Project C8 (finished)

Project C8 – Thomas Rung and Michael Hinze: Adjoint Shape Optimisation of Floating Bodies

Scientific Background and Motivation

International shipping is responsible for the transport of around 90% of the global trade. The dominant role of shipping is attributable to the low fuel consumption per tonne-km of transported cargo. However, the mere magnitude of around 45-50 thousand operating merchant vessels puts environmental and economic aspects of shipping more and more into the focus of optimisation efforts. The seaborne pollution as well as approximately 50% of the direct operating costs for shipping are related to fuel consumption, which in turn is governed by the resistance of the vessel. The latter is largely controlled (approximately 75%) by steady hydrodynamic contributions, i.e. the wave drag in calm water and the friction drag along the wetted surface. Therefore, reducing these drag contributions- even by a few per mille- is highly appreciated from commercial and environmental perspectives.

Aims and Objectives

The present proposal is concerned with the development of a robust, holistical and reliable optimisation framework for the hydrodynamic shape optimisation of free-floating ship hulls exposed to immiscible two-phase flows. Adjoint methods will be used in a parameter-free, gradient-based optimisation environment to capture wave and friction drag at Froude- and Reynolds-numbers of practical interest. Specific interest refers to accurate and robust adjoint two-phase flow models including an adjoint compressive interface treatment inspired by a Cahn-Hilliard Reynolds-Averaged Navier-Stokes approach, a dynamic change in the floating position, a novel reduced adjoint turbulence treatment as well as an improved technique for partially wetted shapes subjected to manufacturing constraints. Results will be transferable to the optimisation of other marine engineering applications, e.g. the design of near-shore operating renewable energy devices harvesting ocean waves in the surge zone close to a free surface.

PhD student: Niklas Kühl

PhD panel: Thomas Rung (advisor), Michael Hinze (co-advisor)

Niklas Kühl successfully defended his PhD on 21 September 2021

Publications

1. Kühl, N.: Adjoint-Based Shape Optimization Constraint by Turbulent Two-Phase Navier-Stokes Systems. PhD thesis, Hamburg University of Technology, 2021.

2. Bletsos, G., Kühl, N. and Rung, T.: Adjoint-Based Shape Optimization for the Minimization of Flow-Induced Hemolysis in Biomedical Applications. Engineering Applications of Computational Fluid Mechanics, 15(1):1095-1112, 2021.

3. Müller, P.M., Kühl, N., Siebenborn, M., Deckelnick, K., Hinze, M. and Rung, T.: A Novel p-Harmonic Descent Approach Applied to Fluid Dynamic Shape Optimization. Structural and Multidisciplinary Optimization, 2021.

4. Kühl, N., Müller, P.M. and Rung, T.: Adjoint Complement to the Universal Momentum Law of the Wall. Flow, Turbulence and Combustion, 2021.

5. Kühl, N., Kröger, J., Siebenborn, M., Hinze, M. and Rung, T.: Adjoint Complement to the Volume-of-Fluid Method for Immiscible Flows. Journal of Computational Physics, 440: 110411, 2021.

6. Kühl, N., Müller, P.M. and Rung, T.: Continuous Adjoint Complement to the Blasius Equation. Physics of Fluids, 33(3):033608, 2021.

7. Kühl, N., Hinze, M. and Rung, T.: Cahn-Hilliard Navier-Stokes Simulations for Marine Free-Surface Flows.Experimental and Computational Multiphase Flow, 2021.

8. Kühl, N., Müller, P.M., Stück, A., Hinze, M., Rung, T.: Decoupling of Control and Force Objective in Adjoint-Based Fluid Dynamic Shape Optimization, AIAA journal, 57(9), pp.4110-4114, 2019

9. Kröger, J., Kühl, N., Rung, T.: Adjoint Volume-of-Fluid Approaches for the Hydrodynamic Optimisation of Ships. Ship Technology Research. 65(1), 47-68, January 2018.

More details can be found on the homepage.