What is Laminar Flow?

Laminar flow is particles within a fluid that travel in a parallel line. Every layer of particles moves smoothly without disruption between one another. In a laminar flow, the fluid experience does not swirl nor eddies from its primary path. The particles remain close to a solid surface, moving in a straight line and parallel. The fluid in contact with the horizontal object remains stationary while the other layers slide over one another. The flow is regular and extremely predictable.

What if we could show you that scientific facts can pertain to real-life applications? An interesting dynamic occurs every day inside of you with our constant blood flow stream or by freezing water. Laminar flow is present in various aspects of our lives without our knowledge or apprehension. Let us explore what laminar flow is and how we use it in our everyday life!

For instance, smoke rising from a cigarette is undergoing a laminar flow. Once it grows a short distance from the cigarette, the smoke generally changes to a turbulent flow. The smoke’s trajectory faces pressure variations in space and time, which results in a flow transition.

Laminar flow vs Turbulent flow

In contrast to Turbulent flow, Laminar flow remains constant. The flow channel is relatively small, and the viscosity is high. Also called streamline flow, its properties throughout the fluid remain continuous. In fact, most liquids are turbulent except went they reach boundaries approaching a stable state.

Oil running through a thin tube is yet another example. The liquid is very thick and dense, and thus the Reynolds number indicates a laminar flow.

A flow can either be laminar, turbulent, or stuck somewhere in between. Measured by the Reynolds number, a flow is determined by the ratio between every fluid’s speed and thickness. The more viscous, the faster the fluid flows without transitioning to a turbulent state.

When a neat, calm pattern breaks down, a flow becomes turbulent.  Fluid flows often change from one to another when facing a new abrupt feature such as a wind gust. Turbulent flow is a flow regime that undergoes several fluctuations, which results in lateral mixing. The directions from each particle are chaotic and without real understanding. The constant change in behavior makes it impossible to measure correctly.

Laminar flow Reynolds number

Osborne Reynolds first studied the distinction between both flows in the second half of the 19th century. A milestone in fluid dynamics study, several variating factors could potentially affect the transition between laminar and turbulent flows.  A Reynolds number is a dimensionless number that helps predict the type of flow within a selected condition. In general, a laminar flow is less than 2000 and turbulent flow over 4000.

Laminar flows add both academic and industrial values. Often used for simulation techniques, laminar flows serve as a benchmark for new developments.  From the industrial point of view, it is often used to develop flows with low density and viscosity. It is often the case for ventilation systems and natural convection.

Laminar flow concept

These widely used techniques increase our understanding of fundamental concepts. Whether it is running water or through a complex application, laminar flow is an important scientific phenomenon that accompanies us throughout our lives. A great example is the Supreme Air Product Air knife. The pressurized air is restricted along two long plates and two short plates which creates a uniform laminar flow of pressurized air.