Transverse Ribs Research Articles

Design of concrete canoe reinforced with composite reinforcement

To participate in international competitions on concrete canoe among students at the Department of concrete and masonry structures KNUBA has been designed and manufactured concrete canoe reinforced composite reinforcement. The design of the canoe was modeled and calculated in the PC «LIRA-SAPR».The problem of this article is to determine the optimal thickness of the walls of the canoe, the composition of basalt fiber and the scheme of reinforcement of the canoe to ensure its strength and crack resistance, as well as sufficient buoyancy. To achieve the minimum weight of the canoe it is customary to use non-metal reinforcement.The dimensions of the wooden canoe were accepted for the concrete canoe project. In terms of canoeing has a lenticular shape. The total canoe length is 4,3 m and maximum width is 900 mm. The minimum height of the board is 400 mm. According to the accepted manufacturing technology, the walls and canoe bottom have a three-layer construction, consisting of an inner and outer layer of basalt fiber concrete 3… 5 mm thick and an inner layer of expanded polystyrene foam 10 mm thick. To strengthen the most intense zones in the outer layer of basalt fiber reinforced carbon mesh. In the transverse direction, transverse ribs (frames) made of expanded polystyrene 20 mm thick and 20… 30 mm high are arranged. Along the upper sides of the sides, along the keel rib and along the frames, basalt reinforcement with a diameter of 6 mm (2 rods) was installed.To calculate the canoe, its calculation model was developed in the LIRA-CAD PC. The canoe model is made in the form of a shell made of flat triangular finite elements. Linear elements were also added to model the basalt reinforcement. Linear and flat elements are rigidly connected at the nodes.According to the manufacturer, the modulus of elasticity of the rod reinforcement is 70∙103 MPa, and the temporary tear resistance - 1100 MPa, density -1,9 g/m3. The basalt fiber was adopted with a thickness of 20 mkm and a length of 50 mm.Two-component waterproofing solution SILTEK V-33/E-33 was used as the concrete matrix. The amount of basalt fiber was 3%. To determine the characteristics of basalt fiber concrete test cubes with an edge of 75 mm and samples-"eight" were made. As a result of the test, the tensile strength of basalt fiber was compressed at 8.4 MPa and the axial tensile strength was 1.8 MPa.The obtained design characteristics were used to introduce finite element stiffnesses.Canoe loading was applied on its own weight, the weight of two 80 kg paddles and hydrostatic water pressure.As a result of the calculation, mosaics of stresses were obtained. They showed the most intense zones, which were reinforced with carbon mesh.After experimental and numerical studies, we came to the conclusion that non-metallic composite reinforcement can be used in the construction of light structural elements. Such structures are absolutely not susceptible to corrosion. In the future, it is necessary to investigate structural elements that are used in the aquatic environment, such as pontoons, platforms for waterfront homes and more.

Numerical simulation of liquid–gas interface formation in long superhydrophobic microchannels with transverse ribs and grooves

Superhydrophobic microchannels have evolved recently as an accepted strategy to mitigate the hydrodynamic resistance tendered in micro-constrictions. In this work, hydrodynamics of a hydrophobic microchannel realized by entrapping air in the cavities located between transversely oriented ribs is numerically investigated. An interface formed between the liquid and air/vapor in the confinement facilitates a resistance free slipping surface for the flowing water. The shape of the meniscus is determined by the pressure difference between air and liquid and is classified as convex, flat, and concave depending on the protrusion angle. Several applications require a long hydrophobic channel in which the liquid pressure decreases lengthwise; consequently the interface shape changes as well. In this regard, a mathematical model is proposed to predict the protrusion angle at a specific distance from the inlet of microchannel. This is incorporated in the computational fluid dynamics (CFD) simulations to define the static geometry of the interface which is varying throughout the length of the channel. Moreover, the boundary is treated as a combination of flat no-slip and curved shear-free regions to mimic the ribs and cavities. Further, the evolution of interface morphology is captured using the volume-of-fluid (VOF) scheme by considering a static contact angle at the solid surface to check the validity of the suggested model. Dynamically evolved protrusion angle is measured for various liquid–gas interface pressures and it is observed that the theoretical scaling proposed by Laplace and Young is well obeyed. Though CFD–VOF simulation scheme is an effective tool for predicting the pressure dependent liquid–gas meniscus and concurrent hydrodynamics of the ribbed microchannel, it is resource intensive. The present study demonstrates that the developed model for static boundary may be adopted alternatively to predict the hydrodynamics of a long hydrophobic microchannel by saving computational resources.

Investigation of the Effect of Reinforcing Diaphragms Ribbed Panels on their Carrying Capacity

It has been established that structural analysis of ribbed panels on the carrying capacity of standard cross-sections is presented as reinforced concrete T-shaped or I-beams. However, this approach does not allow factoring in the effect of transversal ribs (diaphragms) on the accounting result for two groups of limit states. As a rule, transversal ribs are used in slabs with a greater width and serve mainly to provide its bending strength across the width mode transversely. It should be mentioned that a slab is calculated according to the beam theory based on structural mechanics models that characterize its behavior approximately in either direction along standard cross-sections. The theory of plate and shell can define the behavior under steady load of such a slab more precisely. However, applying this theory is attended with certain difficulties because of steel collaboration in multiple directions, as well as having material nonlinearity in the model. The work investigates ribbed floor panels which are modeled using modern software. The authors studied samples with prestressed and nonprestressed reinforcing as well as with or without transversal ribs. Finally, the authors find out that it is worth considering transversal ribs with regard to their reinforcement in stress calculations for standard cross-sections along a slab length. It can contribute to the development of correcting coefficients and specification of the section of the calculating theory of building constructions. The authors obtained innovative outcomes.

Influence of Rib Stiffness and Limited Long-Term Junction Strength on Geogrid Performance

The description of the behavior of geogrids in reinforced soil constructions usually ignores long-term behavior and possible failure modes of junctions between longitudinal and transverse ribs. Two proposals have been made during recent years to overcome this drawback. The first analytic approach applies only to rigid geogrids and assumes a specific tensile-shear failure mode of geogrid junctions. The second numerical approach applies also for non-rigid geogrids and takes into account different modes of junction failure. This note discusses the two approaches focusing on the effects of rib stiffness and limited strength, different failure modes and degradation of junctions. It is shown that the mentioned effects should be considered in geogrid design, because they may alter significantly the long-term geogrid performance.

Jet vortex heat transfer in turbulent air flow around a plate with a slit rib

Experimental study and numerical simulation of vortex heat transfer in turbulent air flow around the plate with permeable transverse rectangular ribs at qw = const have been made. Confusor, diffuser and constant cross-section slits as well as the constant gap between the plate and the lower wall of the rib are considered. Mean and fluctuation profiles of velocity and temperature along the midsection of the plate in the sections of the turbulent boundary layer are measured using both a Pitot–Prandtl microprobe with a microthermocouple and a Dantec Dynamics hot-wire anemometer. To calculate spatial separated flow of incompressible liquids, the Reynolds-averaged Navier–Stokes equations closed by five turbulence models are adopted. The use of the k-ε two-parameter model with the Kato–Lauder modification (SKE-KL) provides a satisfactory agreement between numerical predictions and experimental data. So this model is selected as the basic one. The influence of the throttling effect on the turbulent separated flow structure and relative heat transfer coefficient when changing the slit shape and size is analyzed. The integral characteristics including total heat transfer coefficient, hydraulic losses and thermal-hydraulic performance are also compared. It is shown that the presence of a slit can eliminate secondary separation zones on the plate and decrease recirculation flow regions behind a rib. The rib with a confusor slit has the highest thermal-hydraulic performance that is by 15% more than that of the solid rib.

Effect of vibration frequency on settlement characteristic of reinforced embankment by geogrid with strengthened nodes using DEM simulation

Geogrid with strengthened nodes (GSN) is a new reinforcement system that is formed by attaching blocks of a certain thickness to the joints of the longitudinal and transverse ribs of an ordinary biaxial geogrid to form strengthened nodes. A series of discrete element method (DEM) simulations were performed to investigate the dynamic response of GSN-reinforced embankment at various vibration frequencies and compare the reinforcing effect of GSN with that of the ordinary geogrid. It was concluded that the settlement ratio of the loading platen at the top of the unreinforced and reinforced embankment decreases with the increase of the vibration frequency. As the frequency increases, the difference between the settlement ratios decreases, which is especially evident in the reinforced embankment. At the same frequency, GSN performs better in restricting the settlement ratio than the ordinary geogrid, and as the frequency increases, the reinforcing effects of both the ordinary geogrid and GSN decrease. The displacement fields of the simulated embankments were analyzed. It was found that the movement of soil particles below the loading platen is restricted due to the presence of the geogrid, resulting in less settlement of the loading platen and smaller lateral deformation of the embankment slope, compared with the unreinforced embankment. As for the GSN-reinforced embankment, the strengthened nodes provide resistance to soil particles, leading to a more effective reinforcing effect, so that the displacement vectors are even smaller.

A novel process for axial closed extrusion of ring part with mesh-like ribs

Fabrication of high-performance ring parts with mesh-like ribs becomes the focus of concern in aerospace industry. The axial closed extrusion (ACE) process is proposed in this work to manufacture this kind of parts. The processes for ACE of ring part with mesh-like ribs under the single punch motion (SPM) and double punches motion (DPM) modes are designed, which innovatively adopts the integrated mold consisting of several equal circular-arc-shaped dies to smoothly extract the extruded ring part with mesh-like ribs from moulds. The stress state in the deformed workpiece in the process of ACE is analyzed, and the critical conditions of both punch instability and sleeve fracture are obtained. In accordance with the stable conditions of ACE, ring part with mesh-like ribs, billet and moulds are precisely designed as well as the stroke of punch. The FE model for ACE of ring part with mesh-like ribs is established by using dynamic explicit DEFORM-3D software, the accuracy of which is validated by the narrowed experiments with a ratio of 4. By means of the reliable FE model, the metal deformation behaviors in the process of ACE under the SPM and DPM modes are comparatively analyzed. Results show that in ACE of ring part with mesh-like ribs the deformation at longitudinal rib is more inhomogeneous than that at transverse rib, and the growth speed of transverse rib is larger than that of longitudinal rib. Compared to the SPM mode, the effective strain under the DPM mode is smaller and distributed more homogeneously, and the temperature in the final extruded part under the DPM mode is lower and distributed more regularly. The forming force under the SPM mode is larger than that under the DPM mode, and the forming force markedly ascends with the increase of the extrusion speed. The results of numerical analysis and experiments demonstrate that the ACE process proposed in this paper is feasible and it has great potential to form ring part with mesh-like ribs.

New combined heat transfer enhancement techniques used in laminar flow through non-circular ducts

The problem of heat transfer enhancement using different combinations of transverse ribs, transverse corrugations and twisted-tape insert with oblique teeth, twisted tape with centre clearance and helical screw-tape insert in square and rectangular channel was investigated. The study also involved the thermohydraulic performance of inserts in non-circular channels in the laminar regime. Non-circular channels having aspect ratios of 1, 0.5 and 0.33 were considered. The techniques used for heat transfer augmentation in the present study were and the problem was (1) transverse ribs with twisted tape with oblique teeth, (2) integral transverse corrugation and centre-cleared twisted-tape insert, (3) transverse rib and helical screw-tape insert, (4) axial ribs and centre-cleared twisted-tape insert and (5) integral transverse rib and centre-cleared twisted-tape insert. These combined fin geometry are supposedly important from possible heat transfer enhancement point of view. In the channels, the combined influence of insert geometry such as rib pitch, rib height, twist ratio of twisted tape, twisted tape tooth horizontal length and twisted tape tooth angle was studied. The experiment was carried out using Servotherm oil as the working fluid, which had a wide range of Prandtl number (430–530). Uniform heat flux boundary condition was used. The methods used in the experiment have been discussed in the text of the presentation. The important results of the experimental investigation showed that the thermohydraulic performance using a combination of inserts was better than that of bare ducts and that of the individual enhancement technique acting alone. Both the increase in pressure drop and heat transfer augmentation occurred due to the addition of inserts, but heat transfer enhancement dominated over the increase in pressure drop. Nusselt number and friction factor correlations have also been developed and are presented in this paper. The experimental program considered different fin arrangements with various parameters and therefore, it should be very helpful in designing heat exchangers of different shapes and sizes used for industrial purpose. It is concluded from the present investigation that 31–52 per cent increase in heat duty at constant pumping power and 25–36 per cent reduction in pumping power at constant heat duty are achievable. This is the novelty of the present work since no such study and the observations have been made earlier. These types of combined fin configurations have not been tried before. The findings are likely to have good impact in the industry.

Nusselt number and friction factor behaviour of circular wavy transverse ribs artificially roughened solar air heater

The present study deals about the fluid flow and heat transfer behaviours of circular wavy wall transverse rib artificially roughened SAH. The circular wavy ribs are used in the solar air (SAH) heater with different undulation (N) and constant amplitude (A) below absorbing plate at testing zone for the present numerical investigation. Heat transfer behaviour varies about number of undulation with the intention that the optimum undulation of circular wavy wall transverse rib is necessary for better performance of SAH. The FLUENT v 14.5 is used to solve the governing equations (mass, momentum and energy). The RNG (k- ε) model is utilized to capture the turbulent effects and also the SIMPLE algorithm is used to couple the pressure and velocity. The geometrical parameter, pitch (p/e) ranges from 7.14 to 14.28 and relative roughened height (e/D) ranges from 0.021 to 0.042 are taken. The Reynolds numbers (Re) is varied between 3800 and 18000 for the constant heat (q) flux of plate 1000 W/m2. The results, Nusselt number (Nur/Nus) enhancement, and friction (fr/fs) factor performance are presented.

Mastering of New Rebar Profiles and Roll Materials in the Rolling Production of the EVRAZ ZSMK

The 250-1 continuous small-section mill of the JSC “EVRAZ Joint West-Siberian Metallurgical Plant” is specialized in manufacturing rebars No. 10 and No. 12 and equal angles Nos. 2–4 from workpieces with cross sections 100 × 100 mm in size. The production of rebars from carbon and low-alloy steels was mastered according to the standards of Europe, South-East Asia, and America. The production of rebars is performed both by the slitting process and without longitudinal slitting of the breakdown bars. The durability of the rebar roll passes of the finishing stands is, to a great extent, determined by the shape of grooves made at the bottom of the streams and used to form transverse ribs. The lowest durability of the passes of finishing stands is observed in the case of rolling of sections with crescent edges. In these passes, we observe the fractures of the working surface accompanied by the formation of cracks and crumbling. We tested cast iron of different grades intended for rolls of the finishing group with a minimal Shore hardness equal to 60. The best operating parameters were obtained for rolls made of nodular cast iron and alloyed with chromium, nickel, molybdenum, and vanadium.

Nusselt number and fluid flow analysis of solar air heater having transverse circular rib roughness on absorber plate using LCT and computational technique

The present study compares the heat transfer distribution over the absorber surface of a solar air heater using liquid crystal thermography (LCT) technique along with a CFD technique. The heat transfer distribution over the absorber surface is measured using the LCT technique. Computational analysis (CFD) is performed using ANSYS FLUENT 16.2 code with a general algorithm for the air flow to visualize the characteristics and distribution of the flowing air through the duct. The LCT measurement shows a two-dimensional temperature distribution as a color dispersal over the absorber surface. Comparison of the results for two different parameters having relative roughness pitch (P/e) and relative roughness height (e/D) are represented in graphical form as the effect of Nusselt number and friction factor obtained using LCT with computational technique over Reynolds number (Re) ranges of 8,551–11,149. The image captured by the CCD Camera of the LCT techniques to give a temperature distribution over the surface and the results are scrutinized for optimum values for the considered range of parameter studied resulting for maximum values of heat transfer rate at roughness pitch ratio of 10 with a minimum penalty of frictional losses. This shows approximately similar values obtained from both the approaches.

A fourteen-faced hexangulaconulariid from the early Cambrian (Stage 2) Yanjiahe Formation, South China

AbstractExtant medusozoans (phylum Cnidaria) are dominated by forms showing tetraradial symmetry, but stem-group medusozoans of early Cambrian age collectively exhibit tetra-, bi-, penta-, and hexaradial symmetry. Moreover, the developmental and evolutionary relationships between four-fold and other types of radial symmetry in medusozoans remain poorly understood. Here we describe a new hexangulaconulariid, Septuconularia yanjiaheensis new genus new species, from Bed 5 of the Yanjiahe Formation (Cambrian Stage 2) in the Three Gorges area of Hupei Province, China. The laterally compressed, biradially symmetrical periderm of this species possesses 14 gently tapered faces, the most of any hexangulaconulariid described thus far. The faces are bordered by longitudinal ridges and crossed by short, irregularly spaced transverse ribs. Longitudinally, the periderm consists of three regions that probably correspond, respectively, to an embryonic stage, a transient juvenile stage, and a long adult stage. Septuconularia yanjiaheensis may have been derived from six-faced Hexaconularia (Fortunian Stage), which is morphologically intermediate between Septuconularia yanjiaheensis and Arthrochites. Furthermore, conulariids sensu stricto, carinachitids, and hexangulaconulariids may constitute a monophyletic group united by possession of an organic or organophosphatic periderm exhibiting longitudinal (corner) sulci, a facial midline, and offset of transverse ribs along the facial midline.UUID: http://zoobank.org/01a972aa-aef3-4eef-a9a5-c2d8c3dda615

Simulation and experiment study on segregation mechanism of rice from straws under horizontal vibration

In order to separate rice and straws in dustpan and reveal its segregation mechanism, the discrete element method is used to establish the mathematical models of rice and straws and the dynamic behaviour of binary mixed system (rice and straws) under horizontal vibration is simulated. The results show that rice and straws in dustpan present apparent stratification in the vertical direction and straws are located above rice. The comprehensive application of kinetic energy theorem, theoretical mechanics, and fluid mechanics can provide a reasonable explanation for the segregation mechanism. The volume concentration of rice is used to quantify the degree of segregation. During the study, the problem of low energy in some areas of the system is found, together with the existence of convective rolls formed by mixed particles in motion, which result in an incomplete segregation of rice and straws, and the volume concentration of rice obtained is 0.87. By adding transverse ribs on the bottom plate and the arc wall of the dustpan, the micro-vibration of the bottom particles is enhanced, the system energy is increased, and the convective rolls are eliminated, and finally the volume concentration of rice obtained is close to 1. The influences of frequency and amplitude on layering effect are discussed and the method of selecting best vibration parameters is indicated. In the end, the experiment is designed and conducted, demonstrating that DEM is an effective method to simulate and analyse granular segregation.

Interaction of the metal plasma flows with surfaces of complex geometric shapes

The features of coating formation using vacuum-arc discharge plasma on the inner surface of a cylindrical cavity with transverse ribs in the form of a diaphragm are considered. The mathematical model is developed and expressions for calculation of thickness of coatings are received. The effect of the diaphragm on the thickness distribution and uniformity of the coating is shown. Compression areas directly in front of the barrier affecting the coating deposition rate were found.

Experimental and CFD analysis of solar air heater duct roughened with multiple broken transverse ribs: A comparative study

Lower thermal performance of conventional solar air heaters (SAH) can be enhanced by implementing small sized roughness elements on the air-flow side of the absorber plate. This article presents the results of a comparative study of two novel ribs arrangement namely multiple broken transverse ribs and square wave shaped ribs for performance enhancement in SAH’s. The investigation incorporates rib parameters as P/e = 10, e/D = 0.043 and W/w = 7 for both arrangements and investigated at six levels of Reynolds number ranging 3000–18,000. The effect of two different multiple shaped ribs on heat transfer and friction factor characteristics has been investigated using experimental and numerical investigation. The optimum parameters based on thermo-hydraulic performance has been evaluated. The CFD methodology has been validated for the smooth and roughened duct. Maximum thermal enhancement of 2.50 times with corresponding pumping power penalty of 3.92 times is obtained for square wave shaped ribs whereas in case of multiple broken ribs, the enhancements are 3.24 and 3.85 times respectively. The experimental results are illustrated and justified with the visualization of flow pattern and contours of temperature, pressure and turbulence.

Mechanical Performances of Transverse Rib Bar During Pull-Out Test

To evaluate mechanical performances of the transverse rib bar and reveal anchoring mechanism between the grout and steel bar, a series of pull-out tests were carried out, the numerical simulations and theoretical analysis of grout failure modes were also analyzed. Results show that the grout in front of the transverse rib display wedge-shape damage and the simulation results verify this damage forms. The formula of the effective transverse rib angle, the grout strength and anchorage force were derived based on elastic thick-wall cylinder theory. During the pull-out tests, the radial stress of the grout lagged the tangential stress reaching the ultimate tensile strength with the inner pressure increasing. The anchoring force of the transverse rib bar increases with the increase of the grout strength, and with the increase of the effective transverse rib angle. These conclusions provide the theoretical basis and technical support for the engineering practice.

A Comparative Study of Performance of Low Reynolds Number Turbulence Models for Various Heat Transfer Enhancement Simulations

The goal of this study is to evaluate the computational fluid dynamic (CFD) predictions of friction factor and Nusselt number from six different low Reynolds number k–ε (LRKE) models namely Chang–Hsieh–Chen (CHC), Launder–Sharma (LS), Abid, Lam–Bremhorst (LB), Yang–Shih (YS), and Abe–Kondoh–Nagano (AKN) for various heat transfer enhancement applications. Standard and realizable k–ε (RKE) models with enhanced wall treatment (EWT) were also studied. CFD predictions of Nusselt number, Stanton number, and friction factor were compared with experimental data from literature. Various parameters such as effect of type of mesh element and grid resolution were also studied. It is recommended that a model, which predicts reasonably accurate values for both friction factor and Nusselt number, should be chosen over disparate models, which may predict either of these quantities more accurately. This is based on the performance evaluation criterion developed by Webb and Kim (2006, Principles of Enhanced Heat Transfer, 2nd ed., Taylor and Francis Group, pp. 1–72) for heat transfer enhancement. It was found that all LRKE models failed to predict friction factor and Nusselt number accurately (within 30%) for transverse rectangular ribs, whereas standard and RKE with EWT predicted friction factor and Nusselt number within 25%. Conversely, for transverse grooves, AKN, AKN/CHC, and LS (with modified constants) models accurately predicted (within 30%) both friction factor and Nusselt number for rectangular, circular, and trapezoidal grooves, respectively. In these cases, standard and RKE predictions were inaccurate and inconsistent. For longitudinal fins, Standard/RKE model, AKN, LS and Abid LRKE models gave the friction factor and Nusselt number predictions within 25%, with the AKN model being the most accurate.

Pull-out test of interface characteristics between geogrid and sand

In order to study the friction characteristics of the reinforcement-soil interface, the effects of normal stress, percentage of transverse ribs,.geogrid width and pull-out velocity on the interaction mechanism of reinforcement-soil interface and the forces acting on the transverse ribs of geogrid are studied by means of the middle-scale pull-out test of the bidirectional geogrid and soil. The results show that with the increase of the normal stress of the interface, the pull-out resistance of the ribs increases significantly and the pull-out displacement becomes smaller when the single-width pull-out force reaches the ultimate tensile strength of the grid. Due to the squeezing effect of sand on the geogrid, the more uniform distribution of the cross-ribs of the geogrid is, the more favorable the force of the reinforcement is; the ratio of the interfacial friction to the total pull-out force decreases with the increase of the percentage of the transverse ribs, and the pull-out force of the narrower geogrid is slightly smaller than that of the wider grid under the same pull-out displacement. The longitudinal strain of the geogrid increases first and then decreases in the length direction, and the strain peak position gradually moves away from the loading end as the pull-out force increases, which indicates that the force acting on the geogrid is the transferable and inhomogeneous during the drawing process, and the maximum value is gradually moved toward the middle of the reinforcement due to the influence of the drawing deformation of the reinforcement.

Surviving the marine environment: two new species of Mallomonas (Synurophyceae)

ABSTRACTThe genus Mallomonas consists of single-celled flagellates covered with siliceous scales and bristles and is well known in freshwater environments. Two new marine Mallomonas species were collected from Dongho Beach, Jeollabukdo, Korea. To fully understand the taxonomy of the new species, we performed molecular phylogenetic analysis based on a concatenated dataset and observed morphological features using light and electron microscopy. For the phylogenetic analysis, we used a combined dataset from five gene sequences: nuclear small subunit (SSU) and large subunit (LSU) rDNA and plastid LSU rDNA, rbcL and psaA genes. The new species M. cuspis sp. nov. grouped with M. heterospina and M. oviformis in the section Planae. It had scales with a broad shield marked with V-shaped internal ridge that lacked submarginal ribs and a dome. The other new species, M. marina sp. nov., clustered with M. cratis, M. pseudocratis, M. asmundiae and M. striata var. serrata in section Striatae and had scale characters that matched the group, including a well-developed posterior submarginal rib and series of transverse ribs on the shield and dome. In addition, we investigated the effect of salinity on growth rate and cell morphology. The two marine species represented high growth rate between salinities of 10 and 30 psu, suggesting that both species are well adapted in marine environments. When exposed to salinities of 0 and 5 psu, they underwent cell enlargement.

Effect of Surface Wave on Development of Turbulent Boundary Layer Over a Train of Rib Roughness

Abstract In this paper, detailed experimental results are reported to study the effect of the surface wave of different frequencies on unidirectional current over the bed-mounted train of rib roughness. The model roughness used in this study is transverse square ribs that lengthened across the entire width of the recirculating wave channel. The center-to-center rib pitch (P) was constant during the experiments, thus generating a broad range of near-bed flow patterns for each of the three different surface wave frequencies studied here. The relative submergence associated with the roughness height (k) was 8, which fall in the category of large roughness. Velocity measurements were conducted using acoustic Doppler velocimeter (ADV), and a surface wave of different frequencies was generated using the plunger-type wavemaker. The measured velocity data were analyzed to determine the relative importance of mean flow over the train of rib roughness. Mean velocity profiles illustrate the well-known downward shift from the flat surface data of the semi-logarithmic portion of the law of the wall. The width of the turbulent boundary layer increases with the superposition of surface wave compared to that of the current-only flow. The results also show that the mean reattachment length decreases due to the superposition of surface wave on unidirectional current.