Velocity fields and optical turbulence near the boundary in a strongly convective laboratory flow

Matt, Silvia; Hou, Weilin; Goode, Wesley; Hellman, Samuel

doi:10.1117/12.2229800

Cited by 3 publications

(2 citation statements)

References 3 publications

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“…The refractive index of the water depends on pressure P, temperature T, salinity S, and wavelength 𝜆 [12][13][14] . In the real marine environment, n changes quickly and randomly in the time and space [15][16][17] . In this model, we use the refractive index equation to study changes of n caused by changes of T and S, and the refractive index equation is shown in equation (1).…”

Section: Simulation Modelmentioning

confidence: 99%

Monte Carlo simulation of turbulence induced by temperature and salinity changes on underwater light transmission performance

Xiang,

Chen

2024

Sixth Conference on Frontiers in Optical Imaging and Technology: Novel Technologies in Optical Systems

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As a common dynamic phenomenon in seawater, turbulence can affect the performance of underwater light transmission. Monte Carlo turbulence model is used in this paper, and this model is based on the Monte Carlo method to simulate the transmission of photons in turbulence with changing refractive index. The results show that the received light intensity probability density distribution is lognormal under weak, moderate and strong turbulence. With the increase of the variations of temperature and salinity, the intensity of turbulence is enhanced, and the effect on the received light intensity is increased, which is manifested by the gradual increase of the scintillation index as well as the asymmetry of the probability density distribution of the received light intensity. In addition, it is found that the asymmetry of the probability density distribution of the received light intensity is affected by the field angle of the receiving end and the divergence angle of the transmitting end.

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Section: Simulation Modelmentioning

confidence: 99%

Monte Carlo simulation of turbulence induced by temperature and salinity changes on underwater light transmission performance

Xiang,

Chen

2024

Sixth Conference on Frontiers in Optical Imaging and Technology: Novel Technologies in Optical Systems

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“…The model used in [10], which is based on the step-by-step tracing and interaction of propagating photons with the turbulent cells with different refractive indices and sizes from transmitter (Tx) to the (Rx), is adopted here as shown in According to previous studies, n variation depends on the pressure P, temperature T, salinity S and wavelength λ, and it changes randomly and rapidly in turbulent dynamic underwater environments [23], [25], [26]. To simplify the model, we have accounted all the effective factors in n variation using a single parameter of Δn, which now can be used to indicate the turbulence strength.…”

Section: B Simulation Modelmentioning

confidence: 99%

System parameters effect on the turbulent underwater optical wireless communications link

Vali

Ghassemlooy

Michelson

2019

Optik

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In underwater optical wireless communications (UOWC) the link performance is greatly affected by the turbulence. Turbulence is due to the random variations of the refractive index of water, which leads to both intensity (i.e., fading) and phase fluctuation of the optical beam. The effects of turbulence on link performance depend on the choice of system parameters. In this paper, the effects of the transmission link span, divergence angle of the transmitted Gaussian beam, receiver's (Rx) aperture diameter and field of view (FOV) on the UOWC link performance under the turbulence condition is investigated. The results show that, lognormal and negative exponential distributions fit well with the probability density function of the received light intensity under weak-to-strong and saturated turbulence regimes or for a link span longer than 120 m. The goodness of fit test is performed to validate the conformity of the two distributions with the simulation results. The scintillation index (SI) variation as a function of the four mentioned parameters under different turbulence regimes is investigated. It is shown that, for a 100 m link span and under weak turbulence, while the effect of transmitter's FOV on SI is negligible, increasing the transmitter's divergence angle by 1.72º and decreasing the Rx's aperture diameter by 9.2 cm, increases the SI by 53 times and 77 times, respectively.

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Introducing SiTTE: A controlled laboratory setting to study the impact of turbulent fluctuations on light propagation in the underwater environment

Matt¹,

Hou²,

Goode³

et al. 2017

Opt. Express

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Small-scale spatial variation in temperature can lead to localized changes in the index of refraction and can distort electro-optical (EO) signal transmission in ocean and atmosphere. This phenomenon is well-studied in the atmosphere, where it is generally called "optical turbulence". Less is known about how turbulent fluctuations in the ocean distort EO signal transmissions, an effect that can impact various underwater applications, from diver visibility to active and passive remote sensing. To provide a test bed for the study of the impacts from turbulent flows on EO signal transmission, and to examine and mitigate turbulence effects, we set up a laboratory turbulence environment allowing the controlled and repeatable variation of turbulence intensity. The laboratory measurements are complemented by high resolution computational fluid dynamics simulations emulating the tank environment. This controlled Simulated Turbulence and Turbidity Environment (SiTTE) can be used to assess optical image degradation in the tank in relation to turbulence intensity, as well as to examine various adaptive optics mitigation techniques.

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Velocity fields and optical turbulence near the boundary in a strongly convective laboratory flow

Cited by 3 publications

References 3 publications

Monte Carlo simulation of turbulence induced by temperature and salinity changes on underwater light transmission performance

Monte Carlo simulation of turbulence induced by temperature and salinity changes on underwater light transmission performance

System parameters effect on the turbulent underwater optical wireless communications link

Introducing SiTTE: A controlled laboratory setting to study the impact of turbulent fluctuations on light propagation in the underwater environment

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