Rib Height Research Articles

The effects of wall proximity on the turbulent flow field in a square duct structured with detached divergent ribs on one wall

The effect of the wall proximity of detached 60∘ divergent ribs applied on one wall in a square duct on the turbulent flow field was investigated. Laser Doppler anemometry (LDA) measurements were conducted for different clearance-to-rib-height ratios in the range of 0.1–1.0 at a Reynolds number (based on the rib height and mean bulk velocity) of 5000. Mean velocities, Reynolds stresses, triple velocity correlations as well as skewness and kurtosis were determined and yield deep insights into the turbulent flow field. The results showed that a geometry-induced secondary fluid motion occurred above and below the rib. The variations in the highly three-dimensional flow field close to the ribs and the geometry-induced secondary flow motion with the clearance-to-rib-height ratio determined the development of the wall-bounded flows and separating shear layers. Large recirculation regions on the bottom duct wall were prevented by the fluid exiting the gap below the detached ribs and separated shear layers pivoted upward in lateral direction. With decreasing wall proximity, lower mean vertical flow velocities above the ribs and the increasing upward fluid flow originating from the flow in the gap attenuated an intense interaction of the separated shear layers with the wall-bounded flow within the inter-rib spacing. Since turbulent structures originated in the shear layers, distributions of high-order statistic moments depend strongly on the shear layer development. Reynolds stresses and triple velocity correlations increased in the direction of the side walls near the rib due to the lateral flow motion, and their peak regions moved away from the wall with increasing clearance-to-rib-height ratios.

Experimental study on heat transfer and friction characteristics for hybrid roughened duct used in solar heat collector

ABSTRACT This study presents a novel hybrid roughness configuration for solar heat collectors (SHCs), combining wired roughness and protrusion rib roughness to address the global demand for sustainable energy solutions. By leveraging wired roughness to induce localized turbulence near the absorber plate and protrusion ribs to disrupt the laminar sublayer without adding significant material mass, the proposed design enhances thermal performance while minimizing environmental and economic costs. The experimental investigation evaluates the effects of relative roughness width (W/w), gap width (d/e), and relative rib height (e/D) on the Nusselt number (Nu), friction factor (f), and thermohydraulic performance parameter (THPP). Results highlight the optimal configuration of W/w = 5, d/e = 4, and e/D = 0.045, achieving a maximum THPP of 3.20 at a Reynolds number of 19,000. This configuration significantly improves heat transfer efficiency while maintaining hydraulic resistance within acceptable limits, offering a sustainable and cost-effective pathway to enhanced solar thermal energy systems. These findings provide a robust framework for advancing SHC technology, aligning with global sustainability goals by promoting renewable energy utilization and reducing dependence on fossil fuels.

Analytic model of outer rib height for thin-walled cylindrical rings in spin-extrusion forming processing

Analytic model of outer rib height for thin-walled cylindrical rings in spin-extrusion forming processing

Comparative study to analyze the overall performance of upstream and downstream wedge ribs microchannels using thermal lattice Boltzmann method

The thermal lattice Boltzmann method (TLBM) is used to analyze the overall performance for upstream and downstream wedge ribs microchannels (MC) under slip flow conditions. The thermal–hydraulic enhancement criterion is investigated to evaluate the performance of the channel and compare it for various roughness MC. In order to improve the channel performance, two alternative artificial roughness geometry, upstream and downstream wedge ribs, are taken both on the top and bottom walls of the microchannel with aspect ratio (AR) 7, where AR = L/H; L and H are channel length and height respectively in micrometer (μm). This study focused on simulating temperature profiles, velocity vectors in terms of stream lines, pressure gradients, and friction factor in terms of Poiseuille number as well as heat transfer rate in terms of Nusselt number (Nu). The overall performance of the channel is calculated based on flow friction and heat transfer rate for different Knudsen numbers (Kn) ranging from 0.01 to 0.10 with upstream and downstream wedge ribs height up to 20% of channel height. The results have been compared with previously published work and are found a very good agreement. The analysis revels that, the vortices are formed behind each upstream wedge rib, whereas they are created in front of each downstream wedge rib. The size and shape of vortices are influenced by Kn. As Kn increases from 0.0 to 0.10, the fluid circulation area becomes smaller for upstream wedge ribs MC, while it is changing very slowly for downstream wedge ribs MC; hence, the pressure gradient is also responsible for changing Kn. The flow friction is linearly decreased with increasing Kn but significantly increased with ribs height. But compared to the smooth channel, the friction is significantly increased for upstream and downstream wedge ribs MC. The average rate of heat transfer in terms of Nu is also linearly decreased with increasing Kn, but Nu increased with ε for lower Kn and decreased for higher Kn. Therefore, compared to smooth MC, Nu increased and decreased for the same for upstream and downstream wedge ribs MC. Finally, the performance enhancement (η) is calculated, and it is found that η decreased with increasing Kn for upstream and downstream wedge ribs MC. The higher performances are indicated for lower Kn as well as lower ribs height. For all cases, the better performance is noted for downstream wedge ribs MC compared to upstream MC.

Transition to turbulence in rough plane Couette flow

This DNS study considers transition to turbulence in plane Couette flow (pCf) with a rough stationary wall and a smooth moving wall. The roughness elements are square ribs of height $k=0.2h$ (where $h$ is the half-channel height). Two different pitch separations, $\lambda =2k$ and $10k$ , are considered, i.e. d-type and k-type roughness, respectively. The transition in both rough pCf cases takes place through a stage of alternate laminar–turbulent bands aligned in an oblique fashion. However, roughness causes a shift in the transitional Reynolds number ( $Re$ ) range. In the k-type roughness, stable bands are observed in the range $Re \in [300, 325]$ , which is a downwards shift from the transitional $Re$ range for the smooth pCf ( $Re \in [325,400]$ ). The d-type roughness, on the other hand, surprisingly shifts the transitional $Re$ range upwards to $Re \in [350,425]$ . This peculiar behaviour is associated with the ability of the ribs to shed and regenerate vorticity. Large-scale components extracted using a filtering process relate to the transition bands and flow parallel to the oblique laminar–turbulent boundaries. Counter-rotating vortices are present in the turbulent regions of the flow field, which exist in tandem with the high- and low-velocity streaks. Another interesting observation is the secondary Reynolds shear stresses, $-\overline {v^{\prime }u^{\prime }}$ and $-\overline {w^{\prime }v^{\prime }}$ , which are non-zero in the transitional regime, in contrast to the turbulent regime where they are negligible.

Machine learning prediction of interfacial bond strength of FRP bars with different surface characteristics to concrete

Fiber-reinforced polymer (FRP) bars have been implemented in civil infrastructures as internal reinforcement. The bond strength of FRP bars to concrete depends on the surface characteristics considerably. This study used machine learning (ML) techniques to explore the influence of bar surface types on the bond properties quantitatively. A database including 158 FRP bars-concrete pull-out testing results was compiled. The geometric factors, including rib spacing (wc), rib width (wf) and rib height (rh), were proposed to quantify the surface configurations of FRP bars. Twelve ML models were trained to predict the interfacial bond strength. The ML models demonstrated higher accuracy in predicting the bond strength compared to eight existing equations from the literature. Among these models, CatBoost exhibited the highest accuracy, with an RMSE 58.3 % lower than the most accurate existing equation. CatBoost was utilized in parametric research on the influencing factors, and demonstrated that wf had the highest weight contribution to interfacial bond strength. Additionally, this study effectively combines ML models with physical meaning-driven analysis methods, resulting in a practical and interpretable equation for calculating FRP bars-concrete interfacial bond strength.

A study on the effect of channel structures on flow and heat transfer performance of cold plate with double-layer serpentine microchannel

As the power consumption of electronic components continues to rise, liquid cooling technology has become the mainstream solution for cooling electronic devices. This study designs a double-layer serpentine microchannel cold plate with a ribbed structure and firstly investigates the effects of the flow path on thermal–hydraulic performance of the cold plate. Through orthogonal numerical tests, the impact of rib height, number of rib truncations, rib truncation gap, and rib end deviation distance on thermal–hydraulic performance of cold plate is analyzed, along with their significance. Based on the results of the orthogonal test, the optimal rib structure parameters are determined. Results show that the parallel flow path has a more uniform flow distribution and approximately 2.5 % lower thermal resistance of the cold plate than the series flow path. Higher rib height leads to a higher convective heat transfer coefficient, more uniform internal flow distribution, and lower thermal resistance. When the rib height increases from 0.3 mm to 3 mm, the convective heat transfer coefficient increases 18 %, and the thermal resistance of the cold plate decreases 12 %. Compared to the initial structure, the optimized structure at the highest PEC has total thermal resistance and pressure drop reduced by 5.5 % and 7.4 %, respectively, while the structure with the lowest thermal resistance has a 7.9 % reduction in thermal resistance but a 27 % increase in pressure drop.

Influences of submerged V-broken rib geometry on the hydrothermal performance of vortex and engulfment flow regimes within a T-channel

The current research presents a three-dimensional numerical study of detailed hydrothermal performance in a T-channel fitted with staggered V-broken ribs under laminar vortex and engulfment flow regimes (Re = 50 to 250) using CFD software tool FLUENT. Comprehensive parametrical investigations are executed to probe the influences arising from the geometrical parameters alterations of the V-broken ribs on the flow field and convective heat transfer characteristics in T-channel. A set of geometrical parameters involving, the orientation rib angles (θ = 30°, 45°, 60°), the pitch-to-outlet-channel width ratio (p/Wo = 1, 1.5, 2), the length-to-outlet-channel width ratio (l/Wo = 0.5, 0.75, 1), the height-to-outlet-channel height ratio (h/Ho = 0.2, 0.3, 0.4), and the staggered inclined rib arrangements (forward, backward, and mixed), are considered. With regard to all examined geometrical parameters, the presence of staggered V-broken ribs consistently enhances fluid mixing and convective heat transfer performance as compared with that without ribs. In addition, the findings illustrate that the V-broken ribs mounted on the bottom wall of the T-channel have approximately the same PEC at 45° and 60° orientation angles with a PEC of 2.23 at Re = 250. At Re = 250, the PEC improves by 40 % and 53 % in comparison to the standard T-channel for the 2 cm and the 4 cm of longitudinal pitch, respectively. Regarding, V-broken rib lengths of 1.5 cm and 1 cm, PEC shows similar trend and eventually reaches double, while the PEC for a 2 cm rib length is smaller than that of 1 and 1.5 cm. The results also exhibit that the smaller rib height of 2 mm gives higher PEC, approximately 2.15, in comparison to 3 mm and 4 mm. Finally, the backward V-broken rib arrangement provides the best PEC of the T-channel, around 2.42.

Analysis of Base Pressure Control with Ribs at Mach 1.2 using CFD Method

This paper discusses the control of base pressure by passive means, where the jet is issued from a converging nozzle at sonic Mach number under a favorable pressure gradient. The effect of employing annular ribs on the enlarged duct and its impact on the flow field, as the passive control mechanism from a converging nozzle at the sonic Mach number, is investigated numerically in this study. The velocity distribution and base pressure changes are analyzed using a numerical compressible turbulence flow model. Initially, the rib is positioned at 16 mm (1D) from the base of the duct. Later, the rib position is shifted from 1D to 2D and then to 3D and 4D. The effect of variation of the rib positions, as well as its height from 1 mm to 3 mm, keeping the width of the rib fixed to 3 mm, is studied. The nozzle pressure ratio varies from 1.5 to 5, and the rib location is 1D and 2D. The velocity variation in the duct with and without rib placement is also analyzed. The results revealed comprehensive spread observations from the positive analysis of base pressure variation in ducts with no ribs and ribs with heights of 1 mm and 2 mm. The base pressure increased significantly with increasing nozzle pressure ratio for both rib heights compared to a smooth duct. It is also deduced that the highest base pressure is achieved at an aspect ratio of 3:1 when placed at 4D.

Premixed Combustion Characteristics of Hydrogen/Air in a Micro-Cylindrical Combustor with Double Ribs

Hydrogen is a promising zero-carbon fuel, and its application in the micro-combustor can promote carbon reduction. The structural design of micro-combustors is crucial for combustion characteristics and thermal performance improvement. This study investigates the premixed combustion characteristics of hydrogen/air in a micro-cylindrical combustor with double ribs, using an orthogonal design method to assess the impact of various geometric parameters on thermal performance. The results indicate that the impact of rib height, rib position, and inclined angle is greater than rib width and their interactions, while their influence decreases in that order. Increased rib height improves mean wall temperature and exergy efficiency due to an expanded recirculation region and increased flame–wall contact, but negatively affects temperature uniformity and combustion efficiency. Although double ribs enhance performance, placing them too close may reduce heat transfer due to the low-temperature region between the ribs. When the double ribs are positioned at the axial third equinoxes of the micro-combustor, the highest mean wall temperature is achieved. Meanwhile, with a rib height of 0.3 and an inclined angle of 45°, the micro-combustor achieves optimal thermal performance, with the mean wall temperature increasing by 61.32 K.

Scaling Heat Transfer and Pressure Losses of Novel Additively Manufactured Rib Designs

Abstract Rib turbulators are a key cooling feature that enables increased heat transfer on the interior of gas turbine components. As metal additive manufacturing becomes available for developing turbine parts, it is becoming increasingly important to understand how the surface roughness intrinsic to this manufacturing method impacts the performance of rib turbulators. To explore what impact roughness has on rib turbulator performance, several relevant scale test coupons were manufactured on two different additive machines out of IN718. Additionally, several coupons were built at large scales to effectively reduce the relative roughness size impacts and determine scale effects. A range of different wavy broken rib designs, varying both rib wavelength and orientation within a channel were evaluated. Coupon geometry and surface roughness were characterized using both computed tomography scans and optical profilometry. Variations between the print methods were found to have limited impact on the surface roughness, but significant impact on the accuracy to meet the design intent with rib heights varying by 30%. Following characterization, coupons were flow tested and it was found that the ribs that more regularly disturbed the flow as a function of their geometry most significantly enhanced heat transfer and pressure drop. The performance index of the broken wavy ribs was similar to other advanced rib designs, such as broken or V shaped ribs, but augmentations to heat transfer and pressure drop were generally lower. The rib performance was compared as a function of relative roughness, and it was found that increases in relative roughness resulted in increased friction factor and heat transfer, especially at higher Reynolds numbers.

Energy, Exergy, environmental and economic based experimental investigation of solar air heater using a novel arc rib geometry

To enhance the thermal efficacy of solar air heaters, the most efficient method is to disturb the viscous layer by roughening the surface using the artificial rib. In this research, a discrete apex-down arc-shape rib geometry on a roughened plate is used to examine the energy-exergo and economic- environmental based performance of solar air heater. By changing the Reynolds number from 3000 to 14,000 and maintaining a gap width to rib height ratio of 4, a relative height rib ratio of 0.045, and a pitch to rib height ratio of 10, the effects of arc rib angles of 30, 45, and 60 degrees are studied. The environmental exergy loss was determined to be substantial, between 70 % and 80 %. Maximum system to air exergy loss occurs at Reynolds number of 3000 with 5.64 W. At a temperature parameter of 0.0377 m2K/W, both the thermal and exergetic efficiencies are at their highest, at 77.60 % and 3.81 %, respectively. In comparison to a plate having a plain surface, the suggested apex-down discrete arc rib performs better based on energy payback time, usable yearly energy, and enviro-economic criteria. Finally, at rib angle of 30°, the conditions that optimize the heat transfer and energy payback time, energy cost, exergo-economic, and enviro-economic characteristic of the current artificially roughened geometry of solar air heater.

Statistical Evaluation of the Geometric Properties Steel Bars for Reinforced Concrete in Botswana

Uncertainties in construction materials, especially steel reinforcing bars, have multiplying adverse impacts on the integrity and reliability of constructed facilities from construction to service life stages. Botswana depends on importation of rebars to meet the ever-increasing demands for buildings and reinforced concrete civil infrastructure. The study assessed the mass and geometric properties of the two most utilized steel reinforcing bars, designated as M1 and M2, in Botswana. With the aid of digital analytical balance and Vernier calipers, measurements of mass per unit length and the relative rib area (RRA), which depends on nominal diameter, rib height, rib spacing, and longitudinal rib or gap thickness were made from 3000 standard bars each of nominal sizes from 8 mm to 25 mm randomly sampled at the suppliers’ depots/warehouses and various construction sites in Gaborone and Francistown. The RRA is a measure of the surface geometry for interfacial bonding between steel reinforcing bar and the surrounding concrete. The geometric properties of each steel bar type of the nominal sizes were characterized in terms of the statistical parameters and compared for compliance with standard specifications such as CS2 (2012), ISO 15630, ACI A408. The actual mass and diameter of bars were within the tolerance of ± 1% of the respective nominal size which satisfied all the standard requirements. Only the 8 mm diameter M2 bars did not have longitudinal ribs/gaps. ACI specifies a range of 0.10 to 0.14 for RRA, while CS2/ISO 15630 only specifies for the minimum RRA values of 0.040 for 8 to 12 mm bars and 0.056 for 16 to 25 mm bars. M2 bars of 10 mm dia. bars did not satisfy CS2/ISO 15630 requirements. However, M1 (8 mm and 12 mm) and M2 (10, 16 and 25 mm) bar sizes are below the minimum and M2 bars of 20 mm diameter are above the recommended RRA values of ACI A408. These would reduce the load carrying capacity of RC members reinforced with the unsatisfactory bar sizes.

Numerical investigation of different transverse Rib shapes on thermal convection in a channel filled with nanofluid

With the growing interest in energy optimization, corrugated surfaces are arguably an excellent choice, finding applications in areas as diverse as heat exchangers, automobiles, building energy efficiency, and chemical reactors. However, due to the poor thermal properties of conventional fluids, heat transfer is limited. The introduction of nanoparticles into fluids is a promising solution to improve their thermal performance. This paper does a detailed numerical analysis of how different factors affect the forced convection heat transfer in a two-dimensional ribed channel. The shape of the ribs is one of the factors that are looked at, along with some new parameters like e/H, which is the ratio of rib height to channel height, and L2/P, which is the test section to the pitch between the ribs. The aim is to determine the optimum geometry that maximizes the Nusselt number while minimizing the pressure drop. The study also examines the effects of nanoparticle type and concentration on heat transfer and fluid flow characteristics. To this end, the continuity, momentum, and energy equations were solved with the finite volume method using the SIMPLE scheme with the k-ε turbulence model at different Reynolds numbers ranging from 4000 – 14,000. The results indicate that triangular ribs with ratios e/H = 0.15 and L2/P = 4 increase the Nusselt number by 63.3 % while reducing the pressure drop by 22 % compared with the other cases. The improvement in heat transfer in the water-SiO2 case was the greatest compared with the other nanofluids tested. Particle size fraction and Reynolds number increased the Nusselt number in ribbed channels by 20.7 % compared with water.

Research on improving heat transfer performance by using wavy ribs with different cross sections

Based on the change of the cross section in blade internal cooling channel rib caused by the service wear, starting from the widely used rectangular cross section, the most likely isosceles trapezoid and rectangular-semicircular cross section are considered, and the extreme design of the cross section (isosceles triangle) and the tentative exploration (spindle) are carried out. In this paper, the numerical calculation of SST k-ω turbulence model and the experimental research method of TSP measurement are used to thoroughly investigate the impact mechanisms of five different wavy rib cross-sections on the flow and heat transfer in turbine blade ribbed channels. The results show that different rib cross-sections alter the flow and heat transfer in channel by modifying flow allocation in height and width directions. The inclined sidewalls of the wavy ribs accumulate most of cooling air near the rib, which is the ultimate cause of the significant cooling effect. Under small rib radius and small rib angle, the heat transfer advantages of isosceles triangle and isosceles trapezoid cross-section wavy ribs are more obvious, which are increased by 14.88 % and 20.66 % respectively, but their friction factor is also 1.2 ∼ 2.0 times that of rectangular cross-section. The heat transfer of the large rib height on the isosceles triangular and isosceles trapezoidal cross-section wavy ribs is increased by 73.29 % and 185.31 %. Changes in Reynolds number have minimal impact on the friction factor, but significantly impact the overall heat transfer.

Preparation of Aluminum-Based Superhydrophobic Surfaces for Fog Collection by Bioinspired Sarracenia Microstructures.

Freshwater shortage is a growing problem. Inspired by the Sarracenia trichome fog-trapping and ultrafast water-transport structure, a series of hierarchical textured surfaces with high-low ribs with different wettabilities was prepared based on laser processing combined with dip modification. Through fog-collection performance tests, it was found that the samples with superhydrophobicity and low adhesion had the best fog-collection effect. In addition, it was observed that the fog-collection process of different microstructured samples was significantly different, and it was analysed that the fog-collection process was composed of two aspects: directional condensation and directional transport of droplets, which were affected by the low ribs number and rib height ratio. A design parameter was given to create the Sarracenia trichome-like structure to achieve a fast water transport mode. This study provides a good reference for the development and preparation of fog-collection surfaces.

Optimizing heat transfer in solar air heater ducts through staggered arrangement of discrete V‐ribs

AbstractThis research paper details an experimental study on airflow dynamics in a solar air heater. The heater's design incorporates unique, discrete V‐shaped ribs with staggered elements to enhance thermal performance. The study investigates the influence of various roughness parameters on flow characteristics. These parameters include a relative coarseness pitch (P/e) ratio of 12, a rib inclination angle (α) of 60°, a relative coarseness height (e/Dh) of 0.043, and a staggered element arrangement with a positioning ratio (p′/P) of 0.65. Additionally, the investigation includes scenarios with three gaps (Ng) between elements and a gap‐to‐rib width (g/e) ratio of 4. The research focuses on how changes to the Reynolds number, ranging from 3000 to 14,000, and alterations to the ratio of staggered element positioning to rib height (r/e), from 2 to 5, impact the flow dynamics. The outcomes indicate a significant boost in heat transfer performance, with the Nusselt number rising to 3.76 compared with a conventional smooth duct. The highest thermal efficiency recorded was 86%, at an r/e ratio of 3.5. These results underscore the potential of using discrete V‐ribs with staggered elements in rectangular ducts to improve heat transfer efficiency.

Fatigue performance of innovative open-rib orthotropic steel deck for super-long suspension bridge

This paper presents experimental and numerical studies on the fatigue performance of an innovative orthotropic steel deck (OSD) with open-ribs, apple-shaped cut-outs, and additional transverse ribs, which is employed by the Zhangjinggao Yangtze River Bridge. This bridge is set to become the world's longest suspension bridge upon completion. A full-scale section of the OSD was fabricated and subjected to fatigue loading with a total cycle of 12.3 million times. The interested cracking-prone fatigue details include rib-to-deck and rib-to-crossbeam welded joints, along with the apple-shaped cut-outs of the crossbeam. Experimental results indicated that fatigue cracks initiated separately beneath the deck plate, on the flange of the rib, and at the rib-to-crossbeam welded joint, with equivalent stress amplitudes of 159 MPa, 148 MPa, and 99 MPa at 2 million cycles, respectively. In addition, detailed finite element model of the OSD was developed using ABAQUS and validated against the experimental results. The effects of the geometry dimensions and structural details of the bridge deck, longitudinal ribs, crossbeams and transverse ribs that influence the fatigue performance of this OSD were analyzed and discussed. Parametric analyses revealed that increasing the thickness of the deck plate, the thickness or the height of the longitudinal rib, and the number of transverse ribs can effectively reduce the stress amplitudes at corresponding fatigue details, which therefore improves their fatigue performance. This study provides useful references for the fatigue evaluation and design of OSDs with open-ribs and apple-shaped cut-outs.

Numerical study on dynamic response of a novel ribbed thin-walled UHPC box-type utility tunnel under gas explosion

At present, RC utility tunnels are widely used in urban utility tunnels. As a typical confined space, the complex load effect generated by the internal gas explosion of the gas tank of utility tunnel may lead to local damage or overall destruction of the structure of RC utility tunnel. Therefore, it is an important topic to improve the anti-explosion capability of the utility tunnel and ensure the normal operation of the utility tunnel after gas explosion. UHPC structure is considered to have excellent anti-explosion performance, so a ribbed thin-walled UHPC utility tunnel structure was proposed, which improved the overall stiffness and anti-explosion performance of the UHPC utility tunnel through the ribbed section. In view of the shortcomings of fluid-solid coupling method in gas simulation, Computational Fluid Dynamics (CFD) was used to calculate the overpressure distribution after gas explosion in UHPC utility tunnel. The accuracy of UHPC constitutive model and prestress simulation method was verified by testing results from the gas explosion on unbonded prestressed UHPC slab. The gas explosion damage mechanism of ribbed thin-walled UHPC utility tunnel, UHPC-NC combined utility tunnel and RC utility tunnel were comparatively analyzed. And the pre-fabricated stiffener height, UHPC slab thickness and UHPC strength were investigated on the anti-explosion performance of ribbed thin-walled UHPC utility tunnel against gas explosion. It is found that the UHPC strength needs to be enhanced dramatically to improve the blast resistance. The anti-explosion capability of utility tunnel can be effectively increased by increasing the rib height or increasing the thickness of the UHPC utility tunnel structure, and the damage pattern of the utility tunnel can also be changed from flexure-shear failure to bending failure. The results of the study can provide a reference for the damage analysis and anti-explosion design of ribbed thin-walled UHPC utility tunnels.

Numerical Investigation of Grooved Obstacle on Heat Transfer Inside A Heated Duct

Flow and heat transfer are simulated numerically in a 2-dimensional centerline- ribbed square duct for different values of the rib height to the duct height (Blocking ratio BR). The blocking ratio of these rectangular obstacles 0, 0.5 and 0.75 are examined. Three values of velocity (0.1, 1 and 4m/s) as inlet working conditions were used. The top and bottom face of the duct are subjected to 1000 W/m2 heat flux. The heat transfer and flow structure with Ansys-Fluent inside a square duct in the presence of rotating vortex generators were studied and the influence of the blocking ratio (BR) on both heat transfer and fluid flow are examined. Numerical simulation was performed by using Ansys-Fluent 18. . In general, the enhancement raticon of heat transfer could reach 54%.