Overset Mesh and CFD Simulates a Clean Room Smoke Test

clean room environmentRecent innovations in ANSYS 18 overset mesh have made it possible to use computational fluid dynamics simulations to model the smoke tests that provide useful guidance in designing clean rooms.

Ensuring Clean Rooms are Actually Clean

In the healthcare and electronics industries, process contamination is a primary concern. They manufacture these sensitive products in clean rooms where the concentration of airborne particles is controlled to specified limits. For example, a Class 100 clean room keeps particles of 0.5 microns or larger to less than 100 per cubic foot of air. Even in these controlled environments, particles are constantly being created and can settle on and contaminate surfaces and products.  

To ensure sterility and eliminate cross-contamination, the engineering team must accurately model air flow in the cleanroom environment. Accurate air-flow modeling requires capturing the effects of the moving manufacturing equipment such as a robot arm on the airflow within its environment.

Physical Smoke Tests

Smoke tests, also known as airflow visualization tests, provide visual evidence of airflow direction. Unfortunately, smoke tests can be difficult and time consuming to carry out and to document. Check out this video:

What if the first pass could be carried out virtually without every having to suit up and set foot in the clean room?  What if problematic areas could be identified up front so that the actual smoke test resources can be used more productively?

Fluid Dynamics Simulation

Using overset mesh in combination with the relative mesh-motion capabilities of ANSYS Fluent makes it a straightforward process to simulate the flow induced by the motion of a robot with five separate translating and articulating components. The robot’s base, each arm and an end-effector are meshed as overset components. In addition, a collar mesh is used at the intersection between the final arm and the spherical wrist of the end-effector so that the spherical region of the end-effector geometry penetrates the arm geometry to allow 3-degree-of-freedom articulation.

overset mesh ansysoverset mesh

Section through the overset mesh for a multi-axis robot operating in a clean room. Five moving component grids are meshed, including the robot’s base, each arm
and the end-effector. A collar mesh is used at the intersection
between the final arm and the end effector’s wrist.

In ANSYS Fluent, multiple overset components may be included in a single overset interface, greatly simplifying problem setup. In fact, no explicit interface setup is required; Fluent software automatically creates an appropriate interface when the solution is initialized, if the user has not done so.

Though the complete motion is quite complex, each segment of the robot’s arm moves in pure rotation relative to the segment to which it is linked. The relative mesh-motion capability in Fluent allows the user to specify the motion of each component in terms of these simple rotations in the frame of reference of the preceding component. There is no need to directly specify the complex motion that results from the combination of translation and rotation of the various components.

CFD solution shows air movement flowing from ceiling inlets past the moving robot arm and exiting through outlets in the floor. The blue iso-surface represents
an updraft of dirty air from the floor.

Overset Mesh can Speed, Simplify Fluid Dynamics Simulations with Moving Parts

Engineering problems commonly require simulation of fluid flows with complex moving geometry. In ANSYS 18, Fluent’s overset mesh provides a valuable alternative to its existing suite of remeshing and mesh-smoothing methods, applicable to cases in which traditional approaches might be unsuitable.  Find out how overset can speed and simplify your simulations.

One thought on “Overset Mesh and CFD Simulates a Clean Room Smoke Test

  1. When are the overset mesh tutorials going to be posted on the customer portal?

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