Turbulent Water Research Articles

Effects of substrate, water flow, and turbulence in raceway culture of the high-value agarophyte Pterocladiella capillacea

One reason most commercial seaweed aquaculture is done extensively is that land-based intensive culture is expensive. Seaweed growth in land-based raceways can be bolstered by high water flows and turbulence, and a better understanding of this may mitigate production costs. We investigated flow conditions in raceway culture of Pterocladiella capillacea, a source of pharmaceutical grade agar. We tested the effects of ploidy level (carpospores, tetraspores), substrate (rope, glass slide), and flow type in raceways (turbulent, laminar) and the laboratory (no flow) on the survival and growth of sporelings. We also assessed the effect of flow rates (1.5, 4, 10 cm s−1) and flow type (turbulent, laminar) on the growth of adult P. capillacea. Sporeling survival 48 h post-settlement was unaffected by flow type, and carpospores survived better than tetraspores on ropes. After four weeks, sporelings in raceways survived better on ropes than on glass slides, and sporelings derived from carpospores survived better on ropes than those from tetraspores. Sporelings grown in raceways were 5.8 times larger than those in the laboratory, but flow types had little effect within raceways. Seaweeds grown from carpospores grew 1.2 times larger than tetraspore in the raceways. Flow rate and type had little effect on the growth of adults, and their growth was slow possibly because of smothery by epiphytes. This study suggests P. capillacea spores are amenable to raceway culture, but adults do not fare as well in similar conditions.

Simulation of vertical core-annular flow with a turbulent annulus

The Reynolds-Averaged Navier Stokes (RANS) with the Launder & Sharma low-Reynolds number k−ε model was used to simulate core-annular flow in the same configuration with vertical upflow as considered by Kim & Choi (2018), who carried out Direct Numerical Simulations (DNS), and by Vanegas Prada (1999), who performed experiments. The DNS are numerically very accurate and can thus be used for benchmarking of the RANS turbulence model. There is a large ratio between the oil and water viscosities, and the density difference between the water and oil is only small. The frictional pressure drop was fixed and the water holdup fraction was varied. Differences between the RANS and DNS predictions, e.g. in the wave structure and in the Reynolds stresses, are discussed. Despite the shortcomings of the considered Launder & Sharma low-Reynolds number k−ε model in RANS, in comparison to DNS, the RANS approach properly describes the main flow structures for upward moving core-annular flow in a vertical pipe, like the travelling interfacial waves in combination with a turbulent water annulus. The Fanning friction factor with RANS is 18% lower than with DNS, and the holdup ratio with RANS is only slightly higher than with DNS (i.e. it has a slightly larger tendency to accumulate water in RANS than in DNS).

Flow Turbulence and Pressure Fluctuations in a Hydraulic Jump

Turbulence and pressure fluctuations are key elements in the bed protection design of hydraulic structures. However, their roles in a hydraulic jump are not yet fully understood, and the nature of their relationships are not conclusive. In order to better understand the relationships between pressure fluctuations and flow characteristics of a hydraulic jump downstream of a weir, detailed measurements of flow kinematics using the nonintrusive techniques of particle image velocimetry and bubble image velocimetry and pressure using voltage-type pressure gauges were carried out in this study. The physical modeling of the hydraulic jump was carried out using the simultaneous measurements of pressure and turbulent flow properties. The distributions of flow properties, such as water level and velocity, were assessed in each case. Based on the measurements, the correlations between the pressure fluctuations and the variables were investigated by coupling the statistical values of the variables at the same points. The analysis results show that the water level and turbulence intensity are the main factors influencing the pressure fluctuations in the hydraulic jump. Using these factors, an empirical formula and dimensionless numbers are proposed to show that the pressure fluctuations depend on the bubble flow behavior.

Tidal turbulence in medium depth water, primarily a model study

Tidal energy is considered to be one important future source of renewable energy. There is presently a strong development in new technology, and there is an emerging need to e.g., describe the turbulence intensity and its characteristics in a tidal stream. In this study we consider a high resolution Large Eddy Simulation (LES) in water with 80 m depth and a tidal stream with a maximum volume mean flow amplitude of 2 ms-1. the simulation is designed to describe turbulence characteristics at a developer site outside Holyhead in the Irish Sea. We find that the turbulence intensity and characteristics has clear time dependence, and that it is 100% stronger on the retarding tidal current as compared to the accelerating tidal current. We also find that it depends on the distance from the bottom. The turbulence is highly anisotropic with much longer length scales in the flow directions than perpendicular to flow direction. The simulation setup and results for mean flow quantities and turbulence measures are discussed in the presentation. Finally, results are compared with results from a ship mounted ADCP for mean flow characteristics and for turbulence quantities.

Numerical investigation of entropy generation of turbulent flow in twisted tri-lobed tubes

Twisted tri-lobed tubes have garnered attention due to their exceptional heat transfer efficiency and straightforward fabrication. Existing literature lacks comprehensive assessments of the overall heat transfer performance of twisted tri-lobed tubes from the perspective of energy loss and irreversibility. This research aims to investigate entropy generation during turbulent water flow within twisted tri-lobed tubes, examining the influence of geometric parameters on local and average entropy production. Findings indicate that larger small circle radius (r) and straight lengths (l), coupled with smaller transition circle radius (R) and twist pitch lengths (p), result in diminished local and average heat transfer entropy production while enhancing local and average frictional entropy production, with heat transfer entropy generation dominating the overall entropy production. Additionally, with increasing Reynolds numbers, all twisted tubes demonstrate an increasing trend in average frictional entropy production, except for some cases (Case 1-Case 4) that exhibit an initial rise followed by a decline in average heat transfer entropy generation. Among the examined Reynolds range, Case 4 displays lower overall irreversibility compared to a plain tube. Following the second law of thermodynamics, Case 4 is preferred. The findings and methodology contribute to enhancing the thermodynamic evaluation of convective heat transfer in twisted tri-lobed tubes.

A Life Outside.

How do the morphologies of organisms affect their physical interactions with the environment and other organisms? My research in marine systems couples field studies of the physical habitats, life history strategies, and ecological interactions of organisms with laboratory analyses of their biomechanics. Here, I review how we pursued answers to three questions about marine organisms: (a) how benthic organisms withstand and utilize the water moving around them, (b) how the interaction between swimming and turbulent ambient water flow affects where small organisms go, and (c) how hairy appendages catch food and odors. I also discuss the importance of different types of mentors, the roadblocks for women in science when I started my career, the challenges and delights of interdisciplinary research, and my quest to understand how I see the world as a dyslexic.

Integrated numerical modeling to quantify transport and fate of microplastics in the hyporheic zone.

Despite the significance of rivers and streams as pathways for microplastics (MP) entering the marine environment, limited research has been conducted on the behavior of MP within fluvial systems. Specifically, there is a lack of understanding regarding the infiltration and transport dynamics of MP across the streambed interface and within the hyporheic sediments. In this study, transport and retention of MP are investigated using a new numerical modeling approach. The model is built as a digital twin of accompanying flume experiments, which are used to validate the simulation results. The model accurately represents particle transport in turbulent water flow and within the hyporheic zone (HZ). Simulations for transport and infiltration of 1µm MP particles into a sandy streambed demonstrate that the advection-dispersion equation can be used to adequately represent particle transport for pore-scale sized MP within the HZ. To assess the applicability of the modeling framework for larger MP, the experiment was repeated using 10µm particles. The larger particles exhibited delayed infiltration and transport behavior, and while the model successfully represented the spatial extent of particle transport through the HZ, it was unable to fully replicate hyporheic transit times. This study is the first to combine explicit validation against experimental data, encompassing qualitative observations of MP concentration patterns and quantification of fluxes. By that, it significantly contributes to our understanding of MP transport processes in fluvial systems. The study also highlights the advantages and limitations of employing a fully integrated modeling approach to investigate the transport and retention behavior of MP in rivers and streams.

The TU Wien Turbulent Water Channel: Flow control loop and three-dimensional reconstruction of anisotropic particle dynamics.

A horizontal water channel facility was built to study particle dynamics in a turbulent flow. The channel is sufficiently long to produce fully developed turbulence at the test section, and the width-to-height ratio is sufficiently large to avoid the sidewall effect for a large proportion of the cross-section. The system was designed to study the dynamics of complex-shaped particles in wall-bounded turbulence, the characteristics of which can be finely controlled. A maximum bulk velocity of up to 0.8ms-1 can be achieved, corresponding to a bulk Reynolds number of up to 7 × 104 (shear Reynolds number ≈1580), and flow parameters can be controlled within ±0.1%. The transparent channel design and aluminum structures allow easy optical access, which enables multiple laser and camera arrangements. With the current optical setup, a measurement volume of up to 54 × 14 × 54 mm3 can be imaged and reconstructed with six cameras from the top, bottom, and sides of the channel. Finally, the in-house developed reconstruction and tracking procedure allows us to measure the full motion of complex objects (i.e., shape reconstruction, translational, and rotational motions), and in this instance, it is applied to the case of microscopic, non-isotropic polyamide fibers.

CFD analysis of turbulent free high-speed water jet issuing from circular and non-circular nozzle geometry in context of abrasive slurry jet machining

CFD analysis of turbulent free high-speed water jet issuing from circular and non-circular nozzle geometry in context of abrasive slurry jet machining

Heat transfer enhancement in pillow-plate type heat exchanger with SCWSCs using an entropy and exergy generation approximation technique

The design and development of the Pillow-plate heat exchanger (PPHE) are attracting more interest in the research and scientific communities in recent years. In this manuscript, a new investigation is performed to examine the heat transfers and fluid flow characteristics for different streamwise lengths with Staggered Circular Welding Spot Configurations. To analyze the heat transfer and friction factor parameters total of 25 different designs of dh/XL is considered, 1000 ≤Re≤ 16,000. In addition, to optimizing the exergy efficiency and thermal evaluation factor, some dimensional and non-dimensional thermodynamic and thermal-hydraulic influencers, including thermal and frictional entropy generation, thermal and frictional exergy destruction, Nusselt number, friction factor, Bejan, entropy generation number are calculated by considering the second law efficiency approach based on thermo-dynamics for turbulent single-phase water flow in PPHE as wavy surface using SST transition k−ω method and entropy and exergy approximation technique. Based on the computational results obtained, increasing the streamwise lengths with SCWSPs, the ‘elliptical recirculation vortex’ is essential and significantly enhances the thermal performance factor. The maximum exergy and thermal performance factor are improved by 41.58% and 1.54 in the dh/XL = 0.078 and 0.044 at Re = 1000, respectively.

Insights into the relation between vertical cloud structure and dynamics of three polar lows: Observations from COMBLE

AbstractThe vertical structure of three polar lows is described using profiling radar, lidar, and passive remote sensors deployed at a coastal site in northern Norway. The data were collected as part of the Cold‐air Outbreaks in the Marine Boundary Layer Experiment (COMBLE). These data are examined in the context of satellite imagery, operational weather radar reflectivity imagery, and output from the AROME Arctic model. A comparison to satellite images shows that AROME‐Arctic captured the polar lows well. All three polar lows form in marine cold‐air outbreaks and are surrounded by open‐cellular convection typical of such outbreaks. Two of the lows form in a forward shear environment and one under reverse shear. Initially, the three polar lows are comma shaped; two of them transition to be more spiraliform at their mature stage and have mostly cloud‐free warm cores. The warm cores are the result of a warm‐seclusion process. All three lows have stratiform precipitation bands, marked by little cloud liquid water, and rather high surface precipitation rate. The vertical drafts and turbulence in these stratiform clouds are generally weak. All three lows also have convective clouds, which have stronger vertical drafts, stronger turbulence, and pockets of high liquid water content.

Detection of Secondary Microplastics in an Aquatic Mesocosm by Means of Object-Based Image Analysis

When plastics are discarded, they do not biodegrade and instead break down over time into progressively smaller particles, termed secondary microplastics, which adversely impact biota and human health as well as persist in the environment for centuries. Our research objective was to evaluate the capabilities of object-based image analyses in detecting compositionally varied microplastics suspended in an aquatic mesocosm under no-slip and turbulent water conditions. We found that the presence of polypropylene, polyethylene terephthalate, and low-density polyethylene microplastic pollution in both single-type and mixed-type suspensions was not detectable by either average red (R), average blue (B), average green (G), or average RBG pixel intensities, but was significantly detectable by means of total RBG pixel intensity from digital imagery of the surface-water. Our findings suggest that object-based image analyses of surface waters to quantify pixel information is better suited for monitoring the presence and absence of suspended microplastics, rather than for the stepwise determination of microplastic concentrations. We propose the development of a smartphone application to facilitate citizen-science monitoring of microplastic contamination as well as comment on future applications utilizing drone imagery to boost cloud-based mapping spatiotemporal plumes.

Aerosolization flux, bio-products, and dispersal capacities in the freshwater microalga Limnomonas gaiensis (Chlorophyceae)

Little is known on the spreading capacities of Limnomonas gaiensis across freshwater lakes in Northern Europe. In this study, we show that the species could successfully be aerosolized from water sources by bubble bursting (2-40 particles.cm−3), irrespectively of its density in the water source or of the jet velocity used to simulate wave breaking. The species viability was impacted by both water turbulences and aerosolization. The survival rate of emitted cells was low, strain-specific, and differently impacted by bubble busting processes. The entity “microalga and bionts” could produce ethanol, and actively nucleate ice (principally ≤−18 °C) mediated soluble ice nucleation active proteins, thereby potentially impacting smog and cloud formation. Moreover, smallest strains could better cope with applied stressors. Survival to short-term exposure to temperatures down to −21 °C and freezing events further suggest that L. gaiensis could be air dispersed and contribute to their deposition.

Performance Analysis of Underwater Optical Communication System in Turbulent Link

Underwater wireless optical communication (UWOC) systems have been identified as a suitable replacement technology with high data rates over relatively medium transmission ranges for underwater communication. In the research, we propose a new optical hybrid modulation format for carrying the letters over underwater wireless optical communication (UWOC) system. This hybrid modulation format combines pulse position modulation (PPM) with digital pulse interval modulation (DPIM) to increase the transporting speed. The proposed UWOC system is experimentally investigated in the laboratory over a clean and turbulent water channel. The message was electrically modulated in the transmitter with PPM-DPIM format and then applied to a laser diode. The laser diode emitted light at a wavelength of 650 nm with a power of 60 mW. At the receiver, the photodiode, with its amplifier circuits, sends the received signal to the microprocessor to restore the origin message. The results showed that the received power and signal-to-noise ratio (SNR) decreased with elongating the transmission distance. In addition, the attenuation is raised with increasing distance. The bubbles source is also situated at distances of 25 cm, 50 cm, and 75 cm from the transmitter in turbulent waters. The results showed that locating the bubble source decreases the system's performance. The best results were obtained when the bubble source was 75 cm away from the transmitter. Finally, the hybrid modulation formats (PPM-DPIM) can increase the speed of letter transmission, reduce the bit error rate (BER), and minimize the effect of scattering and attenuation in water channels.

Ablation‐Limited Erosion Rates of Permafrost Riverbanks

AbstractPermafrost thaw is hypothesized to increase riverbank erosion rates, which threatens Arctic communities and infrastructure. However, existing erosion models have not been tested against controlled flume experiments with open‐channel flow past an erodible, hydraulically rough permafrost bank. We conducted temperature‐controlled flume experiments where turbulent water eroded laterally into riverbanks consisting of sand and pore ice. The experiments were designed to produce ablation‐limited erosion such that any thawed sediment was quickly transported away from the bank. Bank erosion rates increased linearly with water temperature, decreased with pore ice content, and were insensitive to changes in bank temperature, consistent with theory. However, erosion rates were approximately a factor of three greater than expected. The heightened erosion rates were due to a greater coefficient of heat transfer from the turbulent water to the permafrost bank caused by bank grain roughness. A revised ablation‐limited bank erosion model with a heat transfer coefficient that includes bank roughness matched our experimental results well. Results indicate that bank erosion along Arctic rivers can accelerate under scenarios of warming river water temperatures for cases where the cadence of bank erosion is set by pore‐ice melting rather than sediment entrainment.

Performance analysis of UAV assisted triple-hop mixed FSO/RF/UWOC system with altitude optimization

Abstract In this paper, we propose a unmanned aerial vehicle (UAV) assisted triple hop mixed FSO/RF/UWOC system to establish a communication between distant users. In the proposed system, the source sends information signal towards a hovering UAV such as drone acting as a first intermediate node via FSO link modelled by Gamma-Gamma distribution. The drone further transmits the received signal to the second intermediate node located on a floating vehicle (FV) on the ocean surface via a RF link modelled by the Nakagami-m fading distribution and from where it is finally forwarded towards the deep ocean destination via visible light channel (VLC) link which is modelled by Exponential Generalized Gamma (EGG) fading distribution. Both the relay nodes act as decode and forward relays. For this asymmetric triple hop mixed communication system, we obtain a new exact closed form analytical expression for the outage probability and also study its behaviour at high signal to noise ratio (SNR) regime. Additionally, the UAV altitude optimization is also carried out for the proposed system to find the optimal altitude of the UAV and the optimal elevation angle to maximize the system’s performance. The numerical simulation results illustrate the accuracy of the proposed system model and present the influence of the various link parameters such as atmospheric path loss, turbulence, pointing errors, angle-of-arrival fluctuations, multipath fading parameter, water turbulence, and scintillation on the performance of the proposed system.

Harmful algal bloom aerosols and human health.

Harmful algal blooms (HABs) are increasing across many locations globally. Toxins from HABs can be incorporated into aerosols and transported inland, where subsequent exposure and inhalation can induce adverse health effects. However, the relationship between HAB aerosols and health outcomes remains unclear despite the potential for population-level exposures. In this review, we synthesized the current state of knowledge and identified evidence gaps in the relationship between HAB aerosols and human health. Aerosols from Karenia brevis, Ostreopsis sp., and cyanobacteria were linked with respiratory outcomes. However, most works did not directly measure aerosol or toxin concentrations and instead relied on proxy metrics of exposure, such as cell concentrations in nearby waterbodies. Furthermore, the number of studies with epidemiological designs was limited. Significant uncertainties remain regarding the health effects of other HAB species; threshold dose and the dose-response relationship; effects of concurrent exposures to mixtures of toxins and other aerosol sources, such as microplastics and metals; the impact of long-term exposures; and disparities in exposures and associated health effects across potentially vulnerable subpopulations. Additional studies employing multifaceted exposure assessment methods and leveraging large health databases could address such gaps and improve our understanding of the public health burden of HABs.

Effects of water movement and temperature on Rhizophydium infection of Planktothrix in a shallow hypereutrophic lake.

Grand Lake St. Marys (GLSM) is a popular recreational lake located in western Ohio, United States, generating nearly $150 million in annual revenue. However, recurring algal blooms dominated by Planktothrix agardhii, which can produce harmful microcystin toxins, have raised concerns about water safety and negatively impacted the local economy. Planktothrix agardhii is host to a number of parasites and pathogens, including an obligate fungal parasite in the Chytridiomycota (chytrids). In this study, we investigated the potential of these chytrid (Rhizophydium sp.) to infect P. agardhii blooms in the environment by modifying certain environmental conditions thought to limit infection prevalence in the wild. With a focus on temperature and water mixing, mesocosms were designed to either increase or decrease water flow compared to the control (water outside the mesocosm). In the control and water circulation mesocosms, infections were found infrequently and were found on less than 0.75% of the Planktothrix population. On the other hand, by decreasing the water flow to stagnation, chytrid infections were more frequent (found in nearly 3x as many samples) and more prevalent, reaching a maximum infection rate of 4.12%. In addition, qPCR coupled with 16S-18S sequencing was utilized to confirm the genetic presence of both host and parasite, as well as to better understand the effect of water circulation on the community composition. Statistical analysis of the data confirmed that chytrid infection was dependent on water temperature, with infections predominantly occurring between 19°C and 23°C. Additionally, water turbulence can significantly reduce the infectivity of chytrids, as infections were mostly found in stagnant mesocosms. Further, decreasing the water circulation promoted the growth of the cyanobacterial population, while increasing water agitation promoted the growth of green algae (Chlorophyta). This study starts to explore the environmental factors that affect chytrid pathogenesis which can provide valuable insights into controlling measures to reduce the prevalence of harmful algal blooms and improve water quality in GLSM and similarly affected waterbodies.

Application of artificial intelligence and communication technology to water and energy balance models

Abstract The precise correction of water and energy balance is a significant difficulty in studying turbulence energy balance and water flow for agricultural purposes. The need for efficient water and energy management is growing as the world struggles to keep up with rising water and energy demands. This research examines artificial intelligence (AI)'s impact on the water flow and energy balance confluence subnetwork of sensing elements from all the original network's nodes. The study proposed an AI-based optimized sensor energy balance model (AI-SEBM) that uses pressure data to maintain energy balance in turbines and save water with the optimized energy source for agriculture usage. This research explores the potential for installing Kalpan hydraulic turbines, which are most effective during half-load operation, and to forecast all loads with little computing effort to balance energy in turbulence. To anticipate daily pressure readings and energy consumption across all nodes in the network, an AI-based optimization wireless sensor network is designed for communication and linked to an energy balance system. Sensors are strategically deployed at the network's nerve centres. The maximum flow algorithm is used for a grid representing the water and energy balance to determine the positions of the virtual nodes.

Experimental analysis of enhanced solar still operating with induced turbulence.

This work experimentally investigates the performance of solar still with induced turbulence (SWIT) which operates with a novel approach for improved productivity. A metal wire net has been submerged in basin water of still and direct current vibration micro motor has been used to develop small intensity vibrations in wire net. These vibrations serve to induce turbulence in basin water and also break the thermal boundary layer between still surface and water to enhance the evaporation. The energy-exergy-economic-environment analysis of SWIT has been performed and compared with conventional solar still (CS) of identical size. The overall heat transfer coefficient of SWIT is found to be 66% more in comparison of CS. The SWIT provided 53% increase in yield and it is 55% more thermally efficient than CS. The average exergy efficiency of the SWIT is found to be 76% higher than that of CS. The cost of water from SWIT is 0.028 $ with a payback period of 0.74years and the carbon credit gained by SWIT is found to be 105 $. The productivity of SWIT has also been compared for intervals of 5, 10, and 15min between the induced turbulence to find suitable interval duration.