Name: turbulent flow in pipes and mixing
Uploaded: 2025-02-13T15:43:34.000Z
Duration: 1 min 24 s
Channel: JoVE

Turbulent flow is a fluid movement marked by chaotic shifts in pressure and velocity.
Unlike laminar flow, turbulent flow displays complex, irregular patterns with significant mixing.
Initially, the flow remains stable. As the velocity rises, small disturbances known as &#34;turbulent spots&#34; appear.
Once the Reynolds number crosses a certain threshold, typically around 4,000, these spots merge, leading to fully developed turbulence.
In pipes, turbulent flow has three main zones. First is the viscous sublayer, a thin layer near the wall where flow behaves like laminar flow, with velocity increasing linearly with distance from the wall.
Next is the buffer layer, a transition zone where viscous and turbulent forces mix, forming a logarithmic velocity profile known as the logarithmic law of the wall.
Finally, in the outer layer, turbulent eddies dominate, driving random motion and mixing.
Due to its distinctive flow pattern, turbulent flow is crucial in engineering applications such as enhanced mixing in wastewater treatment, energy dissipation in spillways, and sediment buildup prevention in rivers.

turbulent flow

Turbulent Flow

Turbulent flow is characterized by unpredictable fluctuations in velocity and pressure, which result in a chaotic fluid movement distinct from the orderly patterns of laminar flow. While laminar flow is governed by smooth, parallel layers with minimal mixing, turbulent flow exhibits highly irregular, three-dimensional patterns. This behavior arises due to instabilities in the fluid&#39;s velocity profile, and amplifies as the flow velocity increases. Minor disturbances, known as turbulent spots, appear once the flow reaches a critical speed. When the Reynolds number &#8212; a dimensionless quantity expressing the ratio of inertial to viscous forces in a fluid &#8212; exceeds a threshold of around 4,000, these spots coalesce, generating fully developed turbulence.
Structure of Turbulent Flow in Pipes
In pipe systems, turbulent flow comprises three distinct regions: the viscous sublayer, the buffer layer, and the outer layer. The viscous sublayer forms close to the pipe wall, a thin boundary where viscous forces dominate, and the flow behaves similarly to laminar flow. Here, velocity follows a near-linear profile influenced by fluid viscosity, providing a stable region within the otherwise chaotic turbulent flow.
Above the viscous sublayer lies the buffer layer, a transitional zone where viscous and turbulent forces contribute to fluid motion. This region is marked by a logarithmic velocity profile that conforms to the logarithmic law of the wall, representing a balance between viscous and turbulent interactions. Further from the wall, turbulent eddies drive fluid movement in the outer layer, promoting rapid mixing and random motion across the flow.
Engineering Applications of Turbulent Flow
The chaotic nature of turbulent flow makes it advantageous in numerous engineering applications where mixing and energy dissipation are crucial. For instance, wastewater treatment systems rely on turbulent flow to enhance the mixing of chemicals, promoting efficient contaminant removal. In hydraulic engineering, turbulent flow dissipates energy in spillways, preventing structural damage by controlling water velocity. The turbulent mixing process also reduces river sediment buildup, maintaining navigable waterways and protecting aquatic ecosystems.

Turbulent flow is a fluid movement marked by chaotic shifts in pressure and velocity.
Unlike laminar flow, turbulent flow displays complex, irregular ...

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JoVE Core

Civil Engineering

Unit 1

Flow in Pipes

KEY TERMS AND CONCEPTS

turbulent flow in pipes and mixing

Turbulent flow is a fluid pattern with irregular changes in speed and pressure. It looks chaotic when compared with laminar flow, which moves in smooth, parallel layers with little mixing. In turbulent flow, the motion is highly irregular and three-dimensional.

This behavior starts when the fluid speed becomes high enough to create instabilities in the velocity profile. Small disturbances, called turbulent spots, can appear at a critical speed. As the Reynolds number, a ratio of inertial forces to viscous forces, rises above about 4,000, those spots merge and fully developed turbulence forms.

In pipes, turbulent flow has three main regions. The viscous sublayer sits next to the pipe wall and is very thin. In this region, viscous forces dominate, and the flow acts more like laminar flow. The velocity changes almost linearly here because viscosity has a strong effect.

Above that is the buffer layer. This is a transition zone where both viscous and turbulent forces shape the flow. Its velocity profile follows a logarithmic pattern, which matches the logarithmic law of the wall. Farther from the wall, the outer layer contains turbulent eddies that drive random motion and fast mixing.

The strong mixing in turbulent flow is useful in engineering. Wastewater treatment systems use it to mix chemicals and help remove contaminants more efficiently. Hydraulic engineering also relies on turbulence to dissipate energy in spillways and reduce the risk of structural damage. Turbulent mixing can also limit sediment buildup in rivers and help protect aquatic ecosystems.

Turbulent Flow in Pipes and Mixing

general characteristics of pipe flow i

Pipe Flow Regimes and Reynolds Number

Pipe flow is the movement of fluids through fully enclosed conduits such as water pipes and hydraulic hoses. These pipes are built to handle high-pressure gradients that drive the fluid forward. That is different from open-channel flow, where gravity is the main driving force. Rectangular conduits, such as air conditioning and heating ducts, usually work at lower pressures and are less suited for high-pressure use. Osborne Reynolds first classified pipe flow with dye injection experiments. He...

general characteristics of pipe flow ii

Pipe Entrance Length and Pressure Changes

Pipe flow changes as fluid moves from the pipe entrance to a fully developed state. At the entrance, the velocity profile is still adjusting. Viscous effects create a boundary layer along the wall, and that layer grows until it fills the whole pipe cross-section. When the boundary layer merges across the pipe, the flow becomes fully developed. At that point, the velocity profile stays steady along the pipe length. The distance needed to reach this state is called the entrance length. It...

laminar flow

Pipe Flow Patterns and Pressure Loss

Pipe flow patterns can be smooth, changing, or chaotic, and laminar flow is the smoothest form. In laminar flow, fluid particles move in parallel paths with very little mixing between layers. This happens when viscous forces are stronger than inertial forces. The flow regime in a pipe is often described with the Reynolds number, a dimensionless value that depends on fluid density, flow speed, pipe diameter, and dynamic viscosity. A Reynolds number below about 2100 usually means laminar flow.

laminar flow: problem solving

Pipe Size for Laminar Air Flow

Laminar flow in a pipe means the fluid moves in smooth, parallel layers with very little mixing or turbulence. In fluid mechanics, keeping flow laminar is important when engineers want precise control of flow behavior. The Reynolds number is the key value used to check this. It is a dimensionless number that depends on the fluid’s speed, density, viscosity, and the pipe’s diameter. A Reynolds number of 2100 or lower shows laminar flow. Higher values lead to turbulence. For air flowing through...

Turbulent flow is a fluid pattern with irregular changes in speed and pressure. It looks chaotic when compared with laminar flow, which moves in smooth, parallel layers with little mixing. In turbulent flow, the motion is highly irregular and three-dimensional. This behavior starts when the fluid speed becomes high enough to create instabilities in the velocity profile. Small disturbances, called turbulent spots, can appear at a critical speed. As the Reynolds number, a ratio of inertial...

turbulent flow: problem solving

Carbonation Flow and Reynolds Number

Carbonation uses carbon dioxide gas to dissolve gas into a liquid, as in carbonated drinks. Efficient carbonation depends on temperature, pressure, and flow conditions. By controlling these factors, more CO2 can dissolve in the liquid. Temperature plays a major role in CO2 solubility. Here, both the CO2 gas and the liquid are cooled to 20°C. Lower temperatures increase solubility, so a larger volume of gas can dissolve. Pressure also helps drive carbonation. At 20°C, the CO2 gas is...

major losses in pipes

Pipe Pressure Drop from Wall Friction

Pipe pressure drop from wall friction is a major loss in fluid flow. As a fluid moves through a pipe, friction along the pipe walls removes energy. That energy loss shows up as a drop in pressure. The size of the drop depends on the flow conditions and on the physical properties of both the fluid and the pipe. Flow in a pipe is often described as laminar or turbulent using the Reynolds number. This dimensionless number compares inertial forces with viscous forces in the fluid. In laminar flow,...

minor losses in pipes

Pipe Fittings and Valve Head Loss

Pipe fittings and valves can cause head loss in a pipe system. These losses happen when flow is disturbed by bends, expansions, entries, exits, and other components. The fluid loses energy because the flow becomes less steady and more turbulent. Valves are a major source of minor loss because they block or guide the fluid path. A closed valve or a partly closed valve adds resistance and creates turbulence. The amount of energy loss depends on the valve shape, its position, and the way the flow...

single pipe systems

Pipe Flow Problems by What You Know

Pipe flow problems are grouped by the information that is known and the result that needs to be found. In fluid mechanics, these are often called Type I, Type II, and Type III problems. Each type uses fluid properties, pipe details, and operating conditions to answer a different engineering question. In a Type I problem, the fluid density and viscosity are known. The pipe diameter, length, and surface roughness are also known. The flow rate or average velocity is given, and the goal is to find...

multiple pipe systems

Pipe Flow Paths in Series and Parallel

Multiple pipe systems move fluids through connected pipe paths in engineering networks. They help control flow distribution, pressure, and head loss. These systems are grouped into series, parallel, loop, and network configurations, and each one behaves differently. In a series configuration, fluid passes through one pipe segment after another. The flow rate stays the same through every segment. Head loss builds up across the path, so the total loss from entry point A to exit point B is the...

pipe flowrate measurement

Comparing Orifice, Nozzle and Venturi Meters

Orifice, nozzle, and Venturi meters are used to measure fluid flowrate in pipes by narrowing the flow area. The smaller opening makes the fluid move faster and lowers the pressure. The pressure difference, together with Bernoulli’s principle and real-world corrections, is used to calculate flowrate. The orifice meter is the simplest and least expensive option. It uses a flat plate with a hole in the center to create a measurable pressure drop. It is often used in water treatment, oil and gas...

pipe flowrate measurement: problem solving

pipe-flowrate-measurement-problem-solving

Spray Tank Pipe Flow Rate Calculation

Spray tank pipe flow rate calculation uses fluid mechanics to find how fast pesticide moves through a pressurized system. The tank is pressurized to 150 kPa and holds the liquid at a height of 0.80 meters. The liquid then travels through a 1.9 meter pipe with a diameter of 0.015 meters and an angle of 0.698 radians before reaching a 0.007 meter nozzle that sprays the pesticide. Accurate flow rate matters because the pesticide must be applied evenly across the plants. The first step is to find...

design example: designing a residential plumbing system

design-example-designing-a-residential-plumbing-system

Residential Plumbing Flow and Pressure Design

Residential plumbing flow and pressure design starts with water demand, flow rate, and pressure needs. These systems are sized by looking at how many people live in the home and what fixtures they use. The goal is to provide reliable water delivery while keeping the system efficient. A key part of the design is the Reynolds number. This dimensionless value helps classify flow in a pipe as laminar, which is smooth, or turbulent, which is more mixed and irregular. It depends on factors such as...

key terms and concepts

Learn how turbulent flow forms in pipes, why the Reynolds number matters, and how turbulence improves mixing in wastewater treatment, spillways, and rivers.

Turbulent Flow in Pipes and Mixing | JoVE K12

JoVE Core Civil Engineering offers a foundational exploration of essential construction materials such as bricks, stones, steel, wood, and concrete, along with fluid mechanics topics like flow over immersed bodies, open channel flow, and dimensional modeling. It also covers key surveying concepts, including leveling, traverse adjustments, curve design, topographic mapping, and geospatial technologies (GPS & GIS). Science-in-action videos showcase laboratory research on materials, fluids, and surveying practices in real-world engineering systems.

civil engineering

Turbulent Flow in Pipes and Mixing

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