Rib Shape Research Articles

CFD Analysis on the Thermal Hydraulic Performance of an SAH Duct with Multi V-Shape Roughened Ribs

This study presents the heat transfer and fluid flow characteristics in a rib-roughened SAH (solar air heater) channel. The artificial roughness of the rectangular channel was in the form of a thin circular wire in discrete multi V-pattern rib geometries. The effect of this geometry on heat transfer, fluid flow, and performance augmentation was investigated using the CFD (computational fluid dynamics). The roughness parameters were a relative discrete distance of 0.69, a relative rib height of 0.043, a relative rib pitch of 10, a relative rib width of 6.0, and a flow-attack-angle of 60°. The discrete width ratios and Reynolds numbers ranged from 0.5 to 2.0 and from 2000 to 20,000, respectively. The CFD results using the renormalization k-epsilon model were in good agreement with the empirical relationship. This model was used to investigate the heat transfer and fluid flow characteristics in the multi V-pattern rib roughened SAH channel. The thermo-hydraulic performance was found to be the best for the discrete width ratio of 1.0. A discrete multi V-pattern rib combined with dimple staggered ribs also had better overall thermal performance compared to other rib shapes.

Heat transfer and fluid flow characteristics in air duct with various V-pattern rib roughness on the heated plate: A comparative study

This article presents three dimensional CFD (computational fluid dynamics) investigation of local Nusselt number and local friction factor ratios in an air channel with various V-pattern ribs as roughness elements employed on one wall. The various ribs such as, V-pattern rib, protrusion rib in V-pattern, dimpled rib in V-pattern, and V-pattern rib combined with groove have been considered in the study. The CFD analysis on heat transfer and fluid flow characteristics is conducted to investigate the overall effects of the various V-pattern rib shapes on the thermal hydraulic performance. The results found that V-pattern rib with a combination of groove roughness shapes provides better thermal hydraulic performance than other comparable V-pattern rib roughness shapes.

617 5軸制御マシニングセンタにより創成される小型高強度スパイラルべベルギヤの特性に関する考察(GS11,13 工作機械制御,研究討論セッション)

We have developed a small size and high strength spiral bevel gear fabricated by five axis controlled machining center. In the present report, we propose a novel spiral bevel gear with the rib at the end of tooth width to reinforce the tooth bending strength, which is machined with a ball-nose end-mill tool. We investigate the influence of the rib shape on the bending stress at the tooth root and the tooth deflection and demonstrate the effect of rib reinforcement at the proposed spiral bevel gear. As a result, a guideline is found to design the small size and high strength spiral bevel gear with the rib at the end of tooth width.

Numerical simulation of effective efficiency of a discrete multi V-pattern rib solar air channel

The use of artificial roughness in the form of repeated ribs has been found to be an efficient method of improving the heat transfer to fluid flowing in the channel. In this study, performance of solar air channel as a function of discrete multi V-pattern rib shapes has been investigated. The e/D was varied from 0.022 to 0.043, Gd/Lv was varied from 0.24 to 0.80, g/e was varied from 0.5 to 1.5, α was varied from 30° to 75°, P/e was varied from 6.0 to 12.0 and W/w was varied from 1.0 to 10.0. A methodology has been developed for the prediction of effective efficiency. Based on the values of effective efficiency, an optimization has been carried out to determine the set of data of roughness shapes parameters that correspond to better effective efficiency for given values of operating parameters of the air channel. Design plots have been represent to depict the data of individual roughness shapes parameters that characterize the optimum condition as a function of performance parameter and intensity of radiation. It was observed that the maximum values of effective efficiency for e/D of 0.043, Gd/Lv of 0.69, g/e of 1.0, α of 60°, P/e of 8.0 and W/w of 6.0. Discrete multi v-rib shape has been found to be better thermohydraulic performance (effective efficiency) as comparison to other rib shapes solar air channels.

Glued Joint Behavior of Ribs for Wood-Based Composite Plates

This article presents experimental investigations of composite sandwich plywood plates with cell type core and their connections between skin layers of birch plywood and a core of straight and curved plywood honeycomb-type ribs. This shape of core ribs provides several improvements for these plates in the manufacturing process as well as improves the mechanical properties of plywood plates. This specific form of ribs allows simplifying the manufacturing of these plates although it should be detailed and improved. The most typical cases (series of specimens) were compared to the results obtained from FEM (ANSYS) simulations. All thicknesses of elements are chosen according to plywood supplier assortment. Standard birch plywood (Riga Ply) plates were used - three layer plywood was chosen for skin elements (Surfaces) and three or five layer plywood was chosen for edge elements. Different bond pressures were taken to compare their influence on joint strength and stiffness.

Numerical study of laminar flow and heat transfer in microchannel heat sink with offset ribs on sidewalls

A numerical investigation has been carried out to examine the characteristics of laminar flow and heat transfer in microchannel heat sink with offset ribs on sidewalls. The three-dimensional equations considering entrance effect, conjugate heat transfer, viscous heating and temperature-dependent properties are solved for the fluid flow and heat transfer in the microchannel heat sink. Five different shapes of offset ribs are designed, including rectangular, backward triangular, isosceles triangular, forward triangular and semicircular. Results show that the offset ribs result in significant heat transfer enhancement and higher pressure drop. Depending on the different offset ribs and Reynolds number (190 ≤ Re ≤ 838) studied in the present work, Nusselt number and friction factor for the microchannel heat sink with offset ribs are 1.42–1.95 and 1.93–4.57 times higher than those for the smooth one, leading to performance evaluation criteria of 1.02–1.48. Further, as a consequence of significant pressure drop, the microchannel heat sink with offset ribs gradually loses its advantage as an effective heat transfer enhancement method at higher Reynolds number.

Effects of Rib Shapes on Heat Transfer Characteristics of Turbulent Flow of Al2O3-Water Nanofluid inside Ribbed Tubes

In this paper, convection heat transfer of Al2O3-water nanofluid turbulent flow through internally ribbed tubes with different rib shapes (rectangular, trapezoidal and semi- circular) is numerically investigated. For each rib shape, the optimum geometric ratio and volume fraction were calculated using entropy generation minimization technique. The governing equations in steady state and axisymmetric form have been solved using Finite Volume Method (FVM) with the SIMPLE algorithm. A uniform heat flux was applied on the wall. A single-phase approach has employed to model the nanofluid. Nanoparticles size is 20 nm and nanoparticles volume fraction and Reynolds number were within the ranges of 0-5% and 10,000-35,000 respectively. Comparisons between the numerical results and experimental data show that among different turbulence models, k-e model with enhanced wall treatment gives better results. The results indicate that the heat transfer increases with nanoparticles volume fraction and Reynolds number but it is accompanied by increasing pressure drop. The simulations demonstrate that trapezoidal and semi-circular ribbed tubes have higher Nusselt number than the rectangular ribbed tubes with the same diameters. Correlations of heat transfer have obtained for different ribbed tubes. In evaluation of thermal performance and pressure drop, it is seen that the ribbed tubes with Al2O3-water nanofluid flow are thermodynamically advantageous. For each rib shape, the optimum geometric ratios are also presented.

V 형 rib과 dimple로 구성된 SAH 덕트에서의 총괄 열성능에 대한 수치적 연구

This paper presents the thermal hydraulic performance of a three dimensional rib-roughened solar air heater (SAH) duct with the one principal wall subjected to uniform heat flux. The SAH duct has aspect ratio of 12.0 and the Reynolds number ranges from 2000 to 12000. The roughness has relative rib height of 0.045, ratio of dimple depth to print diameter of 0.5 and rib pitch ratio of 8.0. The flow attack angle is varied from 35° to 70°. Various turbulent flow models are used for the heat transfer and fluid flow analysis and their results are compared with the experimental results for smooth surfaces. The computational fluid dynamics (CFD) results based on the renormalization k-epsilon model are in better outcomes compared with the experimental data. This model is used to calculate heat transfer and fluid flow in SAH duct with the compound roughness of V-shaped ribs and dimples. The overall thermal performance based on equal pumping power is found to be the highest (2.18) for flow attack angle of 55°. The thermo-hydraulic performance for V-pattern shaped ribs combined with dimple ribs is higher than that for dimple rib shape and V-pattern rib shape air duct.

Numerical study of nanofluid forced convection flow in channels using different shaped transverse ribs

A numerical investigation is performed to study the effects of different rib shapes and turbulent nanofluid flow on the thermal and flow fields through transversely roughened rectangular channels with Reynolds number ranging from 5000 to 20000 and uniform heat flux of 10kW/m2. Considering single-phase approach, the two-dimensional continuity, Navier–Stokes, and energy equations were solved by using the finite volume method (FVM). The optimization was carried out by using various rib shapes (rectangular shape, triangular shape, wedge pointing upstream, and wedge pointing downstream) in two arrangements (in-line and staggered) and three different aspect ratios (w/e=0.5, 2, and 4) to reach the optimal geometry with maximum performance evaluation criterion (PEC). The main aim of this study is to analyze the effects of nanoparticle types (Al2O3, CuO, SiO2, and ZnO), concentration (1–4%), and nanoparticle diameter (30–80nm), on the heat transfer and fluid flow characteristics. Simulation results show that the ribbed channels' performance was greatly influenced by rib shapes and their geometrical parameters. The highest PEC was obtained for the in-line triangular ribs with w/e=4 at Re=5000. It is found that the water–SiO2 shows the highest heat transfer enhancement compared with other tested nanofluids. The Nusselt number through the ribbed channels was enhanced with the increase of the particle volume fraction and Reynolds number, and with the decrease of nanoparticle diameter.

A numerical study of particle deposition in ribbed duct flow with different rib shapes

The effects of surface rib shapes on particle deposition in turbulent duct air flows were numerically studied based on the Reynolds stresses model (RSM) with UDF code correction and the discrete particle model (DPM). The shapes of the rib cross sections were square, triangular and circular. The ratios of rib height to duct diameter e/D were 0.1. The present air velocity distributions for both smooth and ribbed ducts as well as particle deposition velocity in a smooth duct are all in good agreement with previous related study data. An efficiency ratio has been defined to evaluate the particle deposition enhancement ratio together with the increase of flow drag. It is found that the square ribs have the maximum enhancement efficiency on particle deposition, compared with the other rib shapes. The maximum efficiency ratio can reach about 400 for small particles (τp+<1) but only about 2 for large particles (τp+>1) when the rib shape is square. Moreover, the mechanisms of particle deposition enhancement for different rib shapes were investigated and analyzed.

Effect of roughness width ratios in discrete multi V-rib with staggered rib roughness on overall thermal performance of solar air channel

This work presents the outcomes of a computational fluid dynamics (CFD) analysis of thermal-fluid flow characteristics in solar air channel having discrete multi V-rib with staggered rib roughness. Four different turbulence models (RNG k–ε model, realizable k–ε model, standard k–ε model and SST k–ω model) were tested for smooth solar air channel. The RNG k–ε model was finally selected as the most suitable one. The effect of relative width ratios of discrete multi V-rib with staggered rib shape on the average Nusselt number, average friction factor and overall thermal performance have been studied. The average Nusselt number has the maximum value in the discrete multi V-rib with staggered rib shape for a relative width ratio of 6.0. The heat transfer enhancement parameter shows also the highest value for the relative width ratio of 6.0 and the lowest value for the relative with ratio of 1.0. The present study shows that the overall thermal performance of discrete multi V-rib with staggered rib shape is around 6% higher as compared to other rib shapes.

Structural-optimization-based design process for the body of a railway vehicle made from extruded aluminum panels

The railway vehicle manufacturing industry faces increasing pressure to enhance performance and safety while minimizing weight, manufacturing cost and fuel consumption. Structural optimization is a very effective way to design the structure of the body of a railway vehicle so that it meets design requirements. There is a trend to manufacture the body of a vehicle using extruded aluminum. The design of a vehicle body to be built from extruded aluminum panels is considered in this paper. Each aluminum panel is made of sandwich panels that are welded together. The weight and stiffness of the structure are determined by changing the shape and thickness of the webs and ribs. A design process based on structural optimization is proposed to design the shape of the rib and the thickness distribution of the aluminum-based body. The design process is divided into three steps. First, topology optimization is performed to obtain the conceptual design of the ribs under given loading conditions while maximizing the stiffness of the structure. The results of the topology optimization are incorporated into the decision about the shape of the ribs that is performed in the next step. Second, the optimization technique for the shape of the ribs is developed using a design-of-experiments approach. An orthogonal array is used to obtain the optimum combination of the rib shapes. The shapes of the ribs are defined into four types. The characteristic function to find the optimum combination is defined by the maximum stress and the maximum displacement. Finally, size optimization is performed to reduce the weight of the structure while still meeting the design requirements. The thickness values of the webs and ribs are used as design variables. Design constraints are defined so that the maximum stress of the entire structure and the maximum displacement of the side sill are less than the allowable values. A systematic design process of an aluminum body for a railway vehicle is established that reduces its weight while maintaining sufficient strength, and new rib shapes are obtained.

Designing and optimization of new composite pallet

The original code KEDRO for design of experiments, analysis and multiobjective robust optimization is used for designing of a new composite pallet. Firstly code is tested for non-deterministic optimization of the two bar truss problem. Then robust optimization problem of composite pallet is solved. The FE-model of the composite pallet is considered and solved accurately as multi-ply shell structure. The fiber-reinforced polymer material mechanical properties and two main operation cases of the loaded pallet are taken into account during deterministic structural optimization procedure. Next, the same problem is considered as non-deterministic taking into account possible uncertainties of the pallet supporting conditions. In both cases shape is defined using CAD based NURBS curves. Appropriate shapes of the stiffness ribs are found for best performance of the structure. As a result of optimization, the competitive design of composite pallet is developed.

Comparison of a load bearing capacity for composite sandwich plywood plates

&lt;p class="R-AbstractKeywords"&gt;&lt;span lang="EN-US"&gt;This article shows numerical investigations of composite sandwich plywood plates with birch plywood faces and a core of straight and curved plywood honeycomb-type ribs in comparison to standard plywood plates and other core type plates. &lt;/span&gt;&lt;/p&gt;&lt;p class="R-AbstractKeywords"&gt;&lt;span lang="EN-US"&gt;This shape of core ribs provides several improvements for these plates in manufacturing process as well as mechanical properties. &lt;/span&gt;&lt;/p&gt;&lt;p class="R-AbstractKeywords"&gt;&lt;span lang="EN-US"&gt;The influence of core element shapes on stiffness in longitudinal direction of a plate is insignificant although it is possible to vary with stiffness in transverse direction of these plates by changing form of plate’s ribs. The results are describable as specific strength or stiffness (stiffness to mass or strength to mass ratio etc.) in both directions. &lt;/span&gt;&lt;/p&gt;&lt;p class="R-AbstractKeywords"&gt;&lt;span lang="EN-US"&gt;The various results depending on chosen variables (according to strength-stiffness criteria) plywood composite macrostructure is obtained for one span plate with uniformly distributed loading. The results show that it is possible to reduce material consumption causing reduction in stiffness but in general increasing stiffness to weight ratio for about 30% or even more if it is possible to increase height of a plate more than maximum standard plywood plate.&lt;/span&gt;&lt;/p&gt;&lt;p class="R-AbstractKeywords"&gt;&lt;span lang="EN-US"&gt;All thicknesses of elements are chosen according to plywood supplier assortment.&lt;/span&gt;&lt;/p&gt;&lt;p class="R-AbstractKeywords"&gt;&lt;span lang="EN-US"&gt;A various thicknesses of plywood sheets (0/90/0+90/0·n) are taken for straight ribs as well as various plates coverings for waved part of ribs the 3 layer plywood was taken (90/0/90) or (0/90/0) due to simplification of manufacturing process. &lt;/span&gt;&lt;/p&gt;&lt;p class="R-AbstractKeywords"&gt;&lt;span lang="EN-US"&gt;For all parts of plate were Birch plywood plates used, as well as reference plywood were Standard Birch plywood plates chosen.&lt;/span&gt;&lt;/p&gt;

Patterns of Rib Growth in the Human Child

IntroductionWhereas there is substantial information on the changes of the rib cage during childhood and asymmetry of the thorax in children with scoliosis, there are virtually no normative data on the growth of individual ribs throughout childhood. MethodsThe Hamann–Todd (HT) Osteological Collection provided the bones of 32 human specimens aged 1–18 years. A total of 6,226 individual photographs of all vertebral bodies and ribs were obtained from these specimens. Quantitative measurements were taken with image analysis software and the results of 2 of the measurements, the outer costal length (OCL) and the base diameter (BD), are presented here. ResultsWith the exception of the ribs at T12, both the OCL and BD showed linear, statistically significant growth with age for all ribs. The relationship of OCL and BD to each other within each rib was obtained by multiplying and dividing these 2 measurements. The BD × OCL product indicates that the ribs grow through coupled symmetry, by which ribs in the upper and lower thorax start at the same size and grow at the same rate within the pair; ribs 1 and 12, 2 and 11, and 3 and 10. Each rib pair grows at a significantly different rate from all other pairs. Measurements of BD and OCL from a specimen with scoliosis from the collection compared with these normative values were greatly different. The principle that ribs resemble a known geometric form, called the logarithmic spiral, is introduced. ConclusionsThis article is 1 of the first studies of the change in length and shape of normal ribs in an osteology collection of a wide age range of pediatric specimens. The data provide a framework for determining the difference between ribs from normal children and those with scoliosis.

Heat transfer enhancement of turbulent nanofluid flow over various types of internally corrugated channels

A numerical study is carried out to investigate the effects of different geometrical parameters and various nanofluids on the thermal performance of rib–grooved channels under uniform heat flux. The continuity, momentum and energy equations are solved by using the finite volume method (FVM). Three different rib–groove shapes are studied (rectangular, semi-circular and trapezoidal). Four different types of nanoparticles, Al2O3, CuO, SiO2 and ZnO with different volume fractions in the range of 1% to 4% and different nanoparticle diameters in the range of 20nm to 60nm, are dispersed in the base fluids such as water, glycerin and ethylene glycol. The Reynolds number varies from 5000 to 25,000. To optimize the shape of rib–groove channels different rib–groove heights from 0.1Dh (4mm) to 0.2Dh (8mm) and rib–groove pitch from 5e (20mm) to 7e (56mm) are examined. Simulation results reveal that the semi-circular rib–groove with height of 0.2Dh (8mm) and pitch equals to 6e (48mm) has the highest Nusselt number. The nanofluid containing SiO2 has the highest Nusselt number compared with other types. The Nusselt number rises as volume fraction increases, and it declines as the nanoparticle diameter increases. The glycerin–SiO2 nanofluid has the best heat transfer compared to other base fluids. It is also observed that in the case of using nanofluid by changing parameters such as nanoparticle diameter, volume fraction and base fluids the skin friction factor has no significant changes.

Heat transfer and friction characteristics of the microfluidic heat sink with variously-shaped ribs for chip cooling.

This paper experimentally and numerically investigated the heat transfer and friction characteristics of microfluidic heat sinks with variously-shaped micro-ribs, i.e., rectangular, triangular and semicircular ribs. The micro-ribs were fabricated on the sidewalls of microfluidic channels by a surface-micromachining micro-electro-mechanical system (MEMS) process and used as turbulators to improve the heat transfer rate of the microfluidic heat sink. The results indicate that the utilizing of micro-ribs provides a better heat transfer rate, but also increases the pressure drop penalty for microchannels. Furthermore, the heat transfer and friction characteristics of the microchannels are strongly affected by the rib shape. In comparison, the triangular ribbed microchannel possesses the highest Nusselt number and friction factor among the three rib types.

EXPERIMENTAL STUDY OF PRESSURE DROP AND HEAT TRANSFER IN A U-BEND CHANNEL WITH VARIOUS GUIDE VANES AND RIBS

An experimental study was conducted to investigate pressure drop and heat transfer in a U-bend section with various configurations of guide vanes and two kinds of rib shapes on the outer wall. Ten guide vane types were tested. Results highlight that the use of special guide vanes can reduce the pressure drop penalty up to a maximum of 31%. However, guide vanes are usually associated with heat transfer reduction. To further enhance heat transfer, transverse and V-shaped ribs were attached on the outer wall. Thermal performance evaluation showed that the 45 degrees V-shaped downstream-pointing ribs coupled with guide vane configuration 5 give the best thermal performance. The results of this study can be employed to improve the internal design of modern gas turbine blade cooling systems. (Less)

Initial Shape Design and Stability Analysis of Rib for Inflatable Deployable Reflector

This paper proposes a kind of support structure for inflatable deployable reflector. The surface accuracy, which is crucially important to the performance of the reflector, is maintained by support ribs stretched by the tension system. To obtain sufficient surface accuracy, a reverse design algorithm is proposed to design the initial lower-edge shape of the support rib, which is verified by the current experiment. Also, the morphing characteristics of the support rib under different tensions are tested using the Vic-3D whole strain testing system. From the results of the experiments and simulations, some effective control strategies are presented to resist the local buckles of rib. The main approach is to introduce some transverse constraints that are perpendicular to the rib at the local buckling positions. Finally, by comparison between different strategies, an effective control strategy is confirmed to improve the structure accuracy and stability. The results are of greatbenefitto the design and shape control of inflatable antenna reflectors.

Experimental Study and Microstructure Analysis of Aviation Component by Isothermal Forging Process

The isothermal forging process of a typical aviation component with complex shape of high ribs and thin webs was simulated based on the finite-element method, aiming to obtain a set of optimal process parameters. According to the simulation results, the aviation component was successfully formed with a good surface quality by the isothermal forging process. Metallographic analysis shows that recrystallization took place all over the cross section of the forging. The grain size of different areas is basically the same. As indicated by the transmission electron microscope micrographs, dislocations at the surface of the forging have almost the same distribution as those at the core, whereas the dislocations at the surface of the billet by hot forging process are much denser than those at the core. Moreover, the precipitates in the forging by the isothermal forging process were basically of the same small size. On the contrary, larger precipitates were formed at the grain boundaries than in the matrix of the billet through the hot forging process. In one word, uniform grain size and homogeneous distribution of dislocations and precipitates were found in the aviation component by the isothermal precise forging process.