美国Iowa 大学Frederick Stern 教授学术报告
2018 年1 月8 日（星期一）
Prof. Frederick Stern，George D. Ashton Professor of Hydroscience and Engineering, The University of Iowa
报告题目1：URANS/DES V&V for KCS Free Running Course Keeping/ Added Power and Maneuvering/Speed Loss Simulations in Calm Water and Regular Variable Heading Waves
报告题目2：Status CFDShip-Iowa Free Running CFD for ONRT
时 间：2018 年1 月8 日（星期一），上午9:00-12:00
报告题目 3：Added Powering Measurements of KRISO Container Ship Maneuvering in Regular Variable Heading Waves
时 间：2018 年1 月8 日（星期一），下午14:00-17:00
报告 1 ： URANS/DES V&V for KCS Free Running Course Keeping/ Added Power and Maneuvering/Speed Loss Simulations in Calm Water and Regular Variable Heading Waves
CFDShip-Iowa URANS/DES V&V for free running course keeping and maneuvering simulations in calm water and regular variable heading waves, including a wide range of conditions and both body force (BF) and actual propeller (AP) modeling. The V&V follows Stern et al. (2001) and Xing and Stern (2010). Benchmark validation data is provided by Iowa wave basin experiments, which are conducted contemporaneous and interactively with the CFD studies. Results include: computational setup; hydrostatics and heave, pitch and roll natural frequencies; propeller open water; resistance, sinkage and trim; added resistance; calm water self-propulsion; calm water maneuvering; self-propulsion and course keeping in regular head and oblique waves. Integral and local flow analysis is performed and correlated with the validation results to improve the understanding of the physics.
报告2：Status CFDShip-Iowa Free Running CFD for ONRT
CFDShip-Iowa URANS/DES V&V studies are conducted for ONRT free running maneuvering and course keeping using both body force and actual propeller in calm water and regular waves. Course keeping in irregular wave and CFD-based SI were also studied. Additionally, self-propulsion computations in calm water were initially conducted to find the required propeller revolution for simulations in waves. For calm water self-propulsion, the simulation with the actual propeller (AP) provided the lowest error (3%D) among other simulations with different propeller models. For calm water maneuvering, the average errors of motions and trajectories were reasonably small, 7% and 4% for zigzag 2020 and turning circle maneuverings, respectively, using the axisymmetric body force propeller model (ABF). The error of the original system-based model for maneuvering in calm water was relatively large (~15%D) while the tuned model using CFD_based SI could drop the error by 50%. For course keeping in regular waves, the average error for the 1st harmonic amplitude of all motions over all wave headings was 16%D using ABF. The errors were often large for roll motion and velocities. The largest error was for the roll motion in stern quartering waves. EFD and CFD roll decay comparison showed kxx has to be adjusted. Simulations with adjusted kxx dropped the roll error from 95%D to 13%D. An additional simulation with AP propeller model showed the error for the 1st harmonic amplitude of the axial and side velocities drops by 30% and 65% due a better prediction of propeller and hull interaction. For course keeping in irregular waves, CFD showed reasonably small uncertainties for wave and motions (<4%). EFD data uncertainty was twice larger than CFD and more EFD runs are required to provide data for a longer duration and reduce the uncertainty. For maneuvering in regular waves, CFD errors were larger than those in calm water. The largest error was for the drift direction in turning maneuver. CFD simulation with AP is in progress to evaluate the propeller-rudder-hull interaction on the maneuvering characteristics in waves.
报告3：Added Powering Measurements of KRISO Container Ship Maneuvering in Regular Variable Heading Waves
To know more detail of added powering and propeller load fluctuations in regular waves during free-maneuvering, free-running tests of KRISO Container Ship model (KCS) are conducted. KCS 2.7 m model that was used in the previous surge-free added resistance experiments is modified and new free-running system with compact dynamometer is installed. Free-running tests in calm water and in regular variable heading waves are performed at IIHR 40 m × 20 m × 3 m wave basin to obtain 6DOF motions with thrust/torque data. Propeller open water tests were performed at Osaka University towing tank (OU). To evaluate facility bias and scale effects, trajectories, motions and maneuvering characteristic parameters are compared with those of different size model taken at other facilities. Free-running course keeping tests in regular variable heading waves are performed as same conditions with Tokyo 2015 A Workshop on CFD in Ship Hydrodynamics (T2015) case 2.10 and case 2.11. Those results are compared with the data taken at FORCE with 6 m free-running model and OU with 3.2 m model by surge-free mount. In head waves, trends of RAO for heave and pitch are the same under surge-free and free-running. Added thrust/torque and propeller open water efficiency reduction of IIHR and OU become maximum at λ/ L=1.15 where the added resistance was maximum under surge-free condition. In oblique waves, added thrust and torque become larger where the wave encounter angle is from 0° to 45° and both trends agree with other type of container ship. Thrust and torque fluctuations of KCS become larger in beam and following waves. Variation of self-propulsion factors due to wave encounter angles are small in oblique waves.
Prof. Frederick Stern is internationally recognized expert in ship hydrodynamics: computational methods, modeling, wave basin, towing-tank and flume experiments; experimental/computational uncertainty analysis/quantification; and deterministic/stochastic shape optimization. He has authored, co-authored, or edited: 7 international conference proceedings/books; 6 book chapters; 5 committee reports and 12 Quality Manual Procedures for the 21st–25th International Towing Tank Conference; 22 NATO AVT final report chapters; 178 journal articles; 4 moderate review journal articles; 2 online archive articles; 249 conference proceeding papers, and 51 reports. Prof. Frederick Stern is chair of the Steering Committee of the International Workshop on CFD in Ship Hydrodynamics since 2015 and is also a permanent member of the SNH-ONR Paper Selection Committee since 2005.
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