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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 Simulation of Impact Load of Offshore Rocket Recovery on ShipZhi Wang (1) , Shan Ma (1) , Dahui Liu (2)(1) College of Shipbuilding Engineering, Harbin Engineering University
Harbin, Heilongjiang, China(2) CIMC Offshore Engineering Research Institute,Yantai, Shandong, China

ABSTRACT

different working conditions is simulated and compared with theexperimental results in the relevant literatures to verify the accuracy ofthe physical model. Secondly, considering the motion of rocket during
the recovery process, the calculational model of unsteady flow field isdetermined and used to simulate the impact loads on the deck surface
during the recovery process.

The simulation is based on the two-dimensional axisymmetric,
Reynolds-averaged N-S equation and Realizable k-ε turbulence model,
the CFD software STARCCM+ is used to numerically simulate andanalyze the dynamic gas flow field in the process of offshore rocket
recovery. The pressure and velocity load characteristics of impinging
jet during the recovery process and the time history curves of the field
variables at different positions on the deck are studied. The impact load
analysis method of the gas jet on the deck is summarized and analyzed.
The results can lay the foundation for the analysis of ship motion
response under impact load in the recovery process.

THEORETICAL BASIS

KEY WORDS: computational fluid dynamics; marine rocket
recovery; gas jet; overlapped mesh; time series.

INTRODUCTION
In recent years, the Falcon 9 launch vehicle of SpaceX company has
been successfully recovered many times on land and sea. It has formeda mature commercial launch and recovery system, which proves thetechnical feasibility of the launch and recovery scheme of the offshore
rocket, and the cost is low, which has broad commercial application
prospects. When the rocket returns to the deck, the gas jet generates ashort-term continuous and variable impact load on ship. The coupling
effect of gas jet impact load and wave will cause the ship's six-degreeof-freedom motion, among which the pitch and roll have the greatest
influence. Excessive inclination will lead to the problem of rocketalignment and attitude measurement and control in the recovery process,which affects the safety of rocket and ship(Wang F and Cheng HW,2016).

The jet flow of rocket must comply with three major conservation laws:
the mass conservation law, the momentum conservation law and theenergy conservation law,.because the high temperature and pressure, In
addition, the fluid also needs to comply with the appropriate turbulent
motion equation. The turbulence model in this paper uses Realizable kε , The model is more suitable for free flow (jet and mixing layer),rotating uniform shear flow, cavity flow and boundary layer flow. The
results of the above flow process simulation are compared with thestandard k- ε The results of the Realizable k- ε turbulence model aremuch better, especially in the simulation of circular and flat jets. The
specific formulas are as follows:
Mass conservation equation:� ����+ �� ���
�=0(1)Momentum conservation equation ( N-S equation ) :� �����+� ��� �����������

=− �� + �� + �����(2)Energy conservation equation ( first law of thermodynamics ) :Therefore, this paper adopts the following calculation scheme : Taking
the Falcon 9 rocket body and a solid rocket engine as an example, thenumerical simulation method is used to simulate and analyze the gas
flow field on the deck during the rocket recovery process. After the firstrocket engine ignites, the rocket decelerates vertically back to the deck.
In this process, the height of rocket and deck is constantly changing.
Firstly, the static steady flow field of rocket gas wake under two�2 �� � �+ 2 +���+�2 �� ��� �+ 2 +�
���

=����
��
− � + � ��� + ��� �� (3)
�����
���

In the formula, ρ ,u ,p ,q , μ , δij , ��� are the gas flow density, velocity
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