Related Experiment Video
Updated: Mar 19, 2026
11:00
Experimental Investigation of Secondary Flow Structures Downstream of a Model Type IV Stent Failure in a 180° Curved Artery Test Section
Published on: July 19, 2016
12.0K
Phase structure function and spatial coherence in underwater Rayleigh-Bénard turbulence: experimental
Summary
This study experimentally characterizes laser beam propagation through underwater turbulence. Results show turbulence is anisotropic and inhomogeneous, impacting beam coherence and validating oceanic turbulence models for optical communication.
Area of Science:
- Fluid Dynamics
- Optical Physics
- Oceanography
Background:
- Underwater optical communication faces challenges due to turbulence.
- Characterizing turbulence effects on laser beams is crucial for system design.
Purpose of the Study:
- To experimentally determine the phase structure function (PSF) and spatial coherence radius of laser beams in underwater Rayleigh-Bénard (RB) turbulence.
- To investigate the spatial variations and anisotropic/inhomogeneous nature of this turbulence.
Main Methods:
- Utilized a two-channel moiré-based wavefront sensor to analyze a laser beam (λ=532nm) in a controlled water tank.
- Induced RB turbulence via temperature differences and performed measurements at various vertical and lateral positions.
- Reconstructed wavefront phases and computed the PSF in orthogonal directions.
Main Results:
- Underwater RB turbulence was found to be anisotropic and inhomogeneous.
- Turbulence intensity increased with temperature difference, and PSF anisotropy was more pronounced at larger separation distances.
- Spatial coherence radius decreased with higher temperatures and was smaller near tank boundaries.
Conclusions:
- The experimental PSF results align well with the analytical oceanic turbulence optical power spectrum model.
- Findings validate underwater turbulence models and provide critical data for designing reliable underwater optical communication systems.
Related Concept Videos
02:18Interference and Diffraction
53.5K
Interference is a characteristic phenomenon exhibited by waves. When two electromagnetic waves interact with their peaks and troughs coinciding, a resulting wave with enhanced amplitude is produced. This is known as constructive interference. In this case, the two waves interacting are in phase with each other.
53.5K
01:07Propagation of Waves
3.2K
When a wave propagates from one medium to another, part of it may get reflected in the first medium, and part of it may get transmitted to the second medium. In such a case, the interface of the two mediums can be considered as a boundary that is neither fixed nor free.
Consider a scenario where a wave propagates from a string of low linear mass density to a string of high linear mass density. In such a case, the reflected wave is out of phase with respect to the incident wave, however the...
Consider a scenario where a wave propagates from a string of low linear mass density to a string of high linear mass density. In such a case, the reflected wave is out of phase with respect to the incident wave, however the...
3.2K
01:17Steady, Laminar Flow Between Parallel Plates
965
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.
965
01:20Region of Convergence of Laplace Tarnsform
1.4K
The Region of Convergence (ROC) is a fundamental concept in signal processing and system analysis, particularly associated with the Laplace transform. The ROC represents an area in the complex plane where the Laplace transform of a given signal converges, determining the transform's applicability and utility.
Consider a decaying exponential signal that begins at a specific time. When deriving its Laplace transform, the time-domain variable is replaced with a complex variable. This...
Consider a decaying exponential signal that begins at a specific time. When deriving its Laplace transform, the time-domain variable is replaced with a complex variable. This...
1.4K
01:24Turbulent Flow
856
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...
856
01:28Standing Waves in a Cavity
1.6K
A household microwave and lasers are examples of standing electromagnetic waves in a cavity. When two conducting metal plates are placed parallel at the nodal planes, it creates a cavity where standing waves are formed. The cavity between the two planes is analogous to a stretched string held at the points x = 0 and x = L. Here, the distance 'L' between the two planes must be an integer multiple of half of the wavelength. The wavelengths that satisfy this condition are given by:
1.6K