Related Experiment Video
Updated: Apr 28, 2026
10:58
Parametric Optimization Design Method for Friction Plates of Hydro-Viscous Clutches
Published on: July 22, 2025
797
Skin friction on a flapping plate in uniform flow
Uwe Ehrenstein1, Matthieu Marquillie2, Christophe Eloy3
1Aix Marseille Université, CNRS, Centrale Marseille, IRPHE UMR 7342, 13384 Marseille, France ehrenstein@irphe.univ-mrs.fr.
Summary
Calculating drag force from skin friction is vital for understanding swimming and flying energy costs. This study confirms that flapping motions increase drag, supporting the boundary-layer thinning hypothesis.
Area of Science:
- Fluid dynamics
- Biomechanics
- Aerodynamics
Background:
- Accurate measurement of skin friction drag on moving objects is challenging.
- Understanding drag is crucial for calculating energy costs in swimming and flying.
- The 'Bone-Lighthill boundary-layer thinning hypothesis' suggests swimming motions increase drag.
Purpose of the Study:
- To investigate skin friction drag on a flat plate undergoing normal flapping motion.
- To validate the 'Bone-Lighthill boundary-layer thinning hypothesis'.
- To develop a predictive formula for skin friction in unsteady flow conditions.
Main Methods:
- Analysis of laminar boundary layer flow for a simplified model.
- Numerical simulation using a multi-domain, parallel, compact finite-differences Navier-Stokes solver.
- Investigation of time-dependent flow dynamics.
Main Results:
- Longitudinal drag scales with the square root of normal velocity under laminar boundary layer assumptions.
- Navier-Stokes simulations confirm the drag increase due to flapping motion.
- Differences in friction coefficient magnitude were observed between the simplified model and full simulations.
Conclusions:
- Swimming-like motions can increase drag due to boundary layer compression.
- A simplified model provides qualitative agreement but requires refinement for quantitative accuracy.
- A tentative formula for skin friction is proposed for steady and periodic normal velocities.
Related Concept Videos
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
01:02Fluid Pressure over Flat Plate of Variable Width
1.7K
When a flat plate is submerged in a fluid, the fluid exerts pressure on the plate. This pressure can lead to many different phenomena, including drag and buoyancy. To understand the behavior of the fluid over a flat plate of variable width, it is essential to analyze the distribution of the pressure exerted.
The pressure distribution on the plate can be calculated by determining the force that acts on a differential area strip of the plate. Thus, the magnitude of the force is equal to the...
The pressure distribution on the plate can be calculated by determining the force that acts on a differential area strip of the plate. Thus, the magnitude of the force is equal to the...
1.7K
01:05Fluid Pressure over Flat Plate of Constant Width
1.8K
When a body is submerged in water, it experiences fluid pressure acting normal on its surface and distributed over its area. For better design structures, it is crucial to determine the magnitude and location of the resultant force acting on the surface. In the case of a rectangular plate of constant width submerged in water, the pressure increases with depth, resulting in a linearly varying trapezoidal pressure distribution from the upper to the lower edge of the plate.
The resultant force...
The resultant force...
1.8K
01:12Fluid Pressure over Curved Plate of Constant Width
1.5K
When a curved plate of constant width is submerged in a liquid, the pressure acting normal to the plate varies continuously both in magnitude and direction. Calculating the magnitude and location of the resultant force at a point is often challenging for such cases. One of the methods to determine the resultant force and its location involves separately calculating the horizontal and vertical components of the resultant force. This complex calculation can be simplified by representing the...
1.5K
01:22Couette Flow
1.4K
Couette flow represents the flow of fluid between two parallel plates, with one plate fixed and the other moving with a constant velocity. This configuration allows for a simplified analysis using the Navier-Stokes equations, which govern fluid motion under conditions of viscosity and incompressibility. For Couette flow, the assumptions include a steady, laminar, incompressible flow with a zero-pressure gradient in the flow direction. This flow type is beneficial for understanding shear-driven...
1.4K
01:18Newtonian Fluid: Problem Solving
1.1K
Newtonian fluids exhibit a constant viscosity, meaning their shear stress and shear strain rate are directly proportional. This property ensures a predictable and stable response to applied forces, maintaining a linear relationship between force and flow. Examples include water, air, and light oils, consistently demonstrating this proportional behavior regardless of external conditions.
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
1.1K