An Unstructured Finite Volume Method for Incompressible Flows With Complex Immersed Boundaries

A numerical method is developed for solving the 3D, unsteady, incompressible flows with immersed moving solids of arbitrary geometrical complexity. A co-located (non-staggered) finite volume method is employed to solve the Navier-Stokes governing equations for flow region using arbitrary convex polyhedral meshes. The solid region is represented by a set of material points with known position and velocity. Faces in the flow region located in the immediate vicinity of the solid body are marked as immersed boundary (IB) faces. At every instant in time, the influence of the body on the flow is accounted for by reconstructing implicitly the velocity the IB faces from a stencil of fluid cells and solid material points. Specific numerical issues related to the non-staggered formulation are addressed, including the specification of face mass fluxes, and corrections to the continuity equation to ensure overall mass balance. Incorporation of this immersed boundary technique within the framework of the SIMPLE algorithm is described. Canonical test cases of laminar flow around stationary and moving spheres and cylinders are used to verify the implementation. Mesh convergence tests are carried out. The simulation results are shown to agree well with experiments for the case of micro-cantilevers vibrating in a viscous fluid.

Implementation of a Semi-Implicit Pressure-Based Multigrid Fluid Flow Algorithm on a Graphics Processing Unit

A semi-implicit pressure based multigrid algorithm for solving the incompressible Navier-Stokes equations was implemented on a Graphics Processing Unit (GPU) using CUDA (Compute Unified Device Architecture). The multigrid method employed was the Full Approximation Scheme (FAS), which is used for solving nonlinear equations. This algorithm is applied to the 2D driven cavity problem and compared to the CPU version of the code (written in Fortran) to assess computational speed-up.

Probabilistic Approach to Conditional Probability of Release of Hazardous Materials From Railroad Tank Cars During Accidents

This paper describes a probabilistic approach to estimate the conditional probability of release of hazardous materials from railroad tank cars during train accidents. Monte Carlo methods are used in developing a probabilistic model to simulate head impacts. The model is based on the physics of impact in conjunction with assumptions regarding the probability distribution functions of the various factors that affect the loss of lading. These factors include impact velocity, indenter size, tank material, tank diameter, effective collision mass, and tank thickness. Moreover, each factor is treated as a random variable characterized by its assumed distribution function, mean value, and standard deviation (or variance). Reverse engineering is performed to back-calculate the mean values and standard deviations of these random variables that reproduce trends observed in available accident data. The calibrated model is then used to conduct a probabilistic sensitivity analysis to examine the relative effect of these factors on the conditional probability of release. Results from the probabilistic sensitivity analysis indicate that the most significant factors that affect conditional probability of release are impact velocity, effective collision mass, and indenter size.

A New Lattice Boltzmann Model for Phase Transition Process

A new lattice Boltzmann model, which is based on Shan-Chen (SC) model, is proposed to describe liquid-vapor phase transitions. The new model is validated through simulation of the one-component phase transition process. Compared with the simulation results of van der Waals fluid and the Maxwell equal-area construction, the results of new model are closer to the analytical solutions than those of SC model and Zhang model. Since the range of temperature and the maximum density ratio are increased, and the value of maximum spurious current is between those of SC and Zhang models, it is believed that this new model has better stability than SC and Zhang models. Therefore, the application scope of this new model is expanded. According to the principle of corresponding states in Engineering Thermodynamics, the simulations of water and ammonia phase transition process are implemented by using this new model with different equations of state. Compared to the experimental data of water and ammonia, the results show that the Peng-Robinson equation of state is more suitable to describe the water, ammonia and other substances phase transition process. Therefore, these simulation results have great significance for the real engineering applications.

Application of Business Rules in Design Processes to Tackle Uncertainty in Product Development

The development of innovative industrial products and systems, like e.g. aeronautical parts, is characterized by its complex processes under tight constraints. The involvement of multiple disciplines, departments and subcontractors to plan and create the optimal solution to fulfill given requirements under the constraints of time, money and quality leads to an urgent need in professional project management and monitoring. Although project management allows the comprehensive planning of the processes, detailed workflows and their implementation cannot directly be enforced, controlled and documented. Especially the lack in documentation and traceability leads to uncertainty in project execution and monitoring, as well as unconformity within the development of vital and safety critical products and systems. Best practices are substituted by ad hoc steps to meet deadlines like milestones and sync-points. Workflow management systems, which could offer some support to reduce addressed uncertainty, do not cover all involved parties and are not directly linked to the project management, leading to characteristic problems in such development projects. This paper presents a new approach to enforce the implementation of planned project plans in development projects with multiple development parties, based on business rules to increase traceability and documentation as well as to promote the adoption of best practices in project execution. The emphasis is placed on two aspects, namely a methodology of modularization of project plans and the formulation in business rules which are to be executed in business rules management systems as well as the implementation of a best practice repository based on the project plan modules. The modularization of project plans in combination with a linked business rules management system allows on the one hand promoting best practice application in project execution and on the other hand to save gathered project planning knowledge based on the actual implementation of the plan and to reuse it in forthcoming similar projects. A further important advantage is the ability to plan and enforce documentation of the actual execution of work packages and deviation from the plan, with a major impact on traceability. The work presented here has a valuable implication on the traceability in complex development processes and facilitate the application of best practices through project management by providing project plan modules with attached rules for their implementation in workflows.

Water Sport Tow Ropes

With the exception of tubing, towed water sports are afflicted by “wipeouts” that cause the athlete to release the handle of the tow rope. Once released, the resilience of the tow rope allows the rope and handle to spring toward the motorboat with the potential for overtaking the craft and impacting its crew. This paper examines this safety problem; specifically, it analyzes the wakeboard which subsumes water skiing, slaloming, kneeboarding and barefooting. A first order formulation is developed for describing the tow handle trajectory in terms of the system geometry, the skier’s grip strength and the mechanical properties of the tow rope. A rope stiffness criterion is established that guarantees the released tow handle will fall harmlessly into the water as opposed to striking the motorboat. The handle fight time and maximum impact speed are predicted for a worst case scenario. Further, the formulation provides a guideline for refining its conservative predictions by testing rope candidates.

Spot Locator for Autonomous Parking

For a semi-autonomous or fully-autonomous parking system, detecting adequate parking spot is the first step. Ultrasonic sensor possesses a good compromise between cost and performance since the detection range is very small. This paper describes a parking assist system with two ultrasonic sensors mounted at the left front and right front corners of the vehicle. Special signal filtering and processing is derived. Kinematic observer for the vehicle position estimation during search and parking phases is discussed. The suggested algorithm is implemented in Matlab/Simulink and was verified in a test vehicle.

Pendulum Animal Impact Testing

When vehicles collide with large animals, such as cattle, moose, elk or horses, the front seat occupants can be seriously or fatally injured; primarily due to roof deformation. In order to protect the front occupants in these accidents, it is necessary to understand the forces and energy involved in the interaction between the animal and the vehicle roof structure. The authors have developed a pendulum test incorporating an animal dummy to generate similar roof deformation to that experienced in real world animal impact accidents. The energy absorbed by the vehicle roof structure in the accident can then be determined by comparing the accident vehicle roof deformation to the pendulum test vehicle roof deformation. Ultimately, alternative roof structural designs are evaluated to demonstrate that a roof can perform well in this type of accident mode and reduce the risk for serious injuries to the occupants.

Hybrid Method of Engineering Analysis: Combining Meshfree Method With Distance Fields and Collocation Technique

Most of the modern engineering analysis methods (Finite Element, Finite Difference, Finite Volume, etc.) rely on space discretizations of the underlying geometric model. Such spatial meshes have to conform to the geometric model in order to approximate boundary conditions, construct basis functions with good local properties as well as perform numerical integration and visualization of the modeling results. Despite recent advances in automatic mesh generation, spatial meshing still remains difficult problem which often requires geometry simplification and feature removal. Conforming spatial mesh also restricts motions and variations of the geometry and breaks design-analysis cycle. In order to overcome difficulties and restrictions of the mesh-based methods, the alternative analysis methods have been proposed. We present a numerical technique for solving engineering analysis problems that combines meshfree method with distance fields, radial basis functions and collocation technique. The proposed approach enhances the collocation method with exact treatment of boundary conditions at all boundary points. It makes it possible to exclude boundary conditions from the collocation equations. This reduces the size of the algebraic system which results in faster solutions. On another hand, the boundary collocation points can be used to enforce the governing equation of the problem which enhances the solutions accuracy. Ability to use unstructured grids empowers the meshfree method with distance fields with higher level of geometric flexibility. In our presentation we demonstrate comparisons of the numerical results given by the combined approach with results delivered by the traditional collocation technique and meshfree method with distance fields.

Numerical Calculation on Vortex-Induced Vibration of the Circular Cylinder Using Low Reynolds Model in Hybrid Method

Fundamental research on interaction between flow and structure is presented for computation the fluid dynamics of different two-dimensional oscillating models. The Navier-Stokes equations are solved using finite volume method. A multigrid mesh method which was applied to the situation of flow past the stagnating or vibrating cylinder is developed to simulate this type of flow. The interactive results between flow and structure rigid cylinders have been present. The computation fluid dynamic codes mainly with low Reynolds RANS solver are used to solve the impressible viscous Navier-Stokes equations. Finite volume method which is coupled with conformal hybrid mesh method is developed to simulate this type of flow. Numerical investigation focused on the response and the fluid forces on the cylinders and also observed the different shedding model in the wake. The numerical results are compared in detail with recent experimental and computational work. Present numerical comparison also showed that solution using different turbulence model will make the result have a little discrepancy and each turbulence model has respective characteristics in numerical solution on the vortex-induced vibration of the cylinder. In addition, the formation of the 2P vortex shedding model through the lock-in region and the beginning of the shedding model transformation in numerical calculation from 2S model to 2P model has been analyzed.