Hi Md. Jahid Hasan;

Making an accurate 3D model to analyze the real flow of body organs using 3D CAD software will not be very accurate. The method of using CT files that are in STL format is more suitable. Of course, after receiving them, you must convert them into appropriate formats such as step or sat, and use them in CFD analysis software.

There are generic solid anatomical models available from companies like Zygote 3D (see https://www.zygote.com/cad-models ). Of course these represent the heart at only one phase of the cardiac cycle.

To capture the motion of the heart, you will need a gated CTA scan (CT angiography triggered by an ECG to capture different phases). To get the STL (mesh) files described by Seyed Mohammad Mousavi you will need to segment the structures of interest with a software like Mimics or 3D Slicer. Then you will need to clean them up and surface them (e.g. with NURBS) to export STEP or other solid model format that you can import into your simulation software. You can use software such as Geomagic, Rhino or MeshMixer for cleanup and export of STEP files.

Of course, Crispin B. Weinberg is right, solid models only simulate a fixed state of a living organ, if you want to simulate the movement of a living organ due to changes in fluid pressure and velocity, you must perform FSI analysis. This analysis simulates the interaction of the organ structure with the fluid by meshing the organ and fluid environments, and this is not an easy task because you have to know the characteristics of the non-linear stiffness matrix of the organ.

Md. Jahid Hasan Jahid, I made a google search for “Modeling air flow in human lungs”. Many ideas came up. I show some below. I suggest you set up similar searches for all the other organs you’re thinking about. Also, fluids flow in all parts of the human body

1)__ National Library of Medicine

Computational Fluid Dynamics Modeling of Respiratory Airflow in Tracheobronchial Airways of Child and Adult

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234445/

2)__ A numerical simulation of air flow in the human respiratory system for various environmental conditions

https://tbiomed.biomedcentral.com/articles/10.1186/s12976-020-00133-8

3)__ Respiratory airflow in human upper airways response to walking and running for oral breathing condition

https://www.sciencedirect.com/science/article/pii/S2405844022013275

4)__ COMPUTATIONAL FLUID DYNAMICS SIMULATION OF THE AIRFLOW THROUGH THE HUMAN RESPIRATORY TRACT

https://scholar.utc.edu/cgi/viewcontent.cgi?article=1608&context=theses

5)__ Video - Visualization of Airflow Through the Human Respiratory System

https://www.youtube.com/watch?v=yyBLPaU057A

6)__ Video - VPH2020 Conference: modeling for medicine

https://team.inria.fr/reo/respiration_modeling/

7)__ Video - Do-It-Yourself Lungs

https://www.youtube.com/watch?v=fybV8zIGyu8