2D Computational Fluid Dynamics: Vortex Shedding Around a…

What Vortex Shedding Is

Vortex shedding is a phenomenon observed in fluid flow around bluff bodies, where vortices form alternately on opposite sides of the body. This effect can be seen as a series of vortices that are periodically shed from the back of the cylinder or any other obstacle placed in the flow.

The process is driven by the interaction between the incoming fluid and the boundary layer formed around the object, leading to periodic fluctuations in pressure and velocity fields.

Why It Happens

Vortex shedding occurs due to the unsteady separation of the flow from the surface of the cylinder. As the flow approaches the cylinder, it first adheres to the surface forming a boundary layer. However, as the flow continues around the cylinder, this boundary layer can separate and reattach multiple times, leading to the formation of vortices.

The frequency at which these vortices are shed is known as the Strouhal number (St), which depends on the Reynolds number (Re) of the flow. At lower Re values, the shedding becomes more chaotic, while at higher Re, it tends to become periodic.

live demo · related simulation● LIVE

Governing Equations and Simulation

The behavior of fluid flow around a cylinder is governed by the Navier-Stokes equations, which describe the motion of viscous fluids. These equations are nonlinear partial differential equations that must be solved numerically in computational fluid dynamics (CFD) simulations.

In this 2D CFD simulation, the Navier-Stokes equations are discretized using finite difference methods and solved on a grid to predict the velocity and pressure fields around the cylinder.

Real-World Applications

Understanding vortex shedding is crucial in various engineering applications such as aerodynamics, hydrodynamics, and environmental fluid mechanics. For instance, it helps in designing more efficient wind turbines by optimizing their shape to reduce drag and improve power output.

In the field of civil engineering, knowledge of vortex shedding can be used to design structures that are less susceptible to oscillations caused by flow-induced vibrations.

Frequently asked questions

What is the Reynolds number in this context?

The Reynolds number (Re) is a dimensionless quantity that characterizes the ratio of inertial forces to viscous forces and thus determines the nature of fluid flow around an object. In this simulation, it can be adjusted by changing the inflow speed or viscosity.

How does vortex shedding affect bridge design?

Vortex shedding can cause oscillations in bridges, leading to resonance and potential structural failure if not properly accounted for in the design. Engineers use CFD simulations like this one to predict such effects and ensure the stability of their designs.

Can vortex shedding be avoided?

Vortex shedding is an inherent property of fluid flow around bluff bodies, but its intensity can be reduced by designing shapes that minimize separation or by using techniques like flow control devices to alter the boundary layer behavior.

What does a higher Strouhal number indicate?

A higher Strouhal number indicates more frequent shedding of vortices, which is typically observed at lower Reynolds numbers. This can lead to increased drag and other flow instabilities in the wake of the cylinder.

Try it live

Everything above runs in your browser — open 2D Computational Fluid Dynamics: Vortex Shedding Around a Cylinder and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.

▶ Open 2D Computational Fluid Dynamics: Vortex Shedding Around a Cylinder simulation