Related Experiment Video
Updated: May 1, 2026
11:51
Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions
Published on: February 22, 2018
8.2K
Effective medium theory for drag-reducing micro-patterned surfaces in turbulent flows
1Mechanical Engineering Department, Clemson University, 29634, Clemson, SC, USA, ibattia@clemson.edu.
The European Physical Journal. E, Soft Matter
|March 28, 2014
Summary
Microscale surface patterns can reduce skin drag, but mechanisms remain unclear. This study models patterned surfaces as porous media, yielding a formula for skin friction coefficient applicable to superhydrophobic surfaces.
Area of Science:
- Fluid dynamics
- Surface science
- Turbulence modeling
Background:
- Microscale surface patterns are known to reduce skin drag.
- Mechanisms and controlling parameters for drag reduction are not fully understood.
Purpose of the Study:
- To develop a model for turbulent flow over patterned surfaces.
- To elucidate the mechanisms and parameters controlling drag reduction.
Main Methods:
- An effective medium representation treating micro-features as a porous medium.
- Derivation of a closed-form expression for skin friction coefficient.
Main Results:
- A formula for skin friction coefficient based on frictional Reynolds number, viscosity ratio, and geometry.
- Model predictions show agreement with experimental data for superhydrophobic ridged surfaces.
Conclusions:
- The proposed effective medium model provides a framework for understanding drag reduction over patterned surfaces.
- The model accurately predicts turbulent flow behavior for superhydrophobic ridged surfaces across a range of Reynolds numbers.
Related Concept Videos
01:23Drag
633
Drag is a resistive force opposing an object’s motion through a fluid, resulting from surface pressure and shear forces. It comprises two components: a perpendicular one from pressure and a tangential one from shear stress. Accurate drag calculations use pressure and wall shear stress distributions, often determined through Computational Fluid Dynamics (CFD) or wind tunnel testing. The drag coefficient, a dimensionless measure, depends on factors like shape, Reynolds number, Mach number,...
633
01:26General External Flow Characteristics
618
The study of external flow is essential for creating structures and objects that interact efficiently and safely with moving fluids, such as air or water. When a body is immersed in a flowing fluid, it experiences two primary forces: drag, which opposes motion along the flow direction, and lift, which acts perpendicular to the flow. The shape, size, and orientation of the object influence these forces.Streamlined and Blunt Bodies in External FlowObjects in fluid flow are classified as...
618
01:24Turbulent Flow
921
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's velocity profile, and amplifies as the flow velocity increases. Minor disturbances, known as turbulent...
921
01:17Steady, Laminar Flow Between Parallel Plates
1.1K
Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.
1.1K
01:18Boundary Layer Characteristics
945
When a fluid encounters a solid surface, a boundary layer forms due to the interaction between the fluid's motion and the stationary surface. This phenomenon is characterized by a thin region adjacent to the surface where viscous forces dominate, influencing the fluid's velocity profile. The development of the boundary layer begins at the leading edge of the surface and evolves as the fluid moves downstream.As the fluid flows over the surface, friction between the fluid and the wall slows down...
945
01:23Steady, Laminar Flow in Circular Tubes
2.0K
Hagen-Poiseuille flow describes a viscous fluid's steady, incompressible flow through a cylindrical tube with a constant radius R. This flow profile is often applied to understand fluid transport in narrow channels, such as capillaries. It serves as a foundational example of laminar flow. In this model, cylindrical coordinates (r,θ,z) are used to describe the radial (r), angular (θ), and axial (z) dimensions within the tube. For Hagen-Poiseuille flow, the velocity profile is purely...
2.0K