Force Regime Research Articles

Predicting the shape formation of hollow parts with a flange in the process of combined radial-reverse extrusion

The simulation of the process of combined radial reverse extrusion of hollow parts with a flange has established two fundamentally different, in terms of the components of the kinematic modules, calculation schemes CDZ-1.i and CDZ-2.j, taking into consideration the possible shape of the boundary of the section of a metal flow inside a workpiece. The comparison of the dependences of the optimal relative rate of metal outflow in the opposite direction for different schemes indicates significant differences in the resulting values in the course of the deformation process. The relevance of this study is due to making it easier to evaluate the use of the combined extrusion process to produce hollow parts with a flange while maintaining the required dimensions compared to simple deformation schemes. We have identified the lack of detailed studies into the technologies for the introduction of combined extrusion schemes, as well as the absence of technological recommendations for determining the force regime and the shape formation of a semi-finished article. The process of the combined extrusion of hollow parts with a flange was investigated, thereby selecting different types based on the nature of the metal flow depending on the geometric ratios of the deformation process. We have obtained experimental data on the gradual shape formation of a semi-finished product in the process of deformation at different geometric ratios. The limits of using estimation schemes of the process have been defined to obtain data on the increments in a semi-finished product, including in terms of predicting the formation of a shrinkage cavity in the bottom part. It is recommended that a condition of selecting the appropriate scheme should be the condition for a minimum value of the reduced pressure of deformation p i < p j . The resulting recommendations make it easier to predict the shape formation and the force mode of extrusion (a deviation from experimentally obtained data can be reduced to 10 %), which would contribute to evaluating the rationality of the combined extrusion processes while ensuring the required dimensions of a part

Translocation of a Polyelectrolyte through a Nanopore in the Presence of Trivalent Counterions: A Comparison with the Cases in Monovalent and Divalent Salt Solutions.

A polyelectrolyte threading through a nanopore in a trivalent salt solution is investigated by means of molecular dynamics simulations under a reflective wall boundary. By varying the chain length N and the strength E of the driving electric field applied inside the pore, the translocation time is carefully calculated to get rid of the bouncing effect because of the boundary. The results are analyzed under the scaling form ⟨τ⟩ ∼ NαE–δ and four driving force regimes; namely, the unbiased, the weakly driven, the strongly driven trumpet, and the strongly driven isoflux regime, are distinguished. The exponents are calculated in each regime and compared with the cases in the monovalent and divalent salt solutions. Owing to strong condensation of counter ions, the changes of the exponents in the force regimes are found to be nontrivial. A large increase in translocation time can be, however, achieved as the driving field is weak. The variations of the chain size, the ion condensation, and the effective chain charge show that the process is proceeded in a quasi-equilibrium way in the unbiased regime and deviated to exhibit strong nonequilibrium characteristics as E increases. Several astonishing scaling behaviors of the waiting time function, the translocation velocity, and the diffusion properties are discovered in the study. The results provide deep insights into the phenomena of polyelectrolyte translocation in various salt solutions at different driving forces.

Prediction of heat transfer in a circular tube with aluminum and Cr-Ni alloy pins using artificial neural network

ABSTRACT This work aims to estimate the experimental heat transfer coefficients of a circular channel using artificial neural network. The experiments are carried out at a forced turbulent flow regime of 10,000 < Re <50,000. The obtained experimental Nusselt numbers are compared using the ANN (Artificial Neural Network). In the developed ANN structure are showed mean square error (MSE), average relative deviation (ARD %), and correlation coefficient (R2) in modeling of overall experimental datasets of Nusselt number. As a result, it is observed that the heat transfer correlation predicted by ANN are sufficiently consistent with the experimental results.

Contact/impact modeling and analysis of 4D printed shape memory polymer beams

This study examines contact and impact behaviors of shape memory polymer (SMP) beams fabricated by four-dimensional (4D) printing technology. A 3D phenomenological constitutive model is developed to predict visco-elastic-plastic characteristics of SMPs and their shape memory effect in large deformation range for the first time. A novel finite element method (FEM) based on non-linear Green strains is established to analyze the SMP beam under contact/impact loadings. Newmark and Newton-Raphson methods along with an iterative-incremental approach based on a visco-elastic-predictor visco-plastic-corrector return mapping algorithm are implemented to solve FEM governing equations in spatial and time domains. Fused deposition modeling is employed to 4D print samples from polyurethane-based filaments. Thermo-mechanical experimental tests are performed to acquire the parameters needed for the SMP constitutive model. The effects of indentation location, substrate thickness, and edge effect are examined numerically for cylindrical indentation of elastic-plastic SMPs at glassy phase. The validation and application of the Hertzian load-displacement relation for indentation of elastic materials are also clarified. Then, experimental and numerical tests are conducted to examine impact responses of 4D printed SMP beams. Influences of impact position and impactor initial velocity and energy on the responses of the structure in forced and free vibration regimes are studied in detail. The results revealed that the projectile with low velocity or high velocity accompanied with low energy impacted the beam is able to produce plastic deformation. It is shown that the large residual plastic deformation can be fully recovered by simply heating. Due to the absence of similar results in the specialized literature, this paper provides pertinent results that are instrumental in the design of SMP beam-like structures under impact loadings.

Transient weak gravity in scalar-tensor theories

Sub-horizon perturbations in scalar-tensor theories have been shown to grow generically faster than in uncoupled models due to a positive, additive Yukawa force. In such cases, the amount of clustering becomes larger than in the standard cosmological model, exacerbating the observed tension in the σ8 parameter. Here we show instead that in some simple cases of conformally coupled dark energy one can obtain a transient regime of negative Yukawa force, without introducing ghosts or other instabilities.

Experimental Investigation of Heat Transfer of Plane Heat-Removing Surfaces with Plate Finning

Heat transfer of promising heat-removing surfaces with plate-slit finning intended for use in the case of air cooling of heat loaded radio- and microelectronic facilities in forced convection regime has been investigated experimentally. The influence of the depth of slitting fins and of the turning angle of their slit parts relative to the cooling flow direction on the intensity of heat transfer of the finned surface is shown. It has been established that the greatest intensifying effect is observed at the relative depth of the slitting of fins equal to 0.6, which leads to an increase in the intensity of heat release by 20–25%. The turning of the slit parts of the fins leads to heat transfer growth by 50–60% compared with traditional plate-finned surfaces. Improved dimensionless equations are suggested for calculating average heat transfer of surfaces with plate-slit finning under the conditions of forced convection in the range of the Reynolds number values from 2000 to 10,000. The results of investigation can be used in designing new systems of cooling radio- and microelectronic facilities.

ЭКСПЕРИМЕНТАЛЬНЫЕ И РАСЧЕТНЫЕ ИССЛЕДОВАНИЯ ТЕПЛООБМЕНА ПРИ КИПЕНИИ ЖИДКИХ МЕТАЛЛОВ НА МОДЕЛЯХ ТВС БЫСТРЫХ РЕАКТОРАХ В АВАРИЙНЫХ РЕЖИМАХ

Studies of the boiling of alkali metals show that, compared with boiling water, the process of boiling liquid metals has significant features. Cooling of a fuel assembly in accident conditions when accident protection is triggered and circulation pumps are switched off (ULOF) leads to the study of fuel elements cooling at reduced coolant flow rates or even tipping circulation in fuel assemblies. There is only limited data on the boiling of sodium in fuel assemblies in these regimes. The results of a series of experiments on heat transfer and stability of circulation during boiling of a sodiumpotassium alloy on single fuel assembly models and in a parallel fuel assembly system with natural coolant circulation performed at JSC “SSC RF - IPPE” are presented. The results of comparing the data of the calculated and experimental studies are presented. The influence of the surface roughness of the fuel rods on the heat transfer and flow regimes during boiling of a liquid metal in bundles is demonstrated. The results of experimental studies of heat transfer during boiling of sodium in natural and forced convection regimes in a fuel assembly model with a “sodium cavity” located above the reactor core intended to compensate for the positive sodium void reactivity effect in emergency situations with sodium boiling are also presented. It is shown that it is possible to provide continuous sodium cooling of fuel element simulators in fuel assemblies under these conditions. The results of the generalization of data on heat transfer during boiling of liquid metals in bundles and a cartogram of the regimes of two-phase flow during boiling of liquid metals in bundles are presented. The objectives of further research are discussed.

Thermodynamic uncertainty relations and molecular-scale energy conversion.

The thermodynamic uncertainty relation (TUR) is a universal constraint for nonequilibrium steady states that requires the entropy production rate to be greater than the relative magnitude of current fluctuations. It has potentially important implications for the thermodynamic efficiency of molecular-scale energy conversion in both biological and artificial systems. An alternative multidimensional thermodynamic uncertainty relation (MTUR) has also been proposed. In this paper we apply the TUR and the MTUR to a description of molecular-scale energy conversion that explicitly contains the degrees of freedom exchanging energy via a time-independent multidimensional periodic potential. The TUR and the MTUR are found to be universal lower bounds on the entropy generation rate and provide upper bounds on the thermodynamic efficiency. The TUR is found to provide only a weak bound while the MTUR provides a much tighter constraint by taking into account correlations between degrees of freedom. The MTUR is found to provide a tight bound in the near or far from equilibrium regimes but not in the intermediate force regime. Collectively, these results demonstrate that the MTUR is more appropriate than the TUR for energy conversion processes, but that both diverge from the actual entropy generation in certain regimes.

Understanding the paradoxical mechanical response of in-phase A-tracts at different force regimes.

A-tracts are A:T rich DNA sequences that exhibit unique structural and mechanical properties associated with several functions in vivo. The crystallographic structure of A-tracts has been well characterized. However, the mechanical properties of these sequences is controversial and their response to force remains unexplored. Here, we rationalize the mechanical properties of in-phase A-tracts present in the Caenorhabditis elegans genome over a wide range of external forces, using single-molecule experiments and theoretical polymer models. Atomic Force Microscopy imaging shows that A-tracts induce long-range (∼200 nm) bending, which originates from an intrinsically bent structure rather than from larger bending flexibility. These data are well described with a theoretical model based on the worm-like chain model that includes intrinsic bending. Magnetic tweezers experiments show that the mechanical response of A-tracts and arbitrary DNA sequences have a similar dependence with monovalent salt supporting that the observed A-tract bend is intrinsic to the sequence. Optical tweezers experiments reveal a high stretch modulus of the A-tract sequences in the enthalpic regime. Our work rationalizes the complex multiscale flexibility of A-tracts, providing a physical basis for the versatile character of these sequences inside the cell.

Danos causados por medicamentos: responsabilidade civil do produtor no âmbito da legislação portuguesa

Objetivo: analisar, por um lado, o regime jurídico aplicável em caso de danos causados por medicamentos e, por outro lado, as dificuldades que se erigem com as (in)suficiências desse mesmo regime. Metodologia: foi realizada análise bibliográfica sobre este tema. Resultados: resulta do estudo levado a cabo que, muito embora o regime legal em vigor se revele adequado à generalidade dos produtos, o mesmo já não se pode afirmar o mesmo em relação a alguns aspetos de regime quando em causa esteja um produto-medicamento em relação a alguns aspetos de regime, atentas as suas características próprias e a interação com o corpo humano que de imediato se estabelece. Conclusão: à imagem do que sucedeu em outros ordenamentos jurídicos europeus, poderia equacionar-se legislar especificamente sobre a responsabilidade civil decorrente de danos causados por medicamentos, como é o caso da Alemanha, ou consagrar algumas diferenças de regime quando em causa esteja um medicamento, como sucedeu em Espanha.

Numerical study on drag and lift coefficients of a marine riser at high Reynolds number using COMSOL multiphysics

Flow around a marine riser in water at the drag crisis regime was investigated using numerical modelling. In this regime, the drag coefficient drops off at a certain Reynolds number due to a change from laminar to turbulent flow. The aim is to investigate the capability of turbulence model to predict drag coefficient through COMSOL Multiphysics, a computational fluid dynamic (CFD) transient solver and compared against existing numerical models and experiment by Maritime Research Institute Netherlands (MARIN). Numerically, drag and lift forces depend on the point of separation from the cylinder in which different turbulence modelling will result in varying separation point and will lead to different vortex formation and the drag force. Reynolds Average Navier-Stokes (RANS) was employed using the k-ε and Menter’s Shear Stress Transport (SST) turbulence model in two-dimensional CFD simulation. Six Reynolds numbers, similar to the test case, were considered. It can be concluded that the standard k-ε turbulence model, can only provide a good approximation at high turbulence regime, which is Reynolds number of 3.15 × 105 and higher. While, SST turbulence model can provide a good approximation at subcritical regime which before the sudden drop of drag force regimes.

Conformation and dynamics of a self-avoiding active flexible polymer.

We investigate conformations and dynamics of a polymer considering its monomers to be active Brownian particles. This active polymer shows very intriguing physical behavior which is absent in an active Rouse chain. The chain initially shrinks with active force, which starts swelling on further increase in force. The shrinkage followed by swelling is attributed purely to excluded-volume interactions among the monomers. In the swelling regime, the chain shows a crossover from the self-avoiding behavior to the Rouse behavior with scaling exponent ν_{a}≈1/2 for end-to-end distance. The nonmonotonicity in the structure is analyzed through various physical quantities; specifically, radial distribution function of monomers, scattering time, as well as various energy calculations. The chain relaxes faster than the Rouse chain in the intermediate force regime, with a crossover in variation of relaxation time at large active force as given by a power law τ_{r}∼Pe^{-4/3} (Pe is Péclet number).

Experimental insights into the mechanism of heat losses from a cylindrical solar cavity receiver equipped with an air curtain

We report on the effectiveness of an air curtain to mitigate convective heat losses from a heated cylindrical cavity receiver operated at fixed tilt (15°) and yaw angles (0°). The cavity was heated electrically with a controller to maintain a constant inside temperature of 300 °C, varying wind speed, air curtain velocity and discharge angle. It was found that the greatest convective heat losses occur over the lower internal surfaces of the cavity for all cases, spanning both natural and forced convection regimes, while a discharge angle of 30° relative to the face of the cavity is more effective than a parallel curtain, which was found to increase heat losses. It was also found that, for a discharge angle of 0°, increasing the velocity of the air curtain leads to higher convective heat losses. However, for a curtain discharge angle of 30°, increasing the air curtain velocity can reduce heat losses by up to 60%. The measured distribution of air temperature across the aperture plane and convective heat losses through the surface were used to provide insight into the causes of these observations. These results suggest that, for tilted, tower-mounted cavity receivers, the orientation of an air curtain should be directed with a component towards the wind, rather than parallel to the aperture plane.

THE VIRTUAL POWER PLAN INTERACTION AND ACTIVE CONSUMERS ANALYSIS, IN THE FRAMEWORK OF THE HIERARCHICAL SYSTEM WITH THE LIBERALIZED LIMITATIONS

Ukraine's energy development is under review in the regime of reform and legislative forces. The path toenergy liberalization will not be a new process in the development of the EU and US energy sectors, but it will notbe fully implemented in Ukraine. The liberal energy main features are the guarantee of a secure overall system,efficient operation and electricity vacancies use for competitors. The success of the electricity market, not usingadequate regulatory policies, and the participating entity's profitability. Offered by virtual power plants andconcepts of energy collaboration - a global trend that is actively promoted and implemented in their regions. It canactually be used for the domestic development of the energy sector. As a result, the state and main stages ofreforming the Ukrainian energy market are analyzed. The stages, transitional, criterion and possible conservationin enterprises and liberalized energy markets are evaluated. The main factors that should make the implementationof energy market liberalization are described. For the active consumers, who are the main element of the transitionand placement of the larger-scale libero, the energy market remains negative, experiencing and experiencing aconscious and active energy value in the world.

Molecular interactions and forces of adhesion between single human neural stem cells and gelatin methacrylate hydrogels of varying stiffness

Single Cell Force Spectroscopy was applied to measure the single cell de-adhesion between human neural stem cells (hNSC) and gelatin methacrylate (GelMA) hydrogel with varying modulus in the range equivalent to brain tissue. The cell de-adhesion force and energy were predominately generated via unbinding of complexes formed between RGD groups of the GelMA and cell surface integrin receptors and the de-adhesion force/energy were found to increase with decreasing modulus of the GelMA hydrogel. For the softer GelMA hydrogels (160 Pa and 450 Pa) it was proposed that a lower degree of cross-linking enables a greater number of polymer chains to bind and freely extend to increase the force and energy of the hNSC-GelMA de-adhesion. In this case, the multiple polymer chains are believed to act together in parallel like ‘molecular tensors’ to generate tensile forces on the bound receptors until the cell detaches. Counterintuitively for softer substrates, this type of interaction gave rise to higher force loading rates, including the appearance of high and low dynamic force regimes in de-adhesion rupture force versus loading rate analysis. For the stiffer GelMA hydrogel (900 Pa) it was observed that the extension and elastic restoring forces of the polymer chains contributed less to the cell de-adhesion. Due to the apparent lower extent of freely interacting chains on the stiffer GelMA hydrogel the intrinsic RGD groups are presumed to be “more fixed” to the substrate. Hence, the cell de-adhesion is suggested to be mainly governed by the discrete unbinding of integrin-RGD complexes as opposed to elastic restoring forces of polymer chains, leading to smaller piconewton rupture forces and only a single lower dynamic force regime. Intriguingly, when integrin antibodies were introduced for binding integrin α5β1, β1- and αv-subunits it was revealed that the cell modifies the de-adhesion force depending on the substrate stiffness. The antibody binding supressed the de-adhesion on the softer GelMA hydrogel while on the stiffer GelMA hydrogel caused an opposing reinforcement in the de-adhesion. Statement of SignificanceConceptual models on cell mechanosensing have provided molecular-level insight to rationalize the effects of substrate stiffness. However most experimental studies evaluate the cell adhesion by analysing the bulk material properties. As such there is a discrepancy in the scale between the bulk properties versus the nano- and micro-scale cell interactions. Furthermore there is a paucity of experimental studies on directly measuring the molecular-level forces of cell-material interactions.Here we apply Single Cell Force Spectroscopy to directly measure the adhesion forces between human neural stem cells and gelatin-methacrylate hydrogel. We elucidate the mechanisms by which single cells bind and physically interact with hydrogels of varying stiffness. The study highlights the use of single cell analysis tools to probe molecular-level interactions at the cell-material interface which is of importance in designing material cues for regulating cell function.

Nitrosative stress affects the interaction of integrin alphaIIbbeta3 with its ligands

Binding of integrin alphaIIbbeta3 (αiibβ3) to its ligands is a highly restricted and regulated mechanism. Any modification of the protein structure yields a dysfunctional role, especially in a redox environment. Here, we examine the effect of nitrosative stress on the αiibβ3 reconstituted into nanodiscs. Using single molecule force spectroscopy, we measured the interaction between αiibβ3 and its ligand RGD and found that in the presence of exogenous nitric oxide (NO) two force regimes are generated: a low force regime of ~100pN indicating the presence of integrin in a normal status, and a broad spectrum of high force regime (~210–450pN) suggesting the protein modification/aggregation. By high resolution atomic force microscopy imaging, we demonstrate that both NO and nitrite (a stable product formed from NO) are involved in destabilizing the transmembrane protein complex leading to release of αiibβ3 from the lipid bilayer and protein aggregation. Our experimental setup opens new ways for testing in a membrane environment the effect of radical species on integrins under clinically relevant conditions.

Nanotribology of hydrogels with similar stiffness but different polymer and crosslinker concentrations

HypothesisThe stiffness has been found to regulate hydrogel performances and applications. However, the key interfacial properties of hydrogels, like friction and adhesion are not controlled by the stiffness, but are altered by the structure and composition of hydrogels, like polymer volume fraction and crosslinking degree. ExperimentsColloidal probe atomic force microscopy has been use to investigate the relationship between tribological properties (friction and adhesion) and composition of hydrogels with similar stiffness, but different polymer volume fractions and crosslinking degrees. FindingsThe interfacial normal and lateral (friction) forces of hydrogels are not directly correlated to the stiffness, but altered by the hydrogel structure and composition. For normal force measurements, the adhesion increases with polymer volume fraction but decreases with crosslinking degree. For lateral force measurements, friction increases with polymer volume fraction, but decreases with crosslinking degree. In the low normal force regime, friction is mainly adhesion-controlled and increases significantly with the adhesion and polymer volume fraction. In the high normal force regime, friction is predominantly load-controlled and shows slow increase with normal force.

Role of Charge Regulation and Fluctuations in the Conformational and Mechanical Properties of Weak Flexible Polyelectrolytes.

This work addresses the role of charge regulation (CR) and the associated fluctuations in the conformational and mechanical properties of weak polyelectrolytes. Due to CR, changes in the pH-value modifies the average macromolecular charge and conformational equilibria. A second effect is that, for a given average charge per site, fluctuations can alter the intensity of the interactions by means of correlation between binding sites. We investigate both effects by means of Monte Carlo simulations at constant pH-value, so that the charge is a fluctuating quantity. Once the average charge per site is available, we turn off the fluctuations by assigning the same average charge to every site. A constant charge MC simulation is then performed. We make use of a model which accounts for the main fundamental aspects of a linear flexible polyelectrolyte that is, proton binding, angle internal rotation, bond stretching and bending. Steric excluded volume and differentiated treatment for short-range and long-range interactions are also included. This model can be regarded as a kind of “minimal” in the sense that it contains a minimum number of parameters but still preserving the atomistic detail. It is shown that, if fluctuations are activated, gauche state bond probabilities increase and the persistence length decreases, so that the polymer becomes more folded. Macromolecular stretching is also analyzed in presence of CR (the charge depends on the applied force) and without CR (the charge is fixed to the value at zero force). The analysis of the low force scaling behavior concludes that Pincus exponent becomes pH-dependent. Both, with and without CR, a transition from 1/2 at high pH-values (phantom chain) to 3/5 at low pH-values (Pincus regime) is observed. Finally, the intermediate force stretching regime is investigated. It is found that CR induces a moderate influence in the force-extension curves and persistence length (which in this force regime becomes force-dependent). It is thus concluded that the effect of CR on the stretching curves is mainly due to the changes in the average charge at zero force. It is also found that, for the cases studied, the effect of steric excluded volume is almost irrelevant compared to electrostatic interactions.

One-dimensional model of hydrogen distribution in confined space based on Froude number

Some hydrogen mitigation study programs have been conducted to figure out the hydrogen distribution characteristics and provide useful information for codes development and validation. However, there is a lack of models with direct relations between hydrogen distribution and a non-dimensional parameter which governs the hydrogen flow, such as Froude number. This deficiency will lead to lack of understandings of the dominated force regimes. Therefore, in this paper, one-dimensional model of hydrogen distribution is built, based on Froude number. With theoretical study and fitting method, a semi-empirical formula is given, which is verified by experimental data obtained from pure plume conditions and buoyant jet conditions. Finally, this newly-built model is employed in typical accidents analysis. Three typical Froude numbers which are based on PANDA and TOSQAN study, are selected to get much closer to the real accidents. According to the evolution of helium concentration and concentration distinction, it can be found that obvious stratification may take place in the middle part and lower part of the containment model, while it turns to be more uniform in the top, corresponding to these three Froude numbers of 3.8, 17 and 280. Moreover, the higher the buoyancy is (Fr = 3.8), the more uniform the helium distribution throughout the containment model will be. The medium momentum will lead to significant stratification, which needs to be paid much attention in reactor design and accident mitigation.

Mixed convection and radiation from an isothermal bladed structure

The total heat transfer from a finned or ‘bladed’ structure may be expected to rise from that of a flat geometry due to a larger area exposed to ambient air. However, this is not always the case because a trade-off can be found between convection and radiation as the bladed geometry and surface temperature are varied. Furthermore, a mixed convection regime adds complexity to the heat exchange between the surrounding air and the heated bladed structure, which is relevant to various applications such as cooling and solar thermal energy. In this study, mixed convection and radiation heat transfer were determined for a cuboid with isothermal blades protruding from one of its sides. A steady-state simulation based on a three-dimensional SST k–ω turbulence model was performed in OpenFOAM to estimate the average convection heat transfer coefficient as a function of structure orientation, convection regime and bladed geometry. A Monte Carlo ray tracing method was employed to calculate view factors for determining the radiation heat transfer coefficient. Wind tunnel experiments validated the combined numerical approach. An increasing pitch angle (starting from the vertical) gradually increased convection heat transfer until a maximum value at ~45° and then significantly decreased it, where both effects were due to a flow behaviour in which vortices between the blades formed (<45°) but then disappeared (>45°). The velocity and wall temperature of the mixed convection flow in between the dominantly natural and forced convection regimes were identified. In comparison to a flat geometry, the bladed structure increased the temperature value at which the heat transfer by convection and radiation equalised, and produced a lower total heat transfer coefficient than the flat configuration at high surface temperatures. Furthermore, flow bifurcations were observed between the blades as their length was increased. In contrast, a large number of blades led to a flow transition where most of the incoming air exited from the side apertures to a lid-driven-like convection with flow recirculation occurring within the blades, which created a thermal barrier that decreased convection heat transfer. These results support the design of bladed or finned structures that enhance or reduce heat transfer by mixed convection and/or thermal radiation.