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01:05Collisions in Multiple Dimensions: Introduction
It is far more common for collisions to occur in two dimensions; that is, the initial velocity vectors are neither parallel nor antiparallel to each other. Let's see what complications arise from this. The first idea is that momentum is a vector. Like all vectors, it can be expressed as a sum of perpendicular components (usually, though not always, an x-component and a y-component, and a z-component if necessary). Thus, when the statement of conservation of momentum is written for a problem,...
01:30Typical Model Studies
Fluid mechanics model studies often utilize scaled-down systems to predict fluid behavior in full-scale environments, such as river flows, dam spillways, and structures interacting with open surfaces. Maintaining Froude number similarity in river models is crucial, as it replicates surface flow features like wave patterns and velocities.
01:34The Fluid Mosaic Model
The fluid mosaic model was first proposed as a visual representation of research observations. The model comprises the composition and dynamics of membranes and serves as a foundation for future membrane-related studies. The model depicts the structure of the plasma membrane with a variety of components, which include phospholipids, proteins, and carbohydrates. These integral molecules are loosely bound, defining the cell’s border and providing fluidity for optimal function.
01:19Fluid Mosaic Model
Scientists identified the plasma membrane in the 1890s and its principal chemical components (lipids and proteins) by 1915. The model for plasma membrane structure, proposed in 1935 by Hugh Davson and James Danielli, was the first model to be widely accepted in the scientific community. The model was based on the plasma membrane's "railroad track" appearance in early electron micrographs. Davson and Danielli theorized that the plasma membrane's structure resembled a sandwich with the analogy of...
01:22Couette Flow
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...
01:17Steady, Laminar Flow Between Parallel Plates
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.
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Related Experiment Video
Updated: May 23, 2026
11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Fluid dynamics of moving fish in a two-dimensional multiparticle collision dynamics model.
Daniel A P Reid1, H Hildenbrandt, J T Padding
1Behavioural Ecology & Self-organization & Theoretical Biology, Rijksuniversiteit Groningen, Nijenborgh 7, Groningen, The Netherlands.
Summary
This study uses multiparticle collision dynamics to model fish swimming, revealing thrust generation in the rear body and a negative correlation between slip ratio and efficiency. Results challenge previous theoretical predictions for undulating fish locomotion.
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Area of Science:
- Fluid dynamics
- Biophysics
- Computational biology
Background:
- Studying animal locomotion fluid dynamics is challenging experimentally.
- Multiparticle collision dynamics (MPCD) offers a computationally efficient method for simulating fluid dynamics.
- Previous MPCD studies were limited to low Reynolds numbers and static or permeable shapes.
Purpose of the Study:
- To investigate the hydrodynamics of an undulating fish at higher Reynolds numbers (1100-1500) using MPCD.
- To analyze drag, thrust, lift, swimming efficiency, wake structure, and force distribution.
- To compare simulation results with empirical data and theoretical predictions.
Main Methods:
- Utilized the multiparticle collision dynamics (MPCD) method.
- Validated MPCD performance with a moving insect wing simulation at Reynolds number 75.
- Simulated an undulating fish model at Reynolds numbers 1100-1500.
Main Results:
- Confirmed resemblance between simulated and empirical fish locomotion data.
- Thrust is generated by the posterior two-thirds of the fish body, contrary to some theories.
- Observed a negative correlation between slip ratio (U/V) and Froude efficiency.
- Constraining sideways acceleration in models leads to artificial resemblance with unconstrained fish.
Conclusions:
- MPCD is suitable for studying fish hydrodynamics at higher Reynolds numbers.
- The study provides new insights into thrust generation and efficiency in undulating fish.
- Model constraints can significantly impact simulation outcomes, highlighting the need for careful model design.