Fluid simulation

Introduction

Author: Aurélien RUMIANO

Patient: Mustafa Amid

Parameters of the study

Flow used for the fluid study 15l/min.
Inspiration phase.
Humidity and temperature are not taken into account.

🛑Disclaimer: I am neither a fluid mechanics researcher nor a doctor. The results I obtain using my fluid simulation software may be approximate. The purpose of these fluid simulations is to give you an idea of the air flow and possible problems related to it.

The illustration below represents the nasal cavity, the anterior part in red, the middle meatus in green and finally the inferior meatus in blue.

The following illustration represents the negative of the nasal cavity, that is to say the air which is inside the nasal cavity. All illustrations that follow will be represented in this manner.

The block that sticks the nostrils simply represents the air around it.

CT-SCAN

The lower turbinates are totally missing throughout the first 2/3 of the nasal cavity.
The septum is deviated, causing an obstruction on the left side (on the right in the image).

Airflow velocity

Description & analysis

The current lines represent the air flow, the speed scale goes from 0 to 2.5 m/s.
Speeds above 2.5 m/s are shown in red.
It can be observed that the air is swirling within the inferior meatus where the inferior turbinates are missing on both sides.
On the left side (on the right in the image), the airflow enters mainly through the inferior meatus due to an obstruction in the anterior part.

Wall Sheer Stress

Description

The areas colored red represent areas where the WSS is greater than 0.2 Pa. That is to say, these are the areas where the air rubs the most against the mucosa and therefore creates the most air sensation.

We can see that the areas where the WSS is the highest are mainly the anterior part. This is a normal phenomenon because this is where the section is the smallest.
The WSS is low at the floor at left of the nasal cavity. At right there is a zone on the floor where the WSS is high, it is where the inferior turbinate is still present.

Airflow imbalance

62% of the airflow passes through the right side and therefore 38% on the left.
So the airflow is not well balanced between the two sides. Enough to cause discomfort.
This is due to the obstruction at left on the anterior part.

Nasal resistance

Description and analysis

The total resistance is around 23 Pa which is a bit high. Mainly due to the obstruction at left. There is more nasal resistance on the left side than on the right, which creates an airflow imbalance between the two sides. According to my little experience in fluid simulation, values between 10 and 20 Pa are normal.

Cross sectiona area

The cross-sectional area peak at around 400 mm² from 30 mm to nostrils. Which is high.
The data of the control group are pulled from a study, but I have seen some non ENS case at around 300mm². So I think that between 200 and 300 mm² the values can be considered normal.

Conclusion

There are two main problems: the deviated septum which causes an obstruction on the left side and the inferior turbinates absent across the first two-thirds of the nasal cavity.
There is also an airflow imbalance between the left and right sides.
Large implants in the inferior meatus along the lateral walls could be beneficial.
Also, maybe straightening the septum to improve the airflow imbalance and the obstruction.