Speech is the one of the oral function due to fluid dynamics. The sibilant [s], one of dental fricative voice, is assumed to be generated from turbulence around the frontal teeth. Large Eddy Simulation with taking the real morphological vocal tract into account was demonstrated. The mean flow of the sibilant [s] separates from the tip of the upper anterior teeth and induces half plane jet along the lower anterior teeth. Δ
on surface of the anterior teeth is assumed to be somehow linked to the location of the high value Powell sound source.