjet propulsion
system has increased its efficiency, before we analyze this increase in efficiency it will be right
to understand the specific characteristics of the method of propulsion together with its advantage
and disadvantage on different operating conditions.
Comparison to Turbomachines
Convectional turbomachine operates with similar principality. The turbomachine systems are
used in absorbing energy and supply mechanical power using the shaft in order to form a higher
stream of energy. The thruster component inside the casing it contains is used to moderate
higher velocities by moving from the external to internal flow, similarly the aeronautical
thrusters developed from propellers and upgraded to jet engines, the same context is observed in
marine thruster that started with paddles and upgraded to waterjet propulsion systems and ducted
propellers.
Comparison with Marine Propellers
Based on past development of the marine propeller, the idea to implement marine propellers
screw to replace waterjet system because their design fixing procedure is simple, but due to the
new development of efficient pumps that are used with waterjet system has changed the thoughts
of using screw propeller. The waterjet propulsion specific characteristic that outshines the marine
propeller includes its ability to achieve higher velocities, it has the best maneuverability and also
the noise produced is moderately low. Since it has a draft that is shallow it can run the craft at a
shallow water but this can be affected by debris or mud which can be accumulated in the system
leading to breakdown of the pump. Its appendage drag at a higher velocity has ability of
achieving a bare hull of about 20% [13]. The cavitation extent between the propeller and wetjet
are totally different, therefore cavitation in wetjet will be produce under the conditions of higher
pressure and higher velocities. In case the trans-cavitating propeller or super-cavitating propeller
will fail to work then waterjet will be the best choice.
Waterjet Systems
In general their exit four types of waterjet propulsion. The four different types of waterjet are
brought about by the geometry of the ducting channel and the installation of the pump. Flush
intake in which the duct will open parallel to intake flow is the conventional intake used. In case
ram intake is used then its opening will be normal to the flow intake.
The figure below shows the parts of the flush intake, this includes duct inlet, pump, steering unit
and nozzle; water will be sucked through the opening intake and will be directed to the channel

duct into the pump, the pumps are classified as either axial, centrifugal or mixed pumps which
will depend on the angle in which the inlet flow will be allowed and the angle in which the flow
outlet will exit. The design of system of waterjet propulsion mainly use mixed and axial flow
pumps, in case multiple waterjet are used then it should be noted that mixed pumps are always
wider if compared to axial pumps.
Figure 1: Intake concepts
In case the flow will pass through the impeller it will move to the nozzle whose role is to ensure
that there is an increase in the flux momentum through ejection of the flow, that will be
accomplished if the nozzle is small or narrow, the shape of the nozzle is contracted to ensure
vena contracta of the jet discharge is in coincidence with the exit of the nozzle. At the vena –
contracta the static pressure will be equal to the ambient pressure at this section.
The waterjet system steer the craft through propulsion using steering nozzle or through the
deflection of the discharging jet through other installations. The angle in which the jet will be
directed will be ±300 [2]. Similarly, the jet momentum flux direction is changed by reversing the
bucket.

Literature review
The research which has been subjected to understanding the context of the system of waterjet
propulsion have been found to be numerous each reflecting on the perspective of operation of
the waterjet propulsion. The chapter will highlight on several published reviews on the
development and efficiency of the waterjet marine propulsion over the years.
In accordance to Purnell [9], the discussion of the methods that are aimed to increase waterjet
performances through usage of boundaries layers having low momentum wide intake flush on a
craft propeller that produces propulsion jet. The parameters of thickness layer, velocity
momentum and velocity energy, are used to project the performance of the waterjet, from his
perspective a large width area of intake will improve the coefficient of propulsive.
Etter et al. [4] idea was to differentiate between the waterjet model test that is driven using craft
with waterjet that is driven with propeller and similarly the performance of hull and experimental
evaluation procedure of the waterjet were also defined and comparison between the method of
convectional propeller and the proposed waterjet were also determined.
The mechanism of how the waterjet hull interacts were performed through propulsion tests, the
force of the jet system components is the core responsibility for the interactions while the
presences of the waterjet will changes the system pressure, the moment and forces which are
formed the system jet is a determination factor that is used to check if the trim angle of the
propelled hull is either big or small as compared to the optimum trim angle [1].
According to Dyne and Lindell [4] it is questionable on applying a method of acquiring and
getting a net thrust from fraction deduction, their application was through introduction of direct
method, where the shaft is given power in absence of repulsive factor. It is during this time that
two methods of controlling volume in order to obtain bare-hull and resistance created by viscous
of the self -propeller derived from theorem of momentum is introduced. The viscous resistance
are used then in calculation of the net thrust that is required, the volume control boundaries are
either upstream or downstream, where axial direction of flow is consistence.
Roberts and Walker [11] developed a theory of two dimensions which had either a boundary and
the other one which had no boundary ingestion layer. They demonstrated how the ingestion of
boundary layers is essential in the new development of boundaries. They also investigated on the
nozzle drag effect.
The analysis showed that the flush intake had no intake drag that was under the operation of the
potential flow, while the state of the viscous drag is negligible. In case where the gradient of
longitudinal pressure is missing that covers the opening intake then there will be no effect caused
by the hull interaction distortion of the potential flow on the jet performance that could be
detected.

Johansson [5] investigated on the vertical force that act on the propulsion of the waterjet unit,
and how the trim angle will change based on the forces and the resistance caused by the craft.
He developed a simulation of two dimensions potential flow to help examine the distribution of
pressure in the system of the waterjet. He carried two experiment; where the first experiment was
restricted to the geometry of the intake while the second the other experiment was confined to a
test on self-propulsion. The prediction of of the performance of hull was produced when the
results from the first experiment were included into savitsky’s. it was noted that vertical forces
are not formed the unit of the waterjet, but the waterjet moment causes a bow down variation
trim.
Van Terwisga et al. [13] investigated on the procedure of a standard test for a system of waterjet,
where the design procedure will require one to understand the intake, pump and the investigation
hull interaction on the waterjet. Based tho them a formula should be introduced when calculating
the momentum and flux energy. The previous formula required inclusion of pressure terms in
defining the momentum and the flux energy. The ITTC highlighted errors due to power
estimations, similarly intake, shape, profiles of the velocities and size of the area in concerned
was discussed.
Van Terwisga [13] demonstrated a compressive review on the modifications of the waterjet, with
several challenges encountered on the trust measurement, emphasis was placed momentum flux,
characteristics of power and efficiency the waterjet system and the its components. In the report
there were two different thrusts deduction portions, where the first demonstrated bare resistance
of the hull to the net thrust and the second one demonstrates the relationship that is between the
net thrust and the gross thrust. The summation of the two deduction thrust is equivalent to the
total thrust. Introduction of correction factor to the momentum velocity leads to formation of
momentum flux., and in case no detailing information is provided on the captured area then it
will be assumed that the captured elliptical area should be 1.5 times larger on width side as
compared to the geometry of the width of the intake. Finally, the test results of the self-
propulsion obtained from both bare hull and the self-propelled hull are fully discussed.
Application of the RANS method was used by Delany et al. [3] to analyze the performance of
two hull forms, both at the full scale and at the model scale. Where the parts of the hull were
shaped in order sustain axial flow waterjet units. The ITTC 1996 method was used to evaluate
the performance of the waterjet. The flux momentum of the jet that is achieved through
combination measurements with the calculated momentum ingested flux, the two are then used
in calculation of the gross thrust. It is demonistrated that the axial flow waterjet is deeper and
smaller when it is compared to the mixed waterjet flow. Therefore, the mixed waterjet will
increase its efficiency because of applying a fluid with low momentum in the boundary layers.
The difference between measured gross thrust and computed gross thrust was by 4%, this
difference is brought about by the existence of different geometry captured areas that are used in

measurement and computations. The analysis of the flow head of the inlet section of the pump
duct channel in absence of shaft, rotating shaft and in presence of the rotating shaft showed that
the flow energy was all equivalent on all the conditions. The only difference parameter that was
identified in all the cases was the velocity.
The code of RANS were used with Rhee et al. [10] for computation of the flow on waterjet hull
propeller and the bare hull by using overset grid with different generation mesh technique.
The analysis of the performance of the waterjet design and the optimization design of a high
speed craft, Kandasamy et al. [6] applied RANS method and the model of actuator disk
responsibly for body force. The results were compared to the results that were obtained from
ITTC procedure. The resistance computed for the bare hull is unser estimated by 2.5% when it is
compare to the values that are measured, while the flow rate are under estimated by about 3%
this is almost half of the error that are were computed by Takai et al. [12]. The accuracy of the
flow rate is improved by the application of a single grid in the duct channel insteady of using
overset grid that results to creation of of interpolation errors. The range of speed for both the
measured and computed thrust fraction deduction is between 0.4 < Fn < 0.7. sinkage is induced
by the waterjet whereas the ristance is increase to about 4% by the trim this do not in cooperate
the interaction effect of the waterjet hull.
Objectives
As per the literature review the physics context on the relationship between waterjet and hull
interaction is not clearly understood, at the same perspective deduction of the negative thrust is
one of the effects attributed to have severely affected the hull.
 To enhance deep understanding of the physics concept in regard to the relationship
between interaction of hull and waterjet, specifically investigating the negative deduction
of the thrust, its occurrence conditions.
 To identify the right and accurate method that will be used in estimation of waterjet
gross thrust.

Methodology
The centrifugal pump has the responsibility of increasing the head of flow. Pressure jump which
can be understood as rise in the abrupt pressure is the essential concept of investigating and
developing marine waterjet propulsion, the method will then be referred to pressure jump
method, on this section of methodology the description theory of this method, together with the
fomation and its combination as a flow solver are investigated.
Formation
The force balance of the hull waterjet system is first formulated, the system parts contribution to
the total resistance are shown on the figure below. Where hull resistance is denoted as RH, while
the drag of the duct channel is denoted as RD, the drag force is denoted as RN, and the force that
is exerted by the impeller is denoted as Fp
Figure 2: waterjet hull system force balance
The force balance on the x – direction will be represented as;
Fp-x = RH + RD-x + RN-x
Pressure jump resulted from the pressure difference on the impeller creates a force of thrust in
the waterjet system. The nozzle geometry sketch is shown on the figure below.
The thrust force denoted as Fp will be transmitted through the shaft that makes angle of Ɵ with
its horizontal plane. The balancing force along x – direction will be represented as;
Fp-x = (Pafter – Pfront) * Aimpeller * cosƟ
= ∆P * Aimpeller * cosƟ
Where,
Pafter and Pfront are pressure that occurs after and before respectively at the impeller disk.
Aimpeller is the area of the impeller disk.

Figure 3: Schematic presentation
Integration of the nozzle resistance
RN-x = ∬
S −nozzle
❑
σ *nxds
Where;
σ is the mean stress
Snozzle is the internal surface of the nozzle chamber
nx is the normal unit vector in x – direction.
∬
S −nozzle
❑
σ *nxds = ∬
S −nozzle
❑
ρ*nxds + ∬
S −nozzle
❑
τ *nxds
ρ is the pressure while τ is the shear stress tensor.
The actual flow is equivalent to two different superposition cases, where the first case involves
the flow in the nozzle chamber in absence of the pressure jump, addition of the pressure rise onto
the first case will result to formation of actual flow, and subtraction of pressure jump in the
nozzle chamber will result to a constant velocity inside the nozzle.
Figure 4: nozzle section
The static pressure after the impeller disk in absence of the system pump, PWOP + pressure jump,
∆ p may be represented as;

∬
S −nozzle
❑
P*nxds = ∬
S −nozzle
❑
Pwop*nxds + ∬
S −nozzle
❑
∆ P*nxds
This can be simplified as;
∬
S −nozzle
❑
∆ P*nxds = ∆P(Aimpeller – Anozzle) * cosƟ
∬
S −nozzle
❑
∆ P*nxds = ∆P(Aimpeller – Anozzle) * cosƟ
The balance equation will therefore be presented as;
∆P * Aimpeller * cosƟ = RH + RD-x + [ ∆P(Aimpeller – Anozzle) * cosƟ + ∬
S −nozzle
❑
Pwop*nxds + ∬
S −nozzle
❑
τ
*nxds]
This can be simplified as;
RTWOP = RH + RD-x +[ ∬
S −nozzle
❑
Pwop*nxds + ∬
S −nozzle
❑
τ *nxds]
Pressure jump balance will be represented as
∆ P = R TWOP
Anozzle∗cosθ
Assumption to this method is that there will be no head loss in the duct channel, this means that
total head at the initial section will be equal to the total head ate end of the system at a constant
pressure jump.
The expression can be presented through Bernoulli’s principle equation;
[P1 + ρgh1 + ½ *ρ*μ12] + ∆P = Patm + ρgh2 + ½ *ρ*μ22
Where,
ρ is the density of water, g is gravitation acceleration, P1 and Patm is the average pressure at the
area of the capture anf atmospheric pressure respectively, h1 and h2 is the average height at the
captured area and at the outlet section.
The SHIPFLOW code is used to calculate the potential flow, boundary conditions of Neumann
are applied on the hull while conditions of the kinematic and dynamic are applied at the exact
point of the free surface.

The SHIPFLOW XBOUND module is used in calculation of the friction resistance on the hull of
the waterjet which is based on the pressure, in the ducting channel the coefficient of friction is
determined by extrapolation means from the hull.
References
[1] K. Alexander, H. Coop, and T. van Terwisga, Waterjet-Hull Interaction Recent Experimental
Results. In SNAME Transaction. Society of Naval Architects and Marine
Engineers, 1994, pp. 87–105.
[2] J. Carlton, Marine Propellers and Propulsion Second Edi., Elsevier Ltd, 2007.
[3] Delaney, K. et al., Use of RANS for Waterjet Analysis of a High-Speed Sealift Concept
Vessel. In First International Symposium on Marine Propulsors SMP’09. Trondheim, Norway.
2009.
[4] R.J., Etter, V. Krishnamoorthy and J.O., Scherer, Model Testing of Waterjet Propelled Craft.
In Proceedings of the 9th General Meeting of the American Towing Tank Conference. Ann
Arbor, Michigan: Ann Arbor Science Publishers, Inc, 1981.
[5] A. Johansson, Trim Effect on High-Speed Craft due to Waterjet-Hull Interaction. MSc
Thesis, KTH Royal Institute of Technology, 1995.
[6] M. Kandasamy et al., ‘‘Integral Force/Moment Waterjet Model for CFD Simulations’’.
Journal of Fluids Engineering, 132(10), 2010.
[7] C. Kruppa, H. Brandt, C. Östergaard, Wasserstrahlantriebe für
Hochgeschwindigkeitsfahrzeuge. In Jahrbuch der STG 62, 1968 pp. 228–258.
[8] P. Lindell, and G. Dyne, Waterjet testing in the SSPA towing tank, 1994.
[9] J.G. Purnell, The Performance Gains of Using Wide Flush Boundary Layer Inlets on Water-
Jet Propelled Craft, Annapolis. 1976.
[10] B. Rhee, and R. Coleman, Computation of Viscous Flow for the Joint High Speed Sealift
Ship with Axial-Flow Waterjets. In First International Symposium on Marine Propulsors
SMP’09. Trondheim, Norway, 2009.
[11] J.L. Roberts, and G.J. Walker, Performance of waterjet propulsion system with boundary
layer ingestion. In Twelfth Australian Fluid Mechanics Conference. Sidney: The University of
Sidney, 1995, pp. 271–274.
[12] T. Takai, M. Kandasamy, and F.Stern, ‘‘Verification and validation study of URANS
simulations for an axial waterjet propelled large high-speed ship’’. Journal of Marine Science
and Technology, 16(4), 2011, pp.434–447.

[13] T. Van Terwisga, and K.V. Alexander, Controversial issues in waterjet-hull interaction. In
International Conference on Fast Sea Transportation, FAST ’95. Lubeck- Travemunde,
Germany, 2002, pp. 1235–1253.