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Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

Numerical Investigation on Hydrodynamic Performance of a Harbor Tug
Song Zhang，Qing Wu
School of Transportation and Logistics Engineering, Wuhan University of Technology, Wuhan, Hubei, P.R. China

Jialun Liu*Intelligent Transportation Systems Research Center, Wuhan University of Technology, Wuhan, Hubei, P.R. China
National Engineering Research Center for Water Transport Safety, Wuhan, Hubei, P.R. China

Yangying HeSchool of Navigation, Wuhan University of Technology, Wuhan, Hubei, P.R. ChinaZhen YangSouthern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, Guangdong, P.R. China

summarized universal empirical methods
maneuverability under different circumstances.

ABSTRACT
Tugs have a simple hull form and good maneuverability. This paper
works on the hydrodynamic performance of an ASD harbor tug with askeg and bilge keels. Virtual oblique towing tests (OTT) and circularmotion tests (CMT) are conducted via the Reynolds-Averaged NavierStokes (RANS) method, to investigate the resistance and moment
characteristics. The obtained low-speed body forces and moments of
the harbor tug hull provide a basis for the establishment of the
maneuverability model and reference for operators to the hydrodynamic
performance of the ship.

topredictship

CFD methods are now widely used to study the hydrodynamic
performance and flow characteristics of the ship. Zhang (Zhang, Liu etal. 2019). Chen (Chen, Zou et al. 2017) carried out CMT tests to study
the forces and moments of the Esso Osaka model with large drift angles.
Based on virtual static and dynamic constraint model tests, Benedetto(Piaggio, Viviani et al. 2018, Piaggio, Villa et al. 2020, Piaggio, Villaet al. 2020) investigated the hydrodynamic forces and moments of anescort tug at slow- and high-speed conditions.
The CFD method has shown its potential in predicting hydrodynamicperformance and ship maneuverability. In the present work, low-speed
virtual OTT and CMT tests are carried out with prism layer andtrimmed cell meshes, k-ω SST turbulence model is utilized, andmoving reference frame (MRF) is adopted to work on thecharacteristics of body force and moment of the tug. Grid convergencestudy and comparisons with NMRI open data to verify the efficiency
and accuracy of the adopted methods. Series studies are conducted toobtain the body force, moment, and surface distribution of the tug.

KEY WORDS: Harbor tug; RANS; OTT; CMT; hydrodynamicperformance.

INTRODUCTION
In the busy harbor areas, tugs are widely used to execute escort, rescue,
berthing-assistant and other missions with low-speed steering. The
operational demands of the tug inspire the study of maneuverability interms of safety, effectiveness and operability. It is delicate andindispensable to study the hydrodynamic performance of the tug incertain motions.

METHODOLOGY
Studied ship and working conditions

Traditionally, experimental and empirical methods are utilized to study
the hydrodynamic forces and maneuverability of a ship. Oltmann(Oltmann and Sharma 1984) studied the hydrodynamic characteristics
of a single crew tanker and a twin-propeller twin-rudder container shipbased on slow-speed constraint model tests, and predicted the forward
and backward motion of the ships. The work of Kho King Koh (Kohand Yasukawa 2012), Fitriadhy and Yasukawa (Fitriadhy, Yasukawa etal. 2015) on the tug-towing system and tug-pusher system enables theprediction of the inland tug assistance system. Yoshimura (Yoshimura1988), Kijima (Kijima, Katsuno et al. 1990), and other scholars

The studied ship is a modified low-speed azimuth stern drive (ASD)
harbor tug with a skeg, upper and lower bilge keels on the port side andstarboard side, and azimuth stern thrusters. To investigate thehydrodynamic performance of the bare hull, the ship model is properlysimplified by eliminating the superstructure and the thrusters. The
principal particulars and the geometry view of the studied harbor tug
are indicated in Table.1 and Fig.1 respectively.

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