Dye Washout with Scalar Transport Equation in ANSYS CFX
Case Study: Blood Flow Through Aortic Arch
Hello, this is Ertan Taskin from Ozen Engineering, Inc. In this video, I'll be demonstrating a method for modeling numerical dye washout using the scalar transport equation in ANSYS CFX. This is a case study of blood flow through the aortic arch.
Introduction
Blood is not an ordinary liquid, and uninterrupted streamline flow is critical for medical device applications due to the potential for thrombus formation caused by flow stasis. This method investigates residence time by numerically modeling dye washout using the scalar transport equation.
Application Overview
This method has recently been introduced for ventricular assist device-specific washout investigations. It relies on solving a scalar transport equation where the scalar represents the dispersion of the dye.
Modeling Details
- The dye concentration, denoted as C, is modeled by solving a convection-diffusion-reaction equation where diffusion and reaction terms are zero.
- The fluid domain is initialized with a dye concentration value of one, while the inlet dye concentration should be zero.
- During the transition, the dye concentration should not be zero, and natural conditions offer different solutions for fluorescence.
Simulation Setup
The mass flow inlet condition was applied for a corresponding volumetric flow rate of 5 liters per minute, which is typical for a ventricular assist device (VAT) flow. For the branches, mass flow outlet conditions were applied with 20%, 10%, and 10% of the inlet flow for branches 1, 2, and 3, respectively. The pressure outlet condition was used for the main outlet.
Workbench Environment
- Geometry and mesh were generated using SpaceClaim.
- The mesh was transferred to both the steady state and transient modules.
- Steady state results were used as input for the transient simulation.
Simulation Process
Pre-Processing
- Inlets and outlets were specified with arrows.
- Additional variables were turned on to define a volumetric scalar and a transport equation in the fluid models section.
- A subdomain was generated with the corresponding flow domain, and sources were defined as zero.
Steady State Simulation
During the steady state simulation, fluids and turbulence were solved, but the scalar transport was not yet activated. The results showed higher velocity entering the aortic arch and portions leaving the flow domain through branches and the main outlet.
Transient Simulation
- The analysis type was set to transient, with total time and time steps defined according to model settings.
- The scalar transport equation was solved alongside fluids and turbulence.
Results
The results demonstrated concentration profiles across the three branches. Initially, no changes were observed, but as the flow affected the branches, the inlet dye reached the outlet regions and gradually reduced over time.
Conclusion
This method is a helpful tool for comparative analysis and can be applied to any problem where residence time is crucial. While demonstrated on an aortic arch with blood flow, it can be applied to any medical device associated with blood flow in various settings.
Thank you for watching.
Hello, this is Ertan Taskin from OZEN Engineering. In this video, I'll be demonstrating a method on modeling numerical dye washout with scalar transport equation in ANSYS CFX. It is a case study of blood flow through the aortic arch.
Blood is not an ordinary liquid; therefore, uninterrupted streamline flow is critical for medical device applications due to the potential for thrombus formation because of flow stasis.
It is a residence time investigation method, which numerically models dye washout using a scalar transport equation. Let me give you a bit more information about the application.
This method has recently been introduced to perform ventricular assist device-specific washout investigation, and the method relies on solving a scalar transport equation where the scalar demonstrates the dispersion of the dye.
The dye concentration, denoted as C, was modeled by solving a convection-diffusion-reaction equation, and in this case, diffusion and reaction terms are zero. The fluid domain needs to be initialized with a dye concentration value of one, while the inlet dye concentration value should be zero.
During the transition, the dye concentration should be zero. The dye concentration should be 1.6 million, not natural. Conditions would offer different plastic solutions to zulip fluorescence.
The burstbox control system affects a flow expressed by action blast speed of 5 to 0 and goes up and down in the ionen. This response is governed by idioms.
The temperature between the acid and alkaline solutions shook out by Filter board bedQ10 main insights of a purulent fluid I yut ICP-C, which is observed here at a precise concentration.
The mass flow inlet condition was applied here for a corresponding volumetric flow rate of 5 liters per minute, which is a typical VAT flow. For the branches, again, mass flow outlet is applied with 20%, 10%, and 10% of the flows at the inlets for branches 1, 2, and 3, respectively.
The pressure outlet condition was used for the main outlet. For the setup, we utilized the workbench environment where different modules are utilized. Let me continue from the model here. As you see, the different components are also shown here.
Geometry and mesh, steady-state CFX, as well as transient CFX. The mesh is transferred to the setup of the steady-state module as well as to the setup of the transient module. The results of the steady-state run are also utilized as an input to the transient simulation.
Let me briefly show you how the geometry looks. Its geometry is generated with the space claim here. Inlets and outlets are here. Corresponding mesh with some prism layers there. However, in many other applications, finer mesh and multiple prism layers might be needed.
In the pre-processing screen of the steady-state CFX, the inlets and outlets are specified with the arrows here. As this is an application of a scalar transport equation, we have to turn the additional variables on and define a volumetric scalar.
We should also define a transport equation in the fluid models section of the model. Lastly, we should generate a subdomain with the corresponding flow domain and then go to the sources and define zero here.
We can control the simulation results with certain outflow controls, such as velocities on different regions as we like to do. While running the simulation, the fluids and the turbulence are solved. However, the scalar transport is not activated yet. The steady-state results are shown here.
This is the state of the simulation. This is the inlet section where the higher velocity actually enters and hits the aortic arch. Some portions are leaving the flow domain from the branches and the main outlet region.
If we go back to the transient setting, we will see that this time the analysis type is transient. We can define the total time and the time steps depending on how the model settings are.
When we go to the export parameters, we see that the scalar transport equation will be solved, including the fluids and the turbulence. The results are obtained and could be demonstrated in different forms, such as concentration profiles as shown here.
For a while during a simulation, nothing happens. But after the flow is affected towards the branches, we start to see the impact of the inlet dye reaching the outlet regions. It gradually reduces down over time.
This method could be a helpful tool to make a comparative analysis and can be implemented to any problem where the residence time is an important parameter. In this case, it is demonstrated on an aortic arch with a blood flow.
However, it can be applied to any medical device associated with blood flow at many different settings. Thank you for watching.
