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Objective:

Learn how to use Boundary Conditions in a Static Analysis. Boundary Conditions (BCs) can be thought of as the environment your part is in. They include Forces, Displacement Restraints, Heat Generation, Pressure, and more. All of the internal and external elements acting on your model. You need a minimum of two BCs to run a simulation. The image below shows the current options for solid simulations on the left, and options for fluid simulations on the right. An image of the available boundary conditions that can be used in nTop.

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Procedure: Static Analysis BC

Looking at the Brake Pedal example, we can identify what BCs we want to use in our Static Analysis. The force is where your foot would be pressing on and the displacement restraint is where the pedal is connected to another piece and fixed in place. A Displacement Restraint is usually required when forces are involved to ensure the part is fixed in space. Without it, the simulation wouldn’t be able to run. A model of a break pedal. There is a force and a displacement restraint applied.

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  1. Create a Force BC:
  • Add a Force block to the workflow
  • Insert the FE Boundary by Body into the Boundary input
  • Set the Vector to (0,0,-600N). This represents a foot acting on the brake pedal head with a factor of safety.
The brake pedal model with the applied force on the pedal. The force block is shown next to the model. A close up of the brake pedal model with the applied force. The downward arrows represent the -600N of Force acting in the negative Z-direction over the entire brake pedal head. If you want more control over the direction of the force, you can edit it using the ‘Frame’ input.
  1. Create a Displacement Restraint BC:
  • Add a Displacement Restraint block
  • Insert the FE Boundary by Flood Fill selection into the Boundary input
Tip: If you left the input of DoFs, you would like to leave it unrestrained. The red icons on the hole represent the restrained boundary. The displacement restraint block and a close up of the brake pedal model showing the applied displacement restraint.

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Procedure: Fluid Analysis BC

An example tube model showing how velocity and pressure can be applied at the inlets. In this pipe example, we want to apply an intake velocity for a fluid. We need to have a second boundary condition applied for the simulation to run, so we will specify a pressure with no magnitude at the other end of the pipe.
  1. Create a Velocity BC:
  • Add a Plane from Normal block and position it at the center of the intake surface. Ensure the normal direction is directed towards the body.
  • Add a Virtual Boundary by Body block. Insert the plane into the Body input.
  • Add a Velocity block. Insert the Virtual Boundary by Body block into the Boundary input. Insert a value of 400 mm/s into the X input box of the Velocity input.
The pipe model next to the nTop notebook. The notebook has the pipe implicit body block, a plane block that is being used to define the inlet boundary, and a velocity block that is being applied to the inlet using the plane. The model shows the plane on the surface of the inlet.
  1. Create a Pressure BC:
  • Add a Plane from Normal block and position it at the center of the outlet surface. Ensure the normal direction is directed towards the body.
  • Add a Virtual Boundary by Body block. Insert the plane into the Body input.
  • Add a Pressure block. Insert the Virtual Boundary by Body block into the Boundary input. Insert a value of 0 Pa into the Magnitude input
The pipe model next to the nTop notebook. The notebook has a plane from normal block that is being used to define the outlet boundary, and a pressure block that is being applied to the outlet using the plane. The model shows the plane on the surface of the outlet. And that’s it! You’ve successfully added boundary conditions to your part. Are you still having issues? Contact the support team, and we’ll be happy to help!

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Download the Example file:

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