Bow shape modification through multi-objective hydrodynamic optimization: Methodology comparison between CAD-based FreeForm Deformation and Mesh-based Radial Basis Function approach

Marine industrial engineering face crucial challenges because of environmental footprint of vehicles, global recession, construction, and operation cost. Meanwhile, Shape optimization is the key feature to improve ship efficiency and ascertain better design. Accordingly, the present paper proposes an automated optimization framework for ship hullform modification to reduce total resistance at two cruise and sprint speeds. The case study is a bow shape of a wave-piercing bow trimaran hull. To this end, a multi-objective hydrodynamic problem needs to be solved. A combined optimization strategy using CFD hullform optimization is presented using the software tools STAR-CCM+ and SHERPA algorithm as optimizer. Furthermore, a comparison is made between CAD-based and Mesh-based parametrization techniques. Comparison between geometry regeneration methods is performed to present a practical and efficient parametrization tool. Design variables are control points of FreeForm Deformation (FFD) for CAD-based method and Radial Basis Function (RBF) for Mesh-based method. The optimization results show a 4.77% and 2.47% reduction in the total resistance at cruise and sprint speed, respectively.

Optimization of freeform surfaces using intelligent deformation techniques for LED applications

For many years, optical designers have great interests in designing efficient optimization algorithms to bring significant improvement to their initial design. However, the optimization is limited due to a large number of parameters present in the Non-uniform Rationaly b-Spline Surfaces. This limitation was overcome by an indirect technique known as optimization using freeform deformation (FFD). In this approach, the optical surface is placed inside a cubical grid. The vertices of this grid are modified, which deforms the underlying optical surface during the optimization. One of the challenges in this technique is the selection of appropriate vertices of the cubical grid. This is because these vertices share no relationship with the optical performance. When irrelevant vertices are selected, the computational complexity increases. Moreover, the surfaces created by them are not always feasible to manufacture, which is the same problem faced in any optimization technique while creating freeform surfaces. Therefore, this research addresses these two important issues and provides feasible design techniques to solve them. Finally, the proposed techniques are validated using two different illumination examples: street lighting lens and stop lamp for automobiles.

Design and Topology Optimization of Lattice Structures Using Deformable Implicit Surfaces for Additive Manufacturing

Additive manufacturing (AM) enables creation of objects with complex internal lattice structures for functional, aesthetic, structural and fabrication considerations. Several approaches for lattice generation and optimization, and their implementations in commercial systems exist. However, these commercial systems are typically independent from a CAD system, and therefore introduces workflow complexities for product lifecycle management. In this paper, we present a unified computer-aided framework for design, computer-aided engineering analysis (CAE) of solids with lattice structures, and freeform topology optimization within the CAD system that enables a seamless workflow. The proposed framework takes as input a solid CAD model and enables rapid generation of different lattice structures as repeated arrangements of lattice template shapes that replace input solid volume. Generated internal patterns are further optimized through freeform modifications to improve structural characteristics of the input model. Lattice modeling and optimization is performed using discrete implicit surface representations for the ease in representing complex topologies and performing modeling and freeform deformation operations. The output of the proposed framework is a polygonal represenatation of the lattified model ready for 3D printing. We have implemented our framework as a plugin to the Siemens PLM NX software system and examples are demonstrated for typical products in aerospace, medical and automotive industries.

Soft-Touch Haptics Modeling of Dynamic Surfaces

Virtual Reality applications strive to simulate real or imaginary scenes with which users can interact and perceive the effects of their actions in real time. Adding haptic information such as vibration, tactile array, and force feedback enhances the sense of presence in virtual environments. Haptics interfaces present new challenges in the situation where it is crucial for the operators to touch, grasp and manipulate rigid/soft objects in the immersive virtual worlds. Soft-touch haptics modeling is the core component in feeling and manipulating dynamic objects within the virtual environments. For adding the haptic sensations with interactive soft objects, the authors first present multiple force-reflecting dynamics in Loop subdivision surfaces, and further the haptic freeform deformation of soft objects through mass-spring Bezier volume lattice. The haptic constraint modeling based on metaballs is experimented to intuitively control the interactive force distribution within the dynamically constructed constraint, making the soft-touch simulation of objects simple to manipulate with enhanced realism.

Soft-Touch Haptics Modeling of Dynamic Surfaces

Virtual Reality applications strive to simulate real or imaginary scenes with which users can interact and perceive the effects of their actions in real time. Adding haptic information such as vibration, tactile array, and force feedback enhances the sense of presence in virtual environments. Haptics interfaces present new challenges in the situation where it is crucial for the operators to touch, grasp and manipulate rigid/soft objects in the immersive virtual worlds. Soft-touch haptics modeling is the core component in feeling and manipulating dynamic objects within the virtual environments. For adding the haptic sensations with interactive soft objects, the authors first present multiple force-reflecting dynamics in Loop subdivision surfaces, and further the haptic freeform deformation of soft objects through mass-spring Bezier volume lattice. The haptic constraint modeling based on metaballs is experimented to intuitively control the interactive force distribution within the dynamically constructed constraint, making the soft-touch simulation of objects simple to manipulate with enhanced realism.

Freeform Deformation Versus B-Spline Representation in Inverse Airfoil Design

Freeform deformation (FFD) is a well established technique for 3D animation applications, used to deform two—or three-dimensional geometrical entities. Over the past few years, FFD technique has aroused growing interest in several scientific communities. In this work, an extensive bibliographic survey of the FFD technique is initially introduced, in order to explore its capabilities in shape parametrization. Moreover, FFD technique is compared to the classical parametrization technique using B-spline curves, in the context of the airfoil design optimization problem, by performing inverse airfoil design tests, with a differential evolution algorithm to serve as the optimizer. The criterion of the comparison between the two techniques is the achieved accuracy in the approximation of the reference pressure distribution. Experiments are presented, comparing FFD to B-spline techniques under the same flow conditions, for various numbers of design variables. Sensitivity analysis is applied for providing further insight into the differences in the performance of the two techniques.