Introducing Flow Turbulence

2016 ◽  
pp. 3-18 ◽  
Author(s):  
David S-K. Ting
Keyword(s):  
Flow Turbulence

scholarly journals Flow Turbulence Characteristics and Mass Transport in the Near-Wake Region of an Aquaculture Cage Net Panel

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 294
Author(s):  
Dongdong Shao ◽  
Li Huang ◽  
Ruo-Qian Wang ◽  
Carlo Gualtieri ◽  
Alan Cuthbertson
Keyword(s):  
Mass Transport ◽  
Near Field ◽  
Lateral Spreading ◽  
Wake Flow ◽  
Wake Region ◽  
Near Wake ◽  
Turbulence Characteristics ◽  
Macro Scale ◽  
Flow Turbulence ◽  
Fish Cages

Cage-based aquaculture has been growing rapidly in recent years. In some locations, cage-based aquaculture has resulted in the clustering of large quantities of cages in fish farms located in inland lakes or reservoirs and coastal embayments or fjords, significantly affecting flow and mass transport in the surrounding waters. Existing studies have focused primarily on the macro-scale flow blockage effects of fish cages, and the complex wake flow and associated near-field mass transport in the presence of the cages remain largely unclear. As a first step toward resolving this knowledge gap, this study employed the combined Particle Image Velocimetry and Planar Laser Induced Fluorescence (PIV-PLIF) flow imaging technique to measure turbulence characteristics and associated mass transport in the near wake of a steady current through an aquaculture cage net panel in parametric flume experiments. In the near-wake region, defined as ~3M (mesh size) downstream of the net, the flow turbulence was observed to be highly inhomogeneous and anisotropic in nature. Further downstream, the turbulent intensity followed a power-law decay after the turbulence production region, albeit with a decay exponent much smaller than reported values for analogous grid-generated turbulence. Overall, the presence of the net panel slightly enhanced the lateral spreading of the scalar plume, but the lateral distribution of the scalar concentration, concentration fluctuation and transverse turbulent scalar flux exhibited self-similarity from the near-wake region where the flow was still strongly inhomogeneous. The apparent turbulent diffusivity estimated from the gross plume parameters was found to be in reasonable agreement with the Taylor diffusivity calculated as the product of the transverse velocity fluctuation and integral length scale, even when the plume development was still transitioning from a turbulent-convective to turbulent-diffusive regime. The findings of this study provide references to the near-field scalar transport of fish cages, which has important implications in the assessment of the environmental impacts and environmental carrying capacity of cage-based aquaculture.

Visible enhanced scattering from air flow turbulence

2001 ◽  
Vol 55 (4) ◽  
pp. 486-491 ◽  
Author(s):  
A. V Kharchenko ◽  
D Grésillon
Keyword(s):  
Air Flow ◽  
Flow Turbulence

Estimation of Flow Turbulence Metrics With a Lateral Line Probe and Regression

2017 ◽  
Vol 66 (4) ◽  
pp. 651-660 ◽  
Author(s):  
Ke Chen ◽  
Jeffrey A. Tuhtan ◽  
Juan Fran Fuentes-Perez ◽  
Gert Toming ◽  
Mark Musall ◽  
...  
Keyword(s):  
Lateral Line ◽  
Flow Turbulence

Effects of flow turbulence on film cooling efficiency

1995 ◽  
Vol 38 (11) ◽  
pp. 2117-2125 ◽  
Author(s):  
V.P. Lebedev ◽  
V.V. Lemanov ◽  
S.Ya. Misyura ◽  
V.I. Terekhov
Keyword(s):  
Film Cooling ◽  
Cooling Efficiency ◽  
Flow Turbulence ◽  
Film Cooling Efficiency

scholarly journals Performance Evaluation of Underwater Wireless Optical Communication System by Varying the Environmental Parameters

Photonics ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 74
Author(s):  
Dong-Chang Li ◽  
Chia-Chun Chen ◽  
Shien-Kuei Liaw ◽  
Shofuro Afifah ◽  
Jiun-Yu Sung ◽  
...  
Keyword(s):  
Optical Communication ◽  
Environmental Parameters ◽  
Artificial Seawater ◽  
Blue Laser ◽  
Laser Source ◽  
Water Tank ◽  
Wireless Optical Communication ◽  
Transmission Distance ◽  
Flow Turbulence ◽  
The Impact

Underwater wireless optical communication (UWOC) has been considered a promising technology for high-speed underwater transmission. Some Gb/s level UWOC systems applying visible light have been demonstrated with a transmission distance of several meters or more. Many of the previous works focus on the advanced technologies to push the systems’ capacity–distance performance. However, practical environmental factors issue such as flow turbulence and temperature variation are seldom studied through specific statistical/theoretical models. In this paper, a UWOC system using a 450 nm blue light laser source was set up using a 1.5-m water tank with mirrors located on both sides for single or multiple reflections corresponding to different transmission distances. The blue laser was modulated by a 1.25 Gbps NRZ-OOK format with PRBS of 7, 24 or 31, respectively, for system performance comparison. The bit error rate (BER) values were measured in 1.5, 3.0 and 6 m, respectively, for system evaluation. At room temperature, the BER value was down to 10 × 10−8 for a 1.25 Gbps data rate in a 6 m transmission. Then, the UWOC transmission system experiment was carried out under several environmental parameters such as temperature, turbulence, artificial seawater by adding salt to simulate practical application in river or sea. When a submerged motor with an output of 1200 L/h was used as a water flow turbulence source, the impact to BER and transmission quality was negligible. For the temperature change issue, the experiment shows that around the original temperature of 25 °C had the best BER as compared to other temperature ranges from 10 to 50 °C. For artificial seawater issues by adding salt to simulate the real seawater environment. The transmission distance was only 3-m instead of 6 m, mainly due to particle scattering and water disturbance. With the motor pump on, the power penalty was 1 dB at 10 × 10−8 BER when compared to the motor pump off.

Morphing Continuum Theory: Incorporating the Physics of Microstructures to Capture the Transition to Turbulence Within a Boundary Layer

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Louis B. Wonnell ◽  
James Chen
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Ad Hoc ◽  
Constitutive Relations ◽  
Turbulence Models ◽  
Continuum Theory ◽  
Transition To Turbulence ◽  
Flow Turbulence ◽  
Good Agreement ◽  
Inherent Advantage

A boundary layer with Re = 106 is simulated numerically on a flat plate using morphing continuum theory. This theory introduces new terms related to microproperties of the fluid. These terms are added to a finite-volume fluid solver with appropriate boundary conditions. The success of capturing the initial disturbances leading to turbulence is shown to be a byproduct of the physical and mathematical rigor underlying the balance laws and constitutive relations introduced by morphing continuum theory (MCT). Dimensionless equations are introduced to produce the parameters driving the formation of disturbances leading to turbulence. Numerical results for the flat plate are compared with the experimental results determined by the European Research Community on Flow, Turbulence, and Combustion (ERCOFTAC) database. Experimental data show good agreement inside the boundary layer and in the bulk flow. Success in predicting conditions necessary for turbulent and transitional (T2) flows without ad hoc closure models demonstrates the theory's inherent advantage over traditional turbulence models.

Sign in / Sign up

Export Citation Format

Share Document