Tuning Vascular Network Boundary Conditions

Categories:

Today, we will tuning 1D vascular network boundary conditions to achieve a desired flow distribution and inlet pressure in Flownex. Flownex allows users to easily specify outflow using the designer, by tuning and optimizing network boundaries to meet a desired set of input criteria. I will be using a characteristic model of the aortic arch through the iliac bifurcation with a prescribed transient inlet flowrate. I will walk through how to use the designer to specify outlet flow distributions at the outlet and the time averaged pressure at the inlet.

This method may be used to mimic patient data, determine the desired resistance or compliance chamber air volume when designing a benchtop model. The designer iterates specified network variables until the desired conditions are met. The designer can be used with individual components, or to set global parameters, dictating multipliers for subsets of boundary condition groups (such as downstream perfusion resistance).

Network Overview

This network will use a specified flowrate boundary condition and a three element windkessel (lumped model) boundary condition. This is a commonly utilized method to model the downstream compliance (from larger vessels) and resistance (primarily from smaller vessels and capillary beds). We will also be using a custom fluid to model blood. This network uses a script defined waveform for the inlet flow. Coefficients were used from this article, but the script can be applied to any Fourier series. This may also be accomplished with the Distributed Control System toolbox by summing the outputs of several waveform generators or by using a function generator component with a flow data set. This simplified model consists of 11 compliant pipes with three element windkessel boundary conditions (accumulators with proximal and distal resistance elements, exiting at atmospheric pressure).

image

This network also uses a global parameter to specify the period in scripts and Digital Control Task components, so we can easily adjust the period of the cardiac cycle.

Determining Flow Distribution

We will initially set our flowrate to the time averaged flowrate of 5.02L/min. We will start with an equivalent distal resistance at each branch. The steady state flow distribution for an equal distal resistance model is shown below.

image 1

We can specify our desired time averaged outflow for each branch. For this network, I will use 0.6L/min for the subclavian arteries, and 0.5L/min for the common carotids and set the Iliac artery flows to 1.41L/min. Our independent variables will be five of the six distal resistances (leaving one arbitrary resistance constant), and our dependent variables will be their resultant flowrates. The designer configuration is shown below.

image 2

Running the designer modifies the admittance of the flow resistance components to provide our desired flow distribution.

image 3

We will use these settings as an approximation of the time averaged flow distribution in transient runs.

Calculating Periodic Averages

Now that our inlet flow profile and outlet flow distribution are specified, we can use the statistics component to determine the time averaged pressure and flow for the inlets and outlets of our model. The statistics component highlighted below shows the time averaged flowrate of the ascending aorta (our inlet).

image 4

We can also create a new page to keep track of our distal resistances. This is very useful in large arterial networks. We can use views of distal resistance components to quickly check properties and determine periodic averages (shown below).

We can also use direct references in quick scripts calculate the total outflow of our system. This can be useful for tracking the mass flows in elastic pipes.

image 7

Using the Designer in Transient Simulations

The designer may also be used with properties obtained (at a specified time) from transient simulation. We will use the designer to set the mean arterial pressure (average pressure over 1 cardiac cycle) of the aorta to 100mmHg (gauge). We can easily scale our resistance to achieve our inlet pressure by running the designer in a transient simulation. I have created a global parameter to scale the distal resistances.

image 8

We can create a new designer configuration to set the scaling factor for our distal resistances. Our system should have a liner relationship between pressure and flow. This allows us to directly raise our inlet mean arterial pressure without modifying our flow distribution. We will use our global parameter (scaling distal resistances) as an independent variable to achieve our desired mean arterial pressure. We will also run the simulation for 30 seconds to allow our waveform to develop after changing our downstream resistance.

image 9

Results

After running the designer, we have achieved our target mean arterial pressure.

image 10

We can also check that our transient flow distribution matches our specifications by plotting the average (over one cardiac cycle) pressure value of each outflow.

image 11

Finally, we can also plot the resulting pressures of our inlet and outlets (upstream of the windkessel boundaries).

image 12

We can also use the designer to tune additional properties of waveforms by modifying properties of boundary conditions or pipes (vessels) using this workflow. Thanks for following along, make sure to check in for future posts.

Categories

Get Your Ansys Products & Support from the Engineers who Contribute to this Blog.

Technical Expertise to Enable your Addictive Manufacturing Success.

PADT Pulse Newsletter Screen Grab from March 2023

PADT’s Pulse Newsletter

Keep up to date on what is going on at PADT by subscribing to our newsletter.


By submitting this form, you are consenting to receive marketing emails from: . You can revoke your consent to receive emails at any time by using the SafeUnsubscribe® link, found at the bottom of every email. Emails are serviced by Constant Contact

Share this post:

Upcoming Events

05/31/2023

Driving Automotive Innovation with Additive - Webinar

05/24/2023

Hill Air Force Base Tech Expo

05/24/2023

Structural Updates in Ansys 2023 R1 (3) – Structural Optimization & Ex

05/23/2023

CROSSTALK 2023: Emerging Opportunities for Advanced Manufacturing Smal

05/10/2023

Signal & Power Integrity Updates in Ansys 2023 R1 - Webinar

04/26/2023

Additive Manufacturing Updates in Ansys 2023 R1 - Webinar

04/20/2023

38th Space Symposium Arizona Space Industry

More Info

04/19/2023

38th Space Symposium
Arizona Space Industry

04/19/2023

Additive Aids for Manufacturing - Webinar

04/18/2023

38th Space Symposium
Arizona Space Industry

04/17/2023

38th Space Symposium

04/13/2023

Venture Madness 2023

04/12/2023

Fluid Meshing & GPU-Solver Updates in Ansys 2023 R1 - Webinar

03/29/2023

8th Thermal and Fluids Engineering Conference

03/29/2023

Structural Updates in Ansys 2023 R1 - Composites, Fracture & MAPDL

03/28/2023

8th Thermal and Fluids Engineering Conference

03/27/2023

8th Thermal and Fluids Engineering Conference

03/26/2023

8TH Thermal and Fluids Engineering Conference

03/24/2023

Arizona BioPreneur Conference | Spring 2023

03/22/2023

2023 Arizona MedTech Conference

03/22/2023

Optimize Jigs & Fixtures with Additive - Webinar

03/15/2023

3D Design Updates in Ansys 2023 R1 - Webinar

03/08/2023

Competitive Advantages of 1D/3D Coupled Simulation - Webinar

03/01/2023

High Frequency Updates in Ansys 2023 R1 - Webinar

02/22/2023

Additive Advantages in Aerospace - Webinar

02/15/2023

Structural Updates in Ansys 2023 R1 (1) - Webinar

02/09/2023

IME 2023: MD&M | WestPack | ATX | D&M | Plastek

02/08/2023

IME 2023 MD&M | WestPack | ATX | D&M | Plastek

02/07/2023

IME 2023 MD&M | WestPack | ATX | D&M | Plastek

01/27/2023

Arizona Photonics Days, 2023

01/26/2023

Arizona Photonics Days, 2023

01/26/2023

TIPE 3D Printing | 2023

01/26/2023

Venture Cafe Phoenix Talent Night - Job Fari

01/26/2023

VFS 2023 Autonomous/Electric VTOL Symposium

01/25/2023

Arizona Photonics Days, 2023

01/25/2023

Building A.M.- Utah: Kickoff!

01/25/2023

TIPE 3D Printing | 2023

01/25/2023

VFS 2023 Autonomous/Electric VTOL Symposium

01/24/2023

VFS 2023 Autonomous/Electric VTOL Symposium

01/24/2023

TIPE 3D Printing | 2023

01/18/2023

2023 AZ Tech Council Golf Tournament

12/21/2022

Simulation Best Practices for 5G Technology - Webinar

12/14/2022

Digital Twins Updates in Ansys 2022 R2 - Webinar

12/08/2022

Tech the Halls - AZ Tech Council Holiday Mixer

12/07/2022

Electric Vehicle and Other Infrastructure Update Panel

11/30/2022

SPEOS Updates in Ansys 2022 R2 - Webinar

11/23/2022

Simulation Best Practices for Electronics Reliability - Webinar

11/16/2022

Discovery Updates in Ansys 2022 R2

11/10/2022

VentureCafe Phoenix Panel: Venture Capital in AZ

11/08/2022

2022 GOVERNOR’S CELEBRATION OF INNOVATION AWARDS + TECH SHOWCASE

11/03/2022

VentureCafe Phoenix Panel: Angel Investment in AZ

11/02/2022

High & Low Frequency Electromagnetics Updates in Ansys 2022 R2

10/26/2022

Simulation Best Practices For Chip-Package-System Design & Development

10/20/2022

Nerdtoberfest 2022

10/19/2022

2022 Southern Arizona Tech + Business Expo

10/19/2022

LS-DYNA Updates in Ansys 2022 R2 - Webinar

10/17/2022

Experience Stratasys Truck Tour - Clearfield Utah

10/14/2022

ASU School of Manufacturing Systems and Networks - Formal Opening Cele

10/14/2022

Experience Stratasys Truck Tour - Midvale Utah

10/12/2022

Experience Stratasys Truck Tour - Littleton Colorado

10/06/2022

Fluids Updates in Ansys 2022 R2 - Webinar

10/05/2022

Experience Stratasys Truck Tour - Colorado Springs

09/29/2022

White Hat Life Science Investor Conference - 2022

09/28/2022

2022 AZBio Awards

09/28/2022

Simulation Best Practices for Rotating Machinery Design & Development

09/21/2022

ExperienceIT NM 2022

09/21/2022

Additive Updates in Ansys 2022 R2 - Webinar

09/14/2022

Rocky Mountain Life Sciences Investor & Partnering Conference

09/08/2022

Ansys Optics Simulation User Group Meeting - Virtual

09/08/2022

Ansys Optics Simulation User Group Meeting

09/07/2022

SI & PI Updates in Ansys 2022 R2 - Webinar

08/31/2022

Simulation Best Practices for Developing Medical Devices - Webinar

08/24/2022

Mechanical Updates in Ansys 2022 R2 - Webinar

08/10/2022

Tucson after5 Tech Mixer: Ruda-Cardinal

08/05/2022

Flagstaff Tech Tour, 2022

08/02/2022

2022 CEO Leadership Retreat

08/01/2022

2022 CEO Leadership Retreat

07/27/2022

Thermal Integrity Updates in Ansys 2022 R1 - Webinar

07/20/2022

Simulation Best Practices for the Pharmaceutical Industry - Webinar

07/14/2022

NCMS Technology Showcase: Corpus Christi Army Depot

07/13/2022

NCMS Technology Showcase: Corpus Christi Army Depot

07/13/2022

Additive & Structural Optimization Updates in Ansys 2022 R1 - Webinar

07/07/2022

Arizona AADM Conference, 2022

06/29/2022

LS-DYNA Updates & Advancements in Ansys 2022 R1 - Webinar

06/23/2022

Simulation Best Practices for Wind Turbine Design - Webinar

06/15/2022

MAPDL Updates & Advancements in Ansys 2022 R1 - Webinar

06/01/2022

Mechanical Updates in Ansys 2022 R1 - pt. 2 Webinar

05/26/2022

Modelling liquid cryogenic rocket engines in Flownex - Webinar

05/25/2022

SMR & Advanced Reactor 2022

05/25/2022

05/24/2022

SMR & Advanced Reactor 2022

05/19/2022

RAPID + tct 2022

05/19/2022

Venture Cafe Roundtable: AI & Healthcare

05/18/2022

Tucson after5 Tech Mixer: World View

05/18/2022

RAPID + tct 2022

More Info

05/18/2022

Signal & Power Integrity Updates in Ansys 2022 R1 - Webinar

05/18/2022

Simulation World 2022

05/17/2022

RAPID + tct 2022

05/11/2022

Experience Stratasys Manufacturing Virtual Event

Search in PADT site

Contact Us

Most of our customers receive their support over the phone or via email. Customers who are close by can also set up a face-to-face appointment with one of our engineers.

For most locations, simply contact us: