How do you say "I'm flaring my nostrils."?

Question

How do you say "I'm flaring my nostrils." in French?

Collins Dictionary and Word Reference say to flare is se dilater.

Therefore, is it « Je me dilate les narines. » ou « Je dilate mes narines. » or can you say both?

Oxford Dictionary

Cambridge Dictionary

Context 1: When I flare my nostrils, I can smell better.

Context 2:

Mom: Why are you wasting your Saturday?

Child: I'm not.

Mom: You're not doing anything right now. Literally.

Child: I am. I am literally flaring my nostrils.

Mom: Get up! 😡

Context 3: A son drove his father's car without permission.

Son: Was dad angry when he found out?

Daughter: He was flaring his nostrils which is what he does when he's really angry. So yes.

Answer 1

There is no such idiom I'm aware of but you might say :

J'ouvre mes narines: (context 1)

Et il ouvrait les narines pour aspirer les bonnes odeurs de la campagne, qui ne venaient pas jusqu'à lui. Gustave Flaubert, Madame Bovary.

Je fronce les narines: (same as the above, but the smell is unpleasant)

Je devine le travail à travers ma lecture, comme je devine le sang rouge du lapin. Soudain, je fronce les narines, je lève la tête, je regarde sévèrement la cuisinière en disant :
— Il est faisandé, votre lapin !
— Pourquoi serait-il faisandé ?
— Parce qu’il pue, parbleu !
Georges Simenon, A la rencontre des autres

Othewise, but softer than what I understand from the English idiom in context 3:

Je fronce les sourcils (I frown)

If you want to show that the father is upset, you will probably not refer to his nostrils but perhaps to the way he breathes: sa respiration s'accélère or il se met à respirer bruyamment.

Finally, both Je me dilate les narines and Je dilate mes narines would raise eyebrows.