Physics - Fluid Question with Solution | TestHub

According to the standard classification of fluid flow based on Reynolds number ($R_e$):

For $R_e<1000$, the flow is streamline or laminar.

For $1000<R_e<2000$, the flow becomes unsteady or transitional.

For $R_e>2000$, the flow is turbulent.

Therefore, the flow becomes unsteady when the Reynolds number is between $1000$ and $1999$.