Fluid Structure Interaction (FSI) Fluid Structure Interaction (FSI)

FEA- and CFD-based simulation design and analysis is playing an increasingly significant role in the development of medical devices, saving development costs by optimizing device performance and reliability, reducing benchtop tests and clinical trials, and helping to speed the regulatory approval process. Developing increasingly complex medical devices requires increasingly capable tools for simulation and testing. Our deep portfolio of simulation and testing solutions allows medical device developers to generate digital evidence of device performance across a range of engineering disciplines, throughout the product life cycle.

Medical applications are typically subjected to a wide range of complex environmental and biological loading conditions. The variability of these conditions makes the physical testing of all possible scenarios both difficult and time-consuming. By using FEA- and CFD-based multidisciplinary and multiphysics simulation technology, our engineers can study a greater number of real-world design behaviors with higher accuracy.

Hydrodynamics is a common application of CFD and a main core of Simulation Dynamics expertise. CFD allows the steady-state and transient hydrodynamics of hydrofoils, submersible vehicles, propellers, impellers, marine structures and marine plant to be computed with extremely high levels of accuracy. System properties such as mass flow rates and pressure drops and fluid dynamic forces such as lift, drag and pitching moment can be readily calculated in addition to the wake effects. This data can be used directly for design purposes or as input to a detailed stress analysis.

Hydrodynamics simulation and optimization is one of Simulation Dynamics’s core expertise. Deep knowledge and experience combined with advanced CFD and FEA software enable us to handle any problem with any level of complexity in very short time. We use CFD tools such as Numeca Fine/Marine, Ansys Fluent, Siemens Star-CCM+ and FEA tools such as Abaqus, Nastran and LS-DYNA together with very experienced engineers to help our customers in:

• ▶ Ship resistance analysis
• ▶ Hydrodynamic interaction between bodies: shielding effects, forward-speed effects
• ▶ Dynamic trim and sinkage behavior
• ▶ Propulsion and propeller performance optimization
• ▶ Ship wake analysis
• ▶ Shaft fatigue and lifecycle calculations of marine shafts — torsional vibration stress levels based on low-cycle, high-cycle and transient fatigue
• ▶ Vortex-induced vibration analysis
• ▶ Whipping and slamming impacts simulation: wave-induced hull vibration and hull-girder collapse assessment
• ▶ Erosion CFD simulation including hydrodynamics effects
• ▶ Offshore equipment stability: buoyancy and center-of-gravity studies
• ▶ Added masses for subsea hardware CFD calculations
• ▶ Hull performance assessment and wave-making CFD solutions
• ▶ Seakeeping behavior in regular or irregular waves
• ▶ Calculation of drag and lift on appendages
• ▶ Sail or wing optimization
• ▶ Ship structural analysis and design with FEA tools such as Ansys, Abaqus and Nastran
• ▶ Hydrodynamic plant & equipment
• ▶ Tidal power system hydrodynamic design
• ▶ Optimal gearbox lubrication
• ▶ Investigation of course-keeping and turning ability
• ▶ Motions analysis of FPSOs (Floating Production, Storage & Offloading units)
• ▶ Manoeuvring at low / variable speed in shallow and confined seaways — unsteady maneuvers: tacking, gybing
• ▶ Torsional vibration simulation with coupled CFD and FEA to identify interaction between components
• ▶ (Unlimited) deep-water / shallow-water condition modeling
• ▶ Floating wind-turbine design and simulation including dynamic elastic response of blades, tower and mooring lines
• ▶ Monohulls / conventional ships
• ▶ Multi-hulls: catamarans, SWATH, trimarans
• ▶ Asymmetric ships (monohulls as well as catamarans)
• ▶ Submarines
• ▶ FEA simulation of torsional vibration regarding ice impact on the propeller
• ▶ Fixed models as well as free-to-trim and sink conditions
• ▶ Coupled hydrodynamic CFD simulation with structural FEA to simulate transient structural behavior in irregular waves
• ▶ Added resistance in waves
• ▶ Combined drift and gyration

Solving thermal problems with CHT limits the engineer to the physical models that are contained within the CFD solver. More complex problems, such as those involving multimaterial structures or more accurate heat transfer coefficient (HTC) boundary conditions, can be solved by linking the CFD solver to a structural solver.

Transferring solid temperature fields from CFD CHT simulations to a structural thermal system makes it possible to take advantage of FSI simulation. The temperatures or HTCs calculated by CFD — and, if desired, the surface loads — are transferred to the structural finite element analysis (FEA) code. The FEA code then calculates the heat transfer and thermal fields in the structure as well as thermal–mechanical stresses.

A characteristic of a one-way fluid–structure interaction (FSI) solution is that the stresses and deformations calculated in the structural solver are not passed back to CFD to update the mesh and recalculate the flow.

Simulation Dynamics’s engineers also use shape-optimization methods to improve heat transfer for given problem conditions. For fatigue assessment we use Simulia FE-SAFE, Ansys nCode DesignLife and FEMFAT to calculate different types of fatigue safety factors from the results of thermo-mechanical simulations. The new design delivers the long life and high quality Simulation Dynamics’s customers expect.

• ▶ Multimaterial thermal/structural coupling via CFD → FEA transfer
• ▶ One-way vs two-way FSI: when to update mesh and flow
• ▶ Fatigue & life prediction with FE-SAFE, nCode DesignLife, FEMFAT

Simulating the thermal performance of a product early in the design phase can save large amounts of time and money by getting the design of the early prototypes right from a thermal management standpoint, thus reducing the need for additional prototypes that might otherwise be required to diagnose and correct thermal issues.

Simple computational fluid dynamics (CFD) software can be used to analyze thermal issues such as determining how heat is transferred through a fluid. But many problems are more complex, such as those that involve multiple mechanisms of heat transfer, where heat is transferred through both solids and structures.

Cases in which the fluids and structures involved in heat flow are closely coupled, so that thermal deflection of the structures affects the fluid flow, are also challenging. Engineers often need to understand how heat is transferred by a number of different mechanisms through a complicated interconnected system in order to understand how their product or process will perform under a given set of conditions. This point is one of the applications of FSI simulation with the coupled CFD–FEA method.

As in isolated FEA and CFD, one of the most profound benefits of FSI analysis is the ability to conduct comprehensive, multi-point optimization of designs. This process allows us to optimize a design to a given set of performance parameters and can be used to tune frequencies, maximize fatigue life, or avoid harmful resonance.

• ▶ Tune natural frequencies and avoid resonance
• ▶ Maximize fatigue life across operating conditions
• ▶ Perform multi-point, multi-physics optimization for performance targets

Applications such as leakage paths and thin film flows where thermal-stress induced structural deformation affects fluid flow present an even more difficult simulation challenge.

These applications can be simulated with two-way coupled CFD and structural thermal simulation. With this approach, the fluid flow solution is applied to the structure and the deformation of the structure is in turn applied to the fluid flow at each time step of the simulation. Two-way CFD and structural thermal simulation made it possible to set up a transient simulation that simultaneously solves the heat transfer coefficients (HTC) and near-wall temperatures in the fluid.

Failure to properly manage thermal performance can lead to inefficient energy use, uncomfortable or even unsafe temperatures, suboptimal performance and lower than expected product life. Engineering simulation is essential to diagnosing and evaluating solutions for thermal problems early in the design process when they can be corrected at the least possible cost and time. Simulation Dynamics’s engineering team can accurately predict thermal performance across a wide range of operating conditions with deep knowledge in FEA and CFD; coupling them gives us the capabilities required to address the most difficult thermal design challenges:

• ▶ Thermal shock resistance for brittle materials immersed in a fluid.
• ▶ Cracking mechanism in materials subject to high temperature gradients
• ▶ Furnace or burner failures
• ▶ Radiators and heat exchanger flow balance
• ▶ Cross flow heat exchanger liquid gas
• ▶ Pins and turbolators pressure drop and trade-offs
• ▶ Kilns transient analysis
• ▶ Thermal shocks on solar panels
• ▶ Cooling jackets — cooling holes position and dimensions
• ▶ Automotive exhaust, turbogas exhaust
• ▶ Defrosting ducts for automotive and home appliances
• ▶ Lamps, automotive headlights