nonviscous

Nonviscous refers to a fluid that is assumed to have zero dynamic viscosity. In fluid mechanics, a nonviscous fluid is also called an ideal fluid or inviscid fluid. The Navier–Stokes equations, which describe real fluid motion, reduce to the Euler equations when viscosity is set to zero. This simplification eliminates the viscous shear stresses and the dissipation of kinetic energy into heat, allowing the flow to be described by conservative forces alone.

The assumption of nonviscous flow is used in many analytical and numerical studies of high‐speed aerodynamics, hydrodynamics, and atmospheric sciences. Potential flow theory, which assumes irrotational nonviscous motion, forms the basis for computing stream functions and velocity potentials around streamlined bodies. Stagnation point theory and the Kutta–Joukowski theorem also rely on inviscid assumptions to predict lift and pressure distributions accurately at high Reynolds numbers.

Despite its utility, the nonviscous model has limitations. It neglects boundary layer effects, viscous drag, and turbulent energy dissipation. Predictive accuracy is restricted to flows far from solid boundaries where viscous forces are negligible. Real fluids always exhibit some viscosity; therefore, corrections such as Prandtl’s boundary‐layer theory or Blasius solutions are introduced to capture viscous phenomena.

Historically, the concept of nonviscous flow dates back to the 19th century when Lagrange and Euler developed the fundamental equations. It has since been used extensively in theoretical studies of fluid dynamics and remains a cornerstone in modern aeronautical engineering, oceanography, and meteorological modeling.