With the addition of a co-simulation interface between MotionSolve and AcuSolve, you can now solve multi-physics problems that involve complex rigid body movement, coupled with fluid flow, that generates pressure forces on the rigid bodies. This capability lets you enhance the fidelity of your multi-body system, letting you generate more realistic results.

In this scenario, MotionSolve computes the displacements and rotations for the rigid bodies, while AcuSolve computes the forces and moments on those bodies.  Both solvers exchange data with each other while stepping forward in time via the TCP socket protocol.  This means that the two solvers can be located on different machines and on different platforms and still communicate with one another.  For example, the CFD simulation can run on an HPC, while the MBS simulation can run locally on a laptop.

Tutorial Objectives

In this tutorial, you will learn how to setup a model in MotionView that will be coupled with AcuSolve.  You will use the MotionSolve-AcuSolve co-simulation interface to couple the rigid body dynamics of a check valve within a pipe with the flow field.  The AcuSolve model has already been setup for you and is located at <installation directory>\14.0\tutorials\mv_hv_hg\mbd_modeling\motionsolve\cosimulation\Check_Valve_Coupled.acs. Steps for running this model in AcuSolve are included as part of this tutorial.

To learn more about how to setup the model in AcuSolve, please refer to <installation_directory>\14.0\acusolve\<platform>\help\acu\acusolve_tut\Tutorials\Check_Valve_Coupled\.

Software Requirements

To successfully complete this tutorial, the following must be installed:

The following scenarios are supported for the MotionSolve-AcuSolve co-simulation:

From the table above, the co-simulation is currently only supported for the Windows 64-bit platform for MotionView and MotionSolve.  You may use either a Windows 64-bit or a Linux 64-bit installation of AcuSolve.

Simulation Environment

The co-simulation interface between MotionSolve and AcuSolve consists of a “middleware” utility executable, acuMSI.exe.  This executable is responsible for:

This is shown schematically in Figure 1 below.

Pipe with a check valve

A check valve is a mechanical device that permits fluid to flow in only one direction.  This is controlled by a shutter body.  Fluid flowing in one direction pushes the shutter body in one direction, thereby opening the valve.  Fluid flowing in the opposite direction pushes the shutter body in the other direction, which causes the valve to shut and prevents flow reversal in the pipe.  Check valves are found in pumps, chemical and power plants, dump lines, irrigation sprinklers, hydraulic jacks, for example.

The geometry that is modeled in this tutorial is illustrated in Figure 2 below. It consists of:

The fluid flow in the pipe is assumed to be axisymmetric.  This allows you to model only a part of the check valve.  In this example, a 30 degree section of the geometry is modeled, as shown by the blue part in Figure 2.  The advantage of doing this is a reduced simulation time while still capturing an accurate solution.

The check valve assembly consists of a disc-like body mounted on a stem.  When fluid flows in the direction specified by the red arrows in Figure 2 above, the fluid forces the shutter body to translate in the same direction as the fluid.  The motion of the shutter body is also affected by a spring damper attached between the shutter body and the perforated plate.  Finally, 3D rigid body contact is modeled between the shutter body and the stop to arrest the motion of the shutter body in the direction of the flow.

For the MBS model, only 1/12 of the shutter body and the perforated plate are modeled.

At the start of the simulation, the flow field is stationary.  A pressure specified at the inlet drives the flow, which varies over time as a piecewise linear function.  This is illustrated in Figure 3.  As this pressure rises, the flow accelerates which in turn pushes the shutter body open and allows flow through the pipe.

This dynamics of this kind of model can be termed as being “tightly” coupled between the two solvers.  This means that the motion of the rigid bodies affects the fluid flow field, which in turn affects the rigid body motion in a cyclical fashion.

The rest of this tutorial assumes that this model has been correctly setup in AcuSolve.  Note that the model is designed to translate the shutter body until it collides with the perforated plate.  The MotionView model has been designed with a contact between these two bodies that causes the shutter body to rebound appropriately.  To allow the rigid bodies to come into contact without the AcuSolve finite element mesh fully collapsing, the perforated plate in the fluid model has been offset by 0.002m in the positive X direction.  This allows the MotionView model to react as specified by the contact entity while keeping the AcuSolve mesh from fully collapsing.

Step 1: Load the model in MotionView

This model is prepared to run in MotionSolve but requires modifications to run in co-simulation with AcuSolve.  These steps are outlined below.

Once the model is loaded into MotionView, the graphical window displays the shutter valve, perforated plate, joint and spring entities, as well as a graphical representation of the spring damper as shown in Figure 4.

The MotionSolve model consists of the following components:

Step 2: Specify the “wet” body that will interact with AcuSolve

To couple with AcuSolve, you need to specify one or more "wet" bodies.  A "wet" body is a body in the MotionSolve model which interacts with the fluid flow and thus has forces and moments acting on it.  Such a body can translate or rotate due to the actuating fluid force/moment as computed by AcuSolve as well as due to any actuating forces/moments in the MotionSolve model.  In this example, we will define a single "wet" body – the shutter body that translates along the X axis due to fluid impinging on it.

To specify a body as "wet" in MotionView, you have to make use of a system definition, which is described below.

This changes the panel selection at the bottom.

The Import Definition dialog is displayed.  Leave the labels as-is and click OK.

A new system called System Wet Body is created in your model.

If you examine the contents of this system under the project browser on the left, you will see the following new components have been created:

At this point, you have setup the model in MotionView to interact with AcuSolve.

Step 3: Run the model without co-simulating with AcuSolve

To make sure that the MotionView model is setup correctly, run the model in MotionSolve and make sure there are no warning/error messages from MotionSolve.

By doing this, you are deactivating the flag which tells MotionSolve that this model is intended for co-simulation with AcuSolve.  Thus, MotionSolve simulates this model as a stand-alone model without co-simulating with AcuSolve.

You may run this model using the Run panel in MotionView and ensure that there are no error or warning messages reported.  This is recommended to ensure that the model works properly before attempting a co-simulation.

If you load the animation H3D generated from running this model, you will see that there is no motion in any of the parts.  This is because all of the actuation for this model comes from AcuSolve, which was disabled for this simulation.

Step 4: Export the model to XML

You may change the default name of the model.

Step 5: Verify the model between MotionSolve and AcuSolve

To successfully run the co-simulation, the model created in MotionView and the model created in AcuSolve must be consistent.  The following criteria need to be met in order for the two models to be consistent.

Note        The names are case-sensitive and must match exactly (see the text in red below).

MotionSolve (.xml):

<!-- MODEL.b_Part1 -->

<Body_Rigid

    full_label          = "Model-Shutter Body"

AcuSolve (.inp):

EXTERNAL_CODE_SURFACE( "Valve wall" ) {

   rigid_body_name                     = "Model-Shutter Body"

See the Run Panel in MotionView to set the print_interval, step size (h_max), and end times.

Note that the units in the MotionSolve and AcuSolve models do not need to match to run the co-simulation; however, the units must match to overlay the results animations in HyperView.  The units in MotionView are set via the Units form shown below:

All values in the MotionSolve model are set with respect to these units settings.

Step 6: Run the MotionSolve and middleware executables for co-simulation from the MotionSolve Run Manager

When you activate this option, the following dialog is displayed and you are prompted for additional options:

You may specify the following options here:

This launches MotionSolve as well as the acuMSI executable.  The MotionSolve run is paused at the first time step – it is now in waiting mode and the co-simulation will start as soon as AcuSolve is run.

Step 7: Run the AcuSolve executable for co-simulation

For this model, the default values are used.  AcuSolve runs using a single processor, and AcuConsole generates the input files and launches AcuSolve.

As the solution starts, an AcuTail window opens.  After executing acuPrep, AcuSolve stops at the acuRun path step.  It’s waiting for the execution of the MotionSolve process.

Soon, AcuSolve and MotionSolve should begin to communicate with one another.  You should be able to see relevant time stepping information in both solver windows.   For example, you should see something like the following in the MotionSolve window at the beginning of the co-simulation:

INFO: [AS-COSIM] Connected to AcuMsi on port 94043

 

INFO: [AS-COSIM] License checked out.

 

…

 

Time=2.000E-06; Order=1; H=2.000E-06 [Max Phi=1.314E-16]

Time=3.600E-02; Order=2; H=2.000E-03 [Max Phi=1.653E-08]

…

The co-simulation should take roughly 15 minutes to complete on a laptop (Intel i7. 2.8GHz).

Note that there is no order dependency on launching the co-simulation – either MotionSolve or AcuSolve can be launched first.

Step 8: Post process the results from the co-simulation

HyperView and HyperGraph can be used to post process the co-simulation results within the HyperWorks Desktop environment.

Animating the Co-simulation Results in HyperView

The animation H3D generated by the MotionSolve part of the co-simulation contains only the results from MotionSolve.  Similarly, the result files from AcuSolve only contain the results for the AcuSolve model.  To animate the results from the co-simulation, follow these steps:

HyperView loads the MotionSolve results file into the graphical window at the first time step.  From this point, you can animate the transient results using Start/Stop on the Animation Slider.

acuTrans -out -to h3d -h3dopt single -ts A

This creates a single .h3d file containing all of the time steps available for the simulation.

 

Once loaded, the graphical window contains both results and can be animated as before.  To visualize the information contained within the AcuSolve results, a Contour plot may be used.  Click on the Contour button, , to display the panel.

This creates a contour plot of the velocity magnitude overlaid with the results from MotionSolve in one window.

Plotting the MotionSolve Results in HyperGraph

You can also interpret the results with a two dimensional plot using HyperGraph.  HyperWorks Desktop can be used in a multi-window layout, allowing both HyperView and HyperGraph to be open at the same time.

 

This automatically adjusts the graphical window to accommodate two pages, defaulting to two instances of HyperView.

Once the .plt file is loaded into HyperGraph, the two outputs are available for plotting.

HyperGraph can be used to create additional traces on the same plot to generate the following plots.