Product: ABAQUS/Standard
This example illustrates the use of the co-simulation capability to perform a fluid-structure interaction (FSI) simulation. This problem considers the effect of an automotive car door closing on a door seal. It is a specific example of general cases where reasonable analysis results can be obtained only by considering the behavior of both the solid and fluid subdomains and their interaction. You can obtain an accurate result for the door closure force history in this problem by modeling the behavior of the air inside the seal in FLUENT and coupling to ABAQUS using the co-simulation capability and the MpCCI code coupling server.
Automotive car door seals generally take the form of hollow extruded sections of elastomeric material that line the perimeter of the door frame. When the door is closed, the seals act to keep water and other material from the environment out of the car, as well as providing some damping for the vibration motion of the door. A secondary role of the door seal is to provide damping resistance to the door as it is closed. In this role the seal can have a significant impact on the character of the door closing behavior, minimizing harshness and providing a quality closing sound. One variable that seal designers consider in controlling this door closing behavior is the air contained in the seal interior and the escape of this air through vents as the seal is compressed. This example problem considers the role of these vents in a case where a door is closed at a relatively fast rate.
The model consists of two subdomains. The structural domain, which consists of the seal and door, is modeled in ABAQUS/Standard. The fluid domain, which consists of the air inside the seal section and through the vent hole, is modeled in FLUENT. The structural and fluid domains share a common boundary located at the interior surface of the seal.
The structural domain is modeled as a three-dimensional periodic section, as shown in Figure 2.3.1–2. The modeled seal section is 50 mm long, with a vent hole 5 mm in diameter positioned at one end. The seal is meshed with C3D8I elements. The car door is modeled with an analytical surface-based rigid body. The seal material is elastic, with a Young's modulus of 60.7 MPa and a Poisson's ratio of 0.4.
The fluid domain is modeled with a hexahedral mesh, as shown in Figure 2.3.1–3. The air has a density of 1.225 kg/m3 and a viscosity of 1.7894 10–6 kg/ms. The FLUENT laminar flow model is used for the fluid solution. Since large-scale deformation of the fluid boundary is expected, the FLUENT moving-deforming-mesh facility is used. Refer to the FLUENT case file for additional details of the solver and moving-deforming-mesh settings for this example.
The ABAQUS and FLUENT models each have loads and boundary conditions that are applied to regions unique to their respective domains and do not directly affect the other model. These are applied without regard to the intent to perform a co-simulation analysis and represent the loads and boundary conditions you might apply to perform an uncoupled analysis. A second category of loads and boundary conditions occur on adjacent, or coupled, regions, where the two models must exchange load and boundary condition information. These are defined using co-simulation interface options particular to each solver, as described below.
The left surface of the seal is fixed, representing adhesion of the surface to the door frame. Symmetry conditions are applied at both ends of the section, resulting in a model of a seal with a vent-hole pitch of 100 mm. A finite-sliding contact interface is defined between the seal outer surface and the door rigid body. The door rigid body has an initial prescribed velocity of 0.25 m/s into the seal, and this velocity is ramped off to zero over a period of 28 ms.
The interior surfaces of the seal, including the interior of the vent hole, are identified as FSI-interfacing regions. The surface nodes will receive concentrated forces, CF, from FLUENT and pass current coordinates, COORD, back to FLUENT.
The fluid domain has an initial pressure of zero, specified as a relative pressure. The outlet surface of the vent hole has a zero-pressure boundary condition.
The exterior surfaces of the air domain, including the interior of the vent hole, are identified as FSI-interfacing regions through user-defined functions (UDFs) in FLUENT. The surface nodes will receive current coordinates, COORD, from ABAQUS and pass concentrated forces, CF, back to ABAQUS.
ABAQUS and FLUENT are configured to communicate results serially at a fixed time period of 10–3 s. Each code also has a nominal time increment of 10–3 s. Automatic time incrementation is used in ABAQUS; hence, increments are made between the co-simulation communication increments. The communication occurs in a serial, Gauss-Seidel, sense, as illustrated in Figure 2.3.1–4. ABAQUS is selected to lead the exchange in this simulation. Refer to the MpCCI user documentation for details on setting the communication time period and designating the leading and following codes.
The result of interest in this simulation is the reaction force on the car door, which is obtained for both the coupled FSI simulation and for an ABAQUS simulation that does not account for the fluid. The simulation is run for 120% of the duration of the closing, or 33.6 ms. The reaction force results are shown in Figure 2.3.1–5. A composite view of the seal and fluid at a time of 7 ms is shown in Figure 2.3.1–6. The reaction force plot clearly shows that a different force history is obtained when the effect of the air in the seal is considered; this effect will be lesser or greater as the door velocity is decreased or increased, respectively.
Door seal closure model without co-simulation.
Door seal closure model with co-simulation.
MpCCI code coupling control file.
FLUENT case file.
represents the fluid pressure communicated from FLUENT to ABAQUS; and 
represents the current configuration information communicated from ABAQUS to FLUENT.
