Rib Shape Research Articles

Combined Effects of Nanofluid and Geometrical Structures of a Parallel Plate Channel With Semicircle Corrugations on Flow Characteristics and Thermal-Hydraulic Performance

Abstract The combination of corrugated surface and nanofluid techniques can boost thermo-hydraulic performance with the ability to make thermal systems more effective and reliable. In this numerical study, the combined effect of different structures of a semicircle-corrugated channel is investigated and examined, as well as different types of nanofluids on thermal and hydraulic performance in the Reynolds number range from 10,000 to 30,000. With respect to the fluid medium, four kinds of nanoparticles Al2O3, CuO, SiO2, and ZnO are used and investigated. The volume fraction of nanoparticles and the diameter of the particles are in the range of 0–0.08 and 20–80 nm, respectively. The findings show that the geometrical structures of the tested channel have a great effect to improve heat transfer enhancement, approvingly around 2.3–3.7 times that of the smooth channel. Furthermore, the outcomes show a dramatic increase in the heat transfer coefficient as the volume fractions of nanoparticles and Reynolds number are increased, and with the decline of particle size, but it accompanied with the increase of shear stress. Among the nanofluids used here, SiO2–water offers the highest enhancement of heat transfer. For all forms tested here, the rib shape of a semicircle-corrugated channel displays the best thermal-hydraulic performance of 2.84 at a volume fraction of 0.08 and Re = 10,000.

Experimental and Numerical Studies of Two-Phase Flow in Ribbed Periodic Vertical Channel

Pressure drop in a ribbed vertical channel was studied for a two-phase (air and water) flow, different shapes of ribs (triangle, semi-circular, and rectangle) were used in this investigation. An experimental rig was constructed with a test channel having the dimensions (10×3×70 cm) that enabled the flow patterns visual observation. An experimental setup of a two-phase was done for the present investigation, as well as a sum of (150) two-phase data with various flow patterns was determined. The used water superficial inlet velocities were in the range (0.0333 - 0.0888 m/s), and the air superficial inlet velocities were in the range (0.0555 - 0.1666 m/s). The experimental pressure drop according to a smooth plate was (41%, 38%, and 35%) for a channel fitted with semi-circle, rectangular and triangular ribs, respectively. The less pressure drop recorded was in the triangular ribbed channel, which indicates that the triangular shaped ribbed channel is the finest shape among the studied ones to lower the pressure drop. As future work, the numbers and dimensions of ribs can be changed to investigate its effect on the two-phase flow and the pressure drop, another suggestion for the future investigations is to include other fluid to have a three-phase flow, also the inclination angle of the duct can be changed to study its effect.

Proposal of bond behavior simulation model by using discretized voronoi mesh for concrete and beam element for reinforcement

This study proposed an analytical method based on the Three Dimensional Rigid Body Spring Model (3D-RBSM) to realistically simulate bond behavior of deformed rebar in concrete. In this method, concrete was modeled by rigid particles using a voronoi mesh with random geometry and rebar was modeled by beam element connected to concrete through a link element that was assigned a suitable local bond model. The proposed model enables to evaluate changes in internal cracking and stress distribution due to variation in cover thickness and rebar diameter. Furthermore, it can simulate the bond stress slip behavior and transition of failure modes. Based on analytical results, it was confirmed that the proposed simplified model can evaluate bond behavior like three dimensional rebar model with rib shape, consequently, it provides an economical and efficient alternative due to lesser computational elements.

Investigation of rib’s effect in cavitation on an axisymmetric separated flow over a longitudinal blunt circular cylinder

The current investigation, determines the effects of rib shape and its parameters on an inner flow in which a circular cylinder exist in the middle. The problem is solved in 2 dimensional methods and the distance from the channel’s entrance to cylinder is 125 mm. Ansys 14.5 is used for modeling the geometry and meshing of the problem and for modeling the turbulence the k − e (realizable) is employed. In this study rib and its four parameters of pitch (p), length (h), rib’s height (e) and the distance from the cylinders’ head to start of rib (a) in a cavitation flow is investigated. The results show that none of rib’s parameters has a direct relation with void fraction. The values for these parameters are different for the maximum or the minimum cavitation; namely if a rib’s pitch increases and surpasses a specific value, it will reduce the effect of the previous rib in the flow. In fact, the turbulence eradicates before it become more turbulent by the next rib. On the other hand, if the rib’s pitch is too small the flow traps between the two ribs and stagnation happens which is the key element in plummeting the pressure and forming cavity. For other parameters either no correlation with void fraction is observed.

Efficient design of curved solar air heater integrated with semi-down turbulators

Recent investigations reveal that curved solar air heaters (SAH) thermo-hydrodynamically performs better in comparison to flat SAH design. Further, it has been observed that down-configurations of turbulators or extended surfaces on the flat plate solar collector significantly enhance the thermal performance. However, scientific literature on thermal performance investigations with down-configurations of ribs in curved SAH are rare. In the paper, we systematically investigate using experimentally validated computational fluid dynamics model for different shapes of down-configuration of ribs. It was observed that half-trapezoidal and quarter-circular shape ribs shows maximum increase in thermal performance i.e. 17% and 16%, respectively, however frictional loss for quarter-circular ribs was observed to be less by about 10% when compared to trapezoidal shape ribs. The exergy recovery is maximum for trapezoidal and circular shape ribs and it is about 35% more than the smooth flat SAH. A new correlation has been developed for Nusselt number variation which has the form as Nu=f[Re,erH] where er is the height of quarter-circle groove. Observed data from the model matches well with the prediction from the developed correlation.

In Situ Experimental Study on the Behavior of UHPC Composite Orthotropic Steel Bridge Deck.

A novel ultra high performance concrete (UHPC) layer composite orthotropic steel deck was adopted in the construction of a new bridge in China to improve the fatigue performance of the orthotropic steel deck plate and reduce the disease of surface wearing layer. In situ experiments were conducted to study the UHPC layer’s impact on the behavior of the orthotropic steel deck. The test vehicle loads were applied on the deck plate before and after UHPC layer paving, the stresses where fatigue cracks usually occur and the deflections of critical sections were measured. The test results verified that the UHPC composite steel deck system could significantly reduce the stress of the rib-to-deck connection region and the stress at the bottom toe of rib-to-diaphragm weld. In addition, it slightly influenced the performance of U shape rib, girder web-to-deck and diaphragm cutout.

Experimental Analysis of different shaped ribs on heat transfer and fluid flow characteristics

There are number of applications such as gas turbines, solar air heating, electronics cooling and heat exchangers, where internal cooling passage is observed. For heat transfer augmentation inside these cooling passages different techniques are used like dimpled surface, wings and ribs. Ribs are used in most of the devices for internal cooling. The ribs disturb the boundary layer and increase the turbulent kinetic energy which enhances the heat transfer rate. Most of the researchers concentrate on square and rectangular shaped ribs. The cross section of the rib plays important role in the production of flow field. The shape of ribs affects on boundary layer separation, attachment and hot spots created. In the present paper heat transfer and fluid flow characteristics from rib roughened rectangular duct with different shapes of ribs were investigated. The experimental set up consists of rectangular channel of aspect ratio 4. The pitch to width ratio was varied as 5, 7.5 and 10 respectively. The Reynolds number was varied as 6000 to 30000. The ribs used for the investigations were square, house and boot shaped. From the investigations it is observed that boot shaped rib is having higher thermal performance than other two geometries

Numerical evaluation of topologically optimized ribs for mechanical components

Topology optimization method helps to minimize the mass or volume of the mechanical elements. In the present work, a methodology is proposed to use the topology optimization method for development of ribs like structure that add strength in the two-dimensional mechanical components. Ribs improve the stiffness significantly for the mechanical or structural components. However, the mass and the volume are also increased by adding ribs. Here a methodology is proposed to optimize the shape and size of ribs with their connections to the main component, which minimizes the overall mass. For illustration, a 2D rotary link of predefined shape and dimension are chosen, on which the ribs are added. The region of ribs is defined by initial design space of specific area such as rectangular, trapezoidal and elliptical. The density-based modified solid isotropic material with penalization approach (SIMP) is used for modeling material properties in continuous setting through interpolation and solved by optimality criteria algorithm. Minimization of compliance is chosen as the objective function, with volume fraction as a constraint ranging from 0.7 to 0.1. A MATLAB code is developed based on boundary conditions to obtain topologies at different geometrical shapes for different volume fraction. A comparison of the different shaped material domain is performed based on maximum deflection and Von-Mises stress values. The rectangular domain is found to be the best for minimum compliance and deflection, however, the trapezoidal domain is found to be the best for minimum stress levels.

Geometric Optimization of a Gas Turbine Blade Cooling Passage using CFD

This work focuses on the rib-turbulated cooling which is a category of impingement cooling and aims at optimizing the geometry of rib-roughened cooling passage of a gas turbine blade. CFD analysis is carried out using Ansys/Fluent to solve the steady RANS equations. Computational domain consists of a long rectangular channel with the length of the channel being 9 times its height. Ratios of rib width, rib height and rib pitch to hydraulic diameter of the channel are taken as 0.1, 0.1 and 1.2, respectively. Numerical simulations are performed to analyze the performance of various rib shapes for Reynolds number, based upon the hydraulic diameter, in a range of 5000 to 50,000. Uniform heat flux of 800 W/m2 is applied to the ribbed wall. Incompressible air is used as the cooling fluid. Turbulent flow conditions are applied to the channel geometry with k-ω turbulence model. The effect of rib cross-section and rib pitch to rib width ratio on the heat transfer and friction factor is observed. The 2D CFD analysis revealed that the presence of ribs has significant effect on thermo-hydraulic performance of the cooling channel. Introducing square ribs in a smooth channel caused the Nusselt number to increase by two-folds. The highest value of Nusselt number was achieved by incorporating right-angle triangular ribs which caused the Nusselt number to increase by further 8%, as compared to the square ribs, and an increase in friction factor of 2.5%. The lowest value of friction factor was observed in semicircular ribs (2.95% less than the square ribs), however, the Nusselt number also decreased by 1.5%, as compared to square ribs. Decreasing rib pitch to rib width ratio increased both the Nusselt number and friction factor for all the cases. For square ribs, decreasing this ratio from 15 to 9 resulted in the rise of Nusselt number by 50% and increase in friction factor by 54%.

Entropy generation analysis due to heat transfer and nanofluid flow through microchannels: a review

This work presents a detailed review of the entropy generation due to the heat transfer and the fluid flow through different channels. The earlier contribution of the researchers in the form of theoretical, numerical and experimental studies on the entropy generation in the conventional or microchannels, with or without disruption in the flow and with or without the use of nanofluids is reviewed. The brief discussion on the microchannels, disrupted microchannels, nanofluids and entropy generation is presented. Studies performed on the channel cross-sectional shapes and rib shapes for thermal performance optimisation are discussed in the paper. Nanoparticles such as Al2O3, Cu, CuO, Ag, SiO2, etc. have been used for preparing the nanofluids along with water, ethylene glycol, etc. as base fluids. Additionally, the effect of disruption in flow field on the entropy generation is also discussed. The disruptions in the form of ribs, cavities, vortex generators, etc. have been taken into account. It is hoped that this review article can provide a basis for further research on the irreversibility analysis of the nanofluid flowing through disrupted microchannels to improve the hydrodynamic and thermal performance of the system.

Entropy generation analysis due to heat transfer and nanofluid flow through microchannels: a review

This work presents a detailed review of the entropy generation due to the heat transfer and the fluid flow through different channels. The earlier contribution of the researchers in the form of theoretical, numerical and experimental studies on the entropy generation in the conventional or microchannels, with or without disruption in the flow and with or without the use of nanofluids is reviewed. The brief discussion on the microchannels, disrupted microchannels, nanofluids and entropy generation is presented. Studies performed on the channel cross-sectional shapes and rib shapes for thermal performance optimisation are discussed in the paper. Nanoparticles such as Al2O3, Cu, CuO, Ag, SiO2, etc. have been used for preparing the nanofluids along with water, ethylene glycol, etc. as base fluids. Additionally, the effect of disruption in flow field on the entropy generation is also discussed. The disruptions in the form of ribs, cavities, vortex generators, etc. have been taken into account. It is hoped that this review article can provide a basis for further research on the irreversibility analysis of the nanofluid flowing through disrupted microchannels to improve the hydrodynamic and thermal performance of the system.

Spinning Process Test and Optical Topography Measurement Technology for the Shell with Longitudinal and Latitudinal Inner Ribs

The paper studies the complicated problem in the spinning process of the shell with longitudinal and latitudinal inner ribs. The finite element software ABAQUS is used to establish the finite element model of the cylindrical shell with the longitudinal and latitudinal inner ribs. The numerical simulation of the spinning process is carried out. The stress distribution and strain distribution of the inner and outer surfaces during the spin-forming process are determined, and the orthogonal test method is used to determine the optimization process test parameters. The influence of the main process parameters on the wall thickness difference of the inner rib shell is obtained by the range analysis: wall thickness reduction rate > rotary wheel feed speed > rotor working angle (arranging according to their influences). And then the corresponding process parameters recommended by the spinning test are given. The measurement problem of inner ribs is solved by building of the robot shape measurement system which helps detect the three-dimensional shape of the inner ribs, and the precision of the spun sample was detected by the point cloud deviation comparison.

Crashworthiness analysis of thin-walled bio-inspired multi-cell corrugated tubes under quasi-static axial loading

This paper proposes a bio-inspired multi-cell corrugated tube for use in energy absorption. The proposed structure consists of two parts: an inner rib and a corrugated tube into which the inner rib is inserted. The structure of the corrugated tube is specified using a cosine expression based on two parameters, that is, the number of cosine wave crests and their amplitude. Two inner ribs with different sections (X-shaped and Y-shaped) were designed and the crashworthiness of the resulting tubes was analyzed. The crashworthiness was determined using the finite-element program LS-DYNA. The numerical results show that the modes of collapse of the multi-cell corrugated tubes can be classified into four types: unstable, diamond, ring, and mixed modes. Each mode is strongly affected by the number of cosine wave crests and their amplitude. By analyzing the force–displacement performance and crashworthiness indicators, it was found that tubes with appropriate number of wave crests and amplitudes, and inner rib shape experience lower initial peak forces and increase energy absorption and specific energy absorption (compared with a traditional straight tube with the same inner rib). The undulation in the load-carrying capacity is also decreased. Thus, the multi-cell corrugated tubes have good crashworthiness.

Rib Design for Improving the Local Stiffness of Gearbox Housing for Agricultural Electric Vehicles

In this work, a rib design process is proposed to improve the local stiffness of gearbox housing for agricultural electric vehicles. Unlike conventional engines, electric powertrain noise includes high frequency factors and pure tones. Considering these characteristics, local stiffness was evaluated in the frequency range of interest for the prediction of dynamic behavior. The local stiffness of the gearbox housing was evaluated using the finite element (FE) model. Experimental modal analysis and FE model update were conducted to ensure the reliability of the results. Using the results of local stiffness evaluations, the stiffness weak point was identified, and the rib design location was selected through a strain analysis. The shape of the ribs was parameterized by width, length, and height, and parameter studies were used to compare the local stiffness increase rate according to the rib design pattern. According to the results, the stiffness increase rate against the same mass was distributed differently according to the rib shape, and the most efficient rib shape was selected from a manufacturing perspective.

Association between ribs shape and pulmonary function in patients with Osteogenesis Imperfecta

The aim of the present study was to test the hypothesis that ribs shape changes in patients with OI are more relevant for respiratory function than thoracic spine shape. We used 3D geometric morphometrics to quantify rib cage morphology in OI patients and controls, and to investigate its relationship with forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1), expressed as absolute value and as percentage of predicted value (% pred). Regression analyses on the full sample showed a significant relation between rib shape and FEV1, FVC and FVC % pred whereas thoracic spine shape was not related to any parameter. Subsequent regression analyses on OI patients confirmed significant relations between dynamic lung volumes and rib shape changes. Lower FVC and FEV1 values are identified in OI patients that present more horizontally aligned ribs, a greater antero-posterior depth due to extreme transverse curve at rib angles and a strong spine invagination, greater asymmetry, and a vertically short, thoraco-lumbar spine, which is relatively straight in at levels 1–8 and shows a marked kyphosis in the thoraco-lumbar transition. Our research seems to support that ribs shape is more relevant for ventilator mechanics in OI patients than the spine shape.

Thermohydraulic performance enhancement of a new hybrid duct solar air heater with inclined rib roughness

In this work, a new hybrid duct configuration of solar air heater is analytically investigated to improve the thermal performance of the system. The proposed design consists of parallel pass air flow paths with rectangular and triangular cross sections at upper and lower sides of the absorber plate. Both the sides of the absorber plates are roughened with inclined shape ribs. The roughness parameters are configured with relative roughness pitch at the bottom of the plate (Pb/eb) of 4–16, relative roughness height of e/Dh ranges from 0.021 to 0.050 and relative angle of arc of (α/60) 0.5–1. Based on the analytical results it is concluded that the maximum effective efficiency is 80.1% for roughness pitch of 8, relative roughness height of 0.021 and relative angle of arc of (α/60) 0.5, at the mass flow rate of 0.045 kg/s at the upper and lower duct. The effect of the mass flow fraction (i) on the thermal performance of the solar air heater is also analyzed. The system improves the thermal and effective efficiency by 22.4% and 18.1% when compared to conventional rectangular duct parallel pass SAH. The design plots are developed to find the optimum values of roughness parameters with respect to ambient conditions.

Experimental study on flow and heat transfer characteristics at onset of nucleate boiling in micro pin fin heat sinks

The micro pin fin heat sink has great application potential in the heat dissipation of high-power LED chips, phased array radars and semiconductor lasers. The onset of nucleate boiling (ONB) is a critical limit in designing heat dissipation systems. A simultaneous visualization and measurement study is conducted to investigate the ONB phenomenon of deionized water in circular, diamond, and oval micro pin fin heat sinks. Experiments are conducted under inlet subcooling of 29.6–49.5 °C, mass flux of 147.4–355.4 kg m−2 s−1 and heat flux of 4.8–55.8 W cm−2. Visualization result indicates that the ONB is always initiated at the surrounding region of a micro pin fin. The effects of additional nucleation sites caused by a micro pin fin and the temperature distribution of the surrounding region captured by an infrared camera can be used to explain the occurrence of the first bubbles. In this study, the effects of inlet subcooling, mass flux, and the cross-section shape of the micro rib on the ONB characteristics are investigated. Results show that the heat flux and wall superheat needed for the ONB increase as the mass flux and inlet subcooling increase. Moreover, the heat flux required for the ONB in the diamond and oval micro pin fin heat sinks is higher than that in the circular one. On the basis of the experimental data, the correlation of heat flux at the ONB in the micro pin fin heat sink is established, with 85.7% of the data falling within an error band of ±15%.

Enhanced heat transfer in a labyrinth channels with ribs of different shape

Purpose The purpose of this study is to enhance the thermal performance in the labyrinth channel by different ribs shape. The labyrinth channel is a relatively new cooling structure to decrease the temperature near the trailing region of gas turbine. Design/methodology/approach Based on the geometric similarity, a simplified geometric model is used. The k − ω turbulence model is used to close the Navier–Stokes equations. Five rib shapes (one rectangular rib, two arched ribs and two trapezoid ribs) and five Reynolds numbers (10,000 to 50,000) are considered. The Nusselt number, flow structure and friction factor are analyzed. Findings Nusselt number is tightly related to the rib shape in the labyrinth channel. The different shapes of the ribs result in different horseshoe vortex and wake region. In general, the arched rib brings the highest Nusselt number and friction factor. The Nusselt number is increased by 15.8 per cent compared to that of trapezoidal ribs. High Nusselt number is accompanied by the high friction factor in a labyrinth channels. The friction factor is increased by 64.6 per cent compared to rectangular ribs. However, the rib shape has a minor effect on the overall thermal performance. Practical implications This study is useful to protect the trailing region of advanced gas turbine. Originality/value This paper presents the flow structure and heat transfer characteristics in a labyrinth channel with different rib shapes.

RBF-based mesh morphing improvement using Schur complement applied to rib shape optimization

PurposeThis paper aims to improve the radial basis fuction mesh morphing method. During a shape optimization based on computational fluid dynamic (CFD) solvers, the mesh has to be changed. Two possible strategies are re-meshing or morphing. The morphing one is advantageous because it preserves the mesh connectivity, but it must be constrained.Design/methodology/approachRBF mesh deformation is one of the most robust and accurate morphing method. Using a greedy algorithm, the computational cost of the method is reduced. To evaluate the morphing performances, a rib shape optimization is performed using the NSGA-II algorithm coupled to kriging metamodels based on CFD. The morphing method is then compared to a re-meshing strategy.FindingsThe authors propose a method, based on Schur complement, to speed-up the greedy process. By using the information of the previous iteration, smaller linear systems are solved and time is saved. The optimization results highlight the interest of using a morphing-based metamodel regarding the resolution time and the accuracy of the interpolated solutions.Originality/valueA new method based on Schur complement is addressed to speed-up the greedy algorithm and successfully applied to a shape optimization.

Analysis of the advantages of 3D printing in the surgical treatment of multiple rib fractures: 5 cases report

BackgroundRib fractures account for a fairly high proportion of chest injuries, ranging from 55 to 80%. The most common mechanisms of injury include: traffic accident, extrusion and falls from significant heights. Besides, the surgical treatment of multiple rib fractures has been accepted by more and more medical professionals. We reported 5 clinical cases of patients with multiple rib fractures undergoing open reduction and internal fixation using 3D printing technology.Case presentationRetrospective analysis of 5 clinical cases of multiple rib fractures from January 2017 to August 2018 in our hospital. A preoperative CT thin slice scan was used to reconstruct the 3D model according to the scanning results, and 3D printing technology was adopted to prepare the rib model. Preoperative reconstruction of the rib’s normal shape and lock plate for the shaped ribs was created according to reconstructed model. For multiple fractures especially patients with severely deformed rib shape, it is suggested to intraoperative shape directly to the metal bone plate fixed on the ribs on both ends of the fracture line, in order to establish a basic support frame. The other various fracture section can be fixed on the lock plate respectively. Postoperative chest radiographs of the 5 patients showed that the internal fixations were in good and natural shape. The thoracic contour was well formed and symmetrically with the contralateral side.ConclusionMaking the rib model and the pre-shaped titanium alloy rib locking plate using 3D printing technology, provided a more minimally invasive and precisely individualized treatment for some rib fracture operations.